Occurrence Of Heat Waves Research Articles

Land-atmosphere feedback exacerbated the mega heatwave and drought over the Yangtze River Basin of China during summer 2022

In the summer of 2022, a record-breaking heatwave and drought event occurred in the Yangtze River (YR) Basin of China, causing great damage to the society and ecosystem. However, the role of land-atmosphere (LA) interactions in driving and reinforcing this event has not been fully studied. In this study, using air temperature, soil moisture (SM), surface sensible heat fluxes, surface latent heat fluxes and radiation fluxes data from ERA5, we analyze the process of this event and reveal the contribution of the LA feedbacks. The results indicate that during the 2022 YR Basin heatwave and drought event, the regional average maximum air temperature and SM reached unprecedented levels of 2.7 standard deviations (SDs) and −3.5 SDs, respectively, compared to the climatology from 1980 to 2021. In August 2022, SM rapidly declined, pushing the region into a rare "dry" state. The dry soil increased the sensitivity of daily maximum air temperature to SM, intensifying the occurrence of heatwaves in the area. Simultaneously, increased downward solar radiation reached surface and most of that converted to sensible heat fluxes due to low soil moisture limitations leading to elevated air temperatures. While similar events have been reported multiple times in regions like Europe and western North America, their occurrence in the "moist" region of the YR Basin of China is exceptionally rare, which suggests an increasing likelihood of such extreme events in this region. Land-atmosphere interactions play an increasingly crucial role in exacerbating extreme conditions, and therefore, more studies such as this are needed for improving predictability of extreme events on a sub-seasonal time scale.

Divergent Drivers of Declining Urban Vegetation Productivity and Transpiration During Heatwaves

AbstractHeatwave events, characterized by high vapor pressure deficit (VPD) and low soil moisture (SM), considerably disrupt the regional carbon and water cycle. However, research pertaining to the impact of heatwaves on vegetation productivity (VPu) and vegetation transpiration (VTu), along with their underlying drivers, particularly in urban areas, remains limited. This study investigates the response of VPu and VTu to heatwave events across 895 global cities from 1990 to 2022. The analysis reveals a notable upward trend in the average heatwave frequency, intensity, and duration across the global cities. Heatwave events demonstrate a detrimental impact on VPu and VTu, resulting in an average decrease of 28% and 26%, respectively, during heatwave occurrences. The attribution analysis reveals divergent driving factors for the decline in VPu and VTu during heatwaves. The decrease in VPu is primarily influenced by SM, contributing 60% to the downward trend of VPu during heatwaves. Notably, VPu displays a sharp downward trend when SM falls below 0.38 m3/m3. In contrast, the primary driver of VTu decline is VPD, contributing more than 66% to the downward trend of VTu during heatwave events. VTu exhibits a significant downward trend when VPD exceeds 1.35 kPa. The results of this study show the important effects of increasingly frequent heatwaves on vegetation transpiration and productivity, and that can be used as quantitative factor to be evaluated when investigating policy measures for the resilience of urban areas.

The role of antecedent southwest summer monsoon rainfall on the occurrence of premonsoon heat waves over India in the present global warming era

Global warming has significantly increased the risk of heat waves (HWs) globally, with India being particularly vulnerable during the summer months (March-June; MAMJ). This study investigated the critical relationship between Indian summer monsoon rainfall (ISMR) and the occurrence of premonsoon HWs in subsequent years across the Indian subcontinent. It has been hypothesized that droughts during the ISMR could lead to more frequent HWs in the following MAMJ period. Using the Indian Meteorological Department's (IMD) gridded observed surface air daily maximum temperature (Tmax) dataset for the period 1951–2023, we analyzed the climatic patterns, interannual variability (IAV), and coefficient of variation (CV) of Tmax across India. The analysis compares two distinct periods: 1951–1999 (P1) and 2000–2023 (P2), with focus on Tmax trends and HW duration, distinguishing between short-duration HWs (SHWs, 2 days) and long-duration HWs (LHWs, 5 days or more). A key purpose of this study is to examine the relationship between the preceding all India summer monsoon rainfall (AISMR) and the occurance of various types of HW in the subsequent premonsoon season. In particular extreme AISMR events, such as droughts or excess rainfall, influence HW occurrence. The findings reveal a significant rise in Tmax across many regions of India during the MAMJ period, with the highest temperatures (> 37 °C) observed in northwestern, central, and eastern coastal areas. Northern India, particularly the Himalayan region, exhibits a greater interannual variability in Tmax, with June showing the most pronounced fluctuations. The study also highlights an increase in the frequency and intensity of HWs, especially in central and southern India, with the Chandigarh-Haryana-Delhi region recording the highest occurrences. A critical finding is the strong inverse relationship between the AISMR and conditions in the subsequent premonsoon season. Specifically, drought in the antecedent AISMR results in reduced soil moisture, which is strongly associated with higher premonsoon Tmax and an increased frequency of extreme heat events across India, particularly in regions prone to severe heat during this season. Drought conditions during AISMR are closely linked to higher HW frequencies in the following summer, especially in the central, northeast-central, and east-coastal regions. The frequencies of HW days, SHWs, and LHWs are significantly greater in years following AISMR droughts than in those following excess rainfall, indicating that drought years are more likely to lead to widespread HW activity. Despite the overall warming trends, some regions, such as the Indo-Gangetic Plain and parts of the Himalayan region, show cooling trends, although these trends are less widespread. The onset of the monsoon in June tends to reduce the intensity and spatial extent of warming, particularly in the central and eastern coastal regions, although significant HW trends persist in northwestern India and along the east coast. This study underscores the crucial role of AISMR in influencing HW events across India and highlights the need for adaptive strategies that account for the interactions between monsoon rainfall and HW risk, providing valuable insights for mitigating the impacts of HWs in the context of global warming.

Compound spatial extremes of heatwaves and downstream air pollution events in East Asia

In light of increasing climate hazards globally that pose risk to public health, the compounded effects of two major hazards, heatwaves and air pollution, have become a focal point for environmental and health research. This study explores the intricate relationship between extreme temperature events in North China (NC) and South China (SC) – two prominent areas of aerosol exposure in East Asia – and the associated changes in aerosol optical depth (AOD) across the region. The heatwave events and regional AOD distribution revealed distinct patterns in their respective regions from June to September. Both NC and SC showed reduced AOD during heatwave events, while downstream regions experienced increased AOD levels. From the perspective of heatwaves in NC and SC, we present a more holistic picture of how large-scale modulators contribute to inducing air pollution hazards across East Asia. The analysis revealed a link between blocking high-pressure system and heatwave occurrences in NC, while a dominant Rossby wave train, influenced by the South China Sea, was identified as a major modulator in SC. Additionally, other large-scale circulatory systems, such as the Western Pacific Subtropical High, the East Asian jet stream, and the South Asian High, also play crucial roles in shaping these events. This suggests the potential for predicting downstream AOD events. The study underscores the importance of understanding the interconnectedness of meteorological and air quality phenomena to mitigate the adverse environmental impacts in East Asia.

The Relationship Between Indian Ocean Subtropical Mode Water Variability and Ocean Temperature Structure

AbstractAs one of the least studied mode waters, the role of the Indian Ocean Subtropical Mode Water (IOSTMW) in influencing the ocean and atmosphere as it is advected in the subsurface remains poorly understood. Taking advantage of the rapid increase of Argo data over the past decade, this study compares the ocean temperature structure during periods of thick and thin IOSTMW. The results indicate notable differences in both temperature and stratification linked to variations in IOSTMW thickness. In terms of temperature, the following phenomena are observed when the IOSTMW is thick: (a) the layer above the IOSTMW experiences colder temperatures, whereas warmer temperatures occur below it; (b) isotherms above the IOSTMW shoal, whereas those below it deepen. As for the stratification, a negative correlation is observed between IOSTMW thickness and stratification at depths between 100 and 300 dbar, suggesting that the presence of thick IOSTMW weakens the stratification within this depth range. Conversely, a positive correlation is observed around 400 dbar, suggesting that thick IOSTMW tends to coincide with a deeper main thermocline. Notably, regions near the Agulhas Current exhibit contrasting characteristics compared to other regions within the study area, indicating the potential impacts of the Agulhas Current meander on ocean temperature structure and the distribution of the IOSTMW. An intriguing question for future studies is how variations in IOSTMW thickness contribute to marine heatwave occurrences and influence atmospheric conditions.

Trend and teleconnection analysis of temperature extremes in New South Wales, Australia

AbstractThis study investigates possible trends and teleconnections in temperature extremes in New South Wales (NSW), Australia. Daily maximum and minimum temperature data covering the period 1971–2021 at 26 stations located in NSW were used. Three indices, which focus on daily maximum temperature, daily minimum temperature, and average daily temperature in terms of Excessive Heat Factor (EHF) were investigated to identify the occurrence of heatwaves (HWs). The study considered HWs of different durations (1-, 5-, and 10-days) in relation to intensity, frequency, duration, and their first occurrence parameters. Finally, the influences of three global climate drivers, namely – the El Niño/Southern Oscillation (ENSO), the Southern Annular Mode (SAM), and the Indian Ocean Dipole (IOD) were investigated with associated heatwave attributes for extended Austral summers. In this study, an increasing trend in both hot days and nights was observed for most of the selected stations within the study area. The increase was more pronounced for the last decade (2011–2021) of the investigated time period. The number, duration and frequency of the heatwaves increased over time considering the EHF criterion, whereas no particular trend was detected in cases of TX90 and TN90. It was also evident that the first occurrence of all the HWs shifted towards the onset of the extended summer while considering the EHF criterion of HWs. The correlations between heatwave attributes and climate drivers depicted that heatwave over NSW was positively influenced by both the IOD and ENSO and negatively correlated with SAM. The findings of this study will be useful in formulating strategies for managing the impacts of extreme temperature events such as bushfires, floods, droughts to the most at-risk regions within NSW.

Association of heat and cold waves with cause-specific mortality in Iran: a systematic review and meta-analysis

Despite the frequent occurrence of heat waves in the Middle East, there is a lack of evidence regarding the overall estimates for the effect of heat waves on mortality in this region. This study aimed to review the effect of exposure to heat and cold waves and daily cause-specific mortality. Four electronic databases were searched. The titles, abstracts, and full-texts of the articles were carefully reviewed by two researchers. Once eligible studies were identified, the required data were extracted. Separate meta-analyses were conducted based on gender, age group, and health endpoint combinations. According to the meta-analysis, heat waves had a statistically significant effect on all-cause mortality with an RR of 1.23 (CI 95%: 1.08, 1.39). Cardiovascular mortality significantly increased in heat waves with an RR of 1.08 (CI 95%: 1.05, 1.10). However, the increase in respiratory mortality was not statistically significant. Compared to young people (age < 65 years old) and women, elderly and men were more vulnerable to heat waves with RRs of 1.31 (95% CI: 1.05, 1.57) and 1.33 (95% CI: 1.08, 1.58), respectively. This study can be beneficial in developing response or adaptation plans for heat waves. Future studies should focus on other specific health endpoints like ischemic heart disease, chronic obstructive pulmonary diseases, etc., and other outcomes such as hospitalization and emergency visits.

Prediction of heatwave related mortality magnitude, duration and frequency with climate variability and climate change information

Given the link between climatic factors on one hand, such as climate change and low frequency climate oscillation indices, and the occurrence and magnitude of heat waves on the other hand, and given the impact of heat waves on mortality, these climatic factors could provide some predictive skill for mortality. We propose a new model, the Mortality-Duration-Frequency (MDF) relationship, to relate the intensity of an extreme summer mortality event to its duration and frequency. The MDF model takes into account the non-stationarities observed in the mortality data through covariates by integrating information concerning climate change through the time trend and climate variability through climate oscillation indices. The proposed approach was applied to all-cause mortality data from 1983 to 2018 in the metropolitan regions of Quebec and Montreal in eastern Canada. In all cases, models introducing covariates lead to a substantial improvement in the goodness-of-fit in comparison to stationary models without covariates. Climate change signal is more important than climate variability signal in explaining maximum summer mortality. However, climate indices successfully explain a part of the interannual variability in the maximum summer mortality. Overall, the best models are obtained with the time trend and the North Atlantic Oscillation (NAO) used as covariates. No country has yet integrated teleconnection information in their heat-health watch and warning systems or adaptation plans. MDF modeling has the potential to be useful to public health managers for the planning and management of health services. It allows predicting future MDF curves for adaptive management using the values of the covariates.

Changes in Global Heatwave Risk and Its Drivers Over One Century

AbstractHeatwaves represent a significant and growing threat to natural ecosystems and socio‐economic structures, making heatwave risk mitigation and prevention an important area of research. In exploring heatwave frequency and intensity from 1901 to 2020, the present study finds a sharp increase in both. The study also finds that the spatial distribution of heatwaves is unequal, the volatility of intensity characteristics has become more prominent over time, and the Gini coefficients of four key heatwave indictors have become larger due to increasing dryness. Although heatwaves occur more frequently in drylands, there is greater cumulative heat in humid areas, resulting in a higher heatwave risk in those areas. The global heatwave risk over the past three decades (1991–2020) has increased nearly five‐fold compared to the early 20th century (1901–1930). Furthermore, GeoDetector analysis indicates that the Palmer drought severity index (PDSI) and downward surface shortwave radiation (Srad) contributing the most in drylands and humid areas (0.29 and 0.41, respectively). The contribution of relative humidity (RH), wind speed (WS), soil moisture (SM), and the normalized difference vegetation index (NDVI) is also significant in humid areas, but is much smaller in drylands. Composite analysis shows that the years with anomalously high heatwave risk correspond to positive anomalies of 500hPa geopotential height and surface pressure. The inhibition of cloud formation due to sinking air and the resulting increase in temperature in the atmosphere may be increasing the risk of heatwave occurrence. This study emphasizes the urgent need to address worsening climate change impacts.

Pronounced spatial disparity of projected heatwave changes linked to heat domes and land-atmosphere coupling

Heatwaves are projected to substantially increase at a global scale, exacerbating worldwide heat-related risks in the future. However, understanding future heterogeneous heatwave changes and their origins remains challenging. By analyzing the output of various climate models from the Coupled Model Intercomparison Project Phase 6, we found pronounced spatial disparity of projected heatwave increases in the Northern Hemisphere, even outstretching seven-fold inter-regional differences in extreme heatwave occurrences, attributed primarily to future changes in heat-dome-like circulations and soil moisture–temperature coupling. Specifically, we found that by the end of the 21st century, the modulations of combined Pacific El Niño and positive Pacific Meridional Mode on magnified heat-dome-like circulations would be translated into summertime hotspots over western Asia and western North America. Amplified soil moisture–temperature couplings then further aggravate the heatwave intensity over these two hotspots. This study provides support for formulating impact-based mitigation strategies and efficiently addressing the potential future risks of heatwaves.

The intensity of a field simulated marine heat wave differentially modulates the transcriptome expression of Posidonia oceanica from warm and cold environments

Marine Heat Waves (MHWs) occurrence has been increasing in the Mediterranean Sea. The effects of field simulated MHWs of different intensity (medium and high temperature) on the transcriptome expression of the endemic seagrass Posidonia oceanica were evaluated considering different origins of the plant. The aim of the study was reached through a common garden transplant experiment in the North-west of Sardinia (Italy), where two P. oceanica meadows characterized by different thermal regimes (cold and warm) were chosen. MHWs were simulated in front of a power plant, that creates a natural laboratory by releasing warm water in the sea. Differential gene expression and GO enrichment analyses highlighted differences in the transcriptomic profiles of plants from cold and warm environments suggesting that the MHWs induced different levels of stress due to different tolerance to the heat event. Plants from both origins activated processes to achieve protein homeostasis, but only cold plants activated an antioxidant defense and altered sugar metabolism, both indicators of heat stress. Within plants of the same origin, a different response to MHW intensity was also detected: while warm plants showed the most complex response at high temperature rather than at medium temperature, cold plants seemed to better cope with the medium temperature intensity rather than with high temperature.

Towards more equitable cooling services of urban parks: Linking cooling effect, accessibility and attractiveness

Global warming and rapid urbanization have caused frequent occurrences of heat waves and urban heat island effect, presenting a significant threat to health of urban residents. Researches have indicated that cooling services provided by parks are essential in alleviating impact of heat wave events and urban heat island effect. However, previous researches on park cooling services center around cooling effect, with a lack of exploration regarding the fairness of such services. To fill this gap, this study quantifies the level of equity in cooling services in 18 parks in the core area of Hangzhou. Through this study, we hope to clarify the current situation of fairness of cooling services in urban parks and provide fairer park cooling services through scientific and reasonable park layouts. This will alleviate the threat of rapid urbanization and climate change to urban residents, and make the urban environment develop in a more livable direction. We assessed the cooling effect using remote sensing and the ArcGIS platform to screen parks with cooling effect and to quantify their cooling service efficiency. We utilized spatial network analysis to quantify the accessibility and origin-destination matrix data to quantify the attractiveness to reflect the level of park cooling services. The results reveal that 18 parks exhibit a noticeable cooling effect, albeit with variations observed among parks. The percentage of urban parks with low accessibility is 77.80%, indicating that the distribution of accessible space presents an uneven status quo. In addition, 72.20% of parks have low attractiveness of cooling services, indicating that some parks have insufficient attractiveness of cooling services. Based on each indicator of cooling services, we categorize urban parks into four types based on supply and demand, and propose adaptive planning measures and intervention strategies to provide a reference for equitable distribution of cooling services in urban parks.

Quantifying urban climate response to large-scale forcing modified by local boundary layer effects

Over the past two decades, the joint manifestation of global warming and rapid urbanization has significantly increased the occurrence of heatwaves and the formation of urban heat islands in temperate cities. Consequently, this synergy has amplified the frequency and duration of periods with tropical nights (TNs) in these urban areas. While the occurrences of such extreme events demonstrate irregular and nonlinear annual patterns, they consistently manifest a discernible rising decadal trend in local or regional climatic data. In urban regions situated amidst hilly or mountainous landscapes, changing wind directions—often associated with uphill or downhill thermal flows—profoundly impact the spread and dispersion of heat-related pollution, creating unique natural ventilation patterns. Using the Lausanne/Pully urban area in Switzerland as examples of hilly and lakeshore temperate cities, this study explores the influence of wind patterns and natural urban ventilation on the nonlinearity of recorded climatic data within an urban environment. This study integrates a mesoscale numerical weather prediction model (COSMO-1), a microscale Computational Fluid Dynamics (CFD) model, field observations, variational mode decomposition technique, and statistical analysis to investigate how wind speed and direction critically influence the nonlinearity of recorded long-term trends of extreme events, specifically focusing on the frequency and duration of TNs in lakeshore and hilly cities. The results strongly indicate a direct correlation between the frequency of TNs and the occurrence of specific moderate wind patterns. These wind patterns are exclusively captured by the microscale CFD model, unlike the mesoscale model, which neglects both urban morphology and complex hilly terrains. The impact of temporal and spatial variability of the wind field on long-term observations at fixed measurement stations suggests that caution should be exercised when relying on limited spatial measurement points to monitor and quantify long-term urban climate trends, particularly in cities located in complex terrains.

Racial/ethnic disparities in the distribution of heatwave frequency and expected economic losses in the US

Previous research on social disparities in heat exposure has not examined heatwave frequency or economic damage at the local or neighborhood level. Additionally, most US studies have focused on specific cities or regions, and few national-scale studies encompassing both urban and rural areas have been conducted. These gaps are addressed here by analyzing racial/ethnic disparities in the distribution of annual heatwave frequency and expected economic losses from heatwave occurrence in the contiguous US. Census tract-level data on annualized heatwave frequency and expected loss from the FEMA’s National Risk Index are linked to relevant variables from the American Community Survey. Results indicate that all racial/ethnic minority groups except non-Hispanic Black are significantly overrepresented in neighborhoods with greater annual heatwave frequency (top 10% nationally), and all minority groups are overrepresented in neighborhoods with greater total expected annual loss from heatwaves, compared to non-Hispanic Whites. Multivariable models that control for spatial clustering, climate zone, and relevant socio-demographic factors reveal similar racial/ethnic disparities, and suggest significantly greater heatwave frequency and economic losses in neighborhoods with higher percentages of Hispanics and American Indians. These findings represent an important starting point for more detailed investigations on the adverse impacts of heatwaves for US minority populations and formulating appropriate policy interventions.

Climatic characteristics of heat wave events (1959–2023) in Jiangxi Province, China

This study investigated the temporal and spatial patterns of heat wave (HW) events in Jiangxi, China. Our analysis is based on the observation data, including daily maximum temperature and daily average air relative humidity from 81 meteorological stations from 1959 to 2023. We also examined the impact of HW events on summer electricity consumption by taking the capital city of Jiangxi, Nanchang, as a case study. The results reveal an overall increase in the frequency of HW events over the past 65 years, with a pronounced increase since 1997, particularly in central and southern Jiangxi. The onset of HW events has generally occurred earlier, while their cessation has been delayed across most areas of Jiangxi Province, resulting in extended HW periods. Economic growth in regions like the Jitai Basin, the Ganfu Plain, and the hilly areas of northeastern Jiangxi has been accompanied by more intense and prolonged HW events. In Nanchang City, the summer electricity load increased by approximately 9% on holidays compared to working days and by about 20% on high-temperature days compared to normal conditions. These insights highlight the need for adaptive strategies to mitigate the impacts of increasing HW occurrences.

Evaluation of the intensity of urban heat islands during heat waves using local climate zones in the semi-arid, continental climate of Tehran

Increasing land surface temperature (LST) and urban heat island intensity (UHII) have been reported to be closely associated with a large number of environmental issues. Understanding LST and UHII rise in cities during heatwaves is crucial for implementing mitigation measures. This paper aims to explain these variations in response to LST and UHII during a heat wave in the metropolis of Tehran in Iran. 13 heat waves were selected and evaluated during the years 2000 to 2020. The average LST was 3.34 °C higher at the same time as the heat wave event compared to the period without the wave. Despite the increase in LST during the heat wave occurrence, UHII experienced lower values compared to the time without the wave. The outputs in this regard show that the average UHII value for the period without a heat wave is 5.11 °C, while during the heat wave, its rate is 3.62 °C. The maximum intensity of the heat island for both periods before and at the same time as the heat wave is related to man-made compact midrise buildings and heavy industry. Extra-local factors during heat waves can lead to diminish land use diversity and vegetation density's effectiveness in reducing UHII.

Cyanide in cassava: Understanding the drivers, impacts of climate variability, and strategies for food security

AbstractThe consumption of cassava, a vital staple food for more than 1 billion people worldwide, holds particular significance in sub‐Saharan Africa (SSA). Expansion in cassava production in SSA is driven by increasing market demand, local consumption, and adaptability to diverse environments. However, cyanide concentration in cassava tubers and products across SSA ranges from 9 to 1148 ppm – most exceed the World Health Organisation's recommended safe level of 10 ppm. Such variation and high cyanide concentrations in cassava products are expected to be exacerbated by climate‐induced increases in the frequency, intensity and occurrence of drought, heat waves and biotic stresses, further jeopardising regional food security. Thus, it is essential to examine cassava production and cyanide toxicity under climate change and their implications for food security in SSA. In this review, we look at the drivers of cassava production and spatial variation in cyanide concentrations across SSA, impacts of climate variability and biotic stresses on cassava cyanide concentrations in SSA, and crop management practices for reducing cyanogenic glucosides in cassava tubers. We surmise that urgent actions are required to adopt improved cassava varieties and management strategies that reduce cassava cyanide toxicity amid climate‐induced challenges in SSA.

Changes in urban heat island intensity during heatwaves in China

With rising occurrence of heatwaves and ongoing urban expansion, urban residents are facing severer heat-related stress under the combined effects of urban heat island (UHI) and heatwaves. Controversial results, however, have been reported regarding whether the UHI is exacerbated during heatwaves. In this study, we used fused ground and satellite daily maximum air temperature data to evaluate the variation of UHI intensities under heatwaves across 225 major cities in mainland China during 2003–2020. Overall, urban areas showed an enhanced UHI intensity of up to 0.94 °C during heatwaves, nearly double compared to normal periods. The interaction between UHIs and heatwaves was sensitive to local background precipitation. Under the similar urbanization and vegetation greenness, the amplified warming in urban areas during heatwaves was more pronounced in wet climates. In megapolitan regions characterized by continuous urban development, the UHI intensified much stronger during heatwaves due to the heat accumulation within urbanized areas and the advection of heat from neighboring cities. Our results contribute to understanding the interactions between UHIs and heatwaves which may strongly increase heat risk in cities. Further work on the variations of this interaction under future warming and consequent impacts on human health and energy use is needed.

A study on the monitoring of heatwaves and bivariate frequency analysis based on mortality risk assessment in Wuhan, China.

The increasingly frequent occurrence of urban heatwaves has become a significant threat to human health. To quantitatively analyze changes in heatwave characteristics and to investigate the return periods of future heatwaves in Wuhan City, China, this study extracted 9 heatwave definitions and divided them into 3 mortality risk levels to identify and analyze historical observations and future projections of heatwaves. The copula functions were employed to derive the joint distribution of heatwave severity and duration and to analyze the co-occurrence return periods. The results demonstrate the following. (1) As the concentration of greenhouse gas emissions increases, the severity of heatwaves intensifies, and the occurrence of heatwaves increases significantly; moreover, a longer duration of heatwaves correlated with higher risk levels in each emission scenario. (2) Increasing concentrations of greenhouse gas emissions result in significantly shorter heatwave co-occurrence return periods at each level of risk. (3) In the 3 risk levels under each emission scenario, the co-occurrence return periods for heatwaves become longer as heatwave severity intensifies and duration increases. Under the influence of climate change, regional-specific early warning systems for heatwaves are necessary and crucial for policymakers to reduce heat-related mortality risks in the population, especially among vulnerable groups.

An Approach to Assess the Impact of High Biaxial Photovoltaic Trackers on Crop Growth and Yield

The growing need for producing renewable energy such as photovoltaic electricity, and the mitigation of the increasing occurrences of heatwaves and drought affecting annual crops, could be addressed by the installation of agrivoltaic systems. Depending on pedoclimatic context, cultivated crop, solar panels technology and implementation configuration, solar panels shading can improve or reduce crop growth and yields. Among photovoltaic installations, solar trackers might have a high development potential. These photovoltaic panels are mounted on a vertical axis at a 7m height. Thanks to their height, their biaxial moving capacity, their small anchoring surface and their punctual structure making plants design easily adaptable to agricultural constraints, they can fit with all types of agricultural systems. The aim of this study was to evaluate the impact of such trackers on crop growth and yields. For this purpose, a set of 6 different fields crop located in western France were studied. Crop phenology, height and yield were investigated. Results showed a delay in crop development near the trackers that was overcome late in the crop cycle, near harvest. For crop height and crop yield, the results showed important spatial variability but without clear trend related to the tracker shadow. The results are discussed in the light of new perspectives, including the consideration of microclimatic and pedological data to better explore the effects of trackers on plant growth and development, the measurement of morphological and physiological traits of plants, the accounting of a multi-trackers effect implemented on the same site, the temporal dynamics of the effect of a tracker.