Spring Heat Research Articles

Observational study on the surface radiation budget and energy balance closure of grassland in the eastern arid region of Northwest China

Based on the observation data of the meteorological environment monitoring system (QT-1010) and the open vorticity correlation system (LI-7500DS), we used the block aerodynamics and energy balance ratio method to analyze the surface radiation budget and energy balance closure characteristics of the grassland in the eastern arid region of Northwest China at different time scales.We found that (1) The daily variation curve of the surface radiation flux is unimodal, and the variation amplitude of each component is as follows: Rs↓> RL↑> RL↓> Rs↑. (2) The monthly peak of each radiation component occurs in summer, and the time of reaching the peak of different components has a lag. The changes of radiation components in sunny and cloudy days are multi-modal. In the precipitation weather, the fluctuation of each radiation flux is unimodal.The average annual surface albedo () is 0.24, which is higher in winter than in summer. There is a linear relationship between surface albedo and soil moisture. (3) The Net radiation (Rnet) dominates the sensible heat in spring and the latent heat in summer. H/Rnet and Gn/Rnet are both positive in a day, H/Rnet and LE/Rnet fluctuate wildly before and after sunrise, and Gn is dominant at night. (4) The energy closure is manifested as summer > winter > Autumn > spring, and the energy closure is good throughout the year.

Changes in the SST Seasonal Cycle in a Warmer North Pacific without Ocean Dynamical Feedbacks

Abstract Climate models project a significant intensification of the sea surface temperature (SST) seasonal cycle over the subpolar North Pacific due to global warming, with the shallower mixed layer widely recognized as the dominant factor. However, employing slab ocean experiments with only ocean–atmosphere thermal coupling, we find a substantial contribution from changes in surface heat flux to this seasonal cycle intensification. In particular, the stronger Newtonian cooling effect in winter acts as a more potent damping than in summer. This differential damping inhibits the warming in colder seasons, significantly contributing to the intensified SST seasonal cycle in the subpolar North Pacific. In addition, consistent phase shifts in the North Pacific are identified across CMIP6 models. In the northwest North Pacific, a phase advance is associated with anomalous heating in early spring, driven by enhanced warm atmospheric advection from lower latitudes and sea ice melting in marginal seas. In contrast, the southeast North Pacific exhibits a phase delay attributed to the anomalous cooling in spring relative to autumn. This cooling is due to weakened trade winds and increased presence of high clouds. The former leads to stronger evaporative cooling in spring, while the latter impedes shortwave radiation from reaching the ocean.

Climate challenges for fish larvae: Interactive multi-stressor effects impair acclimation potential of Atlantic herring larvae

Fish early life stages are particularly vulnerable and heavily affected by changing environmental factors. The interactive effects of multiple climate change-related stressors on fish larvae remain, however, largely underexplored. As rising temperatures can increase the abundance and virulence of bacteria, we investigated the combination of a spring heat wave and bacterial exposure on the development of Atlantic herring larvae (Clupea harengus). Eggs and larvae of Western Baltic Spring-spawners were reared at a normal and high temperature ramp and exposed to Vibrio alginolyticus and V. anguillarum, respectively. Subsequently, mRNA and miRNA transcriptomes, microbiota composition, growth and survival were assessed. Both high temperature and V. alginolyticus exposure induced a major downregulation of gene expression likely impeding larval cell proliferation. In contrast, interactive effects of elevated temperature and V. alginolyticus resulted in minimal gene expression changes, indicating an impaired plastic response, which may cause cellular damage reducing survival in later larval stages. The heat wave alone or in combination with V. alginolyticus induced a notable shift in miRNA expression leading to the down- but also upregulation of predicted target genes. Moreover, both increased temperature and the Vibrio exposures significantly altered the larval microbiota composition, with warming reducing microbial richness and diversity. The outcomes of this study highlight the high sensitivity of herring early life stages towards multiple climate change-related stressors. Our results indicate that interactive effects of rapidly changing environmental factors may exceed the larval stress threshold impairing essential acclimation responses, which may contribute to the ongoing recruitment decline of Western Baltic Spring-Spawning herring.

Intrathermocline Eddy with Lens-Shaped Low Potential Vorticity and Diabatic Forcing Mechanism in the South China Sea

Abstract Intrathermocline eddies (ITEs), characterized by subsurface lens-shaped low potential vorticity (PV), are pervasive in the ocean. However, the abundance and generation mechanisms of these low-PV lenses are poorly understood owing to their weak surface signals and awkward sizes, which present an observational barrier. Using in situ observations of the northern South China Sea (NSCS), a typical ITE with a lens-shaped low PV at a core depth of 30–150 m and a horizontal size of ∼150 km was captured in May 2021. Combined with PV budget analysis, we investigate the underlying generation mechanism of low PVs within these ITEs using high-resolution reanalysis products. The results suggest that wintertime surface buoyancy loss driven by atmospheric diabatic forcing rather than frictional forcing is a crucial favorable condition for the ITE formation. These enhanced surface buoyancy losses produce a net upward PV flux and decrease PV in the weakly stratified and deep winter mixed layer, which are preconditioned by anticyclonic eddies (AEs). While surface heating in the following spring tends to weaken the surface buoyancy loss and gradually causes a downward PV flux, the surface-injected high PV subsequently caps the low-PV water within the surface-intensified AEs and transforms them into ITEs. Approximately 22% of the 58 AEs detected by satellite altimetry in the NSCS are ITEs. More importantly, the lens-shaped low PVs within them are produced primarily by the enhanced surface buoyancy loss during wintertime. These findings provide a new dynamic explanation for the low-PV generation in ITEs, highlighting the crucial role of atmospheric diabatic forcing. Significance Statement Intrathermocline eddies (ITEs), characterized by a lens-like isopycnal structure that bounds low potential vorticity (PV), are active in the oceanic interior. Although a few previous studies revealed the existence of ITEs in the South China Sea, the source and dynamic generation mechanisms of the lens-shaped low PV still remain elusive. We find that the enhanced surface buoyancy loss due to atmospheric diabatic forcing drives an upward surface PV flux and is identified to produce the low PV. The preexisting anticyclonic eddy, combined with seasonal surface heating in spring, can be easily transformed into the ITE. This study provides a new dynamic understanding for the generation mechanism of ITEs’ low PVs and highlights the contribution of atmospheric diabatic forcing.

Climate Change Impacts on Surface Heat Fluxes in a Deep Monomictic Lake

AbstractTurbulent and radiative energy exchanges between lakes and the atmosphere play an important role in determining the process of lake‐mixing and stratification, including how lakes respond to climate and to climate change. Here we used a one‐dimensional hydrodynamic lake model to assess seasonal impacts of climate change on individual surface heat flux components in Lough Feeagh, Ireland, a deep, monomictic lake. We drove the lake model with an ensemble of outputs from four climate models under three future greenhouse gas scenarios from 1976 to 2099. In these experiments, the results showed significant increases in the radiative budget that were largely counteracted by significant increases in the turbulent fluxes. The combined change in the individual surface heat fluxes led to a change in the total surface heat flux that was small, but sufficient to lead to significant changes in the volume‐weighted average lake temperature. The largest projected changes in total surface heat fluxes were in spring and autumn. Both spring heating and autumnal cooling significantly decreased under future climate conditions, while changes to total surface heat fluxes in winter and summer were an order of magnitude lower. This led to counter‐intuitive results that, in a warming world, there would be less heat not more entering Lough Feeagh during the springtime, and little change in net heating over the summer or winter compared to natural climate conditions, projected increases in the volume‐weighted average lake temperature were found to be largely due to reduced heat loss during autumn.

The effects of spring versus summer heat events on two arid zone plant species under field conditions.

Heatwaves are increasingly occurring out-of-season, which may affect plants not primed for the event. Further, heat stress often coincides with water and/or nutrient stress, impairing short-term physiological function and potentially causing downstream effects on reproductive fitness. We investigated the response of water-stressed arid-zone Solanum oligacanthum and Solanum orbiculatum to spring vs summer heat stress under differing nutrient conditions. Heat stress events were imposed in open-topped chambers under in situ desert conditions. To assess short-term impacts, we measured leaf photosystem responses (Fv/Fm) and membrane stability; long-term effects were compared via biomass allocation, visible damage, flowering and fruiting. Plants generally fared more poorly following summer than spring heat stress, with the exception of Fv/Fm. Summer heat stress caused greater membrane damage, reduced growth and survival compared with spring. Nutrient availability had a strong influence on downstream effects of heat stress, including species-specific outcomes for reproductive fitness. Overall, high temperatures during spring posed a lower threat to fitness than in severe arid summer conditions of high temperature and low water availability, which were more detrimental to plants in both the short and longer term. Our study highlights the importance of considering ecologically relevant, multiple-stressor events to understand different species responses to extreme heat.

Long-term Experiment of Hot Spring Heat Recovery Using Rotary Heat Exchanger by Controlling Precipitation

Long-term Experiment of Hot Spring Heat Recovery Using Rotary Heat Exchanger by Controlling Precipitation

A Sweater for You

A Sweater for You Meghana Mysore (bio) It is a terrifying thing to lose your body, I thought as my son Srinivas kneeled before my feet. He was scrubbing my toes because I had become useless and could not wash my own feet. He scrubbed around the gold ring around my big toe, which had become faded. My husband Keshav bought it for me when we first married. Those days were still vivid to me though he was gone now and I was no longer young. I tried not to think too much of those days. It was unbearable before Srinivas arrived. I could not stand to see myself and only myself in the mirror each morning. All I did was make coffee again and again, even at night. Sometimes I ate bare slices of bread. Once, I turned on a burner and left it on. I went to sleep and my next-door neighbor Pooja smelled the smoke. I only turned it off when she came knocking. I didn't know what would've happened otherwise. Sometimes I dreamed it raged on, the burner, and I slept with my blankets wrapped tight around me. In the dream, I couldn't release myself from them as the smoke crept from the kitchen to the bedroom, and I coughed as the smoke grew until Keshav covered my mouth so hard that I stopped breathing altogether. I didn't tell Srinivas about these dreams, and my other son, Karthik, barely called anymore. When I messaged Karthik, I received only a few words in response. "Busy now amma, Ananya has recital. will call later." Most days, he never called. One morning I was trying to call him and he didn't pick up. That morning, I felt like eating—a rarity since Keshav had died. The guavas on the tree outside had begun to ripen. I walked outside to pick some fruit and saw a beautiful glistening guava up on the branches. I reached for it but missed it, even on my tiptoes, and the next thing I knew I was on my back on the hard ground. I tried to move, but each minuscule motion felt like needles thrashing through my spine. I stayed on the ground for some time until the spring heat subsided and wind brushed through the trees. The crickets began to sing their monotonous song. I somehow made my way back into the house, slowly, holding onto my hip the whole fourteen steps inside, then collapsed on the cot and stayed there for the rest of the night. When I woke, I called Srinivas and told him what happened. He had become my reliable son. "I'll come, Amma. I'll find a way to get a week off work. I can come. Don't worry." He had stayed for months; his job allowed him to work remotely. I wished for him to be selfish like his brother, to not leave his family for me, but if he hadn't, I might have been dead. I suppose somewhere inside I still wanted to live. It had been a week since the hip replacement surgery. The recovery had been slow. Srinivas rubbed calamine lotion onto my feet. "Your feet have become very cracked," he said. His feet had been cracked like this too when he was a child, and I used to rub calamine lotion all over them after he returned from playing in the cricket field with Karthik. [End Page 208] I've become you as a child, I thought. I didn't speak much these days because most of what I said was interpreted by Srinivas as a cry for help. I must have seemed too crazy or sick to say anything normal. "What, Amma?" he asked. I knitted my lips together tight. He went back to scrubbing the lotion on my feet. As Srinivas grew into an adult he spent his days trying to get away from the house and his father. I understood his impulse, though I would never say it out loud. Karthik, the older of my sons, was often at school late, so I would be left alone in the house with Keshav...

Numerical study of aerosol radiative forcing over East Asia and the impacts of cloud coverage and relative humidity

The spatiotemporal characteristics of aerosol direct radiative forcing (RF) and the relative contributions from aerosol species, as well as the impacts of cloud coverage and relative humidity on aerosol direct RF were quantified in East Asia using a regional climate model. Generally, the total aerosol produces net RFs of −12.78 W m−2 at surface, 1.72 W m−2 at TOA (top-of-atmosphere), and atmospheric heating of 14.50 W m−2. It was found that dust, black carbon, and sulfate made dominant contributions to the total RF at surface and TOA, and all aerosol species induced atmospheric heating, whereas more than 96% of which was induced by dust and black carbon. The remarkably seasonally decreasing tendency of the total and the absorbing aerosol RFs was found from spring to winter at surface. Moreover, dust contributes relatively larger to the positive TOA RF and to the atmospheric heating in spring and summer, which were weakened and smaller than black carbon in other seasons. Sensitivity studies further demonstrated cloud strengthens the dust and black carbon direct RF and weakens the other species direct RF at TOA, while induces weak direct RFs of all aerosol species at surface. Particularly, cloud induced larger reduction in dust longwave RF than shortwave leads to remarkable enhanced net surface direct RF of dust, especially in JJA. The aerosol swelling effect induced by relative humidity strengthens aerosol direct RF at both TOA and surface. The percentage changes in aerosol RF and its seasonal amplitude by cloud are considered larger at TOA than surface, however, the effects of relative humidity distribute relatively uniform vertically. Meteorological factors impact on scattering aerosols direct RF is assumed larger than absorbing aerosols. The impacts of cloud on aerosol direct RF are compared to the relative humidity and are supposed to be more important at TOA and surface.

The Spring Heat Source Over the Qinghai–Tibetan Plateau Linked With the Winter Warm Arctic–Cold Siberia Pattern Impacting Summer Drought in China

The atmospheric heat source over the Qinghai–Tibetan Plateau (QTP) in spring has an important impact on the climate of the surrounding regions. However, there have been few systematic studies of the dominant mode of the heat source and the cross-seasonal connections with the preceding winter and following summer. Using a distinct empirical orthogonal function (DEOF) decomposition method, we obtained the leading mode of the spring heat source over the QTP and the surrounding regions and analyzed its precursors in the previous winter and lagging effects in the following summer. Our results show that the first mode (DEOF1) was characterized by a warm plateau and cold surrounding regions. The positive phase was significantly associated with the warm Arctic–cold Siberia (WACS) pattern (r = 0.39, p = .01) and the La Niña-like SST anomaly in the Pacific in the preceding winter and the following East Asian subtropical summer monsoon (r = –0.44, p = .01), resulting in a widespread drought in China during the following summer. The cold anomaly in Siberia and the warm anomaly at mid-to low latitudes in winter associated with the WACS pattern coincide with the DEOF1 mode of the heat source over the QTP and its surroundings through change of meridional temperature gradient and wave-flow interactions. A mid-latitude wave train excited by the WACS and the thermal difference in the meridional direction of the spring DEOF1 mode caused high-pressure anomalies over the QTP and the mid-latitude region of East Asia, influencing central and eastern China. This anomaly was not conducive to the northward advancement of the East Asian summer monsoon, resulting in drought in most of China in spring and summer. The cross-seasonal relationship between the main mode of the spring heat source on the QTP and the preceding winter WACS pattern and the following East Asian summer monsoon can be used as a reference in climate prediction studies.

Association of the shift of the South Asian high in June with the diabatic heating in spring

Association of the shift of the South Asian high in June with the diabatic heating in spring

Season-sex interaction induces changes in the ecophysiological traits of a lizard in a high altitude cold desert, Puna region.

Functional traits are those characteristics of organisms that influence the ability of a species to develop in a habitat and persist in the face of environmental changes. The traits are often affected by a multiplicity of species-dependent and external factors. Our objective was to investigate thermal biology of Liolaemus ruibali in a high altitude cold desert at the arid Puna region, Argentina. We address the following question: do sex and seasonal variations in environmental temperature induce changes in the ecophysiological traits? We measured and compared the operative temperatures between fall and spring; and between sexes and seasons, we compared the ecophysiological traits of lizards, microenvironmental temperatures and thermoregulatory behavior. Air and operative temperatures were different between seasons. We found an effect of season-sex interaction on field body temperatures, preferred temperatures, panting threshold and thermal quality. The voluntary and critical temperatures presented seasonal variation in relation to changes in environmental temperatures, suggesting thermal acclimatization. We note behavioral changes between seasons, with the substrate being the main resource for gaining heat in spring. We conclude that Liolaemus ruibali is an efficient thermoregulator; it is a eurythermic lizard and presents phenotypic plasticity in different ecophysiological and behavioral traits induced by sex and seasonality. In addition, we predict that this population could buffer the effects of projected global warming scenarios.

The quantitative comparison of contributions from vapour and temperature to midsummer precipitation in China under the influence of spring heat source over Tibet Plateau

AbstractThe thermal forcing of the Tibet Plateau (TP) causes circulation anomalies that may affect the East Asian monsoon. Hence, summer precipitation in China has a close relation to the previous heat source over TP. The saturation of the atmosphere is the precondition of precipitation, so variations of vapour and temperature adjust the generation of precipitation synergistically. The heating of TP exerts impacts on summer precipitation in China, essentially, through modulating vapour and temperature. The goal of this study is to identify whether the variations of temperature or vapour dominate in the end. Besides, according to the heating characteristics over TP, a more accurate area of spring (March–May) heat source is chosen to indicate the midsummer (July) precipitation in China. The configuration of contributions of temperature and vapour can be divided into two cases. One is that vapour and temperature both increase or decrease, so they play inverse roles. It is easy to find the dominant element in this circumstance. The other is that vapour and temperature have concurrent effects. In this case, their significances need to be further compared. The method based on the linkage of the precipitation and relative humidity is used to quantitatively compare the effects of temperature and vapour. The results are robust and can complement the qualitative analysis with circulations and temperature. In years that there is intense heating on west TP, the Yangtze River basin (YZRB) is controlled by more vapour transport from oceans. The downstream of the Yellow River basin (YLRB) is affected by the dry and cold northerly winds. Dominance analysis shows that vapour general plays a more important role in two major river basins. Maybe not exactly coincide with someone's envision, not all the places are dominated by the vapour. Around northeast China, temperature contributes little more than vapour.

Experimental study on the influence of different heating methods on thermal runaway of lithium-ion battery

Due to the fact that lithium ions are subjected to different thermal abuses during services, this paper introduces heating of lithium-ion batteries with different State of Charge (SOC) by means of a spring heating ring and a cylindrical heating rod. The results show that with the increase of SOC, the thermal runaway phenomenon of lithium-ion battery increases dramatically. Under the same SOC, owing to the better heat transfer efficiency of the spring heating coil and the more uniform internal heating of the battery, the temperature of the battery heated by cylindrical heating rod and the start temperature of thermal runaway are higher than that of the battery heated by spring heating coil. The energy required to cause thermal runaway of battery decreases with the increase of SOC. The first decrease of battery voltage is the signal of obvious self-generated heat inside the battery. Under the same SOC, the battery heated by cylindrical heating rod needs to absorb more heat to touch the thermal runaway. The battery will produce toxic gas after thermal runaway, and the severity of battery thermal runaway directly affects the proportion of electrolyte. This work can provide some guidance for the domino effect and early warning of thermal runaway of lithium-ion batteries.

Premature leaf discoloration of European deciduous trees is caused by drought and heat in late spring and cold spells in early fall

While leaf discoloration of many temperate and boreal tree species has been delayed in response to global warming, climatic stress such as severe drought can cause premature leaf discoloration. We investigated whether leaf discoloration is synchronized within and across tree species and under which climatic conditions premature leaf discoloration occurs (i.e. exceptionally early dates of leaf discoloration within the lower 5 % percentile). We analyzed 16’865 observations of leaf discoloration from nine deciduous tree species (beech, silver birch, horse chestnut, larch, large-leaved linden, rowan, small-leaved lime, sweet chestnut, sycamore) from a phenological network in Switzerland. We considered observations of leaf discoloration from 222 stations that were located between 200 and 1933 m and covered the period 1971–2018. Leaf discoloration of most species has been significantly delayed by 1.5 to 3.3 days per decade from 1996 to 2018. We detected a synchronous temporal pattern of leaf discoloration both within and across species. For most species, premature leaf discoloration occurred in years with very warm and dry spring-summer conditions or with very cool fall temperatures. Premature leaf discoloration was observed in 10-40 % of all stations during these years, whereas the long-term mean was 4-6 %. Growing degree days in May and June were significantly higher and the climatic water balance in June was significantly lower in years with premature leaf discoloration compared to years with regular leaf discoloration, especially for drought sensitive species such as beech. Similarly, minimum temperatures in September were consistently lower in years with premature leaf discoloration. Our study provides the first systematic and long-term assessment under which climatic conditions premature leaf discoloration occurs. We expect that the future increase in the frequency and severity of droughts in Europe will likely increase the risk of premature leaf discoloration.

Hot and cold flavors of southern California\u2019s Santa Ana winds: their causes, trends, and links with wildfire

Santa Ana winds (SAWs) are associated with anomalous temperatures in coastal Southern California (SoCal). As dry air flows over SoCal’s coastal ranges on its way from the elevated Great Basin down to sea level, all SAWs warm adiabatically. Many but not all SAWs produce coastal heat events. The strongest regionally averaged SAWs tend to be cold. In fact, some of the hottest and coldest observed temperatures in coastal SoCal are linked to SAWs. We show that hot and cold SAWs are produced by distinct synoptic dynamics. High-amplitude anticyclonic flow around a blocking high pressure aloft anchored at the California coast produces hot SAWs. Cold SAWs result from anticyclonic Rossby wave breaking over the northwestern U.S. Hot SAWs are preceded by warming in the Great Basin and dry conditions across the Southwestern U.S. Precipitation over the Southwest, including SoCal, and snow accumulation in the Great Basin usually precede cold SAWs. Both SAW flavors, but especially the hot SAWs, yield low relative humidity at the coast. Although cold SAWs tend to be associated with the strongest winds, hot SAWs tend to last longer and preferentially favor wildfire growth. Historically, out of large (> 100 acres) SAW-spread wildfires, 90% were associated with hot SAWs, accounting for 95% of burned area. As health impacts of SAW-driven coastal fall, winter and spring heat waves and impacts of smoke from wildfires have been recently identified, our results have implications for designing early warning systems. The long-term warming trend in coastal temperatures associated with SAWs is focused on January–March, when hot and cold SAW frequency and temperature intensity have been increasing and decreasing, respectively, over our 71-year record.

Interannual covariability of summer monsoon precipitation in Yunnan, China, and diabatic heating anomalies over the Arabian Sea–Bay of Bengal

Covariability of summer monsoon precipitation in Yunnan and diabatic heating anomalies over the Arabian Sea–Bay of Bengal (AS–BOB) is analyzed using ERA-Interim monthly reanalysis data and monthly mean precipitation data from 124 stations across Yunnan, China. Singular value decomposition analysis indicates a seesaw pattern associated with the diabatic heating over the AS–BOB and summer monsoon precipitation in Yunnan over interannual timescales. When the diabatic heating over the AS–BOB is weaker (stronger) than the climatology during the summer monsoon season, more (less) summer monsoon precipitation generally occurs in Yunnan. A significant correlation between the diabatic heating over the AS–BOB and summer monsoon precipitation in Yunnan begins in late spring–early summer and persists throughout the summer. The AS–BOB diabatic heating in late spring–early summer may thus have a prediction potential for summer monsoon precipitation in Yunnan. The anomalous low-level winds associated with the diabatic heating anomalies over the AS–BOB influence the Indian summer monsoon trough, the vertical motion in Yunnan, and then the summer monsoon precipitation. Numerical experiments based on a linear baroclinic model confirm the key physical process revealed in the observational diagnosis. These experiments also indicate that the diabatic heating over the AS–BOB has a greater impact on summer monsoon precipitation in Yunnan than does diabatic heating around Yunnan on the atmospheric circulation over the AS–BOB. The diabatic heating anomalies over the AS–BOB contributed to the severe summer droughts in Yunnan in 2010, 2011, and 2013 by influencing the circulation.

Exploring atmospheric circulation leading to three anomalous Australian spring heat events

Australian maximum temperatures have reached record values in recent austral springs and are projected to increase further in a warming world. We focus on three record spring heat events in September 2013, October–November 2014 and October 2015, and examine the anomalous atmospheric circulation associated with these events in reanalysis and a sub-seasonal to seasonal prediction system, POAMA, to identify factors contributing to extreme heat over Australia. We find that an anomalous equivalent barotropic cyclonic circulation southwest of Australia and a quasi-stationary wave train formed by an upper-troposphere anticyclonic circulation over southern Australia and barotropic cyclone southeast of Australia are important features in these heat events, though the wave train was only observed in the latter two events. This wave train appears to be linked to the tropics, and particularly the tropical Indian Ocean, suggesting that teleconnections to the tropical Indian Ocean can be important for monthly spring extreme heat formation in Australia. However, the forecast relationship with the tropical Pacific Ocean was over-represented at the cost of the relationship between the Indian Ocean and upper-troposphere anomaly, limiting the ability of POAMA to forecast the full extent of the month- or 2 month-long heat extremes at zero lead time. This means that the model might underestimate the magnitude of future extreme heat events in spring, a factor that should be assessed in the next generation of seasonal forecast models.

Micrometeorological Characteristics in the Atmospheric Boundary Layer in the Seoul Metropolitan Area during High-Event and Non-event Days

This study focused on comparing the meteorological conditions in the Atmospheric Boundary Layer (ABL) on high-event days and non-event days in the Seoul Metropolitan Area (SMA). We utilized observed PM10 and meteorological variables at the surface as well as at the upper heights. The results showed that high-event days were consistently associated with lower wind speed, whereas wind direction showed no particular difference between high-event and non-event days with frequent westerlies and northwesterlies for both cases. During high-event days, the temperature was much warmer than the monthly normal values with a sharp increasing trend, and Relative Humidity (RH) was higher than the monthly normal, especially on high-event days in February. During high-event days in spring, a double inversion layer was present at surface and upper heights. This indicates that stability in the multi-layer is an important indicator of higher PM10 concentrations. Net radiation in spring and winter is also closely associated with higher PM10 concentrations. Strong net radiation resulted in large sensible heat, which in turn facilitated a deeper mixing height with diluted PM10 concentrations; in contrast, PM10 concentrations were higher when sensible heat in spring and winter was very low. We also confirmed that convective and friction velocity was higher on non-event days than on high-event days, and this was especially obvious in spring and winter. This indicated that thermal turbulence was dominant in spring, whereas in winter, mechanical turbulence was dominant over the SMA.

Modulation of springtime surface sensible heating over the Tibetan Plateau on the interannual variability of East Asian dust cycle

Abstract. Previous observational evidence and numerical simulations have revealed that the surface sensible heating in spring (March–April–May, MAM) over the Tibetan Plateau (TPSH) can affect the Asian regional hydrological cycle, surface energy balance, and climate through altering atmospheric heat source of the Tibetan Plateau (TP). This study aims to investigate the impacts of MAM TPSH on the interannual variability of East Asian dust cycle by using CAM4-BAM (version 4 of the Community Atmosphere Model coupled to a bulk aerosol model), MERRA-2 (version 2 of the Modern-Era Retrospective analysis for Research and Applications) surface dust concentration, and TPSH measurements. Our simulations show that the surface dust concentrations over the East Asian (EA) dust source region and over the northwestern Pacific (NP) in MAM are significantly positively correlated with TPSH, with regionally averaged correlation coefficients of 0.49 for EA and 0.44 for NP. Similar positive correlations are also shown between the MAM TPSH measurements averaged over the 73 observation sites and the surface dust concentration from MERRA-2. Simulation-based comparisons between strongest and weakest TPSH years reveal that, the MAM surface dust concentration in the strongest TPSH years increases with relative differences of 13.1 % over EA and 36.9 % over NP. These corresponding differences are found in MERRA-2 with 22.9 % and 13.3 % over EA and NP, respectively. Further simulated results show that the processes of whole dust cycles (e.g., dust loading, emission, and transport, as well as dust deposition) are also significantly enhanced during the strongest TPSH years over EA and NP. Through enhancing the TP heat source, stronger TPSH in MAM generates an anticyclonic anomaly in middle and upper troposphere over the TP and over the downstream Pacific region, respectively. These atmospheric circulation anomalies induced by the increased TPSH result in increasing the westerly winds over both EA and NP, which in turn increases dust emissions over the dust source, and dust transport over these two regions, as well as the regional dust cycles. These results suggest that addressing the East Asian dust changes in the future climates requires considering not only increasing greenhouse gas emissions but also the variations of the TP's heat source under global warming.