Number Of Heat Waves Research Articles

Heat Wave Trends in Canadian Regions

ABSTRACT Despite their widespread impacts, there has been limited work to quantify how heat waves have changed in Canada. With no standard definition of a heat wave, we consider two different types of heat waves: climatological heat waves defined by the exceedance of a climatological percentile threshold and heat-warning heat waves which are based on the absolute threshold criteria for issuing heat warnings in Canada. These two heat waves represent different types of events with different primary impacts. We find the type of heat wave strongly influences the number of heat waves each year and the regional patterns of where such events are more prevalent. After the evaluation of climatologies, considering station observations and spatially complete gridded datasets, trends in annual metrics of heat waves were calculated for Canadian regions. Climatological heat waves increased in frequency, duration, and cumulative intensity between 1961 and 2020 across the country and in most regions. Heat-warning heat waves have increased over Northern and Atlantic Canada.

Heat Waves in Portugal During the 2001–2024 Period: An Overview

The present contribution addresses the Heat Waves (HWs) which occurred in Portugal’s mainland during the first 24 years of the XXI century: the number of HWs, their frequency, duration and geographic localization, among other impacts, are described. In a complementary perspective, due to the significant impacts of the 2003 HW, specifically in terms of mortality, a more detailed analysis of this event is performed. For the present analysis, HWs were identified using a modified version of the Heat Wave Duration Index (HWDI) proposed by the World Meteorological Organization (WMO). During the XXI century, between 2001 and 2024, 95 HWs occurred in the Portuguese mainland. In 2024, eight HWs occurred, followed by 2009, 2015 and 2017, with seven HWs each; in terms of monthly distribution, August (17) and May (16) displayed the highest values. HWs are now included in the World Health Organization agenda of natural hazards, enhancing the importance of these events. It is time to start considering HWs and their significant impacts as an important issue, especially in countries with older populations, like Portugal.

Has Climate Change Affected the Occurrence of Compound Heat Wave and Heavy Rainfall Events in Poland?

In the recent decades, an ongoing increase in maximum temperature during summer has been observed in Poland, especially in the central-southern and southeastern areas. This raises the vulnerability of these regions not only to heat waves and drought but also to floods. The potential effect of compound heat waves and extreme rainfall events may be more serious than the effects of these events occurring separately. This research is the first attempt in Poland to investigate whether the presence of a heat wave increases the likelihood of extreme rainfall events, if so, by how much, and whether this changes with warming. For this purpose, we used daily maximum temperature values and 6 h precipitation datasets from 44 meteorological stations in Poland for the 1966–2024 period. It was proven that compound heat wave and extreme rainfall events occurred in Poland with spatially differentiated frequency. They occurred the least frequently on the coast and the most frequently in southwestern, southeastern, and northeastern Poland. The extreme rainfall occurred most often between noon and midnight on the last heat wave day. During these hours, the likelihood of extreme rainfall is, on average, 3.5 times higher than that expected according to climatology norms. With warming, the frequency of days with these compound events increases at the rate of 1.22 days per decade, and the frequency of compound events increases at a rate of 3.75 events per decade. Although a detailed analysis of the mechanisms responsible for such events is planned for further research, the preliminary study revealed that in most cases, the approach of a cold front with a mesoscale thundercloud system was responsible for heat wave termination with extreme rainfall. Since we cannot prevent the growing number of heat waves or heavy precipitation events that terminate the heat wave events in Poland, the adaptation strategy needs to be implemented to meet the sustainable development goals regarding climate actions. This refers primarily to urban planning, agriculture (agroecosystems), social health, and well-being.

Thermal comfort conditions of the Dnipropetrovsk region in the modern period

The study aims to investigate the thermal comfort conditions of the Dnipropetrovsk region for the period 1991–2020, based on modern approaches. The physiologically equivalent temperature (PET) was used to determine the thermal bioclimate in the Dnipropetrovsk region. PET calculations were performed using the RayMan model, which is a microscale model for calculating radiation fluxes in simple and complex environments. Daily data measured at 00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, and 21:00 UTC from six weather stations of the meteorological network of the Ukrainian Hydrometeorological Centre (Dnipro, Kryvyi Rih, Pavlohrad, Nikopol, Komisarivka, Synelnykove) for the period 1991–2020 were used to analyze thermal comfort conditions in the Dnipropetrovsk region. The study of the bioclimatic conditions of the Dnipropetrovsk region showed that in the winter months (December–February), extreme cold stress prevails, with a frequency of occurrence ranging from 94.5% to 99.8% across the region. Starting from the second decade of May until the second decade of September, heat stress of different intensities was observed in the region, with the highest frequency in the second decade of July, ranging from 39.1% in Dnipro to 50% in Nikopol. The highest frequency of strong and extreme heat stress was observed in the first decade of August, ranging from 10.7% to 17% in different parts of the region. During daytime hours, the highest frequency of extreme heat stress in the region was observed in the first decade of August, ranging from 5.1% to 13.3%. The daily variation of PET during the period with the most strenuous hot conditions throughout the year (July’s third decade and August’s first decade) was similar to the daily variation of air temperature, with minimum values after sunrise (03:00 UTC) and maximum values after midday (12:00 UTC). The most comfortable conditions were found in the morning and evening hours (06:00 UTC and 18:00 UTC, respectively). In the city of Dnipro, the number of heat waves (HW) increased from 16 to 33 in the period 1991–2020 compared to the normal climatic period (1961–1990). The mean PET value during HW events in Dnipro during the period 1991–2020 was 39.7°C, while during the summer months, it was nearly 10°C lower (29.9°C).

Long-term trends of heat waves and ecosystem responses in Jiaozhou Bay, the Yellow Sea

Long-term trends of heat waves and ecosystem responses in Jiaozhou Bay, the Yellow Sea

Changes in duration and intensity of waves of heat and cold on the territory of Belarus over the period from 1955 to 2021

The impact of modern climate warming on the characteristics of heat and cold waves on the territory of Belarus has been analysed. Since 1988, the number of heat waves and strong thaws has significantly increased (less than 15% of all registered heat waves and strong thaws occurred in the pre-warming period of 1955–1987), while the number of frost and summer cold waves has decreased. The average duration of frost and summer cold waves has decreased by 0.5–1.5 days, the average duration of strong thaws has increased by 1 day, while the changes in the duration of heat waves have been less significant. The greatest changes in temperature have been observed for strong thaws and frost waves (increase of up to 0.8°C). Heat waves are characterized by a decrease in the average duration by 1 day and the smallest temperature changes, because due to increase in average values, summer temperatures got closer to thresholds for a heat wave. Despite the effect of modern warming, frost waves remain the most intense type of extreme temperature episodes in Belarus. The spatial distribution of temperatures during heat and cold waves is either uniform or determined by seasonal temperature gradients.

Why Will a Small Increase in Global Temperature Lead to a Large Increase in the Number of Heat Waves? Truncation and Extreme Events

This article shows why small changes in a distribution can have outsized effects on extreme events. The paper uses as an initial example, consider the marathon runners. By working through a hypothetical situation using real data from the 2019 Boston marathon, the authors find that if all runners increased their speed by 5%, the number the number of runners with a sub 2:30 time would increase by 160%. The paper illustrates just how common this effect is, by considering the effect of “truncation” on several real-world data sets for tropical storms, daily temperatures and obesity.

Climatology of Wet-Bulb Globe Temperature and Associated Heat Waves in the U.S. Great Plains

Abstract Extreme heat such as that seen in the United States and Europe in summer 2022 can have significant impacts on human health and infrastructure. The Occupational Safety and Health Administration (OSHA) and the U.S. Army use wet-bulb globe temperature (WBGT) to quantify the impact of heat on workers and inform decisions on workload. WBGT is a weighted average of air temperature, natural wet-bulb temperature, and black globe temperature. A local hourly, daily, and monthly WBGT climatology will allow those planning outdoor work to minimize the likelihood of heat-related disruptions. In this study, WBGT is calculated from the ERA5 reanalysis and is validated by the Oklahoma Mesonet and found to be adequate. Two common methods of calculating WBGT from meteorological observations are compared. The Liljegren method has a larger diurnal cycle than the Dimiceli method, with a peak WBGT about 1°F higher. The high- and extreme-risk categories in the southern U.S. Great Plains (USGP) have increased from 5 days per year to 15 days from 1960 to 2020. Additionally, the largest increases in WBGT are occurring during DJF, potentially lengthening the warm season in the future. Heat wave definitions based on maximum, minimum, and mean WBGT are used to calculate heat wave characteristics and trends with the largest number of heat waves occurring in the southern USGP. Further, the number of heat waves is generally increasing across the domain. This study shows that heat wave days based on minimum WBGT have increased significantly which could have important impacts on human heat stress recovery.

Determination of heat wave definition temperatures in Spain at an isoclimatic level: time trend of heat wave duration and intensity across the decade 2009–2018

BackgroundIn line with WHO guidelines for the implementation of public health prevention plans targeted at the impacts of high temperatures, a heat wave definition temperature (Tthreshold) was calculated for 182 so-called “isoclimatic zones” (IZ) in Spain. As the dependent variable for determining this Tthreshold, we analysed daily all-cause mortality data (ICD-10: A00-R99) for each IZ across the period 2009–2018. The independent variable used was the mean value of the maximum daily temperature of the summer months recorded at meteorological observatories in each IZ. We used Box–Jenkins models to ascertain mortality anomalies, and scatterplots to link these anomalies to the temperatures at which they occurred, thereby determining the Tthreshold for each IZ. We then calculated how many heat waves had occurred in each IZ, as well as their intensity, and analysed their time trend over this period.ResultsThe results showed that in 52.5% of the IZ, the percentile of the maximum temperatures series of the summer months to which Tthreshold corresponded was below the 95th percentile of the meteorological heat wave definition in Spain: indeed, it only coincided in 30.7% of cases. The geographical distribution of these percentiles displayed great heterogeneity as a consequence of the local factors that influence the temperature–mortality relationship. The trend in the number of heat waves analysed indicated an overall increase in Spain at a rate of 3.9 heat waves per decade, and a similar rise in mean annual intensity of 9.5 °C/decade. These time-trend values were higher than those yielded by analysing the trend in meteorological heat waves based on the 95th percentile.ConclusionsThe results obtained in this study indicate the need to use a heat wave definition based on epidemiological temperature–mortality studies, rather than on values based on meteorological percentiles. This could be minimising estimated health impacts in analyses of future impacts attributable to heat.

Heat wave characteristics: evaluation of regional climate model performances for Germany

Abstract. Heat waves are among the most severe climate extreme events. In this study, we address the impact of increased model resolution and tailored model settings on the reproduction of these events by evaluating different regional climate model outputs for Germany and its near surroundings between 1980–2009. Outputs of an ensemble of six EURO-CORDEX models with 12.5 km grid resolution and outputs from a high-resolution (5 km) WRF (Weather Research and Forecasting) model run are employed. The latter was especially tailored for the study region regarding the physics configuration. We analyze the reproduction of the maximum temperature, number of heat wave days, heat wave characteristics (frequency, duration and intensity), the 2003 major event, and trends in the annual number of heat waves. E-OBS is used as the reference, and we utilize the Taylor diagram, the Mann–Kendall trend test and the spatial efficiency metric, while the cumulative heat index is used as a measure of intensity. Averaged over the domain, heat waves occurred about 31 times in the study period, with an average duration of 4 d and an average heat excess of 10 ∘C. The maximum temperature was only reproduced satisfactorily by some models. Despite using the same forcing, the models exhibited a large spread in heat wave reproduction. The domain mean conditions for heat wave frequency and duration were captured reasonably well, but the intensity was reproduced weakly. The spread was particularly pronounced for the 2003 event, indicating how difficult it was for the models to reproduce single major events. All models underestimated the spatial extent of the observed increasing trends. WRF generally did not perform significantly better than the other models. We conclude that increasing the model resolution does not add significant value to heat wave simulation if the base resolution is already relatively high. Tailored model settings seem to play a minor role. The sometimes pronounced differences in performance, however, highlight that the choice of model can be crucial.

Evaluating the Present and Future Heat Stress Conditions in the Grand Duchy of Luxembourg

The impact of elevated air temperature and heat stress on human health is a global concern. It not only affects our well-being directly, but also reduces our physical work capacity, leading to negative effects on society and economic productivity. Climate change has already affected the climate in Luxembourg and, based on the results of regional climate models, extreme heat events will become more frequent and intense in the future. To assess historical conditions, the micro-scaleRayManPro 3.1 model was used to simulate the thermal stress levels for different genders and age classes based on hourly input data spanning the last two decades. For the assessment of future conditions, with a special emphasis on heat waves, a multi-model ensemble of regional climate models for different emission scenarios taken from the Coordinated Regional Climate Downscaling Experiment (CORDEX) was used. For both, the past and future conditions in Luxemburg, an increase in the heat stress levels was observed. Small differences for different age groups and genders became obvious. In addition to the increase in the absolute number of heat waves, an intensification of higher temperatures and longer durations were also detected. Although some indications of the adaptation to rising air temperatures can be observed for high-income countries, our results underscore the likelihood of escalating heat-related adverse effects on human health and economic productivity unless more investments are made in research and risk management strategies.

Observed changes in the characteristics of heat waves in hot and dry regions of Iran

Research on heat waves is greatly important not only due to their effect on social, economic, and ecological systems, but also due to the complexity of the processes that create them. Therefore, this research mainly investigated the trend of long-term changes in various characteristics of heat waves in hot and dry regions of Iran. For this purpose, the daily maximum temperature data of 15 meteorological stations in the central and southeastern parts of Iran were used from 1985 to 2018. Using the excess heat factor (EHF) index, five different features of heat waves including the number of heat waves (HWN), heat waves duration (HWD), heat waves frequency (HWF), heat waves mean (HWM), and heat waves magnitude (HWA) were extracted for all the studied stations. Then, their trend of long-term changes was analyzed using the Sen’s slope estimator nonparametric method. The results showed that on a regional scale, all five characteristics of heat waves have an increasing trend at a significance level of 95%, so an increase of 0.5 events per decade has been observed for the HWN. The trend of long-term changes in the HWD has also indicated an increase of 0.91 days per decade. The HWF has shown more drastic changes than other characteristics of heat waves, so in every decade 2.61 days have been added to the frequency of days contributing to the occurrence of heat waves. The regional intensity of HWM and HWA also show an increase of 0.1 and 0.4 °C in each decade, respectively. These findings show the importance of choosing a suitable index for monitoring different characteristics of heat waves. The EHF index is a suitable index, which can be one of the efficient indices in this regard.

How persistent and hazardous will extreme temperature events become in a warming Portugal?

How persistent and hazardous will extreme temperature events become in a warming Portugal?

Parametric heat wave insurance

This paper proposes a flexible framework for structuring and pricing parametric heat wave insurance. The framework is based on a general heat wave definition formulated in terms of an underlying temperature index. The definition can be varied in terms of the heat wave duration, intensity, measurement period and underlying index. This construction makes it straightforward to create contracts tailored to insure against heat events of many different types. A single stochastic model for the underlying index can be used to price all contracts. We consider contracts with payments that depend on the number of heat waves of a certain type occurring in the measurement period and derive the necessary pricing relations based on a general model structure encompassing several popular temperature models in the literature. An empirical case study is performed using data for Berlin where the daily maximum temperature is used as the underlying index. Model implied heat wave probabilities are consistent with historical patterns, point to high likelihoods for short duration heat events of different threshold temperatures and non-negligible risks for future heat waves of extreme temperatures and durations never before observed.

Climate change and the environment - trends and possible consequences

Climate change is one of the greatest challenges of modern humanity. It is evident that climate change during the last two decades have affected our areas very intensively. This mainly refers to the increase in air temperature throughout the year, but also in all seasons. The increase in air temperatures during the winter caused a smaller number of days with the appearance of snow, but also days when the snow cover remains on the ground. In addition, climate change has caused and disrupted the normal distribution of precipitation in the form of rain in the territory of the Republic of Srpska and Bosnia and Herzegovina, as well as in the region of Southeastern Europe. It is interesting that over the past two decades, the number of days without precipitation has increased, as well as the number of days with intense precipitation. This is precisely what caused the increasingly frequent and intense occurrence of droughts as well as river, torrential and urban floods in the territory of Bosnia and Herzegovina. Unfortunately, the consequences for the population, their lives, infrastructure and property are increasing. Climate models indicate that in Europe, temperature and precipitation trends in the 21st century will continue in the same direction as during the second half of the 20th century. This means that the temperature will continue to rise the most in the winter season in Northern Europe, and during the summer season in Southern Europe. On the other hand, precipitation shows greater regional and seasonal variability, with the precipitation increasing inNorthernEurope anddecreasing inSouthern Europe.Also, based on previous research, an increase in extreme events in Europe is projected, especially in the form of heat waves, droughts and intense rainfall. There is an evident tendency to increase the number of heat waves and intense precipitation based on climate models. Such trends and changes point to a serious problem of more frequent and intense occurrences of drought and water deficit, and to the need for more significant integration of climate change into planning and strategic documents. Certainly, future research is also necessary, where it is necessary to include projections of climate indices, especially temperature extremes and intense precipitation that can cause the occurrence of fluvial and torrential floods.

Potential impact of climate change on shifting the calendar of rainfed crops produced in Jordan

Climate change alters the usual pattern of rainfall distribution and temperature in the East Mediterranean region. We investigated the impact of climate change on true season onset, and crop calendar for field crops grown in areas with Semi-Arid-Sub-Humid Mediterranean climate. Analysis showed a clear reduction of annual rainfall for the zone with rainfall more than 200 mm, and above 1°C rise in air temperature for all zones. Generally, the rainfall reduction occurred, in descending order, along the South-North direction. A new approach is proposed to identify the true season onset and the end of the effective rainy season. Shifting the true season onset consequently reduces the crop-growing season and hence the yield. Reducing annual rainfall and the length of effective rainfall season, rising air temperature, and the sharp increase in the number of heat waves will have profound negative impacts on both plant growth and yield.

THE IMPACT OF HEAT WAVES ON THE LEVEL OF AIR POLLUTION IN KYIV

Air pollution level in big cities is heavily influenced by meteorological factors, including heat waves (HWs). During the last decades, the number of HWs and their intensity has increased worldwide including in Ukraine. Heat waves are more intensive in big cities, because of manmade surfaces and fewer green zones. The aim of this study is to investigate the impact of heat waves on the level of air pollution in Kyiv. The research is based on the concentrations of formaldehyde, nitrogen dioxide, and sulfur dioxide measured on 6 monitoring stations during the summer months of 2017–2021 in Kyiv. These monitoring stations are characterized by very different concentrations of air pollutants. Data from daily observations of maximum air temperature for the periods 1961–1990 and 2017–2021 are employed for the identification of HW episodes for the summer period. To describe pressure conditions favoring the occurrence of heat waves, daily values of sea-level pressure (SLP), the height of the geopotential height of 500 hPa, and temperature on the 850 hPa pressure surface were used. The research showed the effect of heat waves on the concentrations of nitrogen dioxide, formaldehyde, and sulfur dioxide in the air of Kyiv. The concentrations of these pollutants during the heat wave events at all studied monitoring stations (regardless of the initial level of air pollution) and a gradual decrease in concentrations after the HWs finished have been found. The circulation processes caused to the formation of HWs over the territory of Ukraine were analyzed. It was shown that during the heat waves that occurred in Kyiv within the years 2017–2021, in all cases, except for one, the baric field formed over the studied territory had almost the same structure and shape. It is confirmed that the formations of heat waves in Kyiv are associated with anticyclonic formations in the atmosphere. Therefore, the influence of heat waves on the concentrations of formaldehyde is explained by the fact that during the HWs, there are very favorable conditions for the course of photochemical reactions from precursor substances, which leads to an increase in the concentration of this pollutant, while the influence on the concentrations of sulfur dioxide and nitrogen dioxide is caused by the fact that heat waves are characterized by all features of anticyclonic weather (like low wind speeds (or calm), inversions, etc.) which are favorable conditions for the accumulation of pollutants in the atmosphere.

Spatio-Temporal Analysis of Heatwaves Characteristics in Greece from 1950 to 2020

Heatwave events are of major concern in the global context, since they can significantly impact ecosystems, economies and societies. For this reason, more detailed analyses of the characteristics and trends of heatwaves represent a priority that cannot be neglected. In this study, the interannual and decadal variability of seven indices of heatwaves were investigated during the warmest period of the year (June–August) by using an enhanced resolution reanalysis model (ERA5-Land) over a 71-year period (1950–2020) for the area of Greece. Heatwaves were defined as periods where two thresholds, based on a modified version of the Excess Heat Factor index (EHF) and the 95th percentile of the maximum daily temperature, were exceeded for at least three consecutive days. Greece experiences almost yearly 0.7 heatwaves on average during the whole period of study, while this value has increased by ~80% since 1990. Trend analysis revealed that heatwaves have become more frequent, longer, and more intense since 1950. The percentage of the land area that experiences at least one heatwave per year was almost doubled in the examined period. An increasing trend in the number of heatwaves that occurred in June was identified.

Exacerbated heat in large Canadian cities

Exacerbated heat in large Canadian cities

Increased occurrence of high impact compound events under climate change

While compound weather and climate events (CEs) can lead to significant socioeconomic consequences, their response to climate change is mostly unexplored. We report the first multi-model assessment of future changes in return periods for the co-occurrence of heatwaves and drought, and extreme winds and precipitation based on the Coupled Model Intercomparison Project (CMIP6) and three emission scenarios. Extreme winds and precipitation CEs occur more frequently in many regions, particularly under higher emissions. Heatwaves and drought occur more frequently everywhere under all emission scenarios examined. For each CMIP6 model, we derive a skill score for simulating CEs. Models with higher skill in simulating historical CEs project smaller increases in the number of heatwaves and drought in Eurasia, but larger numbers of strong winds and heavy precipitation CEs everywhere for all emission scenarios. This result is partly masked if the whole CMIP6 ensemble is used, pointing to the considerable value in further improvements in climate models.