Warm Air Research Articles

Enhancing natural ventilation in buildings with double-pass inclined solar chimneys: a sustainable solution

Double-pass inclined solar chimneys are innovative structures designed to harness solar energy for natural ventilation in habitats. Unlike traditional chimneys, which rely solely on the buoyancy of warm air for ventilation, double-pass inclined solar chimneys incorporate solar heat to enhance airflow. These chimneys consist of two passageways: an outer transparent cover and an inner absorber plate. The transparent cover allows sunlight to penetrate and heat the absorber plate, which in turn heats the air within the chimney. As the air warms, it rises due to buoyancy, creating a draft that draws cooler air from the habitat below. This process creates a continuous airflow within the chimney, facilitating natural ventilation. The inclined design of these chimneys maximizes solar exposure throughout the day, optimizing heat absorption and airflow. Additionally, the double-pass conFigureuration enhances thermal efficiency by trapping and utilizing solar heat effectively. By harnessing renewable solar energy, double-pass inclined solar chimneys offer a sustainable solution for ventilating habitats, reducing reliance on mechanical ventilation systems and lowering energy consumption.They provide a cost-effective and eco-friendly alternative for maintaining indoor air quality and comfort in various living spaces.

A Comparison of Extreme and Ordinary Freezing Rain Events of Long Duration and High Integrated Vapor Transport in Eastern North America

Abstract Freezing rain events of long duration (LD, at least 12-h) in two study domains of eastern North America gleaned from the database of McCray et al. (2019) are examined using ERA5 reanalysis-based integrated vapor transport (IVT) to investigate how parent cyclones with high IVT (HIVT; surrogate for atmospheric rivers) contribute to severe freezing rain events. Although not necessary for an LD freezing rain event to occur, HIVT-influenced parent cyclones are associated with most (70%) events occurring in the southeastern Canada/ northeastern U.S. study domain (CAUS) and with the majority (78%) of very long (at least 24-h) LD events in the region over a 38-year period (1979-2016). Comparing extreme and ordinary LD events involving HIVT-influenced parent cyclones over the CAUS and southeastern U.S. study domains shows the importance in extreme events of slow movement and phasing between the continental parent cyclone located over eastern North America and a corresponding mid-latitude anticyclone to the northeast of the CAUS domain that provides cold dry air needed in the near-surface cold layer to offset opposing diabatic effects. A corresponding sub-tropical anticyclone assists the parent cyclone in supplying warm and humid air at mid-levels of freezing rain events to the northern reaches of the study domain, extending spatial and temporal scales of extreme events. Most ordinary LD event parent cyclones are progressive and impact the study domain only briefly. An abrupt end of ordinary LD events having a slow-moving parent cyclone occurs either when its center moves over the study domain or a second, newly dominant cyclone emerges.

Thin‐Plate Spline Interpolation Spatial Modelling of GNSS Retrieved Water Vapour Over Northeast Japan

ABSTRACTThe study investigated precipitable water vapour (PWV) variation over Northeast Japan by using more than two decades (2000 to 2022) of measurements. These data have been extracted from 36 Global Navigation Satellite System (GNSS) networks and interpolated with thin‐plate spline interpolation to understand its spatial variation over the region. PWV annual and seasonal variation is studied and correlated with ERA5 reanalysis observations. These PWV variation shows that the northern part of Northeast Japan which is located at higher latitudes showed a smaller magnitude compared to PWV magnitude in the southern part of low latitudes. This is possible because the cold air is drier and the warm air holds more moisture in the lower southern part. The correlation coefficient variation based on geographical area is visible which quantifies the consistency between GNSS PWV and ERA5 and visualises the effects in sampling. The southern part, where the correlation coefficients are very high (more than 0.80), indicates good agreements between GNSS PWV and ERA5 values and can be considered well‐sampled observations. Moreover, the correlation coefficients drop the values to approximately 0.40–0.60 for poorly sampled observations on the northern coast, pointing out the interannual inconsistency of PWV measurements, which are loosely related to ERA5 observations. Finally, the correlation coefficient between PWV with surface temperature and atmospheric pressure over Northeast Japan is investigated. This is clear from the results that the correlation coefficient between PWV and temperature is around 0.98 for each site, indicating that PWV has a very high dependency on surface temperature. The correlation coefficient between PWV and pressure is highly negative around −0.80, indicating their inverse relationship. We believe the outcomes from this study will contribute to a better understanding of PWV over Japan and the future refinements of atmospheric models over the East Asian region.

The Joint Influences of the South Asian Jet Wave Train and Eurasian Teleconnection on the Wet–Cold Extreme over South China in February 2022

Abstract In February 2022, an extreme wet and cold event hits South China, with the regional precipitation ranking the second highest on record, while the temperature ranked the third lowest since 1979. In this study, the physical mechanisms of this extreme event are investigated from the perspective of multiple time-scale interactions. Results show that the strong confrontation between the warm and moist air advection by the India–Burma trough (IBT) and the invasion of cold air activity related to the strengthening of the East Asian winter monsoon (EAWM) is the key to trigger this extreme event. Further analyses show that the multitime-scale coupling of the South Asian jet wave train and Eurasian (EU) teleconnection is the main reason for the strong cold and warm–moist airflow. The EU teleconnection on both intraseasonal and synoptic time scales plays a key role in triggering this extreme event by strengthening the EAWM. On the synoptic time scale, not only the EU teleconnection but also the South Asian jet wave train plays a key role. They show a stronger intensity on this time scale, and their coupling is obvious. The South Asian jet wave train enhances the moisture supply by deepening the IBT, which further conflicts with the strong EAWM modulated by the EU teleconnection over South China, leading to this extreme wet–cold event. The forecast skills in the Subseasonal to Seasonal (S2S) Prediction project models of this event are evaluated in this paper, and results show that the ECMWF model can successfully predict the extreme precipitation by capturing the coupling of the two wave trains with a 5-day lead time.

Future Climate Change in the Northern Bering Sea

ABSTRACTThe Bering Sea is undergoing major changes from increasing winter temperatures to the north, extreme minimum sea‐ice years in 2018 and 2019, through to an ecosystem reorganisation and negative impacts on communities' economic and subsistence food resources. These events have emerged under a global warming background, with positive feedback processes through a weakened atmospheric Alaskan Arctic Front (AAF) that promotes a self‐reinforcing process of sea‐ice loss, warmer air and sea temperatures, a wavy jet stream, and southerly winds. Interannual variability is still important: during 2021–2024 the Aleutian Low‐pressure system was regionally dominant in supporting a strong AAF, and sea‐ice conditions were observed close to the climatological mean. Before 2017, the AAF, consisting of cold dry air mass to the north and moist relatively warm air mass to the south, was a barrier to northward movement of storms, keeping the northern Bering/Chukchi seas with a cold Arctic climate. That historical situation is ending. Of critical importance is the probable reoccurrence of low Bering Sea sea‐ice years over the next decades and related ecosystem impacts. We propose that radically low sea ice will have a frequency of one to three 2018‐like low sea‐ice events per decade in the coming two decades, based on a historical meteorological analysis and ensemble climate model projections. Arctic temperatures to the north are increasing, weakening their contribution to the AAF. A weakened AAF and low sea‐ice years needs the winter Aleutian low pressure system to be far to the west of its average position, with southerly rather than northeasterly winds, warm years and low sea‐ice extent. From 1948 to 2024 meteorological records, this western location occurred with a range of zero to three times per decade. Communities need to plan for a response to intermittent occurrence of 2018‐like extreme sea‐ice loss and their ecosystem impacts over the coming decades.

Southerly winds and rapid sea ice reductions along the Sea of Okhotsk coast of Hokkaido

The Sea of Okhotsk, between northern Japan and Siberia, is the southernmost sea region of the Northern Hemisphere with seasonal sea ice cover. During early spring, occasional rapid reduction in sea ice cover observed in the southern Sea of Okhotsk can lead to anomalously early disappearance of sea ice along the Hokkaido coast (northern Japan). This study investigated the atmospheric and oceanic processes leading to rapid reduction in sea ice in the southern Sea of Okhotsk during early spring. We detected six events of subseasonal continued reduction in sea ice cover in March between 1993 and 2019. Strong southerly winds with marked thermal advection and moisture transport over northern Japan were observed in five of the six events. The passage of extratropical cyclones brought warm moist air from the south, which led to drifting and melting of sea ice by changing the surface wind speed and surface heat budget in the southern Sea of Okhotsk. The perturbation in sensible heat flux attributable to warm air advection contributed substantially to sea ice reduction, whereas longwave radiation played a secondary role. In addition to the atmospheric processes, an enhanced Soya Current also transports heat from the Sea of Japan, possibly contributing to the sea ice melt. The initial sea ice reduction leads to further sea ice loss through ice–albedo feedback, resulting in prolonged sea ice reductions for 1–2 weeks.

Reduced soil moisture drives leaf anatomical shifts more than chronically elevated temperatures in European temperate trees.

Chronic reductions in soil moisture combined with high air temperatures can modify tree carbon and water relations. However, little is known about how trees acclimate their foliar structure to the individual and combined effects of these two climate drivers. We used open-top chambers to determine the multi-year effects of chronic air warming (+5 °C) and soil moisture reduction (-50%) alone and in combination on the foliar anatomy of two European tree species. We further investigated how these climate drivers affected the relationship between foliar anatomy and physiology/chemistry in young downy oak and European beech trees. After 4 years, reduced soil moisture led to development of thinner leaves with a narrower epidermis and lower gas exchange for oak and beech, but to a lesser extent in the latter. In contrast, prolonged warming did not affect the anatomical and physiological/chemical traits in either species. Warming also did not exacerbate the impacts of dry soils, highlighting soil moisture as the key driver in leaf anatomical shifts. While soil moisture altered oak foliar anatomy, and the physiology and chemistry of both species, our work revealed a limited acclimation potential towards more drought- and heat-tolerant leaves as conditions become drier and warmer, suggesting potentially high vulnerability of both species to future climate predictions.

Long-term variations of global radiation in Central Europe 1950–2020 and their impact on terrestrial surface air warming

Long-term variations of global radiation in Central Europe 1950–2020 and their impact on terrestrial surface air warming

Role of the Europe–China Pattern Teleconnection in the Interdecadal Autumn Dry–Wet Fluctuations in Central China

Based on statistical analyses of long-term reanalysis data, we have investigated the interdecadal variations of autumn precipitation in central China (APC-d) and the associated atmospheric teleconnection. It reveals that the increased autumn rainfall in central China during the last decade is a portion of the APC-d, which exhibits a high correlation coefficient of 0.7 with the interdecadal variations of the Europe–China pattern (EC-d pattern) teleconnection. The EC-d pattern teleconnection presents in a “+-+” structure over Eurasia, putting central China into the periphery of a quasi-barotropic anticyclonic high-pressure anomaly. Driven by positive vorticity advection and the inflow of warmer and moist air from the south, central China experiences enhanced ascending motion and abundant water vapor supply, resulting in increased rainfall. Further analysis suggests that the EC-d pattern originates from the exit of the North Atlantic jet and propagates eastward. It is captured by the Asian westerly jet stream and proceeds towards East Asia through the wave–mean flow interaction. The wave train acquires effective potential energy from the mean flow by the baroclinic energy conversion and simultaneously obtains kinetic energy from the basic westerly jet zones across the North Atlantic and the East Asian coasts. The interdecadal variation of the mid-latitude North Atlantic sea surface temperature (MAT-d) exhibits a significant negative relationship with EC-d, serving as a modulating factor for the EC-d pattern teleconnection. Experiments with CMIP6 models predict that the interdecadal variations in APC-d, EC-d, and MAT-d will maintain stable high correlations for the rest of the 21st century. These findings may contribute to forecasting the interdecadal autumn dry–wet conditions in central China.

The Warming Management Measures May Need to Be Further Enhanced During Scoliosis Correction and Internal Fixation Surgery: A Retrospective Cohort Study.

The incidence of intraoperative hypothermia (IPH) exceeds 70% during spinal surgery, which can lead to many adverse outcomes, including increased intraoperative blood loss/transfusion and delayed recovery. We aimed to evaluate the comprehensive efficiency of a kind of enhanced warming measure on patients undergoing spinal surgery. A retrospective analysis was conducted on the clinical data, surgical procedures, and outcomes of consecutive patients admitted to the department of orthopedics of a hospital from December 2019 to May 2023 and undergoing spinal surgery (scoliosis correction and internal fixation surgery). The impact of the perioperative warming measures on surgical temperature variation and postoperative recovery was analyzed. The surgical patients who received normal active warming measures (quilt, blood transfusion and infusion warming, flushing fluid warming) were the control group (Normal Warming Group [NWG], n = 199), and the enhanced active warming measures (NWG and forced air warming) were the experimental group (Enhanced Warming Group [EWG], n = 201). Incidence of IPH was the primary endpoint of this study. EWG exhibited a significantly reduced incidence of IPH and average frequency of hypothermia per patient compared with NWG (respectively, p < 0.01) and demonstrated notable reductions in intraoperative blood loss, urine output, anesthesia recovery time, and duration of arousal (respectively, p < 0.05, p < 0.01, and p < 0.001). Postoperatively, EWG showed a significantly reduced incidence of shivering (p < 0.001) and had lower costs for postoperative antibiotic use and albumin administration (respectively, p < 0.05 and p < 0.01). So we infer that the occurrence of hypothermia during spinal surgery may seem unavoidable, but EWG can effectively lower the occurrence of IPH and its adverse outcomes, and then somewhat alleviate the postoperative treatment burden. However, given that this study is a retrospective cohort study, it is not yet possible to definitively prove the above conclusions, so we will design relevant prospective clinical studies to prove that the optimization of temperature management may be crucial to ensure optimal overall recovery outcomes.

Dropsonde Observations of the Stable Marine Boundary Layer Beneath Atmospheric Rivers

Abstract An important source of errors in predicting landfalling atmospheric rivers (ARs), and their associated extreme precipitation and streamflow, are inaccuracies in model initial conditions in ARs offshore. These inaccuracies are particularly evident in the marine boundary layer (MBL) where the tendency of ARs to transport warm air poleward over progressively cooler SSTs generates a stable MBL (SMBL). The SMBL’s vertical structure and key modulating processes are documented using &gt;1000 dropsondes along 99 transects of ARs from the AR Reconnaissance and CalWater field campaigns. The SMBL depth, modulated by sensible heat loss to the ocean, is typically 300–800 m in the AR core, with vertical wind shears ranging from 5–50 m s−1 km−1, representing a highly variable decoupling of the AR aloft from conditions at the ocean surface. Simulated backward air parcel trajectories originating from dropsonde locations within the AR core are used to calculate the 24-h change in SST experienced by an air parcel (DSST24) beneath each AR. The DSST24 varies from −13°C to +2°C and is directly related to the strength of the AR and its orientation relative to the SST gradient. The DSST24, therefore, distinguishes weak and strong decoupling regimes (WDR, SDR). In SDR cases, relative to WDR cases, the SMBL is characterized by greater sensible heat loss to the ocean, as well as stronger static stability, vertical wind shear, low-level jet, and horizontal water vapor transport. In SDR cases, the SMBL is deeper in the core than in adjacent warm and cold sectors.

Experimental analysis of a solar air heater using waste mild steel chips as a sensible heat storage material.

Heat storage materials improve the utility of solar air heaters (SAHs) after sunset. This study investigates an improved solar air heater (SAH) performance with baffles and waste mild steel chips as sensible heat storage (SHS) materials. Comparative experimental natural convection heat transfer studies were performed with four different improved air heater setups under similar solar radiation conditions. These setups consist of a flat collector plate (I), a baffled plate collector (II), a flat plate collector with SHS (III) and a baffled plate collector with SHS (IV) respectively. Setups I, II, III and IV were obtained by modifying the same air heater enclosure and each experiment was replicated for three similar sunny days. During the periods, the solar radiation varied in the range of 556-934 W/m2. The maximum thermal efficiencies found for setups I, II, III and IV were 18.76%, 22.40%, 27.21% and 28.22% respectively under natural convection. The highest average useful energy rate was produced by setup IV, followed by setups III, II and I. After sunset, setups III and IV were able to deliver warm air for an extended period of 1h, 18min and 1h, 42min, respectively. It was found that setups III and IV had sensible thermal energy storage reserves of 0.38kJ and 0.53kJ, respectively. The storage efficiencies found for setups III and IV were 60.25% and 70.89%, respectively. Among the four setups, setup IV boasts the most economical energy cost at 1.39 ₹/kWh and having the least payback period of 1year 4months. As a result, the employment of baffles and waste mild steel chips as SHS in a flat plate SAH not only presents a method for harvesting waste for efficient heat retention, but it also effectively uses solar energy for beneficial uses.

Atmospheric warming during rapid sea ice loss over the Barents–Kara seas in winter

AbstractThe atmospheric temperature change associated with rapid sea ice loss events over the Barents–Kara Seas (BKS) is explored. Rapid sea ice loss events are defined as periods with a tendency for sea ice concentration averaged over BKS to be below the fifth percentile of the probability density function distribution during the winters of 1979–2020 for at least three consecutive days. Composite analysis shows that there is a significantly positive bottom‐amplified temperature anomaly ahead of the rapid sea ice loss, which is closely associated with a wave train composed of a Ural blocking and an upstream positive phase of the North Atlantic Oscillation. This structure is favorable for the transport of warm and moist air into the BKS, and therefore, the tropospheric temperature, including the surface air temperature, increases through horizontal warm‐temperature advection, specifically through warm advection of the climatological temperature by the anomalous wind. The cooling over the BKS due to the adiabatic effect and vertical mixing opposes the horizontal warm‐temperature advection above and below about 900 hPa, respectively. However, an increase in skin temperature prominently results from enhanced downward long‐wave radiation, which is also the main contributor to the rapid sea ice loss.

Large eddy simulation of near-surface boundary layer dynamics over patchy snow

The near-surface boundary layer over patchy snow is highly heterogeneous and dynamic. Layers of opposing stability coexist within only a few horizontal meters. Conventional experimental methods to investigate this layer suffer from limitations related to the fixed positions of eddy covariance sensors. To overcome these difficulties, we set up a centimeter-resolution large eddy simulation of flow across an idealised transition from bare ground to snow. We force the simulation with high-frequency eddy covariance data recorded during a field campaign. We show that the model can represent the real flow by comparing it to independent eddy covariance data. However, the simulation underestimates vertical wind speed fluctuations, especially at high frequencies. Sensitivity analyses show that this is influenced by grid resolution and surface roughness representation but not much by subgrid-scale parameterization. Nevertheless, the model can reproduce the experimentally observed plumes of warm air intermittently detaching from bare ground and being advected over snow. This process is highly dynamic, with time scales of only a few seconds. We can show that the growth of a stable internal boundary layer adjacent to the snow surface can be approximated by a power law. With low wind speeds, deeper stable layers develop, while strong wind speeds limit the growth. Even close to the surface, the buoyancy fluxes are heterogeneous and driven by terrain variations, which also induce the frequent decoupling of a thin layer adjacent to the snow surface. Our simulations point the path towards generalizing point-based and aerial measurements to three dimensions.

Efficacy of different warming methods for perioperative hypothermia prevention on body temperature and shivering among transurethral resection patients: A systematic review and meta-analysis study

PurposeThe present study attempts to assess the impacts of distinct warming strategies employed to avert perioperative hypothermia on core body temperature and shivering among transurethral resection patients. MethodsWe performed a comprehensive search of Turkish and English keywords across a range of databases, including PUBMED, Web of Science, Cochrane Library, SCOPUS, Ovid, EBSCOhost, Yöktez, DergiPark, and TR Index, to identify studies on the subject published between January 1, 2001–2024. The search procedure yielded 11 studies to be recruited for meta-analysis. We analyzed the data using the trial version of Comprehensive Meta-Analysis Software (CMA). The degree of heterogeneity was quantified using Higgins I2 tests, while we assessed publication bias through Kendall's Tau and Egger's regression analyses. ResultsThis meta-analysis focuses exclusively on the effects of forced air warming and irrigation fluid warming, as only these methods provided sufficient data to calculate effect size. Our findings demonstrated that while forced air warming significantly affected preoperative (g = 0.279), intraoperative (15th minute, T4) (g = 0.845), postoperative (g = 0.647) body temperature and postoperative shivering (g = −2.279), irrigation fluid warming had a significant impact on postoperative body temperature (g = 1.007) and intraoperative shivering (g = 0.188). ConclusionOverall, our results indicated that forced air warming and irrigation fluid warming can serve as a preventive measure against hypothermia and shivering among transurethral resection patients. Given that other forms of warming could not be included in this research, further studies are recommended to explore scholarly evidence on the efficacy of these methods.

Microphysical Interactions Determine the Effectiveness of Solar Radiation Modification via Stratospheric Solid Particle Injection

AbstractRecent studies have suggested that stratospheric aerosol injection (SAI) of solid particles for climate intervention could reduce stratospheric warming compared to injection of . However, interactions of microphysical processes, such as settling and coagulation of solid particles, with stratospheric dynamics have not been considered. Using a global chemistry‐climate model with interactive solid particle microphysics, we show that agglomeration significantly reduces the backscatter efficiency per unit of injected material compared to mono‐disperse particles, partly due to faster settling of the agglomerates, but mainly due to increased forward‐ over backscattering with increasing agglomerate size. Despite these effects, some materials substantially reduce required injection rates as well as perturbation of stratospheric winds, age of air and stratospheric warming compared to injection of , with the most promising results being shown by 150 nm diamond particles. Uncertainties remain as to whether stratospheric dispersion of solid particles is feasible without formation of agglomerates.

The influence of specific weather types on stroke occurrence: an analysis of 23,000 patients from Augsburg, Germany

ABSTRACT For the first time, the relationships between large-scale weather types and local stroke events in the urban area of Augsburg, Germany are analyzed. Over 23,000 stroke cases (2006 – 2020) were standardized to account for long-term trends and seasonality. Using ERA5 reanalysis data, a composite analysis identified stroke-related atmospheric variables, while seasonal weather types were classified via the neural network algorithm of self-organizing maps. Cyclonic westerlies during the cold season, which transport warm air masses from the Atlantic Ocean to Germany, were a major risk factor for ischemic stroke, while colder easterly conditions reduced stroke incidence. In the warm season, both anticyclonic conditions and westerly/northerly air advection, leading to slightly warmer or distinctly colder temperatures, were linked to increased ischemic stroke risk. Additionally, hemorrhagic strokes in the cold season were triggered by weather conditions contrary to those associated with ischemic strokes and transitory ischemic attacks.

Surface temperature modulations induced by Rossby Wave Breaking over Indian region

Abstract Upper-level Rossby Wave Breaking (RWB) significantly affects surface weather patterns in the subtropical Indian region through influencing wind circulation often resulting in extremes in rainfall and surface temperatures. While the impact of RWB on rainfall is relatively well understood, its role in modulating surface temperatures within the Indian subcontinent is less explored. This study examines the link between pre-monsoon (March to May) RWB events and the occurrence of extreme surface temperatures and heatwaves by considering long-term data of 43 years between 1979 and 2021. We identify 139 RWB events using a potential vorticity (PV) contour searching algorithm over the Indian sub-continent. Our analysis reveals a significant amplification in temperature both to the west and east of the breaking PV streamers. These temperature anomalies, which last for 3–4 days during the breaking events, strongly correlate with the maximum day of breaking. Further, regression analyses explain the reasons behind the temperature enhancement mainly on the western and eastern flank of RWB. It indicates a positive association between upper-level PV anomalies and anticyclonic circulations at 250 hPa, along with subsidence at 500 hPa, leading to drier conditions in the western and eastern regions of the PV streamers. Additionally, the decomposition of temperature anomalies during RWB events reveals that surface warming is primarily driven by diabatic heating on both sides of the centroid, with stronger adiabatic heating in regions of upper-level anticyclonic circulation and significant temperature advection predominantly on the western side of the centroid, resulting in dry weather and the poleward movement of warm air toward the ridges near the PV streamers.

Initiation and evolution of urban-induced precipitation under different background wind speeds: Roles of urban breeze circulation and cold pool

Urban-enhanced precipitation is often observed far downwind of cities, suggesting important roles of background wind. This study examines the impacts of background wind on the initiation and evolution of urban-induced precipitation through idealized ensemble large-eddy simulations with different initial background wind speeds of 0, 1, 2, 3, 4, and 5 m s−1. Without background wind, a strong urban breeze circulation (UBC) initiates a relatively large number of cumulus clouds in the urban area, which exhibit greater cloud top heights than those in the rural area. The early-initiated clouds do not produce precipitation but moisten the middle troposphere, assisting later-initiated clouds to develop into deep convective clouds and produce concentrated precipitation in the urban area. As the background wind speed increases, the UBC weakens. Also, the high-humidity area generated by early-initiated clouds is continuously advected away from the urban area. Consequently, the precipitation initiation is delayed as the background wind speed increases. Precipitating clouds are advected downwind and generate a cold pool, and updrafts are repeatedly produced at the downwind boundary of the cold pool. The downwind-advected clouds are fed by the newly produced updrafts, being a long-lived organized precipitation system that produces a considerable amount of precipitation in the downwind area. This feeding effect is most prominent for a moderate background wind (3 m s−1), causing the precipitation amount and duration to be maximized. For stronger background winds, precipitation is initiated by the mechanical lifting of the warm air of the urban boundary layer over the cool rural boundary layer around sunset.

Arctic and Barents Sea ice extent variability and trends in 1979–2022

The aim of the paper is to assess interannual and decadal variability of the Barents Sea and Arctic ice extent in various seasons for the period from 1979 to 2022.The material for the study was satellite data on the Barents Sea and Arctic ice extent, climate indices, oceanographic data obtained during surveys in the Barents Sea by PINRO and other available information on hydrometeorological conditions of the sea in 1979–2022.Methods of descriptive statistics as well as comparative, correlation, regression, harmonic and cluster analyses were applied.Results: The year-to-year changes in the Barents Sea and Arctic ice extent in various seasons are described for 1979–2022. The modern climate changes, manifested in substantial warming of air and water masses in the Arctic, resulted in a considerable ice extent reduction in the studied areas in recent decades. Well-marked negative trends took place in all months and seasons. The annual mean ice extent was decreasing at a rate of 532 thousand km2 per decade in the Arctic, and at a rate of 105 thousand km2 per decade in the Barents Sea. Over the past 40 years, the ice extent in the Arctic has decreased by 14%, and in the Barents Sea — by half (by 51%), while the ice-free period duration has increased in the Barents Sea from one to three months. Hydrometeorological parameters were identified that are most closely related to the ice extent in the Arctic (|r| ≥ 0.40) and Barents Sea (|r| ≥ 0.60). Reliable regression models were developed that explain 45.2 and 88.0% of its variability, respectively. The contribution of individual factors to the ice extent variability explained by regression equations was quantitatively assessed, and the leading role of air temperature was noted.Practical significance: The obtained results are useful for a better understanding of the climate processes occurring in the Arctic and Barents Sea in recent decades and can be used to assess the impact of climate changes on the main objects of Russian fishery in these areas.