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Abstract Rokko‐oroshi is a northerly local wind blowing in the mega‐city Kobe, Japan. This wind blows from the Rokko Mountains. This study analyzed the three‐dimensional structure of Rokko‐oroshi observed with a near‐surface anemometer and Doppler lidar on January 16, 2023. Furthermore, numerical simulations using the Weather Research and Forecasting (WRF) model revealed the factors responsible for the strong winds. The results showed that Rokko‐oroshi on January 16, 2023 was a bora‐type downslope windstorm. The Doppler lidar observed the strong winds of Rokko‐oroshi and a stagnant layer immediately above them. Numerical simulation results indicated the stagnant layer was formed by mountain‐wave breaking. Under this stagnant layer, the airflow transitioned from subcritical to supercritical, resulting in the strong winds of Rokko‐oroshi. This Rokko‐oroshi was accompanied by a hydraulic jump. The occurrence of the Rokko‐oroshi was supported by an upper‐level critical layer and a lower‐level strong stable layer on the windward side of the Rokko Mountains.

The aim of this study was to climatologically investigate forced and pressure‐driven channelling flow in the Kitakami Basin, Japan, through the use of observational surface wind and sea‐level pressure data collected over 23 years, which corresponded to 15,584 channelling flow events. Our results indicated that forced channelling tends to occur when the direction of the surface geostrophic wind is parallel to the valley axis. Contrastingly, pressure‐driven channelling tends to occur when the component perpendicular to the valley axis of the surface geostrophic wind is larger than that parallel to the valley axis of the surface geostrophic wind. The channelling flow type was determined by the wind direction of the surface geostrophic wind, which was more pronounced when the mountain Froude number of the flow across the valley was less than 1. This indicates that the type of channelling flow depends on the surface geostrophic wind speed. Moreover, neither channelling flow type was dominant when the component parallel to the valley axis of the surface geostrophic wind was slightly larger than the orthogonal component. This suggests that the flow type cannot be explained using the surface geostrophic wind alone, irrespective of whether forced channelling or pressure‐driven channelling is dominant. [ABSTRACT FROM AUTHOR]

Abstract Objective The aim of the present study was to reveal changes in the wind regime by investigating wind-speed data from meteorological stations in western Iran and comparing them in the last three decades (1986–2015). Results Two main groups of daily cycles were identified; one group with a single peak and one group with two or more peaks. Using spectral decomposition technique, it was revealed that the heterogeneity observed in the area in terms of altitude and topography results in differences in the density of the spectra with similar frequencies. Two main daily cycles were also identified for each station. Although there were low frequencies, the intensity of the waves at the examined stations was the consequence of the interaction between the frequency, period, and distribution space. By evaluating harmonics in the area, it was revealed that the variance of the first harmonic is maximized in the south and southwest, while the variance of the second harmonic is maximized in the north and northwest. The positive value ​​of the trend in the first harmonic indicated that the trend of the variance for the first harmonic has increased in the central and eastern parts and has decreased in the northern and western parts.

This study evaluates the swimming behaviour of pre-settled fish larvae of the triplefin Helcogrammoides chil­ensis (Tripterygiidae) in relation to local environmental conditions. Larval aggregations were recorded on rocky reefs off central Chile during the austral summer of 2014 and 2016 to describe their swimming behaviour (i.e. solitary, shoaling, schooling) and relate it to in situ water temperature, wind stress, wind speed and turbulence. Shoaling and solitary behaviour were influenced only by wind-induced turbulence in 2014 and by seawater temperature and wind stress in 2016. Schooling behaviour was not influenced by any of the environmental variables. In situ swimming behaviour of fish larvae has been little investigated, and this work proposes a non-invasive in situ methodology for studying fish larval behaviour.

Japanese society has recently taken a greater interest in foehn warming because it has caused record‐breaking high temperatures and sudden damage to rice crops. This is the first comprehensive climatological study focused on Japan's south foehn, which blows across the Toyama Plain in the Hokuriku region. Climatological analyses, including an objective self‐organizing map and subjective analysis of 198 south foehn cases, revealed that ~68.2% of the foehns occurred while an extratropical cyclone was passing through the Sea of Japan. Approximately 19.7% of the remaining foehns blew while an anticyclone covered Japan. Only 5.1% of all foehns occurred during a typhoon, but very high temperatures occurred when typhoons were approaching. Foehns were observed in all seasons but tended to blow more often in spring, when there are many migratory anticyclones and cyclones. Most of the foehns begin at night and end or pause during the day. This is due to the removal of the nocturnal stable layer and the development of a local daytime pressure gradient on the lee side. The dynamical mechanism provides the primary explanation for Japan's south foehn. Surprisingly, the foehns with precipitation on windward mountains slopes accounted for only ~19.2% of all cases, with ~40.0% being typhoon cases. Most of these are likely of multiple type; a pure thermodynamical type of foehn is a rare occurrence. Numerical simulations and back trajectory analyses for 76 selected foehn cases revealed that the majority of the air parcels originated from the south and passed straight over the Hida Highlands, between two mountain ranges, as a hybrid type of gap and foehn winds. [ABSTRACT FROM AUTHOR]

Data from synthetic aperture radars (SAR) provide new opportunities for observing and studying local katabatic winds (bora and foehn) over the seas in different regions of the Russian Federation and adjacent marine basins. The impact of these winds on the characteristics of small-scale wind waves leads to the formation of characteristic manifestations on the sea surface, which in turn can be seen in SAR images. Satellite SAR data, unlike subsatellite observations, make it possible to see the phenomena in coastal zones and large lakes, estimate their spatial scales, and determine a number of quantitative characteristics. The analysis of the collected SAR images shows that bora-like and foehn-like local winds have similar characteristics and cover vast areas of the inland and marginal seas of the Russian Federation. The similarity of the manifestations of local winds clearly indicates the same physical and aerohydrodynamic mechanisms of their onset and display on SAR images. It is shown that spaceborne SAR data, which are 2D patterns of the 'frozen wind', are extremely useful for studying and monitoring local winds over the seas, especially where the network of weather stations is extremely sparse. [ABSTRACT FROM AUTHOR]

Objective: The aim of the present study was to reveal changes in the wind regime by investigating wind-speed data from meteorological stations in western Iran and comparing them in the last three decades (1986–2015). Results: Two main groups of daily cycles were identified; one group with a single peak and one group with two or more peaks. Using spectral decomposition technique, it was revealed that the heterogeneity observed in the area in terms of altitude and topography results in differences in the density of the spectra with similar frequencies. Two main daily cycles were also identified for each station. Although there were low frequencies, the intensity of the waves at the examined stations was the consequence of the interaction between the frequency, period, and distribution space. By evaluating harmonics in the area, it was revealed that the variance of the first harmonic is maximized in the south and southwest, while the variance of the second harmonic is maximized in the north and northwest. The positive value ​​of the trend in the first harmonic indicated that the trend of the variance for the first harmonic has increased in the central and eastern parts and has decreased in the northern and western parts. [ABSTRACT FROM AUTHOR]

In the Dictionary of the Atmospheric Phenomena there are many winds and complex atmospheric phenomena names in which the prevailing wind acts alongside rain or snow. There are recorded both designations of Romanian winds and foreign winds, each category characterizing the two components of the Romanian meteorological terminology: popular and scientific. For the Romanian urban civilization, living mostly in large and closed spaces, the wind is an atmospheric phenomenon that manifests itself in certain degrees of strength. The rural civilization, defining for Romanians, traditionally preoccupied with agriculture and animal husbandry, as well as the world of fishermen and sailors know the living under the open sky, in the wind, which decisively influences their actions. The overwhelming role of the wind emerges especially from the denominative richness that the sources of the Dictionary of the Romanian Language (DLR) and the Dictionary of the Atmospheric Phenomena (DFA) make available. But the information provided is quite few and sometimes vague about the particularities of these winds, sometimes reduced to indicating the area of manifestation, practically the place where the appropriate name was collected. The definition of these terms raises problems in establishing the directions of the winds, their particularities, being adopted different solutions in the language dictionaries and in the DFA, in agreement with the DLR or in completing the latter. Among the most problematic names of winds in terms of lexicographic treatment can be mentioned: carael, coşava and gorneac, not accidentally borrowed from the languages of neighboring peoples. [ABSTRACT FROM AUTHOR]

This study numerically examined how the locally strong "Karakkaze" wind in the Kanto Plain of Japan is affected by terrain shape, particularly by a convex feature in the mountain range. Our method involved running idealized numerical simulations using the Weather Research and Forecast model with a horizontal grid spacing of 3 km. The results revealed that a strong-wind region formed in the lee area of the convex feature, hereafter the semi-basin, and leeward of the semi-basin. In contrast, weak-wind areas formed adjacent to the strong-wind region. These results were consistent with the basic features of the observed surface wind pattern of the Karakkaze during the winter monsoon. However, such a flow pattern did not appear in the numerical simulation with a mountain range that lacked a convex feature. Sensitivity experiments were also conducted to evaluate the detailed effects of a mountain range with convexity. Sensitivity experiments with different convex shapes revealed that strong winds appeared within and leeward of the semi-basin when the aspect ratio of convexity (ratio of the wave amplitude to the wavelength of the convexity) exceeded about 0.5. Sensitivity experiments on terrain shape suggested that saddles in the mountain range were not essential to the formation of the Karakkaze, but they could affect its strength. Sensitivity experiments on the mountain Froude number, Frm, showed that locally strong winds within and leeward of the semi-basin appeared only when the Frm was in the range 0.42 - 1.04. Sensitivity experiments with surface heat fluxes (SHFs) showed that the basic structure of the strong-wind region in the leeward plain of the convex feature did not depend strongly on SHFs. However, the addition of SHFs reduced the surface wind speed, but increased the size of the strong-wind region. [ABSTRACT FROM AUTHOR]

The Mediterranean is characterized with a large number of local winds. One region in the Mediterranean—the Balkan Peninsula or simply the Balkans—is particularly rich with local winds of different types including downslope and upslope winds, gap flows, and thermally induced breezes from land to sea and vice versa. This study presents the first comprehensive review of all currently known local winds in the Balkans, with coastal winds reviewed separately from inland winds. Besides providing the main climatological and dynamics characteristics of these winds, this paper also hints on the existence of various connections between several local winds that have not been reported previously. In total, this article lists 27 different local winds above the Balkans with 17 and 10 being coastal and inland winds, respectively. By far, the most researched local wind in the Balkans has been the Adriatic bora that blows along the Croatian coast. Interestingly, there are more papers investigating bora than the number of studies on all other winds in the Balkans. Local winds over the Adriatic have been explored more than the winds above the Aegean, and these, in turn, were investigated more often than the winds that blow over the Ionian and Black Seas. The most researched inland wind is the koshava wind that blows over the northern and central Serbia. Typical synoptic situations for most local winds are also provided with the note that the synoptic precursors of few local winds have not previously been documented. Lastly, this article discusses the prospects for further research in this field with the emphasis on the investigation of potential relationships between different local winds in this region. The first review of all local winds above the Balkans (27 in total). Besides providing the main climatological and dynamics characteristics of local winds in the Balkans, this article also finds potential relationships between several local winds. Prospects for further research in this field critically discussed. [ABSTRACT FROM AUTHOR]

The problem of stationary convective flows over a nonuniformly heated wavy surface is studied in the context of a simplified analytical model. It is shown that the horizontally periodic heating of such a surface can lead to a 'thermal wind' effect, i.e., the generation of a uniform horizontal flow far from the surface. [ABSTRACT FROM AUTHOR]

Abstract: Summertime observations of surface radiation budget, energy balance and atmospheric surface layer meteorology were made on an arid valley floor planted with Haloxylon aphyllum to combat desertification in central Iran. The surface microclimate is characterized and compared with other arid regions and the role of ‘desert greening’ on surface fluxes is considered. A high surface albedo (0.265) and large longwave radiation loss produced relatively low net radiation. Energy partitioning was dominated by sensible and ground heat fluxes with opposing diurnal asymmetry governed by strong diurnal variability in eddy diffusivity. The Bowen ratio was 2.53, which fell inside the range of other vegetated arid surfaces. Surface temperature gradients were strong both in the atmospheric surface layer and in the substrate, with consistent lapse conditions by day and inversions at night. The wind regime included a moderate daytime regional wind which displayed Coriolis turning and weaker nocturnal slope flows. Actual evapotranspiration (1mmdy−1) was only a small fraction of potential evapotranspiration. The diurnal pattern of AET indicates strong stomatal control. The desert greening effect of Haloxylon plantations provided atmospheric water and reduced sensible heat flux by up to 40%. [Copyright &y& Elsevier]

An observational dataset from a wintertime field campaign in the Inn Valley, Austria, is analysed in order to study mechanisms of air pollution transport in an Alpine valley. The results illustrate three types of mechanisms: transport by a density current, back-and-forth transport by valley winds, and transport by slope winds. The first type is associated with an air mass difference along the valley. Cooler air located in the lower part of the valley behaves like a density current and produces the advection of pollutants by upvalley winds. In the second type, strong horizontal gradients in pollution concentrations exist close to ground. Multiple wind reversals result in a back-and-forth transport of pollutants by weak valley winds. In the third type, upslope winds during daytime decrease low-level pollution concentrations and cause the formation of elevated pollution layers. [ABSTRACT FROM AUTHOR]

The major topographic, mesoscale, and urban influences on the wind patterns of the City of São Paulo are characterized using one year of surface wind velocity data observed at 11 surface stations within its urban limits. The data was used to study the diurnal and annual variations of wind velocity and horizontal wind divergence within the city. Results showed that the circulation over the investigated area is dominated by three major factors: sea breeze; mountain-valley circulations; and urban effects, such as roughness, building-barrier, and urban heat island. The sea breeze was found to be the dominant feature of the monthly-averaged diurnal variation of São Paulo surface winds during the eight warmest months of the year. The sea breeze front induces a velocity minimum at the time of its passage and a post-frontal afternoon velocity maximum. Mountain-valley thermal effects on the flow can be seen in the temporal divergence/convergence patterns. These thermal effects tend to be more important during colder months, at night, and when the wind velocities are low. Nighttime downslope convergent flows are present over the city during winter and spring and daytime upslope divergent flows are present over the city during summer months. [ABSTRACT FROM AUTHOR]

For many one-way unmanned aerial vehicle payload delivery and remote sensing missions, the heading to the target location and local winds are known. For these missions, only altitude and heading hold features are needed. Further, because the vehicle will not be returning, minimizing cost is a priority. Due to the desire to reduce the physical size of the vehicle, the flight control system needs to be of minimal complexity to facilitate miniaturization. Presented is a prototype altitude/heading hold flight control system that has been developed for use in small, stable UAV platforms. Topics covered in this paper include system architecture, hardware, user interface, and preliminary test-flight results. A brief description of the miniature target aircraft, the Naval Research Laboratory's Micro Tactical Expendable (MITE), will be presented as a representation of the class of vehicle under consideration. [ABSTRACT FROM PUBLISHER]

In the northern Adriatic Sea (the northernmost basin of the Mediterranean Sea) wind forcing plays a key role in shaping the water column structure, circulation patterns and dense water formation. The latter process might be enhanced during winter by local north-easterly wind, the Bora, responsible for intense and long-lasting episodic outbreaks. Although outbreaks of Bora are extensively studied in the context of thermohaline circulation, little is known about their effects on planktonic microbial communities. From late February to early March 2018, a persistent and strong Bora event caused an unusual drop of seawater temperature (down to 5.7 °C) in the Gulf of Trieste. To investigate the effect of this extreme meteorological event on the coastal planktonic microbes, we evaluated changes in their abundance and cytometric fingerprinting, heterotrophic carbon production rates and the activity of six exoenzymes (β-glucosidase, β-galactosidase, chitinase, lipase, alkaline-phosphatase and leucine aminopeptidase). Additionally, we set up temperature manipulation experiments to investigate the potential limiting effect of the temperature drop on microbial degradation and uptake of organic matter. The dataset clustered in two distinct groups: a cold-affected period (26th February - 8th March), characterised by a reduced particulate organic matter availability and slow metabolic rates, and a recovery one, (12th - 16th March) defined by an overall increase of substrate availability and enhanced heterotrophic carbon production and hydrolysis rates. Our findings revealed that the exoenzymatic activities were constrained at their lower thermal limit during the cold-affected period and that, deviating from the Arrhenius' linear response to temperature, the prokaryotic growth was limited by the interactive effect of temperature and substrate availability. By limiting the microbial processing of organic matter, extreme meteorological events could alter the functioning of the entire planktonic compartment functioning for several days during and after the onset of the phenomenon, affecting the structure of local trophic webs. Image 1 • The intense cold outbreak caused an exceptional surface water temperature drop. • Microbial degradation of organic matter was thermally inhibited. • Microbial growth was temperature-substrate co-limited. • A cold-footprint inhibited the microbial functional recovery once the event ceased. [ABSTRACT FROM AUTHOR]

In this study an attempt is made to investigate the prevailing meteorological conditions during days with high concentrations of PM10 (particles with diameter <10 Mum), collected in the Eordea mountain basin. This is an industrial area in the northwestern mountainous region of Greece. Over the 4-year data-gathering period, the days in which the United States Environmental Protection Agency 24-h PM10 standard was exceeded (episode days), were identified in relation to prevailingsynoptic scale and local meteorological conditions. The results indicated that days with increased PM10 concentrations in this area can be grouped into four categories in relation to their synoptic circulation characteristics. The highest concentrations were found to be associated with stagnant conditions. Under these conditions, local circulations developed in the area, resulting in recirculation and accumulation of pollutants. [ABSTRACT FROM AUTHOR]