Extreme Heat Waves Research Articles

Revealing trends in extreme heatwave intensity: applying the UNSEEN approach to Nordic countries

The increase in heatwave intensity, causing heat stress and crop failures in many regions is a concerning impact of global climate change. In northern Europe, significant interannual variability previously prevented robust assessments of trends in heat extremes. However, with a large-ensemble seasonal hindcasts and archived forecasts dataset covering 1981–2022 multiple realisations of weather patterns can be pooled and assessed. What are recent trends of extreme temperatures? Has the risk for a 100-year heatwave event increased in Northern Europe? We apply the UNSEEN (UNprecedented Simulated Extremes using ENsembles) approach to assess the credibility of the model ensemble and use non-stationary extreme value analysis to quantify recent trends in extreme 3-day heatwaves in late spring and early summer (May to July). We find significant non-stationarity and positive trends in annual maximum heatwave intensity. We also show that heatwave volatility, i.e. the risk of clearly outstanding heatwaves, is highest in central Scandinavia.

Simulating the Western North America heatwave of 2021 with analogue importance sampling

During the summer of 2021, the North American Pacific Northwest was affected by an extreme heatwave that broke previous temperature records by several degrees. The event caused severe impacts on human life and ecosystems, and was associated with the superposition of concurrent drivers, whose effects were amplified by climate change. We evaluate whether this record-breaking heatwave could have been foreseen prior to its observation, and how climate change affects North American Pacific Northwest worst-case heatwave scenarios. To this purpose, we use a stochastic weather generator with empirical importance sampling. The generator simulates extreme temperature sequences using circulation analogues, chosen with an importance sampling based on the daily maximum temperature over the region that recorded the most extreme impacts. We show how some of the large-scale drivers of the event can be obtained form the circulation analogues, even if such information is not directly given to the stochastic weather generator.

Environmental Refuges during Summertime Heat and Elevated Ozone Levels: A Preliminary Case Study of an Urban “Cool Zone” Building

The combination of extreme heat waves and ozone pollution is a major health hazard for urban populations in the summertime, particularly for the most sensitive groups such as children, the elderly, the unsheltered, and those with pre-existing health conditions. The “Cool Zone Program”, operated by the Salt Lake County Aging and Adult Services, identifies areas in the county and Salt Lake City facilities where members of the public can escape the summer heat, hydrate, and learn about available programs. We measured indoor and outdoor temperature and ozone for a pilot study at a designated Cool Zone location during the 22 August–6 September 2019 period and found that the building provided substantial heat relief and protection from more than 75% of the outdoor ozone. We observed a nearly 35 min delay for the outdoor ozone to be reflected on the indoor readings, providing an action window for ventilation scheduling changes to protect against the highest ozone levels during the day. Our findings show that it is critical to re-think and formulate action plans to protect vulnerable populations from excessive heat and pollution events during the summer.

Thermodynamic characteristics of extreme heat waves over the middle and lower reaches of the Yangtze River Basin

In August 2022, an exceptionally long-lasting heat wave (HW) affected the middle and lower reaches of the Yangtze River basin. This study uses the JRA55 daily reanalysis datasets to elucidate the thermodynamic characteristics of the daily evolution of historical extreme HWs in this region via the heat budget equation. HWs are generally characterized by the occurrence of anticyclonic circulation anomaly throughout the troposphere and positive air temperature anomaly with the maximum amplitude in the boundary layer. The anticyclonic anomaly can induce compression heating in the entire troposphere and warm zonal advection in the boundary layer. Meanwhile, due to the reduced cloud cover, more shortwave radiation reaches the ground surface, and the sensible heat flux becomes an important source of diabatic heating before the onset of HWs. The accumulated excessive heat in the HWs is primarily damped through the emission of longwave radiation and meridional thermal advection. For the HW in August 2022, its extreme persistence is mainly caused by prolonged adiabatic heating, enhanced diabatic heating during the developing stage and weakened diabatic cooling during the decay stage. The upper-level portion of the anticyclonic circulation anomalies is linked to the strengthened South Asia High. After applying the state-of-the-art dynamic metric, i.e., local finite wave activity, we reveal that the formation of the anomalous South Asia High in August 2022 is associated with the Stokes drift flux rather than the dispersion of Rossby wave energy. This characteristic sets it apart from other extreme HWs.

Relative Contributions of Large‐Scale Atmospheric Circulation Dynamics and Anthropogenic Warming to the Unprecedented 2022 Yangtze River Basin Heatwave

AbstractThe unprecedented 2022 Yangtze River Basin (YRB) heatwave is a threat to human society and natural ecology, so the understanding of its underlying drivers is critical to regional climate adaptation and resilience. Here we conducted a multi‐method attribution analysis on the contribution of atmospheric circulation change and anthropogenic impacts to the occurrence probability and intensity of this extreme heatwave. Based on the nonstationary statistical analysis, the 2022 YRB heatwave is a 1‐in‐900‐year event and a 1‐in‐110‐year event with and without considering the 2022 YRB heatwave in the fitting, respectively. The large‐scale meteorological condition analysis shows that the 2022 YRB heatwave is featured with an anomalous high‐pressure system that favors a hot and dry atmospheric column, overlaid by anomalous subsidence and clear skies which leads to warming and greater solar heating. The ensemble constructed circulation analogue analyses show that the circulation anomaly fails to explain the observed 2022 YRB SAT anomalies fully. Specifically, 46% (0.132 ± 0.027°C decade−1) of the observed SAT trend during 1979–2022 (0.290 ± 0.048°C decade−1) is caused by anthropogenic warming and the associated thermodynamic feedback, while the remaining 54% (0.157 ± 0.038°C decade−1) of the trend is caused by changes in the large‐scale atmospheric circulation. Our findings on changes in atmospheric circulation patterns associated with YRB heatwave and anthropogenic contributions to YRB heatwave could provide valuable information for climate adaptation and mitigation strategies in the context of a warming climate.

Mechanical performance of CRTS II slab tracks in reinforced-unreinforced transition zone in extreme heat events

Anchors have been widely utilized to reinforce the CRTS II slab tracks. The mechanical performance of the tracks in the reinforced-unreinforced transition zone exposed to extreme heat waves can be very complex due to the difference in mechanical properties between the two kinds of track segments. This paper investigates the damage behavior of the tracks in the reinforced-unreinforced transition zone in extreme heat events. A finite element model of the CRTS II slab track in the transition zone has been established and validated, in which the nonlinear mechanical properties of track materials and interfaces are considered by applying the Concrete Damaged Plasticity model and the Cohesive Zone Model respectively. The nonlinear temperature field in the track structure in extreme heat events is applied to the model. Structural damage of the track, including slab-end arching and interfacial failure, in the transition zone under extreme heat is thoroughly investigated. In particular, the effects of joint use of post-installed reinforcement anchors and other track maintenance measures like interface adhesives and concrete joint restoration are studied. The following conclusions are drawn: (1) The more reinforced track-slabs in the transition zone, the milder the track diseases including slab-end arching and interfacial gapping. (2) Joint use of anchor installation and other maintenance measures such as interface adhesives and concrete joint restoration shows a better effect on mitigating track damage than using post-installed reinforcement anchors solely. (3) Concrete joint restoration overweighs interface adhesives in terms of reducing slab-end arching and interfacial damage when they are jointly used with post-installed reinforcement anchors. (4) In the transition zone, track damage surges when the air temperature increases from 42 ℃ to 47 ℃, which is the temperature range for an extreme heat wave. Monitoring of track state in the transition zones is necessary during extreme heat waves. The novel findings are expected to provide some insights into the mechanical performance of slab tracks and help to prevent potential damage to the tracks in the transition zone, which is a common and practical issue in railway engineering.

A Global Assessment of Heatwaves Since 1850 in Different Observational and Model Data Sets

AbstractWe show that ModE‐Sim, a global ensemble of atmospheric model simulations that uses observed ocean boundary conditions and radiative forcings providing 36 members with daily climate information can be used to in‐depth analyze the known spatial and temporal variability of heatwaves in the Northern Hemisphere and Australia during the past 160 years. It can also be used to study actual past extreme events like heatwaves during the El Nino 1877/1878. To analyze past heatwaves we use a novel approach of a transient baseline climatology and compare to different observational data sets. Furthermore, we analyze sea surface temperature anomalies during the most extreme heatwave summers in North America, Europe and Australia and identify the most prominent anomaly patterns over the Subpolar North Atlantic and in the Central Pacific. Using a large ensemble of forced simulations, like ModE‐Sim can consequently contribute to a better understanding of preindustrial heatwaves, their decadal variability and their driving mechanisms.

Underappreciated Emission Spikes From Power Plants During Heatwaves Observed From Space: Case Studies in India and China

AbstractThe frequency, intensity, and duration of extreme heatwaves are projected to increase in the global context of climate change. However, evidence of how anthropogenic emissions respond to heatwaves and further impact air quality remains elusive. Here, we use satellite remote sensing measurements alongside chemical transport model simulations to reveal abrupt variations in primary and secondary air pollutants introduced by extreme heatwaves. We highlight evidence from China and India, where satellite sulfur dioxide (SO2) and nitrogen dioxide (NO2) columns over thermal power plants enhance consistently responding to heatwaves. We attribute such spiked emissions to soaring electricity use and demonstrate that bottom‐up inventories underestimate the emissions from the power sector by 34.9% for the selected case. Elevated emissions facilitate fine particulate matter (PM2.5) and ozone (O3) formation over thermal power plants in an inhomogeneous manner, due to the combined effect of atmospheric oxidizing capacity, thermal decomposition of peroxyacetyl nitrate, planetary boundary layer rise, and air stagnation. Our results underscore the emerging challenge of pollution control attributable to the increasing climate penalty and the necessity of targeted control strategies and alternative energy sources during heatwaves.

Observational Evidence Reveals Compound Humid Heat Stress‐Extreme Rainfall Hotspots in India

AbstractSequential climate hazards, such as “warm and wet” compound extremes, have direct societal implications for highly urbanized regions and agricultural production. While typically extreme temperatures and rainfall are inversely correlated during the summer, extreme humid heatwaves often lead to atmospheric instability and moisture convection, increasing the likelihood of extreme precipitation (EP). Little is known about how heatwave characteristics, such as peak intensity and duration, influence EP at a regional scale. Using high‐resolution, sub‐daily station‐based observational records over five decades (1971–2021) across India, we find a robust increase in the frequency of compound humid heat‐peak precipitation events in all seasons. Our sensitivity analysis of the impact of humid heatwave characteristics on the subsequent sub‐daily rainfall extremes reveals that, with an increase in peak heatwave intensity for a given heatwave duration, >50% of sites show an increase in the magnitude of rainfall; conversely, with an increase in heatwave duration for a given peak heatwave intensity, around 67% sites show a decline in sub‐daily rainfall extremes. An asymmetrical shift toward above‐average precipitation extremes in response to humid heat stress is mainly clustered around low‐elevation, densely populated coastal areas and the irrigation‐intensive Indo‐Gangetic Plains.

The Pacific Northwest Heat Wave of 25–30 June 2021: Synoptic/Mesoscale Conditions and Climate Perspective

Abstract An unprecedented heat wave occurred over the Pacific Northwest and southwest Canada on 25–30 June 2021, resulting in all-time temperature records that greatly exceeded previous record maximum temperatures. The impacts were substantial, including several hundred deaths, thousands of hospitalizations, a major wildfire in Lytton, British Columbia, Canada, and severe damage to regional vegetation. Several factors came together to produce this extreme event: a record-breaking midtropospheric ridge over British Columbia in the optimal location, record-breaking midtropospheric temperatures, strong subsidence in the lower atmosphere, low-level easterly flow that produced downslope warming on regional terrain and the removal of cooler marine air, an approaching low-level trough that enhanced downslope flow, the occurrence at a time of maximum insolation, and drier-than-normal soil moisture. It is shown that all-time-record temperatures have not become more frequent and that annual high temperatures only increased at the rate of baseline global warming. Although anthropogenic warming may have contributed as much as 1°C to the event, there is little evidence of further amplification from increasing greenhouse gases. Weather forecasts were excellent for this event, with highly accurate predictions of the extreme temperatures. Significance Statement This paper describes the atmospheric evolution that produced an extreme heat wave over the Pacific Northwest during June 2021 and puts this event into historical perspective.

Assessing the thermal risks for residents and visitors in traditional Street-facing Dwellings with Eaves Gallery during an extreme heatwave event

Street-facing Dwelling with Eaves Gallery (SDEG) was built for both commercial activities and residential needs. The Eaves Gallery (EG) and courtyards with small sky view factor (SVF) in those dwellings were shaped to prevent the residences or pedestrians from strong sun radiation, heavy rain, or snow. As a climate-adaptive vernacular architecture, it has lasted for hundreds of years in the large areas along the Yangtze River Basin (YRB) of China. Yet, few studies systematically investigate the thermal conditions of these dwellings and validate their climate resilience quantitatively under heat waves. Concerning the extreme weather caused by climate change, this study investigated indoor, semi-outdoor, and outdoor thermal comfort (OTC) of the SDEG in Xiaohe Town of Hubei province, China during the heatwave event in 2022. While mobile and fixed measurements were carried out to capture the data of thermal environments, the skin temperature measurements were implemented to understand the thermal responses of the households. The results found that SDEG was qualified to help indoor households avoid the heat risk with proper thermal behaviors but cannot provide a safe thermal environment for the pedestrians in the semi-outdoor or outdoor space of the EG street throughout the day. This study demonstrated the negative effects of heatwaves on not only the walking visitors but also the livelihood of the residents, which is an appeal to scholars to attention to the heat risks and thermal behaviors of marginalized groups living in various vernacular buildings within the context of high-temperature scenarios under the heatwave conditions.

A GIS-Based Emotion Detection Framework for Multi-Risk Analysis in Urban Settlements

The application of sentiment analysis approaches to information flows extracted from the social networks connected to particular critical periods generated by pandemic, climatic and extreme environmental phenomena allow the decision maker to detect the emotional states of citizens and to determine which areas are most at risk and require specific resilient adaptation interventions. Of particular relevance today is the need to analyze the multiple risks generated by extreme phenomena in urban settlements in order for the decision maker to identify which areas are most at risk and prepare resilient intervention plans with respect to all the phenomena analyzed. In recent years, the COVID 19 pandemic emergency has forced citizens to undergo specific restrictions to protect their health; to these were added critical issues due to the occurrence of extreme climatic or environmental phenomena. In order to monitor pandemic and climate/environmental multi-risks in urban settlements, we propose a GIS-based framework in which an emotion detection method is applied to determine the prevailing emotional categories in urban study areas during pandemic periods and in the presence of extreme climatic phenomena. The framework was tested on a study area based in the six districts of the city of Bologna (Italy) in order to detect, based on the emotions expressed on social channels, which were the most critical city neighborhoods in pandemic periods and in the presence of extreme heat wave climatic events. The results show that the proposed model can represent a valid tool to support decision makers in identifying the most critical urban areas in the presence of pandemic and climate/environmental multi-risks.

Meteorological impacts on the unexpected ozone pollution in coastal cities of China during the unprecedented hot summer of 2022

Surface ozone pollution under climate warming has become a serious environmental issue. In the summer of 2022, abnormal warming spread over most of the Northern Hemisphere and resulted in the abnormal increase in O3 concentrations. In this study, we focused on the coastal cities in China and investigated the O3 trends in July during 2015 to 2022. Four regions with different locations and emission levels were selected for comparison. A significant increase of O3 concentration in July 2022 were observed in the southern coastal cities (16.7–22.8 μg m−3) while the opposite characteristics were found in the northern coastal cities (decrease of 0.26–2.18 μg m−3). The results indicated various distribution patterns of the O3 concentrations responded to heat wave across China. The weakening of East Asian summer monsoon, extension of the western Pacific subtropical high, significant warming, stronger solar radiation, lower relative humidity, less rainfall and sinking motion of atmosphere in 2022 were beneficial for O3 generation and accumulation in the southern coastal areas. Meteorological changes in July 2022 could lead to an increase of 15.6 % in O3 concentrations in southern coastal cities compared to that in 2015–2021, based on the analysis of machine learning. Air temperature was the main contributor to high O3 concentrations in the coast of Fujian province, while other coastal cities depended on relative humidity. This study indicated the challenge of O3 pollution control in coastal areas under global warming, especially in extreme heat wave events.

Who is the major player for 2022 China extreme heat wave? Western Pacific Subtropical high or South Asian high?

A long-lasting, wide-ranging, and record-breaking extreme high-temperature (EHT) event hit China in the summer of 2022, causing adverse impacts on electricity supply, agriculture, and people's livelihoods. The abnormal persistence of the eastward-shifted South Asian high (SAH) in the upper troposphere was the dominant driver of the durative enhancement of EHT and can explain approximately 55.7% of the event's occurrence, compared to the 14.5% contribution of western Pacific Subtropical high (WPSH) to this event. As the SAH extends eastward, the East Asian westerly jet tends to shift northward, the combination of which could have caused persistent descending motion over East China and thus evoked the EHT. The eastward shift of the SAH in summer 2022 was jointly affected by the preceding-spring record-low snow cover over the Tibetan Plateau, the contemporaneous record-low aerosol levels in East China, the record-high precipitation of Indian subcontinent and the record-high sea surface temperature in the North Atlantic since 1990. Notably, during 1990–2022, for the 2022-like EHT, only 38.43% of that is related to the couple of westward-shifting WPSH and eastward-extending SAH. Approximately 47.6% of 2022-like EHT is just corresponding to an abnormally eastward-extending SAH, suggesting the non-negligible role of SAH in the China's EHT prediction.

The 2022 Extreme Heatwave in Shanghai, Lower Reaches of the Yangtze River Valley: Combined Influences of Multiscale Variabilities

The 2022 Extreme Heatwave in Shanghai, Lower Reaches of the Yangtze River Valley: Combined Influences of Multiscale Variabilities

Comparative analysis of peak-summer heatwaves in the Yangtze–Huaihe River Basin of China in 2022 and 2013: Thermal effects of the Tibetan Plateau

In the peak-summer of 2022, the Yangtze–Huaihe River Basin (YHRB) in China experienced its most extreme heatwaves since 1961. Notably, a rare heatwave also occurred in the YHRB in 2013. However, the Tibetan Plateau (TP) exhibited different thermal conditions during those two years. Observational analysis indicates that the 2013 and 2022 heatwaves were closely related to the local anomalous high pressure. The synergistic effects of the East Asian subtropical jet (EASJ), South Asian high (SAH), western Pacific subtropical high (WPSH), and divergence of moisture, supported the formation and maintenance of the high pressure. Compared to 2013, under the synergistic control of these intensified circulation systems in 2022, which led a broader descending motion and stronger heatwaves prevailed over the YHRB. Also, the surface air temperature of TP reached its highest value in 2022, whereas it was not distinctly anomalous in 2013. Corresponding to the TP thermal anomaly, an abnormal high pressure appeared throughout the troposphere over the northern YHRB. The TP heating contributed to the northward strengthening of the SAH and EASJ, which enhanced the anomalous westerly winds to the north of the anticyclone. Moreover, the WPSH extends westward during strong TP heating years. With the cooperation of high pressure and moisture, there was an anomalous meridional circulation pattern with ascending motion in North China and descending motion in the YHRB, accompanied by reduced cloud cover and increased insolation in the YHRB, leading to further intensification of local heatwaves in 2022. This study demonstrates the significant role of TP thermal anomaly in YHRB heatwaves.

Comparative Analysis of the 2013 and 2022 Record-Breaking Heatwaves over the Yangtze River Basin

The Yangtze River Basin (YRB) experienced record-breaking heatwaves (HWs) during the summers of 2013 and 2022. A comparative analysis of their variations and physical causes was undertaken using ERA5 reanalysis data to determine the similarities and differences between their characteristics and mechanisms. The results show that the duration of the 2013 and 2022 HWs rank as the second and first longest, respectively, since the 1950s. Both HWs were associated with anomalous high pressure and descending motions over the middle and lower reaches of the YRB in conjunction with a westward shift of the Northwestern Pacific subtropical high in summer. These high-pressure anomalies over the YRB led to decreases in total precipitation, soil moisture, and cloud cover and increases in surface solar radiation and air temperature, favoring the 2 HWs. However, high-pressure anomalies associated with the 2013 HWs peaked in July, while those associated with the 2022 HWs peaked in August. The 2022 HWs were of longer duration and higher intensity than those in 2013, which was primarily due to the stronger anticyclonic circulation anomalies induced by more intense Rossby wave trains in the mid to high latitudes in 2022. Notably, the zonal sea surface temperature gradient in the tropical Pacific, which was larger in 2022 than in 2013, played a crucial role in triggering the high-pressure anomalies and extreme HWs over the YRB through forcing distinct patterns of northeastward propagating wave trains over East Asia in the 2 years.

Safeguarding Patients with End-Stage Kidney Disease From Climate-driven Extreme Heat and Hurricanes.

5wPatients with end stage kidney disease (ESKD) who receive in-center hemodialysis are disproportionately vulnerable to extreme weather events, including hurricanes and heat waves, that may disrupt access to healthcare providers, and life-sustaining treatments. This current era of climate-driven compounding disasters is progressively elevating the level of threat to the health and well-being of patients with ESKD. This analysis brings together multi-disciplinary expertise to explore the contours of this increasingly complex risk landscape. Despite the challenges, important advances have been made for safeguarding this medically high-risk patient population. Hemodialysis services providers have devised innovative systems for preparing their patients and sustaining, or rapidly reestablishing, hemodialysis services in the aftermath of a disaster, and maintaining open lines of communication with their caseloads of ESKD patients throughout all phases of the event. A description of lessons learned along the path towards improved patient support in disasters, is provided. The article concludes with a detailed case example, describing dialysis providers' effective response throughout Hurricane Ian's passage across the State of Florida in 2022. Based on lessons learned, this analysis outlines strategies for protecting patients with ESKD that may be adapted for future climate-potentiated disaster scenarios.

Extreme heat wave sampling and prediction with analog Markov chain and comparisons with deep learning

Abstract We present a data-driven emulator, a stochastic weather generator (SWG), suitable for estimating probabilities of prolonged heat waves in France and Scandinavia. This emulator is based on the method of analogs of circulation to which we add temperature and soil moisture as predictor fields. We train the emulator on an intermediate complexity climate model run and show that it is capable of predicting conditional probabilities (forecasting) of heat waves out of sample. Special attention is payed that this prediction is evaluated using a proper score appropriate for rare events. To accelerate the computation of analogs, dimensionality reduction techniques are applied and the performance is evaluated. The probabilistic prediction achieved with SWG is compared with the one achieved with a convolutional neural network (CNN). With the availability of hundreds of years of training data, CNNs perform better at the task of probabilistic prediction. In addition, we show that the SWG emulator trained on 80 years of data is capable of estimating extreme return times of order of thousands of years for heat waves longer than several days more precisely than the fit based on generalized extreme value distribution. Finally, the quality of its synthetic extreme teleconnection patterns obtained with SWG is studied. We showcase two examples of such synthetic teleconnection patterns for heat waves in France and Scandinavia that compare favorably to the very long climate model control run.

Unraveling the Impact of Climate Change on Fish Physiology: A Focus on Temperature and Salinity Dynamics

In recent decades, climate change has significantly altered the environmental dynamics of aquatic ecosystems, profoundly impacting the intricate balance of life within them. This review paper delves into the multifaceted impacts of climate change on the physiology of aquatic life, emphasizing temperature and salinity as pivotal ecological factors unique to aquatic environments. The intricate relationship between rising global temperatures and their repercussions on freshwater and seawater habitats forms the cornerstone of this exploration. Elevated temperatures and escalating frequency of extreme heatwave events have reshaped the paradigm for fish survival, pushing them beyond optimal temperature thresholds. Furthermore, the study delves into the interconnection of seemingly disparate abiotic factors, where heightened greenhouse gas concentrations amplify coastal winds, precipitating coastal upwelling. The consequence—nutrient‐rich yet oxygen‐deprived waters—fuels a cascade of challenges, inducing hypoxic conditions that significantly impact aquatic organisms. The plight of fish, as ectotherms finely tuned to environmental fluctuations, is underscored, illuminating their susceptibility to temperature variations. The direct correlation between external and internal temperatures, exacerbated by climate‐induced fluctuations, accentuates the urgency of addressing climate change’s impact on aquatic habitats. This review disentangles the complex web of interconnected environmental shifts, illuminating their far‐reaching repercussions on the physiology of aquatic life. It emphasizes the imperative for collective endeavors aimed at understanding and addressing the challenges imposed by our evolving climate on these indispensable ecosystems.