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Three extreme cold events successively occurred across East Asia and North America in 2020/21 winter. This study investigates the underlying mechanisms for these record-breaking persistent cold events from the isentropic mass circulation (IMC) perspective. Results show that the midlatitude cold surface temperature anomalies always cooccurred with the high-latitude warm anomalies, which was closely related to the strengthening of the low-level equatorward cold air branch of IMC, particularly along the climatological cold air routes over East Asia and North America. Specifically, the two cold surges over East Asia in early winter were results of intensification of cold air transport there, influenced by the Arctic sea ice loss in autumn. The weakened cold air transport over North America associated with warmer northeastern Pacific sea surface temperatures (SSTs) explained the concurrent anomalous warmth there. This enhanced a wavenumber-1 pattern and the upward wave propagation, inducing a simultaneous and long-lasting stronger poleward warm air branch (WB) of IMC in the stratosphere and hence a displacement-type Stratospheric Sudden Warming (SSW) event on January 4. The WB-induced increase in the air mass transported into the polar stratosphere was followed by intensification of the equatorward cold branch and hence promoting the occurrence of two extreme cold events respectively over East Asia in the beginning of January and over North America in February. Results do not yield a robust direct linkage from La Nina to the SSW, IMC changes, and cold events, though the extratropical warm SSTs have contributions to the February cold surge in North America.

A solar air collector (SAC) is a heating device that applies warm air to dry agricultural products and for a variety of engineering purposes. The underside of the absorber plate used discrete double arc reverse shaped artificial roughness, outside testing performance for heat transfer coefficient, h, and thermal efficiency, ηth features of solar air collector were carried out in this article. During the outdoor experimental test, the following parameters were used: relative roughness pitch (p/e) = 8.33, relative roughness height (e/Dh) = 0.027, arc angle (α) = 60°, Reynolds Number (Re) = 3000 to 14000, and aspect ratio (W/H) = 8. Also, the outdoor test was performed at 11:00 A.M. before noon to 2:00P.M. afternoon with solar radiation intensities ranging from 860 W/m2 to 895 W/m2. The impact of various factors on heat transmission and thermal efficiency is compared to that of a smooth absorber duct under identical conditions of flow. Over the smooth duct, the maximum increases in coefficient of heat transfer and thermal efficiency are 2.88 and 1.29 times, respectively.

Energy is the foundation of a sustainable and quality life. In many structures, we need energy to meet our daily needs. The rate of energy consumption is a pattern or gradual lifestyle. Extensive energy sources can be organized into two classifications: regular and non-regular. Solar air heaters are widely used as energy storage equipment to provide warm air at medium temperatures for heating and drying applications. An attempt was made to transfer heat through the absorbent plate using roughness. The experimental assembly was made using several components such as flat glass, wood, collector, entrance and exit door. The collector produces hot air with the aid of solar radiation.

Mid-level stratiform precipitations during the passage of warm fronts were detailedly observed on two occasions (light and moderate rain) by a 355 nm polarization lidar and water vapor Raman lidar, both equipped with waterproof transparent roof windows. The hours-long precipitation streaks shown in the lidar signal (X) and volume depolarization ratio (δv) reveal some ubiquitous features of the microphysical process of precipitating hydrometeors. We find that for the light-rain case precipitation that reaches the surface begins as ice-phase-dominant hydrometeors that fall out of a shallow liquid cloud layer at altitudes above the 0 ∘C isotherm level, and the depolarization ratio magnitude of falling hydrometeors increases from the liquid-water values (δv) to the ice/snow values (δv>0.20) during the first 100–200 m of their descent. Subsequently, the falling hydrometeors yield a dense layer with an ice/snow bright band occurring above and a liquid-water bright band occurring below (separated by a lidar dark band) as a result of crossing the 0 ∘C level. The ice/snow bright band might be a manifestation of local hydrometeor accumulation. Most falling raindrops shrink or vanish in the liquid-water bright band due to evaporation, whereas a few large raindrops fall out of the layer. We also find that a prominent δv peak (0.10–0.40) always occurs at an altitude of approximately 0.6 km when precipitation reaches the surface, reflecting the collision–coalescence growth of falling large raindrops and their subsequent spontaneous breakup. The microphysical process (at ice-bright-band altitudes and below) of moderate rain resembles that of the light-rain case, but more large-sized hydrometeors are involved.

We explore the decoupling physics of a stratocumulus-topped boundary layer (STBL) moving over cooler water, a situation mimicking warm-air advection (WADV). We simulate an initially well-mixed STBL over a doubly periodic domain with the sea surface temperature decreasing linearly over time using the System for Atmospheric Modeling large-eddy model. Due to the surface cooling, the STBL becomes increasingly stably stratified, manifested as a near-surface temperature inversion topped by a well-mixed cloud-containing layer. Unlike the stably stratified STBL in cold-air advection (CADV) that is characterized by cumulus coupling, the stratocumulus deck in the WADV is unambiguously decoupled from the sea surface, manifested as weakly negative buoyancy flux throughout the subcloud layer. Without the influxes of buoyancy from the surface, the convective circulation in the well-mixed cloud-containing layer is driven by cloud-top radiative cooling. In such a regime, the downdrafts propel the circulation, in contrast to that in CADV regime for which the cumulus updrafts play a more determinant role. Such a contrast in convection regime explains the difference in many aspects of the STBLs including the entrainment rate, cloud homogeneity, vertical exchanges of heat and moisture, and lifetime of the stratocumulus deck, with the last being subject to a more thorough investigation in Part II. Finally, we investigate under what conditions a secondary stratus near the surface (or fog) can form in the WADV. We found that weaker subsidence favors the formation of fog whereas a more rapid surface cooling rate does not. Significant Statement The low-lying blanketlike clouds, called stratocumulus (Sc), reflect much incoming sunlight, substantially modulating Earth’s temperature. While much is known about how the Sc evolves when it moves over warmer water, few studies examine the opposite situation of Sc moving over colder water. We used a high-resolution numerical model to simulate such a case. When moving over cold water, the Sc becomes unambiguously decoupled from the water surface, distinctive from its warm counterpart in which the Sc interacts with the water surface via intermittent cauliflower-like clouds called cumulus clouds. Such decoupling influences many aspects of the Sc–sea surface system, which combine to alter the ability of the Sc to reflect sunlight, thereby influencing the climate. This work laid the foundation for future work that quantifies the contribution of such a decoupled Sc regime to Earth’s radiative budget and climate change.

Passenger rolling stock is an important component of passenger transportation services, which should ensure not only traffic safety, but also comfortable transportation conditions. Studies on the energy saving of railway rolling stock have revealed shortcomings in the operating documentation that increase the unproductive consumption of thermal energy by passenger cars during the operation of a heating system with a combined electric-coal boiler in electric heating mode. Experimental measurements confirmed the presence of unproductive losses of thermal energy through the intake blinds of the ventilation system due to the infiltration of outside air during downtime at the points of formation and turnover of passenger cars. Also, experimental measurements showed that there is a leak of warm air through the deflectors to remove exhaust air from the car into the environment. This is their regular mode of operation, but as highlighted in the author's early publications there are two zones of temperature fields in the body of the passenger car with different temperature regimes, which are separated by a decorative ceiling. The results show that the leakage of warm air through the deflectors occurs from the temperature field zone with a higher temperature, which increases the unproductive consumption of thermal energy. Thus, by making appropriate changes to the operating documentation based on the study, the energy efficiency of passenger rolling stock will be greatly improved in its further operation. In particular, it is established that the proposed modernization in order to increase the energy efficiency of the heating system can be carried out at relatively low cost, in modern car repair depots during overhauls, and also needs to be considered when designing new passenger cars.

The infiltration of warm and humid air from the outside into a freezer results in frost accumulation around the evaporator in household refrigerators. This can significantly reduce the cooling capacity of refrigerators. In this study, the pressure, temperature, and frost around a proposed drain tube were monitored through in-situ measurements until the first defrost process (about 54 h). The proposed drain tube has 220 times higher hydraulic resistance and shows 55 times lower inflow in computational fluid dynamics (CFD) analysis. Once the door of the freezer compartment is opened and closed, external warm air replaces the cold air in the freezer. Negative pressure is produced by the shrinkage of this external air under low-temperature conditions. The other role of the drain tube is to vent air between the outside and inside of the refrigerator under negative pressure. To release the negative pressure, the proposed drain tube has a movable shutter. In the CFD results, the secondary inlet increases the inflow by 3.2 times compared to the inflow in an I-type tube. To determine the design, the weight and inner diameter of the drain tube were changed. The performance of the proposed tube was validated by the lack of blockage of discharge until the first defrost process. The movable shutter did not allow the negative pressure to exceed -100 Pa by facilitating air venting after opening the door for 10 seconds and then closing it.

Temperature affects humidity. The interaction of temperature and humidity also directly affects the health and well-being of humans. The relative humidity (RH) of the air is an indication of how much water vapor is in the air at a particular temperature compared with how much water vapor the air could actually hold at that temperature. Air at 100 % relative humidity holds the maximum amount of water possible at that particular temperature and is said to be saturated. Therefore, air at 50% relative humidity, regardless of temperature, is holding half of its total possible water capacity. In essence, cold air cannot hold as much water vapor as warm air. In a closed environment such as a display case, there will be a fixed amount of water vapor, referred to as the absolute humidity. If the temperature inside the case falls then the relative humidity will rise. If the temperature rises the relative humidity will fall. Such changes in relative humidity could be caused by many factors including direct sunlight, spotlights and air-conditioning failures. Research carried out by experimental studies that we can get the humidity ratio and specific enthalpy in a kind of rooms either using The Psychrometric Chart and The formula. The specific humidity or humidity ratio of an air sample is the ratio of the weight of water vapor contained in the sample compared to the weight of the dry air in the same sample. Enthalpy is the amount of heat (energy) in the air per unit mass. Enthalpy is the total amount of energy present in the air, both from air and water vapor contained therein. And, Specific enthalpy of moist air is defined as the total enthalpy of the dry air and the water vapor mixture - per unit mass of dry air. Keywords: Temperature; Relative Humidity; Humidity Ratio; Specific Enthalpy.

The paper examines the influence of the main mode of interannual variability of the North Atlantic climate system—the North Atlantic Oscillation (NAO)—on the hydrophysical and hydrometeorological characteristics of the Nordic seas. A new scheme of the ocean–atmosphere interaction in the Atlantic sector of the Arctic Basin is proposed. In the positive NAO phase, the amount of Atlantic water inflow through the Faroe–Shetland Channel into the Norwegian Sea decreases, as well as the specific heat transfer to the atmosphere. Cyclonic activity becomes more active over the marginal seas of the Eurasian shelf in winter in the positive NAO phase. Cyclone trajectories are displaced to the north, which contributes to advection of warm air to the water area of the Nordic seas, and in the Barents Sea region, the frequency of southerly winds increases. The water temperature in the Nordcape Current in this period rises, and the ice extent of the Barents Sea decreases. The processes in the ocean–atmosphere–ice system in the Western Arctic in the negative NAO phase occur in the opposite direction. These conclusions were obtained for a time interval characterized by negative values of the Atlantic Multidecadal Oscillation (AMO index). During the positive phase of the AMO, which began to prevail in the 2000s, the processes in the ocean–atmosphere–ice system of the Barents Sea apparently occurred mainly under the influence of advection of Atlantic water with elevated temperatures.

High-resolution modeling is implemented to investigate an evolution of two quasi-tropical cyclones (QTC) over the Black Sea: in September of 2005 and 2018. For comparison, the quasi-tropical hurricane Zorba, that developed over the Mediterranean Sea at the end of September 2018, is considered. An assessment of factors leading to the origination and intensification of QTCs is carried out, and the predictability of the phenomenon is studied. The authors tried to reduce the analysis to the parameters obtained directly as a result of mesoscale nonhydrostatic modeling. In all the considered cases, the period of active development of cyclones was preceded by the formation of a core of warm air above the sea surface; the moisture inflow from the lateral boundaries was more important in the moisture balance. It is found that coarser spatial resolution predictions are more successful for large QTCs.

Hujan ekstrem yang melanda wilayah Jakarta sejak tanggal 31 Desember 2019 hingga 1 Januari 2020 menyebabkan sejumlah wilayah di Jakarta terendam banjir. Berdasarkan pengukuran curah hujan harian yang diukur pada tanggal 1 Januari 2020, curah hujan tertinggi terukur sebesar 377 mm di Pangkalan TNI Angkatan Udara Halim Perdana Kusuma. Analisis dari kejadian ini menggunakan Teknik RGB (Red Green Blue) pada citra satelit Himawari-8. Terdapat beberapa skema RGB yang mendukung penelitian ini yaitu, skema 24-Hours Microphysics, Day Microphysics, Night Microphysics, Air Mass dan Day Convective Storms. Hasil analisis time series suhu puncak awan menunjukkan pertumbuhan awan penyebab hujan ekstrem dimulai pada pukul 08.00 JLT dan hujan mulai melanda wilayah Jakarta sekitar pukul 09.15 JLT. Dari skema RGB diketahui terdapat massa udara hangat di wilayah Jakarta yang merupakan pemicu pertumbuhan awan Cumulonimbus. Tujuan dari penelitian ini ialah untuk mengetahui dinamika atmosfer dan sebaran awan konvektif saat terjadi banjir di Jakarta tanggal 31 Desember 2019 – 1 Januari 2020

The dynamic and thermodynamic characteristics of a dust precipitation event that took place on May 11, 2020 in North China are analyzed. With the invasion of cold air from Lake Baikal (107°E, 53°N), the arid area in the southeast of Mongolia (107°–108°E, 47°–48°N) was in a region with a large potential pseudo-equivalent temperature gradient, where interactions between cold and warm air led to instability of the atmospheric stratification, and became the dust source area. Meanwhile, a low-pressure cyclone formed over the area (122.3°E, 47.5°N) to the east of the dust source area. Under the joint action of the westerlies, the cyclone developed and supplied forces to the vertical ascent and transportation of dust. Strong winds carried the dust along the southeast direction to China. As the cyclone strengthened, the cold and humid air from Lake Baikal arrived and supplied water vapor for precipitation over Beijing. On the whole, the low-pressure cyclone provided momentum and water vapor for this dust–precipitation event. It is found that the horizontal helicity belt can be an indicator for the prediction of the dust transport pathway. The quick increase in surface dust concentration to its peak was closely related to the increase in downward movements in the layers above 700 hPa.

As a result of climate warming, glacial meltwater discharge has been increasing in Greenland. During the summers of 2015 and 2016, there were rapid increases in discharge from Qaanaaq Glacier in northwestern Greenland. These discharges resulted in floods that destroyed the road linking the settlement of Qaanaaq to Qaanaaq Airport. Field measurements were performed and a numerical model of glacier runoff was developed to quantify these discharges. The high discharge associated with the 2015 flood, estimated at 9.1 m3 s−1 (hourly mean), resulted from intensive glacier melting due to warm air temperature and strong winds, while the high discharge associated with the 2016 flood resulted from heavy rainfall (90 mm d−1) that led to a peak discharge estimated at 19.9 m3 s−1. The developed model, when used to investigate future glacier runoff under warming conditions, revealed a nonlinear increase in glacial melt with increasing temperature. Additionally, the model forecasted a threefold increase in total summer discharge, owing to a 4 °C rise in temperature. Thus, this study quantified the impact of a changing climate on glacier runoff, which gives insight into future risks of flood hazards along the coast of Greenland.

An explosive cyclone that took place over the Northwestern Pacific from 12 UTC 18 to 18 UTC 21 November 2007 was investigated. The synoptic situations and structure of this cyclone were documented by using the 1°×1° final analysis data of the National Center for Environmental Prediction. This cyclone developed explosively around 18 UTC 19 and reached its maximum deepening rate (MDR, 1.3 Bergeron) around 06 UTC 20 November 2007. At its MDR moment, the surface cyclone center was located in the downstream of the upper-level trough and northern entrance zone of the upper-level jet. The diagnosis using Zwack-Okossi equation suggested that cyclonic-vorticity advection and warm air advection acted to deepen this cyclone, while adiabatic cooling suppressed its development. In an investigation of this cyclone development, numerical sensitivity results obtained by using the Weather and Research Forecasting model showed that the latent heat release in the lower level had less contribution, whereas the surface sensible and latent fluxes played important roles. With a warmer ocean surface, the cyclone tended to intensify. Two topography tests were designed to examine the mountain influences on the development of this cyclone: removing a mountain and doubling the height of a mountain. Results show that the Changbai Mountains suppressed the development of the cyclone by preventing the southern moisture air from invading the inland. Without the moisture air, no latent heat release occurs when this cyclone passes over the Changbai Mountains.

The kitchen is an integral part of all the houses, where unpleasant gases and particulate particles are more effective during cooking time. Inadequate ventilation cannot effectively remove warm air and pollutant, and it will affect human health. In this paper, the computational investigation of the kitchen environment in the lower-income group (LIG) House is carried out which predicts the temperature distribution and exhaust gas motion in the kitchen environment. The kitchen of the LIG house is studied here which is small in size and is connected to rooms. The influence of different ventilation conditions in the kitchen is simulated for the exhaust gas distribution within the flow territory, a multiphase flow model is used. The computational solutions of the temperature distribution and concentration of different exhaust gases are examined. Generally, the human respiratory area is approximately located at 1.1 m high above the ground, hence, it is required to analyse the temperature and exhaust gases in such an area to seek more perceptions into the aerosol study. The results show that the ventilation condition of windows and doors is a direct impact on temperature distribution and motion of exhaust particles.

The subcool zone length is determined in lining of an extra-long railway tunnel subjected to deep influence of piston effect. The air temperature distribution in the outer air–tunnel lining contact zone is determined as function of the velocity of train and the outdoor temperature in the cold season. The authors review the de-icing methods of tunnel lining: warming-up using a self-tuning heating cable; arrangement of an unheated access gallery and heat insulation. The distribution of the hourly average air temperature in an extra-long railway tunnel is analyzed against of sites of fan heaters. The heat power patterns in the tunnel are estimated by the criterion of the required temperature conditions. It is shown that the most efficient arrangement of fan heaters to maintain the required air temperature in the tunnel is their uniform distribution along the length of the tunnel in combination with installation of warm air curtains at the tunnel faces.

Polar lows are intense mesoscale cyclones that develop in polar marine air masses. Motivated by the large variety of their proposed intensification mechanisms, cloud structure, and ambient sub-synoptic environment, we use self-organising maps to classify polar lows. The method is applied to 370 polar lows in the north-eastern Atlantic, which were obtained by matching mesoscale cyclones from the ERA-5 reanalysis to polar lows registered in the STARS dataset by the Norwegian Meteorological Institute. ERA-5 reproduces most of the STARS polar lows. We identify five different polar-low configurations which are characterised by the vertical wind shear vector, the change in the horizontal-wind vector with height, relative to the propagation direction. Four categories feature a strong shear with different orientations of the shear vector, whereas the fifth category contains conditions with weak shear. This confirms the relevance of a previously identified categorisation into forward- and reverse-shear polar lows. We expand the categorisation with right- and left-shear polar lows that propagate towards colder and warmer environments, respectively. For the strong-shear categories, the shear vector organises the moist-baroclinic dynamics of the systems. This is apparent in the low-pressure anomaly tilting with height against the shear vector and the main updrafts occurring along the warm front located in the forward-left direction relative to the shear vector. These main updrafts contribute to the intensification through latent heat release and are typically associated with comma-shaped clouds. Polar-low situations with a weak shear, which often feature spirali-form clouds, occur mainly at decaying stages of the development. We thus find no evidence for hurricane-like intensification of polar lows and propose instead that spirali-form clouds are associated with a warm seclusion process.

Observations from the 2014 Arctic Clouds in Summer Experiment indicate that, in summer, warm-air advection over melting sea-ice results in a strong surface melting feedback forced by a very strong surface-based temperature inversion and fog formation exerting additional heat flux on the surface. Here, we analyze this case further using a combination of reanalysis dataset and satellite products in a Lagrangian framework, thereby extending the view spatially from the local icebreaker observations into a Langrangian perspective. The results confirm that warm-air advection induces a positive net surface-energy-budget anomaly, exerting positive longwave radiation and turbulent heat flux on the surface. Additionally, as warm and moist air penetrates farther into the Arctic, cloud-top cooling and surface mixing eventually erode the surface inversion downstream. The initial surface inversion splits into two elevated inversions while the air columns below the elevated inversions transform into well-mixed layers.

This paper brings out the interconnection of flash rate density (FRD) with convection and stability parameters over Andhra Pradesh (AP), India. The convection parameters include rainfall, relative humidity, specific humidity, surface air temperature (SAT) and air temperature (at 850 mb). The stability parameters include convective available potential energy (CAPE), lifted index, K-index, total totals index (TTI), humidity index and total precipitable water. Both convective and stability parameters indicate good correlation with lightning activity. SAT and AT 850 mb have shown good correlations with lightning, which is a clear indication of interaction between warm air and dry air. CAPE and TTI have shown strong positive correlation with lightning activity. The correlation coefficient between FRD and CAPE is 0.81. We have also studied the influence of convective and stability parameters during lightning and no lightning activity. Later, we also attempted the estimation of lightning activity by using artificial neural network model. By using convection and stability parameters, six learning algorithms were used for training the artificial neural network. Scaled conjugate gradient backpropagation training algorithm has given the better estimation, whereas resilient backpropagation training algorithm has shown the poor estimation of FRD.

The current study investigated the triggering mechanism of a record-breaking heavy rain process in the area near the Tianshan Mountains in Xinjiang, an arid region in China, from July 31 to August 1, 2016, based on the simulation using the Weather Research and Forecasting (WRF) model. The results illustrated that the rainstorm system was generated in the middle atmosphere of the western Aksu region near the Tianshan Mountains and gradually evolved into a multicell linear echo during system evolution. The cold air transported from the Tianshan Mountains partly reached the low altitudes during the downhill process, and the warm southwest air from Aksu was lifted, forming oblique updraft airflow. The other part of the cold air converged with the southeastern warm air in the middle atmosphere, and the transportation and convergence of the water vapor related to the southwestern, southeastern, and oblique updraft airflows provided good water vapor conditions for the storm system. Meanwhile, the inclined upward air transported cloud water and ice-phase particles to high altitudes, mixing the two and generating a large amount of supercooled cloud water, which was very beneficial for the development and maintenance of the storm system. These conditions were favorable for power, heat, water vapor, and water condensate particles, which enabled the development and maintenance of the rainstorm system on the convergence line, thus triggering this rare rainstorm process during the movement to the northeast.

Extraordinarily frequent and long-lasting snowstorms affected China in January 2008, causing extensive social and economic damages. The potential predictability of such extreme events on the sub-seasonal timescale has been evaluated using results from the hindcast experiments by the Beijing Climate Center Climate System Model. The spatial distribution of precipitation during the period can be successfully reproduced with a 10–15 days leadtime, although the intensity is weaker than observations. The model’s success lies in the timely prediction of large-scale atmospheric circulation anomalies, such as the atmospheric blocking over the mid-high latitudes and the southwesterly flow associated with the Bay of Bengal trough in the low latitudes, but the predicted cold air is too strong while the warm air too weak, leading to an underestimation of precipitation along the main rainbelt. Meanwhile, the capture of those circulation anomalies in the initial states and their persistence in subsequent model predictions has played a key role in the predictability of such an extreme event. Detailed analysis has shown that sea surface temperature and low-frequency signals, such as the Arctic Oscillation and the Madden–Julian Oscillation, may also be important during the process.

Summary Data from MERIS onboard Envisat and MODIS onboard Terra and Aqua for 15–16 May 2010 were used to study powerful imprints of atmospheric gravity waves (AGWs) on the western part the Black Sea surface. Two cold fronts crossed the sea following the warm front and caused the AGWs which modulated the sea surface. Imprints of AGWs appeared as stripes of alternating brightness, they had crest length more than a hundred kilometers and wavelength of units of kilometers. Wave amplitude of AGWs imprints, evaluated by a 90%-depth of light penetration into the sea at 490 nm z90, the value inverse to the diffuse attenuation coefficient Kd_490, was units of decimeterxs. MODIS 250-m data of remote sensing reflectance, wind components and atmospheric pressure near the sea surface were obtained by processing the top of atmosphere data with the SeaDAS software package. Negative correlations of fluctuations of z90 with fluctuations of wind stress and atmospheric pressure were found on the transects of more than ten kilometers. The impact of wind stress on the origination of AGW imprints was found to be determinant, while the impact of atmospheric pressure was not more than units of percent.

Warm-sector rainfall (WSR) occurs, by definition, in a warm-air region that is isolated from any forcing related to synoptic frontal boundaries at the surface. This study explores the use of an object-oriented technique to objectively and automatically identify various WSR events over North China from June to September in 2012–17. A total of 768 substantive events are identified over the 6 years. They have a mean maximum rainfall accumulation of 35 mm h−1. Most such events occur over the plains, with two-frequency maxima: one to the south of the Yanshan Mountain Ranges, and the other near the junction of Henan, Shandong, and Jiangsu provinces. WSR-related rainstorms can form in all warm-season months but are most commonly observed between mid-July and mid-August (40% of all events occurred then). Geographically, the region at greatest risk moves gradually northward from mid-June to mid-August, consistent with the progression of the East Asian summer monsoon. There are two diurnal peaks in WSR activity, one from late afternoon to early evening and the other from late evening to early morning. Three classes of upper-level synoptic pattern seem to be conducive to WSR: (i) a “Mongolia front pattern,” (ii) a “northern China front pattern,” and (iii) a “southern front pattern.” All of these patterns are accompanied by warm and moist southwesterly flow at low levels. Prior to WSR events, there is usually an upper-level trough. According to other studies, such a feature is not usually seen for WSR events in South China.

A systematic analysis of the main weather types influencing southern Australian rainfall is presented for the period 1979–2015. This incorporates two multi-method datasets of cold fronts and low pressure systems, which indicate the more robust fronts and lows as distinguished from the weaker and less impactful events that are often indicated only by a single method. The front and low pressure system datasets are then combined with a dataset of environmental conditions associated with thunderstorms, as well as datasets of warm fronts and high pressure systems. The results demonstrate that these weather types collectively account for about 86% of days and more than 98% of rainfall in Australia south of 25° S. We also show how the key rain-bearing weather systems vary throughout the year and for different regions, with the co-occurrence of simultaneous lows, fronts and thunderstorm conditions particularly important during the spring and summer months in southeast Australia.

Hurricane Michael was intensifying as it made landfall devastating areas of the Florida Panhandle including the small town of Mexico Beach. The structure of the hurricane is examined using radar wind data made available from aircraft reconnaissance missions. This showed a dominant warm air advection configuration (winds turning in direction in an anticyclonic fashion with height) around the core of the hurricane. Conventional radiosonde data was also used to study the warm air advection environment east of a deep layered tough system which Michael moved into and which appeared to favour such strong intensification. The structure of this deep trough is also examined and compared with a situation where Hurricane Dennis in 2005 weakened as it approached the coast in much the same region. It appears that the thermal structure of the upper trough at low to middle levels is critical to whether the hurricane intensifies or weakens with the presence of strong cold air advection associated with weakening. Keywords: intensification, warm air advection, cold air advection, upper outflow, deep trough

In the warm summer of 2017, a landslide failed from the south-east side of the Col des Clochettes on the top of the underlying Trajo Glacier. The study area is at an elevation of about 3500 m a.s.l. in the Gran Paradiso Massif and can be hardly reached by walking from Cogne (Aosta Valley, NW Italy). Studies conducted by field surveys, photogrammetry (structure from motion) and satellite images analysis, integrated with the evaluation of data from meteorological stations have been used to reconstruct the phenomenon and infer its causes. The site is very complex to be studied especially due to logistic problems, therefore, measurements and observations that are common practice in other landslides are very difficult to apply here. So, many of the results achieved are not adequately supported by field studies. Anyway, the following factors could have affected the stability of the slope: i) the tectonic structure of the area, which is reflected on the morphology and on the geomechanics characteristics of the rock masses; ii) the meteorological conditions during 3 months before the main failure, resulting in an extremely high temperature compared to historical data. Moreover, the analysis of multitemporal satellite images allowed to recognize that it was not a single landslide but that the phenomenon is articulated over time in at least five failures in about 2 months. Moreover, several predisposing factors may have been playing an important role in causing the instability: the degradation of permafrost (probably affecting rock mass due to the circulation of warm air and water in the discontinuity systems), the alternance of the freeze-thaw cycles and the availability of a considerable amount of water from rainfalls and nival fusion infiltrating deeply in the rock mass. More common causes such as rains and earthquakes have been excluded.

A distributed multi-heat source phased control method was designed with the aim of reducing the heating energy consumption of electric vehicles. The method uses multiple-heat sources, namely battery cooling waste heat, motor cooling waste heat and heat pump air conditioning, to heat vehicles in stages. To design this method, the heat generated by an electric vehicle heating system was first numerically analysed. The distribution regions of various heat sources were then optimised and the functional relationships between the heat produced by multiple heat sources were established. The law of temperature distribution in different regions of automobiles was explored for heat produced by multiple heat sources. The method can synthesise the temperature difference outside of the car, the heat release sequence of the heating components and the comfort requirements of passengers. It can also reasonably select the working mode of warm air. A low-temperature test of warm air conditioning was carried out to compare the difference between this method and the conventional heating method of new energy vehicles. The system saved 60% energy while running at an ambient temperature of −22 °C for 2 h. No power battery energy was needed at −5 °C, verifying the superiority of the proposed method.

Precipitation falling over the coastal regions of Antarctica often experiences low-level sublimation within the dry katabatic layer. The amount of water that reaches the ground surface is thereby considerably reduced. This paper investigates the synoptic conditions and the atmospheric transport pathways of moisture that lead to either virga – when precipitation is completely sublimated – or actual surface precipitation events over coastal Adélie Land, East Antarctica. For this purpose, the study combines ground-based lidar and radar measurements at Dumont d'Urville station (DDU), Lagrangian back trajectories, Eulerian diagnostics of extratropical cyclones and fronts, and moisture source estimations. It is found that precipitating systems at DDU are associated with warm fronts of cyclones that are located to the west of Adélie Land. Virga – corresponding to 36 % of the hours with precipitation above DDU – and surface precipitation cases are associated with the same precipitating system but they correspond to different phases of the event. Virga cases more often precede surface precipitation. They sometimes follow surface precipitation in the warm sector of the cyclone's frontal system, when the associated cyclone has moved to the east of Adélie Land and the precipitation intensity has weakened. On their way to DDU, the air parcels that ultimately precipitate above the station experience a large-scale lifting across the warm front. The lifting generally occurs earlier in time and farther from the station for virga than for precipitation. It is further shown that the water contained in the snow falling above DDU during pre-precipitation virga has an oceanic origin farther away (about 30∘ more to the west) from Adélie Land than the one contained in the snow that precipitates down to the ground surface.

Since the early twentieth century, observations have shown that the ocean surface has warmed almost globally, but the rate of sea surface temperature (SST) rise in the Kuroshio region (KR) has been twice that of the global-mean. This study focuses on the mechanisms driving long-term changes in SST in the KR during the period 1951–2010 using observations, reanalysis data, and 10-member ensembles of historical simulations based on a global climate model (GCM) called MIROC 5.2. The observational data indicates that SST in the KR slightly decreased until around 1980, but rapidly increased afterwards. The MIROC5.2 historical experiment reproduced the observed multidecadal changes in the KR SST, and a signal-to-noise analysis showed that one third to half of the changes were attributable to a forced component, represented by the ensemble mean. Comparison of historical runs with another ensemble in which sulfate aerosols were fixed at preindustrial levels, highlighted that multidecadal SST changes in the KR were primarily driven by sulfate aerosols, contributing to the warming for 1981–2010 as much as greenhouse gases. Analyses of the MIROC5.2 ensemble mean revealed that the key factor for enhanced warming after the 1980s in the KR was a high-pressure trend over the North Pacific. This is because it advects warm air to the northwestern Pacific in the lower troposphere and causes a northward shift in the Kuroshio current. The presence of this mechanism was supported by a significant correlation between SST trends in the KR and high-pressure trends over the North Pacific based on historical simulations from 27 GCMs, and a large ensemble of historical simulations using MIROC6. These results demonstrate the importance of an externally forced atmospheric circulation response over the North Pacific as it relates to enhanced ocean surface warming in the KR.

The August Asian–Pacific Oscillation (APO) plays an important role in the variability of autumn (September ~ October mean) precipitation in central eastern China (CEC). Using observational and reanalysis data, the impact of the August APO on autumn CEC precipitation from 1960 to 2016 was studied. The statistical result showed that August APO is closely linked to the autumn precipitation anomalies in CEC with a significant positive correlation (r = 0.45). Further analysis revealed that when the APO is strong, the strengthened East Asian trough and the North Pacific high / vertical shear occur in the mid-lower / upper troposphere, resulting in anomalous southerly along the East Asia coast, which are favorable for strengthening the anomalous convergence and upward movement of moist warm air from the northwestern Pacific and arid cold air from the north China, introducing more precipitation, but that this configuration became much diminished during weak APO years. The possible mechanism can be explained as the thermal effect in the mid-upper troposphere can last from August until autumn, and the corresponding concurrent thermal effect would lead to anomalies in both atmospheric circulation and precipitation. Additionally, though an evidently negative relationship between preceding Nino indices and autumn CEC precipitation was revealed, the August APO induced changes in autumn CEC precipitation is greater than those of Nino indices, whether interannual or interdecadal changes, further indicating that the APO is an effective signal for precipitation prediction in CEC.

The frost-free refrigerator typically uses a bottom-placed calrod heater to remove frost on evaporator surface. However, the mismatch between full coverage of frost and bottom-up heat transfer extends defrost duration, and warm air intrusion into freezing cabinets (FCs) during defrosting leads to increased FC-temperature rise and overall energy consumption. Therefore, comprehensive measures were applied in this article to enhance defrost performance of the frost-free refrigerator. A special fan cover was adopted which opened during cooling cycles to supply cold air into cabinets normally, but closed during defrosting to block warm air intrusion passage. Moreover, an extra heater (60 W) was inserted in the middle height of the evaporator besides the original bottom one (180 W) to form better frost-heat match. Results show the fan cover and dual heaters altogether reduced defrost duration by 4.5 min and FC-temperature rise by 2.7 °C. Lower FC-temperature after defrost further declined energy consumption for the subsequent recovery cycle, which compensated for its increase for the defrost cycle and dominated the 1.2% reduction in overall energy consumption of the refrigerator. Both measures proved effective in enhancing defrost performance. However, the middle heater may affect cooling cycle performance of the refrigerator, necessitating further investigation.

—Electric heating of hives can be employed to help bee colonies survive cold snaps and minimize honey consumption by bee clusters. However, since our understanding of behavioral patterns of winter bee clusters is limited, this sometimes leads to the death of a colony or induces elevated honey consumption. In this work, the physical processes within the hive environment were modeled using Comsol software version 5.3. The simulation was carried out for a fixed outdoor temperature with variable heater power, as well as for a fixed heater power and variable ambient temperature. Analysis of thermograms indicated that with an operating heating device, the warmest zone shifted to the lower part of the winter cluster, which is biologically plausible. It was also shown that the use of the heaters increased the volume of warm air within a hive, providing the bees with a better opportunity to access new food reserves, which is especially important in the spring. The simulation demonstrated that in a heated hive energy output by the bees at low temperatures decreased from 3600 to 1900 W/m3, that is, by nearly two times. This decrease in the energy output is certain to diminish honey consumption. Simulation was also employed to optimize the power input to the heaters using the criteria of minimum temperature fluctuations within the hive and prevention of heater surface overheating.

The data of atmospheric reanalysis NCEP/NCAR over 1948–2017 (R-1) and NCEP/DOE over 1979–2017 (R-2) have been used to show that variations of the Caspian Sea level are closely correlated with the long-term variations in the field of surface wind in the sea region caused by the transformation of atmospheric circulation over Eurasia. Winds of the eastern and northern rhumbs have been shown to play the main role in variations of evaporation over the Caspian Sea. In the periods of level drop in the Caspian Sea (1948–1976 and 1996–2017), eastern winds dominate, bringing dry and warm air from Central Asia and thus contributing to an increase in water evaporation from the Caspian Sea. In the periods of level rise in the Caspian Sea (1977–1995), northern winds dominate, which cause a decrease in the rate of evaporation. Calculations of evaporation over the Caspian Sea water area using reanalysis data R-1 and R-2 fully confirm these conclusions. A close correlation has been shown to exist between evaporation and the level of the Caspian Sea. The coefficients of correlation between the nonstandardized increments of evaporation and level in the Caspian Sea are –0.86 and –0.75 by R-1 and R-2, respectively. Moreover, the contribution of evaporation to the current drop in the Caspian Sea level by data of improved reanalysis R-2 is greater than that by R-1, because the inflow of air masses from the nearby dry region of the Central Asia according to R-2 has been greater in the recent decade.