Heat Wave Characteristics Research Articles

Associations of Urban and Green Land Covers and Heat Waves in 49 U.S. Cities between 1992 and 2019.

The study aimed to examine how changing land use conditions are related to the occurrence of heat waves. The employed methods were (1) the Urban Expansion Intensity Index (UEII) and the Green Expansion Intensity (GEII) for 49 cities in the U.S. between 1992 and 2019; (2) Spearman correlation analyses of heat wave indicators including frequency, season, duration, and intensity for UEII, and GEII, respectively. Major findings include the following: (1) urban areas have increased rapidly with an average UEII value of 1.5; (2) green Areas have increased at a slow pace, which have a GEII average value of 0.017, where the median value is −0.1, meaning the green area is declining in most U.S. cities; (3) The UEII and heat wave duration show a negative relationship with a significant correlation ( = −0.296 and = 0.04); (4) UEII and heat wave intensity show a positive relationship with a significant correlation ( = 0.32 and = 0.027). It was found that heat wave intensity can be a public health issue in high urban expansion intensity areas. The results imply that cities would be better in a more compact pattern with more expanded green areas to mitigate the negative health impacts of heat waves on citizens in urban areas. It is noticeable that there are some patterns to be investigated further in the context of urban developments and heat wave characteristics.

Dynamics and characteristics of dry and moist heatwaves over East Asia

The increasing frequency of heatwaves over East Asia (EA) is impacting agriculture, water management, and people’s livelihood. However, the effect of humidity on high-temperature events has not yet been fully explored. Using observations and future climate change projections conducted with the latest generation of Earth System models, we examine the mechanisms of dry and moist heatwaves over EA. In the dry heatwave region, anticyclonic circulation has been amplified after the onset of heatwaves under the influence of the convergence of anomalous wave activity flux over northern EA, resulting in surface warming via adiabatic processes. In contrast, the moist heatwaves are triggered by the locally generated anticyclonic anomalies, with the surface warming amplified by cloud and water vapor feedback. Model simulations from phase six of the Coupled Model Intercomparison Project projected display intensification of dry heatwaves and increased moist heatwave days in response to projected increases in greenhouse gas concentrations.

Future population exposure to Australian heatwaves

Heatwaves are Australia’s deadliest natural hazard. Anthropogenic climate change has increased the intensity, frequency and duration of heatwaves over Australia in the past several decades and these trends are projected to worsen in the future. Despite the strong knowledge of heatwave characteristics and their projected changes, there remains a gap in understanding how the Australian population will be exposed to future heatwaves. This study estimates changes in future exposure to heatwaves over Australia. We find that both for continental Australia and its capital cities, the trends in exposure are not projected to increase, but accelerate in the future. For RCP4.5-SSP2 and RCP8.5-SSP5 scenarios, the mean exposure to heatwaves in Australia is projected to increase by ∼29 and ∼42 times by the end of 21st century. Sydney, Melbourne, and Adelaide are the major cities where the population is most exposed to future heatwaves, with this exposure projected to increase by 52, 61, and 56 times respectively under the RCP8.5-SSP5 scenario. The results demonstrate that anthropogenic climate change is the key contributor (over 95%) in enhancing future heatwave exposure and population change on its own plays a relatively minor role (less than 5%). The results of this study are crucial for planning where adaptation measures might be necessary to protect large group of vulnerable Australians to future heatwave exposure.

Future projections of heatwave characteristics and dynamics over India using a high-resolution regional earth system model

Future projections of heatwave characteristics and dynamics over India using a high-resolution regional earth system model

Research on the Characteristics of High-Temperature Heat Waves and Outdoor Thermal Comfort: A Typical Space in Chongqing Yuzhong District as an Example

For the high-density urban space heat wave problem, take the core urban area of the mountainous city of Chongqing as an example, four types of typical urban functional spaces, including commercial areas, residential areas, mountain parks, and riverfront parks, were measured during a heat wave cycle, and the characteristics of high-temperature heat waves in different urban spaces were compared through the analysis of air temperature, surface temperature, relative humidity, solar thermal radiation, and other thermal environment parameters. Combined with the questionnaire research related to the heat comfort of the urban population, the physiological equivalent temperature (PET) was selected to describe the heat sensation of the human body, to summarize the elements and patterns of the influence of heat waves on heat comfort of the population in urban spaces, and to establish a prediction model of outdoor heat comfort in summer. It shows that: (1) temperatures recorded during the heat waves are influenced by urban space elements and are differentiated, with older residential areas recording the highest temperatures, followed by commercial areas, and green park areas comparing favorably with both; (2) crowd thermal comfort is correlated with the thermal environment formed by space elements, PET is significantly positively correlated with air temperature, thermal radiation and surface temperature, and significantly negatively correlated with relative humidity, air temperature and thermal radiation have more influence on thermal comfort has a greater impact, while relative humidity and surface temperature have a relatively small impact; (3) reasonable spatial form and shade planning, vegetation and water body settings, high thermal storage substrate and other design elements can alleviate high-temperature heat waves, reduce the thermal neutral temperature and improve thermal comfort. The research results provide some basis for the investigation of the formation mechanism of high-temperature heat waves in mountainous cities and the optimal design of urban spatial thermal environment.

Centennial changes in heat waves characteristics in Athens (Greece) from multiple definitions based on climatic and bioclimatic indices

Heat Waves (HWs) have received outstanding scientific attention over the past decades, inherent to their devastating societal and environmental effects. Observed and projected trends in HWs characteristics differ between geographical areas and studies, due to varying regional warming rates but also the adoption of different methods to assign a HW. The present study investigates and compares long-term statistics and trends in HWs characteristics (occurrence, duration and timing) from 1900 to 2019, at a very sensitive to climate change area, the eastern Mediterranean, derived from 15 HW definitions. In addition to broadly used definitions based on air temperature thresholds, the study introduces new definitions based on bioclimatic indices, like the UTCI (Universal Thermal Climate Index) and PET (Physiologically Equivalent Temperature). The analysis revealed coherent results, especially between definitions of the same type, but also marked deviations across different definitions, with respect to the magnitude of observed trends. Statistically significant trends (p < 0.01) in the number of HWs events and frequency of HWs days have been found in the area, irrespective of HWs definition. Changes in the timing of HWs - consistent across definitions- have been also found, resulting in the lengthening of HWs season by up to 7 days/decade since the 1960s.

Local climate change indications: Historical trends, multi-model projections and implications in Bilate Catchment, Southern Ethiopia

Climate change is a major factor affecting hydrologic processes, water resources and agricultural productions in a catchment. This study aimed to evaluate the historical trends, future climate changes, characteristics of heat waves, dry and wet months in Bilate catchment, southern Ethiopia. The Mann-Kendal, Theil-Sen estimator were employed to analyse the trends and magnitude of trends of historical temperature and rainfall. Ensemble mean of regional climate models (RCMs) was employed for the future climate projections of this (2021-2050), mid (2051-2070), and end (2081-2100) centuries relative to baseline (1981-2010). Results revealed that the change in temperature under RCP4.5 and RCP8.5 showed an increase in the three future periods. Under the scenarios, the monthly maximum temperature is projected to increase in the range of 0.1 to 2.4 °C and 0.1 to 4.2 °C, respectively. Likewise, the minimum temperature is in the range of 0.1 to 1.9°C and 0.3 to 3.5 °C. Under the scenarios, seasonal rainfall is projected to increase in the range of 124 to 3,009.9 mm and 52.5 to 1111.0 mm; while decreases are from -19.4 to -1679.3 and -243.3 to -2,444.7 mm, respectively. Besides, dry months and heat waves are expected to increase. The combined effect of a reduction in rainfall, increase in heat waves and dry months will likely impact on the people whose livelihood depend on rain-fed subsistence agriculture in the catchment. Water and crop yield reduction are the major implications in this century. These findings raise awareness about the impacts of climate change in the community and regional authorities to endorse development policies.

Об особенностях пространственно-временной изменчивости характеристик волн тепла последних трех десятилетий (Араратская долина, Армения)

The aim of this work to study, identify the repeatability and duration of heat waves of the study area. For it were suggested and decided the following tasks: Findings. The study of regularities of variability of the spatial-temporal distribution of characteristics of heat wave in conditions of regional and global changes of climate is current task of modern geographical science. Extremely high temperatures and heat waves of study area excessively conditioned by the influence of secondary thermal depressions from the Arabian Peninsula, a number of cases that last for 2-3 decades are significantly increased. Tropical thermal depression, forming of extreme hot summers and heat waves, have cycles of activation and weakening, periodicity of which is estimated at 20-22 years. Starting from July (sometimes from the second half of June) to the last ten days of August (sometimes to first half of September), weather conditions of Ararat valley are formed under influence of thermal depression. The invasion of southern and south-eastern tropical warm and dry air currents from the Arabian deserts is increasing. As a result in some years the air temperature in Ararat valley is increased to 40-43 °C, and relative humidity is low than 30%. Heat waves are dangerous weather phenomena, is threat for live and activity, are characterized with some negative consequences. They can be accompanied by droughts and dry winds, forest fires, desertification, disruption of the natural ecosystem, economic damage, decreased working capacity, psychological and sociological consequences, even deaths. Temporal tendencies in course of values of the characteristics of heat wave for last 2-3 decades have positive unambiguous character, more frequent heat waves and extremely warm summers. Heat waves of low and medium intensity have a particularly high frequency. The probability of strong waves is less. The study area is distinguished a characteristic regime and an almost uniform spatial distribution of summer extreme high temperatures. They range from 41,5 to 42,6 °C. The entire study area is vulnerable to heat waves. Heat waves can cause dangerous meteorological phenomena such as droughts or dry winds, which cause great damage to various sectors of the economy, especially agriculture. Therefore the results of the work can be used in the field of agriculture, mitigating and reducing the consequences of possible damage caused. They can also be used in agrometeorological forecasts. In the study area, summer conditions become warmer and drier, which should be taken into account when developing strategic programs for the future development of this area.

Marine Heatwaves Characteristics in the Barents Sea Based on High Resolution Satellite Data (1982–2020)

Marine heatwaves (MHWs) can potentially alter ocean ecosystems with far-reaching ecological and socio-economic consequences. This study investigates the spatiotemporal evolution of the main MHW characteristics in the Barents Sea using high-resolution (0.25° × 0.25°) daily Sea Surface Temperature (SST) data from 1982 to 2020. The results reveal that the Barents Sea has experienced accelerated warming and several more MHWs in recent decades. Since 2004, an amplified increasing SST trend was observed across the entire Barents Sea, with a spatially averaged SST trend of 0.25 ± 0.18°C/decade and 0.58 ± 0.21°C/decade for the northern and southern Barents Sea, respectively. The annual mean MHW frequency, days, and duration over the entire Barents Sea increased by, respectively, 62, 73, and 31% from the pre- to the post-2004 period. More than half of all MHW days occurred in the last decade (2011–2020). The most intense MHW event occurred in summer 2016, which was also the warmest year during the study period. In general, the annual mean MHW frequency was relatively high in the northern Barents Sea, while the intensity and duration were higher in the southern Barents Sea. The highest annual MHW intensity and duration were observed in 2016, 2013, and 2020, respectively, while the highest annual MHW frequency was found in 2016. For the entire Barents Sea, the annual MHW frequency and duration increased significantly (p &amp;lt; 0.05) over the whole study period, with a trend of, respectively, 1.0 ± 0.4 events/decade, which is a doubling of the global average, and 2.4 ± 1.3 days/decade. In terms of the influence of climate variability on MHW characteristics, our findings revealed that the Eastern Atlantic Pattern (EAP) plays a significant role in controlling MHW characteristics, whereas the North Atlantic Oscillation (NAO) has no significant relationship. Sea ice concentrations were found to have a significant negative correlation with MHW characteristics. Strong positive correlations were observed between SST, surface air temperature, and MHW frequency, implying that as global warming continues, we can expect continued rising in MHW frequencies and days in the Barents Sea with huge implications for the ocean ecosystem.

Projections of Future Marine Heatwaves for the Oceans Around New Zealand Using New Zealand's Earth System Model

This paper investigates marine heatwave (MHW) characteristics in New Zealand's Earth System Model (NZESM) simulations for present-day conditions and how they are projected to change in the future in relation to anthropogenic greenhouse gas emissions. Three emission scenarios following the state of the art shared-socioeconomic pathways (SSPs, SSP1 2.6, SSP2 4.5, and SSP3 7.0) are each evaluated with a set of three ensemble members. These analyses are focused on the ocean around New Zealand, where NZESM captures boundary currents and mesoscale eddies, due to its high-resolution nested ocean grid. For present-day conditions, the model overestimates MHW intensity and underestimates the number of annual MHW days for subtropical waters, while some smaller positive biases are present in subantarctic waters compared to observations. Despite this, NZESM agrees with the observational pattern that more intense MHWs and more annual MHW days are found in subtropical waters compared to subantarctic waters. NZESM projects that MHW intensity will increase more strongly in subtropical waters compared to subantarctic waters, while the largest changes in annual MHW days are projected south of Australia and the Tasman Sea in the Subtropical Front (STF) frontal region, which suggests a southward shift of the STF under increased greenhouse gas emissions. Results using a high-emission scenario (SSP3 7.0) show an increase between 80 and 100% of median MHW intensities by the end of the century relative to the present-day for all analyzed coastal regions, and MHW conditions could become permanent year-round by the end of the century.

Heat Wave Trends in Southeast Asia: Comparison of Results From Observation and Reanalysis Data

AbstractSoutheast Asia (SEA), a region climatologically important but limited by data availability, is suffering from serious scarceness of heat wave (HW) research. Using the observational and reanalysis data, we find that in most parts of SEA, HWs are becoming more frequent, longer‐lasting, and stronger, and affect more land areas. The increasing trends of HW characteristics defined by minimum temperatures are larger than those by maximum temperatures, alarming a situation of anomalously warm night. Magnitude of yearly hottest HW event increases faster, and duration of yearly longest HW shows significant trends in more areas than their average counterparts. ERA5 reproduces well the HW trends defined by daily minimum temperatures, but underestimate those by maximum temperature. The data set CHIRTS improves on daily maximum temperature and associated HW trends, but deteriorates on daily minimum temperature. This study highlights the importance of high‐quality data, either observational or reanalysis, on the HW study in SEA.

Classifications and Characteristics of Marine Heatwaves in the Northern South China Sea

The classifications and associated characteristics of marine heatwaves (MHWs) in the northern South China Sea (SCS) have been investigated. Based on the ratio of the area with MHWs to the total area of the northern SCS, the MHWs are divided into three categories, i.e., narrow coverage, moderate coverage, and wide coverage. Different kinds of MHWs (i.e., narrow coverage, moderate coverage, and wide coverage) contribute around 64, 28, and 8% to the total days with MHWs, respectively. Narrow coverage MHW scatters over the northern SCS continental shelf, and moderate (wide) coverage MHWs are concentrated east of Hainan Island (mid of northern SCS continental shelf). Wide coverage MHWs contribute more than 50% to the total MHW cumulative sea surface temperature (SST) anomalies. The cumulative days and temperature anomalies of all kinds of MHWs exhibit significant long-term trends and decadal variability.

Sixfold Increase in Historical Northern Hemisphere Concurrent Large Heatwaves Driven by Warming and Changing Atmospheric Circulations

Abstract Simultaneous heatwaves affecting multiple regions (referred to as concurrent heatwaves) pose compounding threats to various natural and societal systems, including global food chains, emergency response systems, and reinsurance industries. While anthropogenic climate change is increasing heatwave risks across most regions, the interactions between warming and circulation changes that yield concurrent heatwaves remain understudied. Here, we quantify historical (1979–2019) trends in concurrent heatwaves during the warm season [May–September (MJJAS)] across the Northern Hemisphere mid- to high latitudes. We find a significant increase of ∼46% in the mean spatial extent of concurrent heatwaves and ∼17% increase in their maximum intensity, and an approximately sixfold increase in their frequency. Using self-organizing maps, we identify large-scale circulation patterns (300 hPa) associated with specific concurrent heatwave configurations across Northern Hemisphere regions. We show that observed changes in the frequency of specific circulation patterns preferentially increase the risk of concurrent heatwaves across particular regions. Patterns linking concurrent heatwaves across eastern North America, eastern and northern Europe, parts of Asia, and the Barents and Kara Seas show the largest increases in frequency (∼5.9 additional days per decade). We also quantify the relative contributions of circulation pattern changes and warming to overall observed concurrent heatwave day frequency trends. While warming has a predominant and positive influence on increasing concurrent heatwave frequency, circulation pattern changes have a varying influence and account for up to 0.8 additional concurrent heatwave days per decade. Identifying regions with an elevated risk of concurrent heatwaves and understanding their drivers is indispensable for evaluating projected climate risks on interconnected societal systems and fostering regional preparedness in a changing climate. Significance Statement Heatwaves pose a major threat to human health, ecosystems, and human systems. Simultaneous heatwaves affecting multiple regions can exacerbate such threats. For example, multiple food-producing regions simultaneously undergoing heat-related crop damage could drive global food shortages. We assess recent changes in the occurrence of simultaneous large heatwaves. Such simultaneous heatwaves are 7 times more likely now than 40 years ago. They are also hotter and affect a larger area. Their increasing occurrence is mainly driven by warming baseline temperatures due to global heating, but changes in weather patterns contribute to disproportionate increases over parts of Europe, the eastern United States, and Asia. Better understanding the drivers of weather pattern changes is therefore important for understanding future concurrent heatwave characteristics and their impacts.

Changes in global heat waves and its socioeconomic exposure in a warmer future

Heat waves are continuous high temperature processes, which are defined as the daily maximum temperature exceeding the absolute-relative combined high temperature thresholds for more than three consecutive days in this study. Because of its unprecedented casualties, devastating compound disasters and irreversible deterioration trends, heat waves have attracted worldwide concern, while its global changes and socioeconomic impacts still need further study. Using three historical reanalysis data and multi scenario CMIP6 modeled data, Global Heat Wave Toolbox (GHWT) was developed to generate heat wave matrix from 1971 to 2100. The long-term changing characteristics of global heat waves were also analyzed. Next, population and GDP projections are employed to estimate future socioeconomic exposure and risks. The results show that except for high latitudes (latitude greater than 60°), high elevations and some coastal areas, heat waves have visited about 45% (±3%) of the global land area (excluding Antarctica). North Africa, North Australia, South Asia, and the Arabian Peninsula are detected as high heat wave area, where experience more than three heat waves with total duration over 15 days annually. Additionally, the average growth rate of global heat waves under SSP2 4.5 and SSP5 8.5 may be 2–3 times and 3–5 times of that under SSP1 2.6, respectively. Under SSP2 4.5, there may be about 7.32 billion people exposed to heat waves in 2100, accounting for 82.65% of the global population. Economic exposure may reach $433.37 trillion in 2100, accounting for 82.23% of the total global economy in that year. India could have the highest population and economic exposure, follow by populous countries, such as Pakistan and Bangladesh, and major economies, such as China and the United States. Under SSP1 2.6, the increase in heat waves may slow down significantly. Moreover, North Africa, Australia, and Brazil are identified as rapid heat wave growth area. Our study highlights the heat wave of future growth and its socioeconomic impacts, as well as the necessity for climate mitigation and adaptation measures.

Effects of urbanization on heat waves based on the wet-bulb temperature in the Yangtze River Delta urban agglomeration, China

The Yangtze River Delta (YRD) urban agglomeration is one of the six major urban agglomerations in the world and is also one of the world's three most frequent high-temperature areas. The rapid urbanization process significantly affects meteorological air temperatures and relative humidity in urban and rural areas. Therefore, this study investigates the spatiotemporal evolution of heat waves (HWs) based on the wet-bulb temperature (TW) and urbanization effects. The results indicated that (1) the annual maximum TW exhibiting a significant decreasing trend is distributed in the Yangtze River valley and Lake Taihu Basin. The number of HW days showed a significant decrease during both 1980–1999 and 2000–2009. (2) The HW characteristics showed an insignificant decreasing trend in the Yangtze River valley, while it showed an insignificant increasing trend in the YRD. Further, the HW duration, intensity, and peak values showed significant upward trends in the coastal areas of the YRD urban agglomeration. (3) The proportion of HW duration increased from 28% in 1962–1990 to 55% in 1991–2019. The contribution of urbanization to the duration of the high-temperature HWs was 47.8%. Moreover, the impact of urbanization on HWs increased after 1990. (4) Although urban areas had a higher probability of extreme temperatures during 1991–2019, decreases in relative humidity have caused a decreasing trend of HW occurrence. Further, urban with low RH on the HW in urban areas were lower than those in rural and suburban areas. This research provides important evidence and recommendations for assessing the impact of heat waves related to urbanization.

Interactive influence of ENSO and IOD on contiguous heatwaves in Australia

Australian heatwaves have a significant impact on society. Most previous studies focus on understanding them in terms of frequency, duration, intensity, and timing. However, understanding the spatial characteristics of heatwaves, particularly those occurring in contiguous regions at the same time (here referred to as contiguous heatwaves), is still largely unexplored. Here, we analyse changes in spatial characteristics of contiguous heatwaves in Australia during 1958–2020 using observational data. Our results show that extremely large contiguous heatwaves are covering significantly larger areas and getting significantly longer during the recent period (1989/90–2019/20) compared to the historical period (1958/59–1988/89). We also investigated the association of contiguous heatwaves in Australia with interactions of the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) using a large multi-member ensemble of a physical climate model. We found that areal magnitude, total area, median duration, and maximum area of large and extremely large contiguous heatwaves in Australia are significantly higher (lower) during the strong El Niño (Es), strong El Niño co-occurring with strong IOD positive (Es-IPs), and with moderate IOD positive (Es-IPm) (co-occurring strong La Niña with the strong IOD negative (Ls-INs)) seasons relative to the neutral seasons (where both ENSO and IOD are in neutral phase). During the Es, Es-IPm, and Es-IPs seasons, the large-scale physical mechanisms are characterised by anticyclonic highs over the southeast and cyclonic lows over the northwest of Australia, favouring the occurrence and intensification of heatwaves in Australia. These results provide insights into the driving mechanisms of contiguous heatwaves in Australia.

A Stepwise-Clustered Simulation Approach for Projecting Future Heat Wave Over Guangdong Province

A heat wave is an important meteorological extreme event related to global warming, but little is known about the characteristics of future heat waves in Guangdong. Therefore, a stepwise-clustered simulation approach driven by multiple global climate models (i.e., GCMs) is developed for projecting future heat waves over Guangdong under two representative concentration pathways (RCPs). The temporal-spatial variations of four indicators (i.e., intensity, total intensity, frequency, and the longest duration) of projected heat waves, as well as the potential changes in daily maximum temperature (i.e., Tmax) for future (i.e., 2006–2095) and historical (i.e., 1976–2005) periods, were analyzed over Guangdong. The results indicated that Guangdong would endure a notable increasing annual trend in the projected Tmax (i.e., 0.016–0.03°C per year under RCP4.5 and 0.027–0.057°C per year under RCP8.5). Evaluations of the multiple GCMs and their ensemble suggested that the developed approach performed well, and the model ensemble was superior to any single GCM in capturing the features of heat waves. The spatial patterns and interannual trends displayed that Guangdong would undergo serious heat waves in the future. The variations of intensity, total intensity, frequency, and the longest duration of heat wave are likely to exceed 5.4°C per event, 24°C, 25 days, and 4 days in the 2080s under RCP8.5, respectively. Higher variation of those would concentrate in eastern and southwestern Guangdong. It also presented that severe heat waves with stronger intensity, higher frequency, and longer duration would have significant increasing tendencies over all Guangdong, which are expected to increase at a rate of 0.14, 0.83, and 0.21% per year under RCP8.5, respectively. Over 60% of Guangdong would suffer the moderate variation of heat waves to the end of this century under RCP8.5. The findings can provide decision makers with useful information to help mitigate the potential impacts of heat waves on pivotal regions as well as ecosystems that are sensitive to extreme temperature.

Heat waves affect prey and predators differently via developmental plasticity: who may benefit most from global warming?

Climate warming is considered to affect the characteristics of heat waves by increasing their duration, frequency and intensity, which can have dramatic consequences for ectothermic arthropods. However, arthropods may respond to heat waves via plastic modifications, which could differently affect a predator and its prey. We examined this assumption using prominent counterparts in biological control, the predatory mite Phytoseiulus persimilis and its prey, the spider mite Tetranychus urticae. Individuals of both species were separately exposed to mild and extreme heat waves during their juvenile development. Both species developed faster during extreme heat waves, but the proportional increase of the developmental rates was higher in the prey. Independent of sex, P. persimilis reached smaller size at maturity under extreme heat waves, whereas the body size modifications were sex-dependent in T. urticae: males became smaller, but females were able to maintain their size. An accelerated development may result in the reduction of the exposure time of susceptible juvenile stages to heat waves and prey stages to predators. Plastic size adjustments caused a shift in the female predator-prey body size ratio in favor of the prey, which may lead to higher heat resistance and reduced predation risk for prey females under extreme heat waves. In conclusion, our findings indicate that species-specific shifts in age and size at maturity may result in lower suppression efficacy of the predator P. persimilis against its prey T. urticae with severe consequences for biological control of spider mites, if global warming continues.

CMIP6 MultiModel Evaluation of Present‐Day Heatwave Attributes

AbstractHeatwave frequency, duration and intensity has increased since the 1950s, a trend likely to continue with anthropogenic climate change. Although climate model projections are an important source of information on how heatwaves and other climate extremes may evolve with climate change it is necessary to understand whether climate models are able to adequately reproduce historical statistics of these events. We provide the first global evaluation of CMIP6 models to characterize heatwave characteristics between 1950 and 2014. Further, we also include a global heatwave evaluation of the CMIP5 models, as no study currently exists. Our results demonstrate that both ensembles underestimate mean heatwave frequency with region‐dependent biases for mean heatwave duration, intensity, and cumulative heat. Comparisons between CMIP5 and CMIP6 show that improvements in skill for the heatwave metrics evaluated here are marginal, suggesting that future improvements in simulating heatwaves may only be possible with significant advances in climate modeling capabilities.

Compound droughts and heatwaves over the Huai River Basin of China: From a perspective of the magnitude index

AbstractCompound droughts and heatwaves have garnered increasing research attentions due to their disastrous impacts on the structure and function of ecosystems and societies. A drought is generally characterized by precipitation deficit, and its negative impact can be amplified by the simultaneous occurrence of a heatwave. More recent studies have highlighted the multi characteristics of compound droughts and heatwaves, which may call for improved efforts on assessing the impact of compound extremes. In this study, a compound drought and heatwave magnitude index (CDHMI) is built to characterize the severity of compound extremes in the Huai River Basin (HRB) during 1961-2017. The CDHMI considers the impact of both drought/extreme heat conditions and the duration of extreme heat. In addition, the magnitude index has been graded according to the degree of severity to detect the most drastic extreme compound events. The results show that from 1961 to 2017, mild and moderate events occurred more often than severe events. A significant increase in all compound events was observed from 2003 to 2017. Compound droughts and heatwaves events, especially in drought status, have increased significantly with the global climate warming in recent decades. The assessment of the impact for compound droughts and heatwaves events over the HRB needs to be improved in the context of global climate changing. Therefore, the CDHMI can be used to accurately assess the risk of compound droughts and heatwaves.