Occurrence Of Heat Waves Research Articles

The Extreme Heat Wave of Summer 2021 in Athens (Greece): Cumulative Heat and Exposure to Heat Stress

The Mediterranean has been identified as a ‘climate change hot spot’, already experiencing faster warming rates than the global average, along with an increased occurrence of heat waves (HWs), prolonged droughts, and forest fires. During summer 2021, the Mediterranean faced prolonged and severe HWs, triggering hundreds of wildfires across the region. Greece, in particular, was hit by one of the most intense HWs in its modern history, with national all-time record temperatures being observed from 28 July to 6 August 2021. The HW was associated with extreme wildfires in many parts of the country, with catastrophic environmental and societal consequences. The study accentuated the rarity and special characteristics of this HW (HW2021) through the analysis of the historical climate record of the National Observatory of Athens (NOA) on a centennial time scale and comparison with previous HWs. The findings showed that HW2021 was ranked first in terms of persistence (with a total duration of 10 days) and highest observed nighttime temperatures, as well as ‘cumulative heat’, accounting for both the duration and intensity of the event. Exceptionally hot conditions during nighttime were intensified by the urban heat island effect in the city of Athens. Human exposure to heat-related stress during the event was further assessed by the use of bioclimatic indices such as the Universal Thermal Climate Index (UTCI). The study points to the interconnected climate risks in the area and especially to the increased exposure of urban populations to conditions of heat stress, due to the additive urban effect.

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.

Roles of Atmosphere Thermodynamic and Ocean Dynamic Processes on the Upward Trend of Summer Marine Heatwaves Occurrence in East Asian Marginal Seas

By analyzing the European Centre for Medium-Range Weather Forecasts reanalysis version 5 (ERA5) dataset, we found increased frequency of marine heatwaves (MHWs) in East Asian marginal seas (EAMS) during the boreal summer (June-July-August) in the recent past. To examine which processes are responsible for the upward trend of MHW occurrence, we performed three numerical simulations using Modular Ocean Model version 5 (MOM5) forced by ERA5 dataset. The first experiment used historical atmospheric variables to force the MOM5 for 1982 to 2020, which reasonably simulated the upward trend of MHWs as well as its dominant variability in terms of temporal and spatial structure in EAMS. The second (third) experiment is the same as in the first except that the atmosphere variables used to force the MOM5 consisted of thermodynamic (dynamic) variables only. The upward trend of MHW occurrence in EAMS is simulated in the first and the second experiment only. We argue that the atmosphere thermodynamic processes, in particular, the shortwave radiative forcing, play a key role in inducing the upward trend of MHW occurrence in EAMS during the boreal summer compared to the ocean dynamic processes.

Joint occurrence of heatwaves and ozone pollution and increased health risks in Beijing, China: role of synoptic weather pattern and urbanization

Abstract. Heatwaves (HWs) paired with higher ozone (O3) concentration at the surface level pose a serious threat to human health. Their combined modulation of synoptic patterns and urbanization remains unclear. Using 5 years of summertime temperature and O3 concentration observation in Beijing, this study explored potential drivers of compound HWs and O3 pollution events and their public health effects. Three favorable synoptic weather patterns were identified to dominate the compound HWs and O3 pollution events. These weather patterns contributing to enhance those conditions are characterized by sinking air motion, low boundary layer height, and high temperatures. Under the synergy of HWs and O3 pollution, the mortality risk from all non-accidental causes increased by approximately 12.31 % (95 % confidence interval: 4.66 %, 20.81 %). Urbanization caused a higher risk of HWs and O3 in urban areas than at rural stations. Particularly, due to O3 depletion caused by NO titration at traffic and urban stations, the health risks related to O3 pollution in different regions are characterized as follows: suburban stations > urban stations > rural stations > traffic stations. In general, favorable synoptic patterns and urbanization enhanced the health risk of these compound events in Beijing by 33.09 % and 18.95 %, respectively. Our findings provide robust evidence and implications for forecasting compound HWs and O3 pollution events and their health risks in Beijing or in other urban areas all over the world that have high concentrations of O3 and high-density populations.

Excess Heat Factor climatology, trends, and exposure across European Functional Urban Areas

In Europe, regional climate change prospects indicate the urgency of adapting to extreme weather events. While increasing temperature trends have already been detected, in the last decades, the adoption of a European heatwave (HW) early-warning index is not yet consensual, partially due to the significant number of alternative algorithms, in some cases adjusted to the measurement of sector-specific impacts (as per the Expert Team on Climate Risk and Sector-specific Indices (ET-SCI)). In particular, the Excess Heat Factor (EHF) has been shown to accurately predict heat-related human health outcomes, in mid-latitude climates, provided that local summer exposure to excess heat is mostly driven by extreme air temperatures, with a lower contribution from relative humidity. Here, annual summaries of EHF-based HW detection were calculated for the European region, using daily maximum and minimum temperatures from the homogenised version of the E-OBS gridded dataset. Annual HW frequencies, duration, mean magnitude, maximum amplitude, and severity were subject to climatology and trend analysis across the European biogeographical regions, considering the 1961–1990 period as the baseline reference for anomaly detection in the more recent (1991–2018) decades. As HW-dependent morbidity/mortality affects mostly the elderly, an EHF-based HW Exposure Index was also calculated, by multiplying the recent probability of severe events per the number of people aged 65, or more, in the European Functional Urban Areas (FUAs). Results show that recent historical EHF-based patterns diverge across European Biogeographical regions, with a clear latitudinal gradient. Both the historical mean and recent trends point towards the greater exposure in the southern European Mediterranean region, driven by the significant increase of HW frequency, duration and maximum severity, especially in the last 3 decades; conversely, annual maximum EHF intensities (i.e., greatest deviations from the local 90th daily mean temperature) are mostly found in the northern and/or high altitude Boreal, Alpine and Continental regions, as a consequence of the latitudinal effect of local climatology on the HWM/HWA indices (this also translates into greater magnitudes of change, in this regions). Nonetheless, by simultaneously considering the probability of Severe HW occurrence in the last three decades, together with the log transformation of people aged 65 or more, results show that greater HW Exposure Indices affect FUAs across the whole Europe, irrespective of its regional climate, suggesting that more meaningful vulnerability assessments, early warning and adaptation measures should be prioritized accordingly.

Isı Dalgası Oluşumlarının Zamansal Analizi: Kano Metropolisi, Nijerya

Heatwaves have become one of the biggest ecological threats to the survival of people in thebiosphere. For the reason, in this study is aimed that is analyzed the temporal occurrences of heatwaves in the Kano between 2009 to 2018 so as and that it devised a protocol against for this menace. Daily maximum temperature is measured at the synoptic hours during the period of extreme heat (hot anddry). With the se temperature values were used to takeout the period of heatwaves using percentile thresholds of 95th. In 2016 it experienced high number of heatwaves occurrences with consecutive 26 days of 40.8°C. The heatwaves is occurred frequently in April and May. This situation, it implies that is identifying as the periods when the occurrence of heatwaves is intense in Kano in April and May.

Substantial increase in daytime-nighttime compound heat waves and associated population exposure in China projected by the CMIP6 multimodel ensemble

This paper presents the projected changes in daytime-nighttime compound heat waves (HWs) (i.e. concurrent occurrence of HWs both in daytime and nighttime) and associated population exposure in China under the shared socioeconomic pathway (SSP)2-4.5 and SSP5-8.5 scenarios based on the Coupled Model Intercomparison Project phase 6 simulations. A comparison with the changes in daytime HWs (i.e. occurring only in daytime) or nighttime HWs (i.e. occurring only in nighttime) is also conducted. The results generally indicate an aggravated risk of compound HWs in China in the future under warmer scenarios. On the national average, the compound HWs are projected to increase persistently toward the end of the 21st century, with larger increase under SSP5-8.5 than that under SSP2-4.5. The greatest changes occur in northwest China and southern China. Compared with the daytime or nighttime HWs, the projected increase of compound HWs is the greatest. Accordingly, the proportion of compound HWs to the total HW events tends to increase and that of daytime HWs tends to decrease toward the end of the 21st century. The substantial increases in the frequency of compound HWs are expected to cause a significant increase in population exposure across the entire country. The projected increase of nationally averaged population exposure is 12.2-fold (7.9-fold) of the current in the mid-century (2046–2065) and further enhances to 16.3-fold (12.4-fold) in the end-century (2081–2100) under SSP5-8.5 (SSP2-4.5). The largest increases are distributed in western China and southern China. These findings raise the necessity and urgency for policy-makers and the public to develop measurements to address compound HW risks.

The Role of Recovery Phases in Mitigating the Negative Impacts of Marine Heatwaves on the Sea Star Asterias rubens

During recent years, experimental ecology started to focus on regional to local environmental fluctuations in the context of global climate change. Among these, marine heatwaves can pose significant threats to marine organisms. Yet, experimental studies that include fluctuating thermal stress are rare, and if available often fail to base experimental treatments on available long-term environmental data. We evaluated 22-year high-resolution sea surface temperature data on the occurrence of heatwaves and cold-spells in a temperate coastal marine environment. The absence of a general warming trend in the data may in parts be responsible for a lack of changes in heatwave occurrences (frequency) and their traits (intensity, duration, and rate of change) over time. Yet, the retrieved traits for present-day heatwaves ensured most-natural treatment scenarios, enabling an experimental examination of the impacts of marine heatwaves and phases of recovery on an important temperate predator, the common sea star Asterias rubens. In a 68-days long experiment, we compared a 37- and a 28-days long heatwave with a treatment that consisted of three consecutive 12-days long heatwaves with 4 days of recovery in between. The heatwaves had an intensity of 4.6°C above climatological records, resulting in a maximum temperature of 23.25°C. We demonstrate that heatwaves decrease feeding and activity of A. rubens, with longer heatwaves having a more severe and lasting impact on overall feeding pressure (up to 99.7% decrease in feeding rate) and growth (up to 87% reduction in growth rate). Furthermore, heatwaves of similar overall mean temperature, but interrupted, had a minor impact compared to continuous heatwaves, and the impact diminished with repeated heatwave events. We experimentally demonstrated that mild heatwaves of today’s strength decrease the performance of A. rubens. However, this echinoderm may use naturally occurring short interruptions of thermal stress as recovery to persist in a changing and variable ocean. Thus, our results emphasize the significance of thermal fluctuations and especially, the succession and timing of heat-stress events.

Engineering Properties and Economic Feasibility Evaluation of Eco-Friendly Rainwater Detention System with Red Clay Water-Permeable Block Body

An integrated rainwater management system is necessary due to the frequent occurrence of localized torrential rainfall and heat waves caused by an abnormal climate. It is necessary to develop a rainwater detention system that can implement rainwater infiltration and detention simultaneously. In this study, the safety, durability, and eco-friendliness of an eco-friendly rainwater detention system developed using an eco-friendly inorganic binder, which involves red clay, were evaluated and its economic feasibility was compared with that of the existing detention system. After 14 days, analysis of the maximum compression load and computational finite element analysis confirmed that the strength standard was satisfied and the structure was safe. No heavy metals or organic compounds were detected in the leaching test. Thus, the eco-friendly rainwater detention system is structurally safe and eco-friendly with no impact on the soil and groundwater environment, and is economically feasible because the construction cost and life cycle cost are approximately 30% and 58% lower, respectively, than those of the existing polyethylene infiltration detention tank system. These results indicate that improved safety, eco-friendliness, and economic feasibility can be achieved, compared to those of the existing system, if the eco-friendly rainwater detention system is applied in the field.

Response of Posidonia oceanica (L.) Delile and Its Associated N2 Fixers to Different Combinations of Temperature and Light Levels

The increasing occurrence of heat waves and water turbidity are threats to the persistence of seagrass meadows. Their effects on the productivity of seagrasses and the functioning of their associated microorganisms have not been studied extensively. The purpose of this study is to assess the effects of different light levels and temperatures onPosidonia oceanica; the endemic seagrass species in the Mediterranean Sea, and their N2-fixing community, which contributes importantly to the nitrogen requirements and high productivity of the plants. Aquarium experiments were conducted in winter, when the plants are more vulnerable to changes in temperature, subjecting them to short-term exposures to an ambient (15.5°C) and elevated temperatures (ambient+5.5°C), and at limited (13 μmol photons m−2s−1) and saturating light conditions (124 μmol photons m−2s−1). Primary production, chlorophyll content, reactive oxygen species production, polyphenols content, thenifHgene expression, N2fixation, and alkaline phosphatase activities were measured in different plant tissues. Plants incubated at ambient temperature and high light exhibited an enhanced total chlorophyll production. Significantly higher gross and net primary production rates were also recorded under ambient temperature and high light conditions, which were approximately two-fold compared to the rest of the treatments. The oxidative stress analyses revealed an increased production of reactive oxygen species in young leaves incubated at ambient temperature and saturating light, while the polyphenols content in top leaves was considerably higher under elevated temperatures. In contrast, the N2fixation and alkaline phosphatase rates were significantly higher under elevated temperature and low light levels. The presence of the N2-fixing phylotypes UCYN-A, -B, and -C was detected through genetic analyses, with UCYN-B demonstrating the highestnifHgene transcription levels at elevated temperatures. These findings emphasize the significant role of irradiance on the productivity ofP. oceanicaand the temperature dependence of the N2fixation process in winter.

Population Exposure Changes to One Heat Wave and the Influencing Factors Using Mobile Phone Data—A Case Study of Zhuhai City, China

The frequent occurrence of extreme high temperature weather and heat waves has greatly affected human life. This paper analyzes population exposure and its influencing factors during a heat wave incident in Zhuhai from 6 to 12 September 2021 based on real-time mobile phone data and meteorological data. The results show that the most areas of Zhuhai are affected by high temperature during this heat wave incident. The hourly population exposure is directly proportional to hourly heat wave coverage. In terms of time dimension, the overall population exposure shows a trend of decreasing and then increasing. In terms of spatial dimensions, high population exposure is concentrated in areas such as primary and secondary schools, colleges and universities, office buildings, and residential areas. Low exposure is distributed in most of the mountainous areas along the southern coast. In addition, the leading factors that cause changes in population exposure in different periods of the heat wave cycle are different, which rely more on either climatic factors or population factors.

Probabilistic Forecast of the Extended Range Heatwave Over Eastern China

Several probabilistic forecast methods for heatwave (HW) in extended-range scales over China are constructed using four models (ECMWF, CMA, UKMO, and NCEP) from the Subseasonal-to-Seasonal (S2S) database. The methods include four single-model ensembles (SME; ECMWF, CMA, UKMO, and NCEP), multi-model ensemble (MME), and Bayesian model averaging (BMA). The construction and verification of reforecasts are implemented by a defined heat wave index (HWI) which is not only able to reflect the actual occurrence of heatwaves, but also to facilitate forecast and verification. The performance is measured by traditional verification method at each grid point of the 105°E to 132°E; 20°N to 45°N domain for the July, August, and September (JAS) of 1999–2010. For deterministic evaluations of HWI forecast, BMA shows a better pattern correlation coefficient than SME and MME and comparable equitable threat score (ETS) with ECMWF and MME. The good performance of ECMWF and MME take advantage of setting the percentile thresholds for forecasting HW. For the probabilistic forecast, the Brier score of BMA is comparable (superior) to that of MME and ECMWF at short (long) lead-time. BMA also demonstrates an improvement on the reliability of probabilistic forecast, indicating that BMA method is a useful tool for an extended-range forecast of HW. Meanwhile, in the real-time extended-range probabilistic forecast, the beginning date, end date, and probability of HW event can be predicted by the HWI probabilistic forecast of BMA.

Long-term analysis of thermal comfort conditions during heat waves in Ukraine

The aim of this study is assessment of thermal comfort conditions during heat waves in Ukraine in the years 1961-2015. The assessment is based on the thermal index Physiologically Equivalent Temperature. This study uses data from 29 meteorological stations across Ukraine. The research showed an increasing frequency of occurrence of heat waves (HWs) in the territory of Ukraine in the last decades. East and south Ukraine (except of coastal stations) experienced the most strenuous human-biometeorological conditions whilst HWs were recorded in the country. Lower mean PET values were found in Western region of the country. The obtained results suggest that the HW event of 2010 was the longest and the most strenuous HW in human-biometeorological terms since 1961.

Implications of Increasing Household Air Conditioning Use Across the United States Under a Warming Climate

AbstractSoaring temperatures and increased occurrence of heatwaves have drastically increased air‐conditioning demand, a trend that will likely continue into the future. Yet, the impact of anthropogenic warming on household air conditioning is largely unaccounted for in the operation and planning of energy grids. Here, by leveraging the state‐of‐the‐art in machine learning and climate model projections, we find substantial increases in future residential air conditioning demand across the U.S.—up to 8% with a range of 5%–8.5% (13% with a range of 11%–15%) after anthropogenic warming of 1.5°C (2.0°C) in global mean temperature. To offset this climate‐induced demand, an increase in the efficiency of air conditioners by as much as 8% (±4.5%) compared to current levels is needed; without this daunting technological effort, we estimate that some states will face supply inadequacies of up to 75 million “household‐days” (i.e., nearly half a month per average current household) without air conditioning in a 2.0°C warmer world. In the absence of effective climate mitigation and technological adaptation strategies, the U.S. will face substantial increases in air conditioning demand and, in the event of supply inadequacies, there is increased risk of leaving millions without access to space cooling during extreme temperatures.

Effects of Heat Stress Exposure and Climate Change on Health and Safety of Outdoor Workers

The studies carried in the world regarding the possible significant influence of climate change on the health and safety of outdoor workers has not been given the due consideration (especially in the least developed and developing countries). Hundreds and thousands of outdoor workers are exposed to elevated temperatures, humid environments and climate extremes in combination with urban air pollution; which is ultimately impacting their safety and well-being. The statistics show that in the past few years, due to the rise in temperature on earth and frequent heat waves within urban settlements, an abrupt increase has been observed in the rate of heat-related health problems. Exposure to extreme heat (exceeding 40 ºC)causes many direct and indirect health hazards, which include vector-borne diseases and exposure to certain harmful chemicals. Currently, the climatic and heat-related effects are decreasing the working capacity of workers and in the future it is projected that the frequency and magnitude of these effects will increase. With the rise in temperature and the occurrence of frequent heat waves in urban areas, the number of health issues due to high (maximum average)temperature has increased rapidly. This article discusses the impacts of heat exposure and climatic change on productivity,health and safety of outdoor workers by summarizing findings from the literature, and eventually recommends control measures for reducing heat exposure at the outdoor work areasand climatic adaptations. In addition, it argues that there is a need for more research about the impacts on health and economic conditions due to heat and climate change in the workplace on global level (especially in developing countries).

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.

Inland heat waves (IHWs) and associated impacts on hydro-biology of aquatic ecosystems in lower Ganga basin, India.

The present study assessed the occurrence and impact of heat waves on the ecology of two ecosystems namely Bhomra wetland and Ganga River stretch, India. The water samples collected from these ecosystems were analyzed for estimating the hydrological and biological variables during heat wave. The inland heat index (IHI) was derived from the climatic variables, relative humidity and temperature. The study indicated the predominant and periodic occurrence of inland heat waves (IHW) with indices ranging from 34.8 to 42.8°C and 35.9 to 43.5°C at the Bhomra and Ganga River stretch respectively during the summer months (March-June). The first two components of the principal component analysis of physico-chemical parameters and heat index explained 45.6% and 59% of the variation in the Bhomra and Ganga River stretch respectively. PCA showed a similar pattern in variation of IHWs and dissolved oxygen, nutrients, hardness and alkalinity, but a distinct pattern with conductivity and TDS in the wetland. IHW exhibited a similar pattern of variation with TDS, conductivity, dissolved oxygen, pH and hardness and distinct pattern with alkalinity, phosphate and nitrate in the river stretch. The first two components of PCA of IHI and plankton abundance explained 89% of the variation and IHI had a similar pattern of variation with the abundance of diatoms and a diverse pattern of variation with blue-green and green algae in the studied ecosystems which might affect the food availability of the associated fishes. The study suggests that IHW influences the water quality and primary producers and also summarizes the impact of IHW on ecosystem services and necessitates mitigation measures.

Compound climate events increase tree drought mortality across European forests

Climate change can lead to the simultaneous occurrence of extreme droughts and heat waves increasing the frequency of compound events with unknown impacts on forests. Here we use two independent datasets, a compiled database of tree drought mortality events and the ICP-Forest level I plots, to study the impacts of the simultaneous occurrence of hot summers, with elevated vapour pressure deficit (VPD), and dry years on forest defoliation and mortality across Europe. We focused on tree drought mortality and background mortality rates, and we studied their co-occurrence with compound events of hot summers and dry years. In total, 143 out of 310 mortality events across Europe, i.e. 46% of cases, corresponded with rare compound events characterized by hot summers and dry years. Over the past decades, summer temperature increased in most sites and severe droughts resulted in compound events not observed before the 1980s. From the ICP-Forest plots we identified 291 (1718 trees) and 61 plots (128 trees) where severe defoliation and mortality, respectively, were caused by drought. The analyses of these events showed that 34% and 27% of the defoliation and mortality cases corresponded with rare compound climate events, respectively. Background mortality rates across Europe in the period 1993–2013 presented higher values in regions where summer temperature and VPD more steeply rose, where drought frequency increased. The steady increase in summer temperatures and VPD in Southern and Eastern Europe may favor the occurrence of compound events of hot summers and dry conditions. Giving that both, local and intense tree drought mortality events and background forest mortality rates, are linked to such compound events we can expect an increase in forest drought mortality in these European regions over the next decades.

Assessment of Heatwave Vulnerability in Korea Considering Socio-economic Indices

The rising heatwave occurrences in recent times due to climate change have resulted in increased mortalities and socio-economic damage. Consequently, several studies have been conducted to examine heatwave vulnerability in Korea. However, most of these studies used the IPCC vulnerability framework and weighting techniques, such as the equal weight and AHP methods, which lacked objectivity in the process of calculating vulnerability. This study employed socio-economic data to measure the heatwave vulnerability index for individual local governments in Korea using the principal component analysis and entropy weighting methods. These techniques ensure that the aggregation of proxies and the weighting process remain objective, unlike previous studies. According to the obtained results, rural areas such as Jeollanam-do, Jeollabuk-do, Gyeongsangnam-do, and Gyeongsangbuk-do, and relatively decrepit urban areas demonstrated high vulnerability scores. In addition, a positive correlation was found between the calculated vulnerability index and mortalities from the recent heatwaves. The heatwave vulnerability index developed in this study can therefore be used to form effective heatwave response policies suited to the conditions of each local government.

Spatial variations in the trend of heatwave over West Africa

The spatial variation of heatwave occurrences and duration were considered using twelve definitions over West Africa. The definitions are based on different temperature thresholds and percentiles. Daily maximum temperatures were obtained from the high-resolution Princeton Meteorological Forcings for West/Central/East Africa data. Temperature threshold-based definitions of the heatwave were found to have more geographical spread in positive trends in heatwave number than percentile-based methods. Trends in the longest heatwave were more pronounced in the temperature threshold indices than percentile-based indices. Our results also showed that the areas with significant trends increased as the definition grew from 2 to 3 days using a temperature threshold of 35°C. The positive trends of the heatwave in the region should be a growing concern for public health officials.