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From 21 August to 15 September 2022, a WindCube v2 Infrared coherent Doppler Lidar (DL) supplied by EKO Co. (Japan) was deployed at the Shigaraki MU Observatory (Japan) near the LQ7 UHF (1.357 GHz) wind profiler in routine operation. Horizontal and vertical velocity measurements from DL were reliably obtained in the [40–300] m height range with vertical and temporal resolutions of 20 m and 4 seconds, respectively. The LQ7 wind measurements are collected with range and temporal resolutions of 100 m and 59 s, respectively, and 10-min average profiles are calculated after data quality control. Reliable LQ7 Doppler data are collected from the height of 400 m. Despite the lack of overlap in the height range, we compared the Turbulence Kinetic Energy (TKE) dissipation rate ε in the daytime planetary boundary layer estimated by the two instruments. A method based on the calculation of the one-dimensional transverse line spectrum of the vertical velocity W from mean W time series (TS method) was applied to DL (ε DL). The same method was also applied to 1-min LQ7 data (ε LQ 7TS) to assess its performance with respect to DL despite the poorer time resolution. A more standard method based on the Doppler Spectral width (DS) was also applied to LQ7 (ε LQ 7DS) from the 10-min average profiles. We tested recently proposed models of the form ε=σ3/ L where σ is half the spectral width corrected for non-turbulent effects and L is assumed to be a constant or a fraction of the depth D of the Convective Boundary Layer (CBL). The main results are: (1) For the deepest CBLs (max(D) >~1.0 km) that develop under high atmospheric pressure, the time-height cross-sections of ε LQ 7DS and ε DL show very consistent patterns and do not show any substantial gaps in the transition region of 300–400 m when ε LQ 7DS is evaluated with L ~70 m , which is found to be about one tenth of the average of the CBL depth (L ~0.1 D). (2) Hourly mean ε DL averaged over the [100–300] m height range is on average about twice the hourly mean ε LQ 7TS averaged over the [400–500] m height range when D >~1.0 km. (3) Hourly mean ε DL averaged over the [100–300] m height range and hourly mean ε LQ 7DS averaged over the [400–500] m height range with L ~0.1 D are identical on average. Consistent with the fact that ε is expected to decrease slightly with height in the mixed layer, (2) and (3) imply an uncertainty as to the exact value of the L / D ratio: ~0.1 D < L <~0.2 D. We have also studied in detail the case of a shallow (D <~0.6 km) convective boundary layer that developed under low atmospheric pressure and cloudy conditions. Despite the fact that hourly mean ε DL averaged over the [100–300] m height range and hourly mean ε LQ 7TS averaged over the [400–500] m height range show more significant discrepancies, maybe due to the different properties of the shallow convection, the time-height cross-sections of ε DL and ε LQ 7DS show more consistent patterns and levels. [ABSTRACT FROM AUTHOR]

As a new type of wind field detection equipment, coherent Doppler wind lidar (CDWL) still needs more relevant observation experiments to compare and verify whether it can achieve the accuracy and precision of traditional observation equipment in urban areas. In this experiment, a self-developed CDWL provided four months of observations in the southern Beijing area. After the data acquisition time and height match, the wind profile data obtained based on a Doppler beam swinging (DBS) five-beam inversion algorithm were compared with radiosonde data released from the same location. The standard deviation (SD) of wind speed is 0.8 m s−1, and the coefficient of determination R2 is 0.95. The SD of the wind direction is 17.7° with an R2 of 0.96. Below the height of the roughness sublayer (about 400 m), the error in wind speed and wind direction is significantly greater than the error above the height of the boundary layer (about 1500 m). For the case of wind speeds less than 4 m s−1, the error of wind direction is more significant and is affected by the distribution of surrounding buildings. Averaging at different height levels using suitable time windows can effectively reduce the effects of turbulence and thus reduce the error caused by the different measurement methods of the two devices. [ABSTRACT FROM AUTHOR]

Experimental investigations are carried out to explore the aerodynamic performance and vortex shedding characteristics of S5010 and E214 airfoil-based wings to provide guidance for the design of MAVs and other low-speed vehicles. Force and wake shedding frequency measurements are carried out in a subsonic wind tunnel in the Reynolds number (Re) range of 4 × 104 - 1 × 105. The measurements with increasing Re show that the slope of the lift curve in the linear region increases by 14% for S5010, while this increment is 11% for E214. The peak lift coefficient of both airfoils reduces with reducing Re. For lower pitch angles, the influence of Re on drag coefficients is less significant, but at higher angles, the drag increases as the Re drops. Unlike pre-stall mountings, the pitch-down propensity of the airfoil enhances in the post-stall region for high Re flows. Moreover, the frequency of shed vortices reduces with rising angle of attack at a given Re. In contrast, the Strouhal number almost remains constant with varying Re at a fixed angle of attack. For S5010 and E214 airfoils, the Strouhal number is noticed to vary between 0.68 - 0.36 and 0.58 - 0.36, respectively, for pitch angle variation of 12°- 28°. The airfoils show a higher Strouhal number than the bluff body wakes, but this difference decreases for high angles of attack mountings. This finding reveals that the wake structure of the airfoil at a high post-stall angle behaves as bluff body wakes. [ABSTRACT FROM AUTHOR]

Floating offshore wind (FOW) is a renewable energy source that is set to play an essential role in addressing climate change and the need for sustainable development. However, due to the increasing threat of climate emergency, more wind turbines are required to be deployed in deep water locations, further offshore. This presents heightened challenges for accessing the turbines and performing maintenance, leading to increased costs. Naturally, methods to reduce operational expenditure (OpEx) are highly desirable. One method that shows potential for reducing OpEx of FOW is LIDAR‐assisted pitch control. This approach uses wind velocity measurements from a nacelle‐mounted LIDAR to enable feedforward control of floating offshore wind turbines (FOWTs) and can result in reductions to the variations of structural loads. Results obtained from a previous study of combined feedforward collective and individual pitch control (FFCPC + FFIPC) are translated to OpEx reductions via reduced component failure rates for future FOW developments, namely, in locations awarded in the recent ScotWind leasing round. The results indicate that LIDAR‐assisted pitch control may allow for an up to 5% reduction in OpEx, increasing to up to 11% with workability constraints included. The results varied across the three ScotWind sites considered, with sites furthest from shore reaping the greatest benefit from LIDAR‐assisted control. This work highlights the potential savings and reduction in the overall levelised cost of energy for future offshore wind turbine projects deliverable through the implementation of LIDAR‐assisted pitch control. [ABSTRACT FROM AUTHOR]

Low‐level Jets (LLJs) play a critical role in triggering nocturnal rainfall in many areas on our planet. Nevertheless, little is known regarding the vertically resolved evolution of LLJs preceding rainfall. Here, the high‐resolution wind measurements from a radar wind profiler network in Beijing are used to monitor the continuous evolution of boundary‐layer jets (BLJs) and synoptic‐system‐related LLJs (SLLJs) before nocturnal rainfall under the southwesterlies synoptic pattern for the summers of 2020–2023. The results show that inertial oscillations precede LLJ‐induced nocturnal rainfall. The typical northward propagation of LLJ is driven primarily by horizontal advection. Starting 48 min before rainfall, the BLJ nose rapidly strengthens and moves downward from 0.8 km above ground level (AGL), while the SLLJ nose moves upward to 2.4 km AGL. This leads to enhanced moisture transport and convergence, which triggers nocturnal rainfall. The findings are of great significance for improving the forecast skill of nocturnal rainfall. Plain Language Summary: The role of low‐level jets (LLJs) in triggering nocturnal rainfall remains elusive, largely due to the dearth of vertical atmospheric observations. To address this issue, we used high‐resolution vertical wind measurements from a radar wind profiler (RWP) network near Beijing to characterize both boundary‐layer jets (BLJs) and synoptic‐system‐related LLJs (SLLJs) preceding nocturnal summer rainfall under the influence of synoptic‐scale southwesterly winds. The LLJs propagate northward ahead of the nocturnal rainfall. The noses of both types of LLJs are found to intensify dramatically within 48 min before nocturnal rainfall, along with warm and moist advection. This implies that the high‐resolution LLJs obtained from the RWP network exert a significant impact on the onset of summertime nocturnal rainfall in Beijing. Key Points: Radar wind profiler network captures the fine‐scale evolution of low‐level jet (LLJ) that triggers the nocturnal rainfallBoundary‐layer (synoptic‐system‐related) jet nose enhanced sharply 48 min ahead of rainfall onsetThe surge in LLJ is key to enhancing moisture transport within 30 min preceding nocturnal rainfall [ABSTRACT FROM AUTHOR]

A major obstacle standing in the way of full‐scale adoption of renewable energy sources is their intermittency and seasonal variability. To better understand the power generation dynamics, the effect of air density due to temperature on power and energy generation figures was modelled. The model uses historical ERA5 data and considers changes in weather patterns in a subarctic climate where seasonal changes are most pronounced. The power generation figures of using a mean and a dynamic air density value were compared and the results show that power generation estimates may be under‐ and overestimated by on average 5% up to 10% in winter and summer, respectively. This can have implications for the sizing of power transmission infrastructure and energy storage in both on‐grid and off‐grid applications as well as power availability. The topic is highly relevant in the Nordic countries where roughly 10% of new global added wind capacity is installed annually. [ABSTRACT FROM AUTHOR]

Soil respiration (Rs) is the largest source of atmospheric CO2, and an accurate understanding of the relationship between near-surface winds, CO2 release from the soil surface, and measurement methods is critical for predicting future atmospheric CO2 concentrations. In this study, the relationship between wind speed and soil CO2 fluxes is elucidated on a global scale through meta-analysis, and the flux measurement methodology is further explored in conjunction with the results of a controlled trial to clarify the uncertainty of the measurement results. The results indicate that near-surface wind speed is positively correlated with soil CO2 release and that near-surface winds result in increased soil CO2 gas release. Wind disturbance affects both the concentration gradient and gas chamber measurements, and the lower calculated soil CO2 release conflicts with the notion that the wind pump effect and Bernoulli effect of negative pressure cause a greater surface gas exchange. The results of the log-response ratios indicate that near-surface winds lead to an underestimation of 12.19-19.75% in widely-used gas chamber method measurements. The results of this study imply that some of the current Rs measurements are biased and that the influence of near-surface winds on Rs measurements needs to be urgently addressed to assess the terrestrial carbon cycle more accurately and develop climate change response strategies. [ABSTRACT FROM AUTHOR]

Sea ports play a major role in the transport of goods worldwide, and knowledge of wind characteristics in these areas is vital to maintaining safety. However, coastal wind flow can be highly complex and turbulent, necessitating additional analysis. A Doppler lidar providing continuous wind profiles is deployed in the Port of Genoa, Italy, to characterize the mean wind velocity and turbulence properties within the coastal surface layer (40–250 m above ground level). Weather conditions, reanalysis data, and transient wind profiles are combined to analyze wind field characteristics on a day which experienced a thunderstorm. We also utilize a method to identify and categorize sources of turbulence through analysis of lidar derived quantities such as wind shear, turbulent kinetic energy, and vertical skewness. Seasonal variations in the wind properties are investigated by selecting data from June (summer) and December (winter). Differences are found in dominant wind direction and the associated frequency of convective mixing, with onshore winds most common in summer and offshore winds in winter. The measured lidar velocity is also compared against Monin–Obukhov similarity theory predictions, showing satisfactory agreement at low heights but struggling to reproduce observations of the stable atmospheric conditions present during winter. Plain Language Summary: Approximately 40% of the world's population lives in the coastal regions. Similarly, seaports host about 80% of the global maritime transport and therefore play a major role in the transportation of goods and services. However, coastal regions and ports are also windy places due in part to strong temperature differences between land and sea. This study uses a remote sensing instrument—Doppler lidar—to measure mean wind velocity and turbulence characteristics in the Port of Genoa, Italy, between 40 and 250 m above the ground. The study first provides a detailed investigation of a case (7 June 2020) that was characterized by variable weather that included rain, thunderstorms, and intermittent sunshine. Seasonal variations in the wind characteristics above the Port of Genoa are investigated by focusing on June (summer) and December (winter) months. Winds that blow from sea to land are most common in summer whereas the winds that blow from land to sea are dominant in winter. The wind measurements are compared against theoretical predictions that are often employed in numerical weather prediction models. A varying degree of similarity between the measured and predicted values is found. Key Points: Analyses of wind variability during a thunderstorm and seasonal wind patterns using Doppler lidar measurements in the Port of Genoa, ItalyClassification of turbulent sources using lidar‐derived quantities and comparison of wind profiles against theoretical predictionsSeasonal analysis of surface heating induced convective‐mixing sources and their frequency [ABSTRACT FROM AUTHOR]

The detection and quantification of strong sea surface winds, reaching up to 25 m·s−1, whether associated with deep convection aloft or not, have been extensively discussed in previous studies. This method involves the combined observation of the same event from both low‐orbit altitude and geostationary (GEO) satellites. Strong surface winds observed by the Sentinel‐1 C‐band synthetic aperture radar (SAR) are robustly associated with deep convective clouds detected by GEO infrared sensors. The current paper aims to generalize the previous assessment of several convective wind events by collecting a larger dataset and comparing these data to in‐situ wind observations. To achieve this, we evaluated wind speeds retrieved from Sentinel‐1 SAR images against corresponding in‐situ wind measurements from all active buoys/stations in the Gulf of Mexico. Significant agreement between satellite‐based winds and in‐situ data was achieved, particularly for wind speeds exceeding 3 m·s−1, with even better agreement for wind speeds over 10 m·s−1. From this dataset, three specific convective cases were extracted to illustrate various stages of convective squall events: before, during, and after the occurrence of a squall peak. In each case, comparison with in‐situ measurements showed that SAR‐estimated wind speeds closely matched observed speeds, including the peak convective winds, which were estimated at 18.90 m·s−1 and measured at 20.69 m·s−1. Furthermore, combining these findings with GOES‐16 sequential images illustrates the temporal and spatial similarity between deep convection areas, estimated strong sea surface wind patterns, and measured wind speeds. [ABSTRACT FROM AUTHOR]

We describe the acquisition and evaluation of data during the ArcWatch II expedition into the Arctic Ocean on board of the icebreaker Polarstern. The data is used to calibrate a hybrid sea ice model that focuses on modeling the marginal ice zone, which is the transition zone between pack ice and the open ocean. We describe the experimental setup used to track the motion of individual ice floes as well as the measurement of the wind and the ocean current. In the literature, the motion of an ice floe in the free‐drift regime is often estimated by Nansen's rule of thumb, which assumes the sea ice drifts at 2%$2\%$ of the wind speed, deflected up to 45∘$45^{\circ }$ in clockwise direction. Analyzing the first datasets, we noticed that observed small ice floes in free drift often have a larger relative angle to the wind direction. Based on numerical simulation we quantify that these larger angles are related to the geometry of larger sea ice floes in the vicinity of the observed ice floe. These large icefloes influence the ocean current, which in turn, impacts the motion of the small ice floes in the surrounding. [ABSTRACT FROM AUTHOR]

Saddle-shaped roofs are one typical kind of large span roofs, but there are few studies on the equivalent static wind load (ESWL) of saddle-shaped roofs, which is important for structural design. This study conducts wind pressure measurements of saddle-shaped roofs with three typical rise-span ratios (f/S=1/6 , 1/8 , 1/12) by wind tunnel tests. Subsequently, the influences of wind and structural parameters on dynamic responses and ESWLs are investigated for 81 single-layer saddle-shaped shells with different structural stiffness, including rise-span ratio, span length, roof mass, and incoming mean wind velocity. The results show that the most unfavorable wind directions of the peak structural responses for single-layer saddle-shaped shells are 60° and 90°, as well as the axisymmetric wind directions corresponding to these two wind directions, i.e., 120°, 240°, 270°, 300°. Finally, a simple fundamental vector is proposed to express the multitarget ESWLs for single-layer saddle-shaped shells to reproduce multiple peak responses at the most unfavorable wind directions. Through parametric analysis, mean pressure coefficients of roof zones are proposed. Within the investigated parameter ranges, the fluctuating ESWL coefficients are expressed as the functions of the reduced structural frequency at the most unfavorable wind directions, which is very convenient for structural engineers to determine the wind loads on main force resisting structural systems. [ABSTRACT FROM AUTHOR]

A sodium lidar (light detection and range) network for the Earth's mesosphere and lower thermosphere (MLT) temperature, wind and sodium density measurements is designed and constructed in the second phase of the Chinese Meridional Project. Five narrowband sodium lidar systems are deployed across various regions in China, designed and developed based on similar principles and structures. They adhere to uniform data processing standards and operate under the same observational protocols. This allows them to form a network of lidar systems capable of detecting temperature and wind fields in the MLT. The preliminary observation results of the lidar near Tibetan plateau is demonstrated in this paper. This lidar network offers horizontal perspectives on large scale that a single‐station lidar system can't provide. Its future observations are expected to advance the understanding of atmospheric waves by studying wave propagation, chemical‐dynamical coupling processes and the horizonal structure of in the MLT region. Plain Language Summary: This paper describes a new lidar (light detection and range) network to observe the mesosphere and lower thermosphere (MLT) region, which is the coldest area in the earth. Five narrow band sodium lidars in this network measure the temperature, wind and sodium density. They adhere to uniform data processing standards and follow the same observational protocols, which define the temporal and range resolution of lidar data, as well as the world geodetic system. The preliminary results for wind, temperature and sodium density are obtained. The lidar network will provide effective means for MLT research. Key Points: Narrowband sodium lidar based on pulsed seeder laser is constructed to measure wind and temperature in the mesosphere and lower thermosphere regionFive lidars distributed in the region of China from 19.5°N to 53.5°N, and from 87.2°E to 122.4°E form a lidar networkPreliminary observation results are demonstrated the ability and potential of the lidar network to conduct more scientific research [ABSTRACT FROM AUTHOR]

This study uses satellite measurements of plasma densities and thermospheric winds to analyze the effects of the November 2021 geomagnetic storm on ionospheric pre‐midnight topside plasma bubbles over South America. Using observations from the Ionospheric Connection Explorer (ICON) and the Global‐scale Observations of the Limb and Disk (GOLD) satellites, we find that pre‐midnight topside plasma bubbles were inhibited over eastern South America during the recovery phase of the storm. This is particularly notable because of the otherwise high occurrence rate of plasma bubbles at these longitudes during this season. This inhibition coincided with the recovery phase of the geomagnetic storm, marked by a northward turning of the z‐component of the interplanetary magnetic field (IMFBz) and quiet‐time values of the SuperMAG Auroral Electrojet Index (SME). We observed a westward turning of the zonal wind before the bubble inhibition, so we conclude the inhibition of topside plasma bubbles is likely related to a westward disturbance dynamo electric field (DDEF) causing a downward E×B $\mathbf{E}\times \mathbf{B}$ drift and suppress the growth of the instability responsible for bubble development. Contrary to theoretical predictions, we do not observe notable changes to the meridional wind during the event. These results provide new insights into the ionosphere‐thermosphere system's response to geomagnetic storms and highlight the role of wind patterns in inhibiting ionospheric irregularities, contributing to better predictive models for these phenomena. Plain Language Summary: Geomagnetic storms negatively affect communication and navigation systems by producing unpredictable changes in ionospheric densities. Plasma bubbles are irregularities in the ionosphere that occur mainly in the equatorial region and may be affected by geomagnetic storms. Studying plasma bubbles is crucial because they can significantly reduce the performance of communication and navigation systems, leading to signal loss or degradation. We conducted a study on how a geomagnetic storm in November 2021 affected the occurrence of pre‐midnight plasma bubbles over South America. Using data from two satellites (ICON and GOLD), we observed that these plasma bubbles disappeared during the storm's recovery phase. Our analysis suggests that this inhibition is likely linked to changes in wind patterns in the ionosphere. Specifically, a westward wind created conditions that prevented the generation of plasma bubbles. This study offers new insights into how winds during geomagnetic storms affect the ionosphere and helps improve predictions for communication and navigation systems affected by these disruptions. Key Points: Pre‐midnight topside plasma bubbles are inhibited over eastern South America during the recovery phase of a geomagnetic stormZonal wind measurements show evidence of wind‐driven electric fields inhibiting plasma bubble formationAlthough theoretical predictions also anticipate changes in the meridional wind, they are not observed [ABSTRACT FROM AUTHOR]

Suspension bridge hangers over 100m are prone to wind-induced vibration. To investigate the vibration characteristics of a suspension bridge hanger over 140m with two cables on a day affected by typhoon Sura, the field measurement of the wind field and acceleration of two cables at different heights was performed. The wavelet transform method was introduced to analyze the time–frequency characteristics of the hanger and girder, while based on the stochastic subspace identification method, the damping ratios of the hanger were identified. The cluster analysis was performed to investigate the relationship between the wind field and hanger vibration. The result of measurement at the site indicated that under the nonstationary wind, the hanger exhibited three different forms of vibration: vortex-induced vibration, buffeting, and another high-frequency vibration. The first two forms may be caused by the incoming wind, and the last one may be due to the vibration of the bridge deck. The vibration was the same between two cables, but different in multiple heights of a cable. For the same cable, there existed a linear relationship between the in-plane and out-of-plane vibration. The hanger exhibited single-mode and multimode vibrations with an elliptical or eight-shaped motion trajectory. For the multimode vibration, a clear energy alternation phenomenon between the dominant frequency and subdominant frequency was found. The out-of-plane acceleration was greater than the in-plane vibration due to the damping difference in the two directions. The wind field was divided into five clusters, and the clusters of the wind field were related to the mode of hanger vibration. [ABSTRACT FROM AUTHOR]

The Chilean Observation Network De MeteOr Radars (CONDOR) commenced deployment in June 2019 and became fully operational in February 2020. It is a multi-static meteor radar system consisting of three ~1º latitudinally separated stations. The main (central) station is located at the Andes Lidar Observatory (ALO, 30.25º S, 70.74º W) and is used for both transmission and reception. The two remote sites are located to the north and south and are used for reception only. The southern station is located at the Southern Cross Observatory (SCO, 31.20º S, 71.00º W) and the northern station is located at Las Campanas Observatory (LCO, 29.02º S, 70.69º W). The successful deployment and maintenance of CONDOR provide 24/7 measurements of horizontal winds in the mesosphere and lower thermosphere (MLT), and permit the retrieval of spatially resolved horizontal winds, vertical winds, and temperatures. This is possible because of the high meteor detection rates. Over 30,000 quality controlled underdense meteor echoes are detected at the ALO each day and in total ~88,000 events are detected each day over the three sites. In this paper, we present the system configuration of the CONDOR and discuss the validation and initial results of its data products. The motivations of deploying the CONDOR system also include the combination of results with other co-located ground-based instruments at the ALO, which provide uniquely cross-validated and cross-scale observations of the MLT dynamics with multiple scientific goals. [ABSTRACT FROM AUTHOR]

Meteorological satellite remote sensing is important for numerical weather forecasts, but its accuracy is affected by many things during observation and retrieval, showing that it can be improved. As a standard way to measure wind from space, atmospheric motion vectors (AMVs) are used. They are separate pieces of information spread out in the troposphere, which gives them more depth than regular surface or sea surface wind measurements. This makes rectifying problems more difficult. For error correction, this research builds a deep-learning model that is specific to AMVs. The outcomes show that AMV observational errors are greatly reduced after correction. The root mean square error (RMSE) drops by almost 40% compared to ERA5 true values. Among these, the optimization of solar observation errors exceeds 40%; the discrepancies at varying atmospheric pressure altitudes are notably improved; the degree of optimization for data with low QI coefficients is substantial; and there remains potential for enhancement in data with high QI coefficients. Furthermore, there has been a significant enhancement in the consistency coefficient of the wind's physical properties. In the assimilation forecasting experiments, the corrected AMV data demonstrated superior forecasting performance. With more training, the model can fix things better, and the changes it makes last for a long time. The results show that it is possible and useful to use deep learning to fix errors in meteorological remote-sensing data. [ABSTRACT FROM AUTHOR]

This paper describes analysis and measurements of the yaw response of tail fins for small wind turbines. It is based on an extension of unsteady slender body theory (USBT) to cover non-slender fins and high angles of incidence, both of which make the theory nonlinear. We provide three main additions to the substantial literature on linearized USBT for tail fins. First, USBT is extended to high angles by modeling the nonlinear vortex dynamics. Second, the restriction to slender bodies is removed by modeling the chordwise load variation. Third, we consider the effect of time-varying wind speed. The extended theory is compared to wind tunnel measurements of the yaw behavior of delta, elliptical, and rectangular tail fins without a rotor and nacelle. The fins were released from initial yaw angles of −40° and −80°; the latter is of sufficient magnitude to show the importance of the nonlinear yaw dynamics. Generally good agreement was found between the theory and measurements, and the theory was shown to be more accurate than a "polar" or quasi-steady model which uses only the lift and drag of a delta planform. Of the three planforms, the rectangular one showed the lowest accuracy in terms of frequency but the damping was accurately predicted. Overall, the results demonstrate the importance of nonlinearity in the response of a yawing tail fin, particularly for the higher aspect ratio fins at large yaw angles. [ABSTRACT FROM AUTHOR]

Near-surface ocean wind measurements are important for weather forecasting, determining surface transports, and estimating air-sea interactions; however, in-situ wind observations are often limited. Previous studies indicate that the equilibrium range of the surface gravity wave spectrum can be used to estimate surface wind velocity. This approach is tested using spectral wave measurements from the Coastal Data Information Program (CDIP) buoy array off Monterey, California. Quality controlled wind vectors inferred from wave spectra are statistically compared to measurements from a nearby National Data Buoy Center (NDBC) buoy, demonstrating strong agreement with the control observations with root mean square errors for speed and direction of 1.8 m/s for all wind speeds and 13.2° for wind speeds greater than 7 m/s. We expand this estimation method to account for biofouling, which causes high-frequency damping of the wave spectrum, and the effects of form factor, which impact the platform's dynamic response to high-frequency waves. The method produces wind-proxy measurements solely from wave spectra and wave-based drag parametrizations, making it useful for operational integration. This work demonstrates the ability to make robust wind velocity estimates using wave data from multiple sources, increasing the coverage of wind information over the coastal and open ocean. [ABSTRACT FROM AUTHOR]

This paper introduces a vision-based displacement measurement method for wind turbine blades in biaxial fatigue testing. Instead of relying on existing strain data, this method collects displacement data to control the loading system. The main idea of this method is to update the pixel radius of the target point. The ratio of the pixel radius of the target point to the actual radius is used as a reference to update the displacement conversion coefficient λ of the next frame image in real-time. Through both static and dynamic experiments, the accuracy and superiority of this method have been verified, and the feasibility of using displacement instead of strain to control fatigue loading has been validated. The data demonstrates that the measurement error between the proposed method and the electronic total station remains within 10%. Compared to the results obtained by the traditional methods, the proposed method has shown significant improvement. The vision-based displacement measurement method not only ensures accuracy but also reduces the complexity of testing, providing more possibilities for fatigue testing of wind turbine blades. [ABSTRACT FROM AUTHOR]

Based on two meteor radars in mid‐latitudes of China, the mid‐latitude lower thermospheric neutral wind responses to the 2015 St. Patrick's Day great storm are investigated. The AE and PCN indices presented the similar quasi‐5‐hour oscillations during the storm. Interestingly, the analogous and close‐correlated storm‐time quasi‐5‐hour oscillations were also observed in both the meridional wind differences at 90–102 km derived from meteor radars. The meridional wind disturbances in the lower thermosphere also showed the extension toward the lower latitudes. It has been found that the enhanced equatorward wind disturbances at 250 km estimated by the Horizontal Wind Model‐14 and Fabry‐Perot Interferometer (FPI) emerged accordingly with the increases of AE and PCN with a time delay. And the enhancements of equatorward (poleward) wind disturbances at 250 km were accompanied by the increments of equatorward (poleward) wind disturbances at 94 km with a time lag of a few hours. It is thus suggested that the multiple intensified Joule heating events with quasi‐5‐hour time intervals were triggered by the successive substorm expansions during the storm. Then the Joule heating events led to the vertical wind and temperature disturbances in the mid‐latitude lower thermosphere via disturbing the thermospheric meridional circulation, which consequently induced the quasi‐5‐hour meridional wind disturbances therein. Plain Language Summary: The neutral temperature and global circulation in the middle and upper atmosphere can be strongly disturbed by the solar and geomagnetic activity. However, the effects of geomagnetic activity on the neutral winds in the mesosphere and lower thermosphere region at middle latitudes have not been fully understood. Using the neutral wind measurements from two meteor radars located at latitudes of 53.5°N and 40.3°N around 120°E meridian in China, we found that the meridional winds at different latitudes showed the prominent and similar disturbance patterns during the 2015 St. Patrick's Day geomagnetic storm. There exhibited the obvious quasi‐5‐hour oscillations in the meridional wind differences at 90–102 km derived from meteor radars. And such wind oscillations appeared to be analogous and close‐correlated to the quasi‐5‐hour oscillations in the AE and PCN indices. The possible contributors and physical processes responsible for such wind disturbances in the mid‐latitude lower thermosphere are discussed. This study is helpful to understand the influences of geomagnetic activity on the neutral winds in the mid‐latitude lower thermosphere region as well as the possible dynamic processes therein. Key Points: Storm‐time quasi‐5‐hour oscillations emerged in both the AE/PCN indices and the meridional winds in the mid‐latitude lower thermosphereThe increments of equatorward/poleward winds at 94 km exhibited the close correspondence and correlation to those at 250 km with a time lagThe successive Joule heating events led to the periodic meridional wind disturbances via disturbing thermospheric meridional circulation [ABSTRACT FROM AUTHOR]

Wind speed and direction variations across the rotor affect power production. As utility‐scale turbines extend higher into the atmospheric boundary layer (ABL) with larger rotor diameters and hub heights, they increasingly encounter more complex wind speed and direction variations. We assess three models for power production that account for wind speed and direction shear. Two are based on actuator disc representations, and the third is a blade element representation. We also evaluate the predictions from a standard power curve model that has no knowledge of wind shear. The predictions from each model, driven by wind profile measurements from a profiling LiDAR, are compared to concurrent power measurements from an adjacent utility‐scale wind turbine. In the field measurements of the utility‐scale turbine, discrete combinations of speed and direction shear induce changes in power production of −19% to +34% relative to the turbine power curve for a given hub height wind speed. Positive speed shear generally corresponds to over‐performance and increasing magnitudes of direction shear to greater under‐performance, relative to the power curve. Overall, the blade element model produces both higher correlation and lower error relative to the other models, but its quantitative accuracy depends on induction and controller sub‐models. To further assess the influence of complex, non‐monotonic wind profiles, we also drive the models with best‐fit power law wind speed profiles and linear wind direction profiles. These idealized inputs produce qualitative and quantitative differences in power predictions from each model, demonstrating that time‐varying, non‐monotonic wind shear affects wind power production. [ABSTRACT FROM AUTHOR]

The accurate prediction of the flow field characteristics of complex mountains is of great practical significance for the development and construction of wind farms, but it is not yet fully understood. The main purpose of this study is to propose a method for the study of flow field characteristics under complex mountain conditions, which can optimize the boundary conditions required for numerical simulation through the wind acceleration ratio and, at the same time, couple the numerical simulation and wind measurement data to reflect the real mountain flow field distribution. The results show that the proposed method has good applicability in complex mountain wind farms, can reproduce the real flow field distribution, and has a certain practical value. Wind speed distribution and turbulence intensity are greatly affected by boundary conditions such as wind speed and wind direction and are also affected by the shielding effect brought by terrain changes. The contrast between 120° and 150° wind direction is more obvious. When the incoming wind moves to the top of a mountain or the ridgeline, it will form a low-speed wake area behind it, resulting in reduced wind speed, increased turbulence intensity, and an unstable flow field. [ABSTRACT FROM AUTHOR]

The coastal regions of Fujian, characterized by a subtropical maritime monsoon climate, experience a high frequency of windy days throughout the year, which significantly impacts residents' lives. Local traditional villages, through long-term practical exploration, have developed a unique "maze-like" spatial layout adapted to withstand harsh wind conditions. This study aims to quantitatively analyze the climatic adaptability advantages of this traditional layout, providing theoretical support for the protection of historical cultural heritage and guidance for modern village construction. The methodology includes field wind measurement for data acquisition, construction of current and regularized divergent models, and comparative numerical simulations under scenarios of strong winter winds and typhoons. The results indicate that wind speeds within traditional villages are generally lower. The layout's nonlinear roads and clusters of buildings form multiple buffer zones that effectively reduce wind speeds. In contrast, areas in the divergent model experience excessively high wind speeds, impacting outdoor activity safety and comfort. The traditional "maze-like" layout encapsulates the climate adaptation wisdom of ancestors, enhancing wind environment regulation, thermal comfort, and disaster resilience. This layout concept merits promotion and innovative application in the new era to construct livable, green, and sustainable human environments. [ABSTRACT FROM AUTHOR]

Current global historical reanalyzes prevent to adequately examine the role of the near‐core surface wind structural properties on tropical cyclones climate trends. Here we provide theoretical and observational evidences that they are crucial for the monitoring of integrated kinetic energy. The kinetic energy balance is reduced to a simple rule involving two parameters characterizing the surface wind structure and directly suggested by the governing equations. The theory is uniquely verified with a database of high‐resolution ocean surface winds estimated from all‐weather spaceborne synthetic aperture radar. Such measurements provide indirect estimates of a multiplicative constant modulating the kinetic energy balance and associated with the system thermodynamics. Consequently, accumulated high‐resolution acquisitions of the ocean surface shall allow to better monitor the integrated kinetic energy and provide new means to tackle climatological studies of tropical cyclones destructiveness. Plain Language Summary: Studying the long‐term climate trends of tropical cyclones is challenging because the historical data is not always reliable. One particular issue concerns the accurate reporting of surface wind properties near the core of these storms in past and present records. This study uses both theory and high‐resolution surface wind observations from satellite radar to highlight the importance of investigating these properties, specifically for monitoring the total energy, which is a measure of a storm destructive potential. Two spatial scales describing the tropical cyclone wind structure are identified and may be efficiently measured thanks to the high‐resolution sensor. The storm energy equilibrium is shown to be controlled by these two spatial scales, in both theory and observations. This equilibrium is also influenced by the temperature characteristics of a storm, which are themselves modulated by environmental and climatological conditions. Consequently, future high‐resolution observations from the satellite radar should help better understanding the dependence of integrated kinetic energy with space and time. Key Points: High‐resolution spaceborne synthetic aperture radar measurements inform on the tropical cyclone kinetic energy balanceThe tropical cyclone integrated kinetic energy balance is controlled by the surface wind decay and thermodynamical characteristicsAccumulating high‐resolution surface wind measurements shall allow to better assess trends in the tropical cyclone destructive potential [ABSTRACT FROM AUTHOR]

As a contribution to closing observational gaps in the atmospheric boundary layer (ABL), the Simultaneous Wind measurement with Uncrewed Flight Systems in 3D (SWUF-3D) fleet of uncrewed aerial systems (UASs) is utilized for in situ measurements of turbulence. To date, the coefficients for the transformation terms used in our algorithm for deriving wind speeds from avionic data have only been determined via calibration flights in the free field. Therefore, we present in this work calibration and verification under laboratory conditions. The UAS measurements are performed in a wind tunnel equipped with an active grid and constant temperature anemometers (CTAs) as a reference. Calibration is performed in x - and y -coordinate directions of the UAS body frame at wind speeds of 2 ... 18 m s -1. For systematic verification of the measurement capabilities and identification of limitations, different measurement scenarios like gusts, velocity steps, and turbulence are generated with the active grid. Furthermore, the measurement accuracy under different angles of sideslip (AoSs) and wind speeds is investigated, and we examined whether the calibration coefficients can be ported to other UASs in the fleet. Our analyses show that the uncertainty in measuring the wind speed depends on the wind speed magnitude and increases with extreme velocity changes and with higher wind speeds, resulting in a root-mean-square error (RMSE) of less than 0.2 m s -1 for steady wind speeds. Applying the calibration coefficients from one UAS to others within the fleet results in comparable accuracies. Flights in gusts of different strengths yield an RMSE of up to 0.6 m s -1. The maximal RMSE occurs in the most extreme velocity steps (i.e., a lower speed of 5 m s -1 and an amplitude of 10 m s -1) and exceeds 1.3 m s -1. For variances below approx. 0.5 and 0.3 m 2 s -2 , the maximal resolvable frequencies of the turbulence are about 2 and 1 Hz, respectively. The results indicate successful calibration but with susceptibility to high AoSs in high wind speeds, no necessity for wind tunnel calibration for individual UASs, and the need for further research regarding turbulence analysis. [ABSTRACT FROM AUTHOR]

High-resolution wind datasets are crucial for ultra-short-term wind forecasting. Penetration of WT installations near urban areas that are constantly changing will motivate researchers to understand how to adapt their models to terrain changes to reduce forecasting errors. Although CFD modelling is not widely used for ultra-short-term forecasting purposes, it can overcome such difficulties. In this research, we will spatially extrapolate vertical profile LIDAR wind measurements into a 3D wind velocity field over a large and relatively complex terrain with the use of stationary CFD simulations. The extrapolated field is validated with measurements at a hub height of three WTs located in the area. The accuracy of the model increases with height because of the terrain anomalies and turbulence effects. The maximum MAE of wind velocity at WT hub height is 0.81 m/s, and MAPE is 7.98%. Our model remains accurate even with great simplifications and scarce measurements for the complex terrain conditions of our case study. The models' performance under such circumstances establishes it as a promising tool for the evolution of ultra-short-term forecasting as well as for the evaluation of new WT installations by providing valuable data for all models. [ABSTRACT FROM AUTHOR]

This study develops and verifies two advanced wake models based on super-Gaussian distribution: three-dimensional (3D) super-Gaussian (3DSG) and 3D anisotropic super-Gaussian (3DASG) models. They have a smooth Gaussian–top-hat shape (a combination of Gaussian and top-hat shapes) in the near-wake region that gradually transitions to a Gaussian shape in the far-wake region. These models are based on the law of mass conservation and considers wind shear effect; hence, they can accurately describe asymmetric wind distribution in the vertical direction. Because of this Gaussian–top-hat shape, the model is more accurate in simulating the wake in the near-wake region. The anisotropic model also considers different wake expansion rates in various dimensions, rendering the model more realistic. The accuracy and generality of the two models are verified using four wake data sets obtained from wind tunnel tests and wind field measurements. The validation includes the prediction of the wake profile and relative error of the models. The results show that the two models can well predict the wake distribution of various sizes of turbines at any spatial location in the full-wake region. [ABSTRACT FROM AUTHOR]

The problem of crystal ice formation inside aircraft turbine engines is well‐documented, and poses a significant risk to safety. The problem is not only one of power loss in flight, but the very real possibility that a flame‐out event could occur due to ice accretion on compressor stators, with potentially catastrophic outcomes. Although many instrumentation systems have been developed for wing ice detection, incipient formation of crystal ice is somewhat more difficult to detect. This is compounded by the need for a noncontact sensor which is robust to in‐flight conditions. This paper proposes an approach to the detection of ice formation based on microwave transmission characteristics across the first and possibly the second stage of the compressor stator. It is shown that noncontact detection is feasible under realistic conditions. The contribution of this paper is twofold. First, the microwave transmission approach is motivated using wind tunnel measurements, and appropriate frequency bands are determined. Next, a signal processing approach involving higher‐order analysis of time‐frequency distribution characteristics is then put forward. Experimental results are presented to support the hypothesis that multiband detection offers a workable approach to the incipient crystal‐ice detection problem. [ABSTRACT FROM AUTHOR]

Large-span roofs can be damaged by uneven snow loads caused by snow drifting. To predict wind-induced snow loads more accurately, this paper proposes a numerical simulation method. The method considers the interaction of wind and snow, the changing characteristics of snow phase boundaries over time, and corrects for snow deposition and erosion flux. The effectiveness of the method was confirmed by simulating wind–snow flow on a three-centered cylindrical shell and comparing the results with wind tunnel measurements. The simulation considered different snowfall conditions and time-varying snow phase boundaries on a large-span shell-shaped roof. The study investigated the influence of snowfall conditions and dynamic changes in snow phase boundaries on snow cover distribution by comparing simulation results. [ABSTRACT FROM AUTHOR]

In this study, we implemented a compact wind direction sensor on a palm-sized quadcopter to achieve wind source localization (WSL). We designed an anemotaxis algorithm based on the sensor data and experimentally validated its efficacy. Anemotaxis refers to the strategy of moving upwind based on information on the wind direction, which is essential for tracing odors propagating through the air. Despite the limited research on quadcopter systems achieving WSL directly through environmental wind measurement sensors, debate remains regarding the relationship between sensor placement and the anemotaxis algorithm. Therefore, we experimentally investigated the placement of a wind direction sensor capable of estimating wind source direction even when propellers are rotating. Our findings demonstrated that placing the sensor 50 mm away from the enclosure of the quadcopter allowed accurate wind direction measurement without being affected by wake disturbances. Additionally, we constructed an anemotaxis algorithm based on wind direction and speed data, which we integrated into the quadcopter system. We confirmed the ability of the quadcopter to execute anemotaxis behavior and achieve WSL irrespective of environmental wind strength through wind source localization experiments. [ABSTRACT FROM AUTHOR]

The migrating diurnal tide (DW1) is derived by fitting Hough Mode Extensions to the TIMED/TIDI near‐global wind measurements within the mesosphere and lower thermosphere between 85 and 100 km from 2004 to 2014. The tidal amplitude peaks around the equinoxes with a large interannual variability of up to 50%. The correlation coefficients between the tidal amplitude variability and the solar cycle as represented by F10.7, stratospheric Quasi‐Biennial Oscillation (QBO), and El Niño‐Southern Oscillation (ENSO) are calculated every 10 days revealing seasonal dependencies. The interannual variability is positively correlated with QBO from spring to fall, maximizing around the equinoxes; anti‐correlated to the solar cycle in early winter; and anti‐correlated to ENSO in early winter and slightly in March. Multivariate linear regressions are performed to quantitatively analyze the linear relationships between the DW1 amplitude and those factors. The fittings perform best with the QBO at 30 and 50 hPa both being considered. The contribution of QBO peaks around January and October may be related to the polar vortex modulated by QBO in the northern and southern hemispheres, respectively. The correlation between the DW1 amplitude and ENSO is negative with time lags <∼5 months during early winter and spring. Key Points: Correlation coefficient is positive for Quasi‐Biennial Oscillation (QBO) from spring to fall; negative for solar cycle in early winter; and negative for El Niño‐Southern Oscillation in early winter and MarchQBO30 and QBO50 contribution peaks may be related to the modulated polar vortex in the northern and southern hemispheres, respectivelyThe DW1 amplitude and the Oceanic Niño Index are negatively correlated with time lags <∼5 months during early winter and spring [ABSTRACT FROM AUTHOR]

In this study, a comprehensive analysis is done on a dual rotor wind turbine (DRWT) in co‐rotating arrangement. First, a co‐rotating dual rotor is designed and its performance is analyzed by blade element momentum theory simulation. Later, the designed co‐rotating DRWT is manufactured and then tested in the field by mounting the wind turbine on a truck. Running the truck steadily at different speeds while logging the performance parameters of the wind turbine, the power curve of the DRWT is obtained. Then, using the power curve of the co‐rotating DRWT and the actual wind measurement data from Çatalca Istanbul, the annual electricity generation of the designed turbine is calculated. The present techno‐economic analysis states that the co‐rotating DRWTs are more efficient compared to single rotor wind turbines (SRWTs), in accordance with the literature. Analyses show that with DRWT, around 22% higher power generation can be achieved. Additionally, the payback period for DRWT was found to be less than 1 year. The marketing strategy for introducing the product emphasizes identifying and targeting early adopters and influencers within the market. The present techno‐economic analysis states that the co‐rotating DRWTs are more efficient compared to SRWTs, in accordance with the literature. [ABSTRACT FROM AUTHOR]

This study investigates the predictability of downslope windstorms located in Santa Barbara County, California, locally referred to as Sundowner winds, from both observed relationships and a high-resolution, operational numerical weather prediction model. We focus on April 2022, during which the Sundowner Winds Experiment (SWEX) was conducted. We further refine our study area to the Montecito region owing to some of the highest wind measurements occurring at or near surface station MTIC1, situated on the coast-facing slope overlooking the area. Fires are not uncommon in this area, and the difficulty of egress makes the population particularly vulnerable. Area forecasters often use the sea-level pressure difference (Δ SLP) between Santa Barbara Airport (KSBA) and locations to the north such as Bakersfield (KBFL) to predict Sundowner windstorm occurrence. Our analysis indicates that Δ SLP by itself is prone to high false alarm rates and offers little information regarding downslope wind onset, duration, or magnitude. Additionally, our analysis shows that the high-resolution rapid refresh (HRRR) model has limited predictive skill overall for forecasting winds in the Montecito area. The HRRR, however, skillfully predicts KSBA-KBFL Δ SLP, as does GraphCast, a machine learning weather prediction model. Using a logistic regression model we were able to predict the occurrence of winds exceeding 9 m s − 1 with a high probability of detection while minimizing false alarm rates compared to other methods analyzed. This provides a refined and easily computed algorithm for operational applications. [ABSTRACT FROM AUTHOR]

Wind turbines emit infrasound and low-frequency noise (ILFN), which can be annoying for people living near wind farms. To assess the acoustic impact of wind turbines on the environment, it is essential to model ILFN propagation during the forecasting stage. This study assesses the effectiveness of three commonly used sound propagation models (ISO 9613-2, CNOSSOS-EU for favourable propagation conditions, Nord2000) in predicting ILFN generated by wind turbines. The performance of these models in modelling ILFN is generally not validated or guaranteed. The analysis covers octave frequency bands ranging from 4 Hz to 250 Hz, and comparisons are made against measurements conducted at a wind farm in Poland. Non-parametric statistical tests were used with a significance level of α = 0.05 to determine significant differences between measured and predicted results. The results show that the Nord2000 method provides accurate calculations, while the ISO 9613-2 method can be used for simplified assessments of ILFN generated by wind turbines during the investment preparation phase. [ABSTRACT FROM AUTHOR]

This study proposes a microscale flow model to estimate mean wind speed, fluctuating wind speed and wind direction over complex terrain considering the effects of topography, atmospheric stability, and turbine wakes. Firstly, the effect of topography is considered using Computational Fluid Dynamics (CFD). Next, a mesoscale model is presented to account for the effect of atmospheric stability. The effect of turbine wakes on the mean and fluctuating wind speeds are then represented by an advanced wake model. The model is validated using the measurement data of a wind farm located in the North of Japan. The measured wind data by Lidar at a reference height are horizontally extrapolated to a nearby met mast hub height and validated by a cup anemometer. Moreover, a novel averaging method is proposed to calculate a directional equivalent Monin–Obukhov length scale to account for the effect of atmospheric stability. Finally, the measured wind data at the reference height are vertically extrapolated and validated at the lidar location. The predicted mean and fluctuating wind speeds show good agreement with the measurements. [ABSTRACT FROM AUTHOR]

The dynamic behaviour of wildfires is mainly influenced by weather, fuel, and topography. Based on fundamental conservation laws involving numerous physical processes and large scales, atmospheric models require substantial computational resources. Therefore, coupling wildfire and atmospheric models is impractical for high resolutions. Instead, a static atmospheric wind field is typically input into the wildfire model, either as boundary conditions on the control surface or distributed over the control volume. Wildfire propagation models may be (i) data-driven ; (i i) theoretical ; or (i i i) mechanistic surrogates. Data-driven models are beyond the scope of this paper. Theoretical models are based on conservation laws (species, energy, mass, momentum) and are, therefore, computationally intensive; e.g. the Fire Dynamics Simulator (FDS). Mechanistic surrogate models do not closely follow fire dynamics laws, but related laws observed to make predictions more efficiently with sufficient accuracy; e.g. FARSITE, and FDS with the Level Set model (FDS-LS). Whether theoretical or mechanistic surrogate, these wildfire models may be coupled with or decoupled from wind models (e.g. Navier-Stokes equations). Only coupled models account for the effect of the fire on the wind field. In this paper, a series of simulations of wildfire propagation on grassland are performed using FDS-LS to study the impact of the fire-induced wind on the fire propagation dynamics. Results show that coupling leads to higher Rates of Spread (RoS), closer to those reported from field experiments, with increasing wind speeds and higher terrain slopes strengthening this trend. Aiming to capture the fire–wind interaction without the hefty cost of solving Navier-Stokes equations, a conceptual framework is proposed: 1) a swarm of unmanned aerial vehicles measure wind velocities at flight height; 2) the wind field is constructed with the acquired data; 3) the high-altitude wind field is mapped to near-surface, and 4) the near-surface wind field is fed into the wildfire model periodically. A series of simulations are performed using an in-house decoupled physics-based reduced-order fire propagation model (FireProM-F) enhanced by wind field "measurements". In this proof of concept, wind velocities are not measured but extracted from physics-based Large Eddy Simulations taken as ground truth. Unsurprisingly, higher measurement frequencies lead to more accurate and realistic predictions of the propagating fire front. An initial attempt is made to study the effect of wind measurement uncertainty on the model predictions by adding Gaussian noise. Preliminary results show that higher noise leads to the fire front displaying more irregular shapes and slower propagation. • Higher wildfire model prediction accuracy normally achieved by coupling it with wind model such as Navier-Stokes equations. • Coupled fire-wind models often too computationally expensive for real-time use in operational contexts. • Prediction accuracy of wildfire model uncoupled from wind model enhanced by periodic inputs of updated wind field. • Wind field to be constructed from UAV swarm measurements, surrogated here to velocities obtained from full CFD simulations. • Proposed method to enhance wildfire model predictions robust to Gaussian noise added to represent measurement uncertainty. [ABSTRACT FROM AUTHOR]

Precise estimation of the thermal updraft environment is important for the effective exploration of wind resources in long-endurance drones. Nevertheless, previous regression algorithms exhibit limitations in accurately evaluating updrafts under new operating conditions, and traditional airborne wind measurement methods are constrained by narrow ranges and sparse spatial sampling. This study addresses these challenges by harnessing continuous temperature data acquired via infrared sensors. The proposed methodology employs a data-driven deep operator network (DeepONet) to map the temperature field to the velocity field. Numerical simulations of two-dimensional Rayleigh–Bénard convection are conducted to simulate sensing measurements under various Rayleigh number R a , used as both training and testing datasets. For the DeepONet framework, a convolutional neural network (CNN) structure is employed as the branch network to extract features from the temperature field. Simultaneously, a fully connected neural network (FNN) is adopted as the trunk network, encoding input functions from fixed sensors. In order to assess the estimation performance in new environments, the training data are under operating conditions within the range of R a = 3 × 10 7 – 6 × 10 7 , and the testing data are under other unknown operating conditions. By compared to the conventional FNN network and the standard DeepONet framework, the DeepONet(CNN) in this study manifests a significant enhancement in estimation performance, demonstrating improvements ranging from 20% to 40% under unknown operating conditions. [ABSTRACT FROM AUTHOR]

Motivated by the need to reduce the noise from train pantographs, numerical simulations are carried out for the flow over finite wall-mounted square cylinders with different aspect ratios at a Reynolds number of 1.5 × 10 4 . Five aspect ratios (height-to-width ratios) are taken into account, namely, 1.4, 4.3, 7.1, 10, and 12.9. The effect of the aspect ratio on the aerodynamic coefficients, the near-wall flow topologies, and the pressure distributions are studied in detail to give insight into the noise generation mechanisms. The pressure rate of change dp/dt on the cylinder surfaces is adopted to evaluate the dipole noise source. It turns out that distributions of dp/dt are closely related to flow evolutions near the free ends and the wall-mounting junctions of cylinders with different aspect ratios. High levels of dp/dt are found close to lateral trailing edges of the cylinder, while the strength grows quickly as the aspect ratio is increased. The far-field noise emitted from these cylinders is predicted using the Ffowcs Williams–Hawkings acoustic analogy and validated with wind tunnel measurements available in the literature. For receivers located in the cross-flow direction, a single acoustic tone near a Strouhal number of 0.1 is observed for cylinders with aspect ratios not greater than seven, while an additional tone at a higher Strouhal number occurs as the aspect ratio is further increased. The underlying mechanism of the tonal noise emitted to the far field is also investigated by combining the noise source localization and dynamic mode decompositions. [ABSTRACT FROM AUTHOR]

Throwing manipulation utilizes virtual driving forces, such as gravity, centrifugal force, and Coriolis force, to extend the workspace and increase the degrees of freedom available for manipulation. However, it is highly sensitive to various uncertainties such as wind disturbance and measurement noise, thereby deteriorating the throwing performance. This study proposes a motion planning method that uses Bayesian optimization to obtain an optimal arm trajectory for throwing manipulation through repeated trials. Bayesian optimization can explicitly account for stochastic uncertainties and obtain an optimal solution with a small number of trials. The key contributions of the proposed method are the explicit modeling of stochastic uncertainties using a Gaussian distribution and the ability to reduce the number of retraining attempts. The efficacy of the proposed motion planning method was validated through extensive experiments. Specifically, in environments with randomly changing wind directions and wind speeds, experiments demonstrated that the proposed method generated throwing motions that were more robust against wind disturbances than conventional methods based on iterative learning methods. Furthermore, even when the throwing target point is changed, the experiments demonstrate that the proposed learning method can learn with fewer trials than the conventional method by utilizing past observation data. [ABSTRACT FROM AUTHOR]

In order to improve the data productivity of a wind tunnel test, the model under investigation in the wind tunnel is moved continuously with a predetermined constant angular speed in the so-called pitch–traverse mode. Alternatively, the wind tunnel model can be moved in the so-called pitch–pause mode, in which it keeps its position for a certain (measurement) time at a fixed pitch position, after which it is moved to the next pitch position. The latter procedure is more time-consuming, so, for the same time interval, the number of measured data points taken in the pitch–pause mode is less than that for the pitch–traverse mode. Since wind tunnel test time can be quite expensive, in most wind tunnel tests where only conventional forces and pressures are recorded with conventional measuring systems, the wind tunnel model is moved in the pitch–traverse mode in order to obtain as much aerodynamic data as possible during the tunnel runtime. The application of the Pressure-Sensitive Paint (PSP) technique has been widely used in wind tunnel testing for the purpose of providing pressure data on wind tunnel models with high spatial resolution. The lifetime-based PSP method has several advantages over the intensity-based method since it often has higher accuracy. Up until now, the lifetime-based PSP technique has mainly been used for wind tunnel testing, where the test model has been moved to the pitch–pause mode. The traditional lifetime method using on-chip accumulation requires multiple (~1000) excitation light pulses to accumulate enough luminescence (fluorescence or phosphorescence) photons on the camera sensor to provide acceptable signal-to-noise ratios and, therefore, it may seem to be not compatible with a continuously moving wind tunnel model. Nevertheless, the present study verifies the application of lifetime-based PSP utilizing on-chip accumulation with a continuously moving wind tunnel model which would make the entire PSP data acquisition compatible with that of the conventional measurements (forces and pressures), as mentioned above. In this paper, the applicability of the lifetime-based PSP technique to a continuously moving wind tunnel model (in pitch–traverse mode) is investigated with the help of measurements in the transonic wind tunnel in Göttingen (TWG). For this investigation, PSP was applied on the delta-wing model DLR-F22, which is to be tested in TWG. The pressure distribution on the wind tunnel model was measured using the PSP lifetime method for both model movement modes (pitch–pause and pitch–traverse mode) so that the corresponding PSP results could be directly compared with each other. In addition, an error analysis of the PSP results was carried out and compared with the conventional pressure measurement results, hence providing an assessment of the accuracy of the PSP results; finally, a recommendation for future PSP measurements could be given. [ABSTRACT FROM AUTHOR]

A model-free adaptive control is proposed for suboptimal guidance correction and control of a prototypical three-stage satellite carrier. For this sake, we consider a nominal guidance for the model of the system and design the adaptive control for a single-input multi-output system exposed to wind disturbance and measurement noise in the rates of inputs and outputs. Then, subsequent to the guidance correction, a differentiation model of the system is estimated and the control policy is realized under some profitable performance constraints to set the satellite in a desirable circular orbit. The simulation results readily reveal the efficiency of the proposed method and its robustness to uncertainties in the system. [ABSTRACT FROM AUTHOR]

The accurate three-dimensional wind field obtained from a Doppler lidar not only helps to comprehend the refined structure of complex airflow but also provides important and valuable solutions for many fields. However, the underlying homogeneity assumption of the typical wind retrieval methods, such as Doppler Beam Swinging (DBS) and Velocity Azimuth Display (VAD) based on a single-lidar, will introduce the measurement uncertainty in complex terrain. In this paper, a new design of a wind measurement campaign involving seven lidars was carried out, which contained the three-lidar-based Virtual Tower (VT) using a time-space synchronization technique and four single-lidars with different elevation angles. This study investigates the performance of VT and VAD measurements under various conditions and evaluates the sensitivity of wind measurement uncertainty of VAD to the horizontal spatial- and probe volume-average effects associated with elevation angles of the laser beam. The inter-comparison results between VT and four VADs show consistent trends with small relative errors under neutral atmospheric conditions with weak wind velocity. Under convective or high Turbulence Intensity (TI) conditions, the relative errors between VT and VAD become larger and more fluctuant. Moreover, it is found that the measurement uncertainty of VAD increases at a given elevation angle with the increasing measurement heights, which is caused by the horizontal homogeneity associated with the conical scanning area. Additionally, the simulated and measured results of four VADs indicate that a larger elevation angle corresponds to a lower measurement uncertainty for a given height. [ABSTRACT FROM AUTHOR]

In this paper, the equatorial thermosphere anomaly (ETA) is investigated using accelerometer measurements to determine whether the feature is density‐dominated, wind‐dominated, or some combination of the two. An ascending‐descending accelerometry (ADA) technique is introduced to address the density‐wind ambiguity that appears when interpreting the ETA in atmospheric drag acceleration analyses. This technique separates ascending and descending acceleration measurements to determine if a wind's directionality influences the interpretation of the observed ETA feature. The ADA technique is applied to accelerometer measurements taken from the Challenging Minisatellite Payload mission and has revealed that the ETA is primarily density‐dominated from 9:00 to 16:00 local time (LT) near 400 km altitude, with the acceleration perturbations behaving similarly between 2003 and 2004 across all seasons. This finding suggests that the perturbations in the acceleration due to in‐track wind perturbations are small compared to the perturbations due to mass density, while indicating that the formation mechanisms across these local times are similar and persistent. The results also revealed that in the terminator region at 18:00 LT the acceleration perturbations deviate appreciably between ascending and descending passes, indicating different or multiple processes occurring at this local time compared to the 9:00–16:00 LT ascribed to the ETA. These results help constrain ETA formation theories to specific local times and thermospheric property responses without the use of supplemental wind measurements, while also indicating regions where in‐track winds cannot always be neglected. Plain Language Summary: Earth's thermosphere, a layer in the upper atmosphere, is a highly variable region that contributes to satellite drag in low Earth orbit. The equatorial thermosphere anomaly (ETA) is a perturbation feature that produces increases and decreases in drag accelerations across the lower latitudes of the thermosphere. Direct measurements of the thermosphere are often limited, so satellite instruments, such as accelerometers, have been used to analyze the acceleration that a satellite experiences due to atmospheric drag to indirectly measure thermospheric properties. However, the measured drag acceleration is dependent on both mass density and wind, making it difficult to determine whether a change in drag across the ETA is due to either property. This has implications on what mechanisms are responsible for its formation. This work introduces an ascending‐descending accelerometry technique to exploit the fact that while acceleration perturbations produced by mass density are independent of satellite direction, those arising from winds can either be positive or negative depending on the relative spacecraft motion. By separating satellite orbits into ascending (south‐to‐north) and descending (north‐to‐south) passes, it can be determined whether drag acceleration perturbations are due to mass density, wind, or a mixture of the two, helping constrain possible formation mechanisms. Key Points: Accelerometer observations of the Equatorial Thermosphere Anomaly (ETA) cannot distinguish between in‐track density and wind perturbationsA new technique is applied to observations determining that the ETA, occurring between 9 and 16 LT, is a density‐dominated featureThe ETA demonstrates repeatable annual behavior for each season, suggesting a common and persistent formation mechanism [ABSTRACT FROM AUTHOR]

Few observational platforms are able to sustain direct measurements of all the key variables needed in the bulk calculation of air‐sea carbon dioxide (CO2) exchange, a capability newly established for some Uncrewed Surface Vehicles (USVs). Western boundary currents are particularly challenging observational regions due to strong variability and dangerous sea states but are also known hot spots for CO2 uptake, making air‐sea exchange quantification in this region both difficult and important. Here, we present new observations collected by Saildrone USVs in the Gulf Stream during the winters of 2019 and 2022. We compared Saildrone data across co‐located vehicles and against the Pioneer Array moorings to validate the data quality. We explored how CO2 flux estimates differ when all variables needed to calculate fluxes from the bulk formulas are simultaneously measured on the same platform, relative to the situation where in situ observations must be combined with publicly‐available data products. We systematically replaced variables in the bulk formula with those often used for local and regional flux estimates. The analysis revealed that when using the ERA‐5 reanalysis wind speed in place of in situ observations, the ocean uptake of CO2 is underestimated by 8%; this underestimate grows to 9% if the NOAA Marine Boundary Layer atmospheric CO2 product and ERA‐5 significant wave height are also used in place of in situ observations. Overall our findings point to the importance of collecting contemporaneous observations of wind speed and ocean pCO2 to reduce biases in estimates of regional CO2 flux, especially during high wind events. Plain Language Summary: The North Atlantic Ocean absorbs a large amount of carbon dioxide (CO2) from the atmosphere. The ocean CO2 uptake mainly occurs during the winter months in a region where a swift ocean current, called the Gulf Stream, carries warm waters from the tropics to northern latitudes. Understanding how much CO2 this ocean region absorbs is important for constraining global scale assessments of the sources and sinks of CO2. In this paper, we reflect on the methods that are typically used to calculate the exchange of CO2 between the ocean and atmosphere. Using new data collected by uncrewed surface vehicles, that resemble small sailboats, in the North Atlantic Ocean in the vicinity of the Gulf Stream, we find that the estimate of the exchange of CO2 is larger when directly measured wind speeds are used in the calculation in comparison to wind speeds from a widely used data product. This result signifies the importance of co‐located sensors on the same observing platform. Key Points: Compared to Saildrone wind speeds, the ERA‐5 reanalysis appears to underestimate the highest wind speed events (>10 m s−1)Co‐located ocean pCO2 and wind speed observations results in larger uptake of CO2 in this region by 9%Using a sea‐state dependent gas transfer velocity leads to a 28% greater ocean uptake of CO2 compared to using a wind‐only equation [ABSTRACT FROM AUTHOR]

• UAVs used for methane flux quantification at a landfill site. • Methane emissions measured: 150.7 kg h−1, with a 1σ uncertainty range of 83.0 kg h−1 to 209.5 kg h−1. • Refined UAV-based mass balance flux method. • Study addresses UAV onboard wind measurements. Accurate quantification of methane emissions from landfills is crucial for improving greenhouse gas inventories and mitigating climate change impacts. Existing methodologies, such as theoretical gas production models and labour-intensive measurement approaches, present limitations including large uncertainties and high operational costs. This study adds to a growing body of research and applications which aim to bridge this gap. To this end, we present a case study using Unmanned Aerial Vehicles (UAVs) equipped with methane and wind instrumentation for a survey of a landfill site in Bury, Manchester, UK, in summer 2022, in order to evaluate and reflect the challenges of the UAV-based mass balance method for quantification of methane emissions from a large heterogeneous source such as landfill. This study offers guidance on defining an appropriate methane background concentration, geospatial interpolation of sampled date, survey sampling strategy, and more importantly, addresses the challenges surrounding UAV wind measurements and spatial characterisation of emission plumes. For the period of the case study, we quantified methane flux for the landfill site to be 150.7 kg h−1 with a 1 standard deviation uncertainty range of 83.0 kg h−1 to 209.5 kg h−1. [ABSTRACT FROM AUTHOR]

Wind field characteristics in a complex topography are significantly influenced by the nature of the surrounding terrains. This study employs onsite measurements to investigate the wind field characteristics at a towering peak protruding out of a steep mountainside, where butterfly−lookalike landscape platform will be constructed; the impact of the surrounding topography on the wind flow is highlighted. The results showed that the blocking effect of the mountains in the mountainous side of the valley caused a significant drop in the mean wind speed from that direction. The stationary test (reverse arrangement test) indicated that the wind speed had a strong nonstationary characteristic, necessitating the employment of a steady and nonstationary wind speed model to assess the wind turbulence characteristics. The three directions' wind turbulence integral scales were critically influenced by the occurrence of the wind speedup effect, unexpectedly resulting in the vertical turbulence integral scale being the greatest of the three. Furthermore, the measured wind turbulence properties under both wind speed models showed certain variations from the recommended specifications. Consequently, the impact of the local terrain and the speedup effect on the wind characteristics must be thoroughly evaluated to ensure the structural stability of structures installed at a similar topography. [ABSTRACT FROM AUTHOR]

Aims. This study covers a thorough statistical investigation of the evolution of interplanetary coronal mass ejections (ICMEs) with and without sheaths through a broad heliocentric distance and temporal range. The analysis treats the sheath and magnetic obstacle (MO) separately in order to gain more insight on their physical properties. In detail, we aim to unravel different characteristics of these structures occurring over the inner and outer heliosphere. Methods. The method is based on a large statistical sample of ICMEs probed over different distances in the heliosphere. For this, information about detection times for the sheath and MO from 13 individual ICME catalogs was collected and crosschecked. The time information was then combined into a main catalog that was used as the basis for the statistical investigation. The data analysis based on this catalog covers a large number of spacecraft missions, enabling in situ solar wind measurements from 1975 to 2022. This allowed us to study the differences between solar cycles. Results. All the structures under study (sheath, MO with and without sheath) show the biggest increase in size together with the largest decrease in density at a distance of ∼0.75 AU. At 1 AU, we found different sizes for MOs with and without a sheath, with the former being larger. Up to 1 AU, the upstream solar wind shows the strongest pileup close to the interface with the sheath. For larger distances, the pileup region seems to shift, and it recedes from that interface further into the upstream solar wind. This might refer to a change in the sheath formation mechanism (driven versus non-driven) with heliocentric distance, suggesting the relevance of the CME propagation and the expansion behavior in the outer heliosphere. A comparison to previous studies showed inconsistencies over the solar cycle, which makes more detailed studies necessary in order to fully understand the evolution of ICME structures. [ABSTRACT FROM AUTHOR]

The powertrain efficiency of most small unmanned air vehicles (SUAVs) depend on the aerodynamic performance of multiple propellers, which must be modelled before its optimisation. To predict propeller performance while capturing interaction effects not accountable for by momentum theories, the Virtual Blade Model (VBM) can be used at much lower costs than conventional Computational Fluid Dynamics (CFD). However, the accuracy of VBM depends on aerofoil polar data that often misrepresent rotational and three-dimensional effects that influence small propellers. In an attempt to expand the capabilities of VBM, it is a common practice to introduce correction models for aerofoil coefficients in its formulation, but the actual effectiveness of such approach for small propeller analysis remains unassessed. In this paper, VBM in OpenFOAM was extended with stall delay and tip loss models, while aerodynamic databases at low Reynolds numbers were built with XFOIL and extrapolated to the full angle of attack range. The accuracy of three VBM versions was validated against wind tunnel measurements of two off-the-shelf small propellers. For the lower-pitch propeller, thrust and power at low advance ratios and efficiency at high advance ratios were significantly improved by the stall delay model. But for the higher-pitch propeller, thrust and power were overpredicted with extended versions of VBM under most operating conditions, which is attributable to an excessive shift of effective angles of attack to the post-stall region by the stall delay model and to uncertainties in extrapolated polar data. The results suggest that without reliable procedures for obtaining polar data, correction models should be implemented in VBM only for the simulation of low-pitch propellers operating at low advance ratios, given their avoidance of the effective angle of attack range where XFOIL and extrapolation methods are mainly expected to fail in predicting lift behaviour. • Stall delay and tip loss models are implemented into VBM, a coupled BET-CFD model. • Small propeller performance is more sensitive to stall delay than it is to tip losses. • At lower advance ratios, thrust and power results are improved by the enhanced VBM. • Unreliable post-stall data inputs into the enhanced VBM cause power overprediction. [ABSTRACT FROM AUTHOR]

The scanner is an important unit of the Coherent Doppler wind Lidar (CDWL) for long range detection. In the compact telescope system, a prism wedge rotating around the optical axis is often added to realize conical scanning of the laser beam. For the focused CDWL, the prism wedge can produce astigmatism in the measuring light, which will change the energy distribution in the detection space. Based on the geometric optics technique, the relation between the wedge parameters and the beam propagation status is analyzed in this paper. A modified range weighting function is also constructed by using the collection efficiency mode. A CDWL with 100 m focused distance was employed in the wind measurement experiments. Compared the measurement data from the CDWL with the anemometer at 50 m and 100 m height at the wind tower, the result indicates that the CDWL detection data is closer to the wind field at 50 m height, which is consistent with theoretical analysis. The optimized wedge parameters and the modified range weighting function are helpful for the further development of the miniaturized and lightweight CDWL. [ABSTRACT FROM AUTHOR]

A new ceramic dressing, free from active antimicrobial or pharmaceutical agents, uses physical binding mechanisms for its absorption capacities and bacterial-binding properties. The purpose of this study was to evaluate wound healing, bacterial-related retention, and diagnostic properties of ceramic dressings in patients with stagnated chronic wounds. Methods: In this monocentric, intra-individually controlled, prospective study, patients with conservatively treated refractory chronic wounds were enrolled. One week before the start of the application with ceramic dressing, it was ensured during a screening phase that chronic wounds showed less than a 10% reduction in wound size. During the 4-week ceramic dressing treatment wound size measurements, wound scoring, measurement of wound exudate amount, wound swabs, and ceramic dressing sonication (low-intensity ultrasound) were carried out. The sonication fluid of the removed ceramic dressing was used for analysis of bacterial retention and compared to wound swabs. Results: A total of 20 patients with a mean age of 64.6 years (±26.2) and 21 chronic wounds were included in this study. After a 4-week treatment, a significant reduction of median wound size from 1178 mm2 (range 104–6300) to 751.5 mm2 (range 16–4819) and better total wound scores were observed (p < 0.001). The sensitivity of bacteria detection was 90.7% in the sonication fluid from the ceramic dressings, while only 76.9% in the conventional wound swabs. Conclusion: The new ceramic dressing seems to have a positive impact on wound healing in chronic wounds. Bacteria-binding characteristics of the investigated ceramic dressing, in combination with its debridement, absorption, and detoxification properties, could contribute to its healing abilities. Based on those results, the investigated ceramic dressing seems to be a promising new treatment option for chronic wounds without the use of any active antimicrobial or pharmacological agents. Moreover, ceramic dressings can also be considered for microbiological diagnostic purposes. [ABSTRACT FROM AUTHOR]