Occurrence Of Heat Waves Research Articles

Future projection of heat waves over China under global warming within the CORDEX-EA-II project

Driven by four global climate models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) (i.e., CNRM-CM5, EC-EARTH, GFDL-ESM2M and MPI-ESM-LR) under the Representative Concentration Pathway 8.5 (RCP8.5) scenario, projections for future changes in heat waves over China are performed by Weather Research Forecasting (WRF) model simulations for future (FTR, 2031–2055) and present (1981–2005) periods. Six heat wave indices are applied to characterize heat waves based on their frequency, duration, magnitude, intensity, accumulated occurrence days and severity. Analyses show that notable increases in heat wave indices cover all of China. More areas will endure more frequent, longer lasting and more severe heat waves in the coming decades. The increasing tendencies of heat wave indices in the FTR period are more significant than those at present, indicating that heat waves will intensify more rapidly in the future. The impacts of climate changes on the accumulated properties of heat waves are more substantial than those on the individual aspects of heat waves. It is also projected that stronger heat waves with prolonged durations and more severe magnitudes will occur more often in the FTR period, whereas relatively weaker heat waves would occur less often. Hence, the occurrence of extreme heat waves shows a more remarkable increase than the occurrence of moderate heat waves. The changes in heat waves can be largely explained by the changes in the dominating high-pressure systems.

Ranking European capitals by exposure to heat waves and cold waves

In warming Europe, we are witnessing a growth in urban population with aging trend, which will make the society more exposed and vulnerable to extreme weather events. In the period 1950–2015 the occurrence of extreme heat waves increased across European capitals. As an example, in 2010 Moscow was hit by the strongest heat wave of the present era, killing more than ten thousand people. The cold extremes will have decreasing tendency as global warming progresses, however due to higher variability of future climates, the cold wave hazard may remain locally important threat. Moreover, the heat and cold-related mortality will be enhanced with foreseen demographic evolution in European cities.Here we focus on larger metropolitan areas of European capitals (EU28 plus Moscow, Oslo and Zurich). By using an ensemble of eight EURO-CORDEX models under the RCP8.5 scenario, we detected heat waves and cold waves events by deployment of Heat Wave Magnitude Index daily and its cold wave counterpart. We introduce a ranking procedure based on ensemble predictions using the median of metropolitan grid cells for each capital, and population density as a proxy to quantify the future exposure.All the investigated European metropolitan areas will be more vulnerable to extreme heat in the coming decades. Based on the impact ranking, results reveal that cold waves will represent some threat in mid of the century but they will not be the major threat in any of European capitals, and that they are projected to completely vanish by the end of this century. On the contrary, in near, but even more so in distant future, extreme heat events in European capitals will be not exclusive to traditionally exposed areas such as the Mediterranean and the Iberian Peninsula. The ranking of European capitals based on their exposure to extreme heat is of paramount importance to decision makers in order to mitigate the heat related mortality, especially with the foreseen increase of global mean temperature. Furthermore, this simple comparative indicator helps communicating the global, complex and impersonal issue of climate change locally thus contributing to raise awareness and call for action.

The occurrence of heat waves in Europe and their circulation conditions

The objective of the paper was to characterize the occurrence of heat waves in Europe between 1976 and 2015 and to determine circulation conditions causing their occurrence. The heat waves were recognized as a sequence of at least 5 consecutive hot days. The hot day was defined as a day on which daily maximum air temperature was higher than 95th percentile of all the values in the analyzed period. The conducted research showed an increase in the number of heat waves and their duration in the analyzed period. The longest heat wave occurred in 2010, in Moscow, which lasted 45 days. The most intense changes were observed in the eastern and south-eastern regions. The occurrence of heat waves was mainly connected with positive anomalies of atmospheric pressure at sea level, geopotential height of 500 hPa, and temperature on isobaric surface 850 hPa.

Mortality prediction of laying hens due to heat waves

Mortality in the production of laying hens is a concern for producers and constitutes a considerable economic loss. Some climatic events, such as heat waves, are directly related to the mortality increasing. The aim of this study was to relate the occurrence of heat waves with laying hens mortality, considering the effect of two different kinds of shed used in egg production. Daily mortality data were obtained from two aviaries located in the city of Bastos-SP for the period of October 2014 to January 2016. The data about the climate were gotten from two meteorological stations located in the cities of Tupa-SP and Rancharia-SP, Brazil, from 2010 to 2015. The heat waves were classified in the climatic database using different definitions recommended in the literature (FRICH et al., 2002; INSTITUTO NACIONAL DE METEOROLOGIA, 2016; ROSSATO; SARTORI; MISSIO, 2003 TEBALDI et al., 2006). Mortality and climate data were related in a single database and were classified into normal and high mortality by data mining using the J48 algorithm. It was possible to associate the occurrences of heat wave and the increase of mortality of laying hens. The classification tree generated identified accurately 71% of occurrences of high mortality and 95% of all mortality data. The classification tree allowed to relate the increase in laying mortality in function of heat waves and allows a prediction of when there will be a bigger chance of high mortality.

Heat waves in Berlin and Potsdam, Germany – Long‐term trends and comparison of heat wave definitions from 1893 to 2017

Heat waves (HWs) are natural hazards characterised by episodes of hot weather. However, in the absence of a universal definition a wide variety of definitions is applied. In this study, ten different air temperature (T) based HW definitions are applied to the urban region of Berlin, Germany, to investigate and compare the occurrence and duration of HWs, and their long‐term trends from 1893 to 2017. We studied how long‐term trends depend on different definition of HWs, as well as if long‐term mean values and trends differ between inner‐city and peripheral locations of Berlin. Generally, results show significant increases in HW occurrence and duration for most definitions, although large differences exist between them. Temporal agreement between the definitions is low, 15 episodes in 125 years are identified by all definitions as HWs. Inner‐city regions of Berlin are subject to more frequent and longer HWs than peripheral regions, if definitions based on daily minimum or mean T are applied. Results also show that trend estimations of HW characteristics for HW definitions with “extreme” values for their detection criteria (e.g., in terms of duration or threshold) are highly sensitive to the applied method. We conclude that depending on the question under investigation, different HW definitions might be optimal and hence attempts for the development of “universal” definitions need to take this into account.

Caracterização Climática de Ondas de Calor no Brasil

According to the state-of-the-art global and circulation models the probability of occurrence of large heat waves in the following decades will increase significantly. Currently, due to their significant impacts in several socio-economic areas such as public health, energy production and consumption and agriculture, there are numerous studies for the Northern Hemisphere regions evaluating this problem. However, for the southern hemisphere and especially Brazil, a similar analysis is lacking, despite its huge geographical area and large population potentially affected. The main goal of this work is to provide a comprehensive diagnostic study of heat waves observed in several large Brazilian cities, including heat waves frequency, seasonal distribution and temporal evolution since the 1960s decade. In general, results indicate the presence of a positive trend in the frequency and duration of heat waves since the 1980s, with special emphasis to cities like Sao Paulo, Manaus and Recife. Brasilia was the city that in the last decades recorded the highest number of heat waves while Rio de Janeiro was the city with the smallest number recorded. In respect to seasonal variability the Autumn/Winter months were the months with the largest number of heat waves recorded.

Strong heat and cold waves in Poland in relation with the large-scale atmospheric circulation

Occurrence of heat and cold waves in Poland in the years 1966–2015 (1966/1967–2015/2016) was described, and their circulation conditions were determined in this study. A heat wave is defined as a period of at least 3 days with Tmax > 30.0 °C and a cold wave as a period of at least 3 days with Tmax <− 10.0 °C. Heat waves occurred most often in central and southern Poland and cold waves in north-eastern Poland. The occurrence of both heat and cold waves is related to high pressure systems. Anticyclonic blocking patterns both in winter and summer inhibit the zonal flow of air masses and intensify the meridional flow. Positive sea level pressure anomalies occurred over the study area, in the case of heat waves up to 3 hPa and in the case of cold waves up to 11 hPa. Perpendicular profiles showing geopotential height and air temperature anomalies in the troposphere were identified for the selected cases of extreme temperature episodes. Centres of geopotential height positive/negative anomalies were detected at the level of 300–250 hPa geopotential height, right over the area of the positive/negative surface temperature extremes.

An Intensified Mode of Variability Modulating the Summer Heat Waves in Eastern Europe and Northern China

AbstractThis study investigates the leading pattern of Eurasian summer heat waves (HWs) using observed and simulated data sets and reveals an intensified mode of variability that bridges the HWs in eastern Europe (EE) and northern China (NC). The concurrent variability of the HWs in EE and NC is primarily driven by an atmospheric circum‐global teleconnection that induces anomalous anticyclones over the two regions. The observed upward trends in EE and NC HW days could be related to the warm sea surface temperatures around Greenland Island, which may weaken the Atlantic westerly jet stream and lead to amplified wave trains at the exit of the jet, resulting in strengthened anticyclones over EE and NC that favor the occurrences of HWs. The Geophysical Fluid Dynamics Laboratory high‐resolution atmospheric model fails to simulate the EE and NC HWs, due probably to the model's poor representation of the South Asian summer rainfall.

Evolution of thermal tolerance in multifarious environments.

Species extinction rates are many times greater than the direst predictions made two decades ago by environmentalists, largely because of human impact. Major concerns are associated with the predicted higher recurrence and severity of extreme events, such as heat waves. Although tolerance to these extreme events is instrumental to species survival, little is known whether and how it evolves in natural populations, and to what extent it is affected by other environmental stressors. Here, we study physiological and molecular mechanisms of thermal tolerance over evolutionary times in multifarious environments. Using the practice of "resurrection ecology" on the keystone grazer Daphnia magna, we quantified genetic and plastic differences in physiological and molecular traits linked to thermal tolerance in historical and modern genotypes of the same population. This population experienced an increase in average temperature and occurrence of heat waves, in addition to dramatic changes in water chemistry, over five decades. On genotypes resurrected across the five decades, we measured plastic and genetic differences in CTmax , body size, Hb content and differential expression of four heat shock proteins after exposure to temperature as single stress and in combination with food levels and insecticide loads. We observed evolution of the critical thermal maximum and plastic response in body size, HSP expression and Hb content over time in a warming only scenario. Molecular and physiological responses to extreme temperature in multifarious environments were not predictable from the response to warming alone. Underestimating the effect of multiple stressors on thermal tolerance can lead to wrong estimates of species evolvability and persistence.

Synoptic climatology and sea surface temperatures teleconnections for warm season heat waves in Saudi Arabia

Little information is available about the synoptic weather patterns and physical factors contributing to the formation and intensity of heat waves (HWs) in Saudi Arabia. The research objectives were to identify the synoptic situations that are related to HW occurrence, to match different HW aspects (frequency and intensity) related to different circulation types, and to examine the possible links/associations between HW days and the sea surface temperature (SST) anomalies of closely associated water bodies (i.e., Mediterranean Sea, Black Sea, Caspian Sea, Arabian Gulf, Arabian Sea, and Red Sea).Using a time-sensitive approach, a HW was defined as a period of at least two consecutive days with a daily maximum temperature equal or higher than the 90th percentile of the monthly maximum and with a daily minimum temperature equal or higher than the 85th percentile of the monthly minimum for the decade in question. Using reanalysis data for 1985–2014, three weather/circulation types were identified using Ward's method for cluster determination. Together, weather types 1 and 3 induced 57.5% of HW days and connected with negative anomalies in sea level pressure with lower heights and warmer temperatures at the 850 hPa level. Weather type 2 induced 42.5% of HW days and was related to positive anomalies at all heights. Intensification of Indian Summer Monsoon Trough and Arabian heat lows were key atmospheric features related to weather types 1 and 3. Anomalies of SSTs of the Red Sea, Arabian Gulf, Caspian Sea, Black Sea, and Mediterranean Sea displayed positive values for both weather types 1 and 3. SSTs anomalies seem to be a more important factor for intensity of a HW day. HWs in Saudi Arabia tend to occur during regional warming due to atmospheric circulation conditions and SST teleconnections.

Global Monsoon Precipitation: Trends, Leading Modes, and Associated Drought and Heat Wave in the Northern Hemisphere

Global monsoon precipitation (GMP) brings the majority of water for the local agriculture and ecosystem. The Northern Hemisphere (NH) GMP shows an upward trend over the past decades, while the trend in the Southern Hemisphere (SH) GMP is weak and insignificant. The first three singular value decomposition modes between NH GMP and global SST during boreal summer reflect, in order, the Atlantic multidecadal oscillation (AMO), eastern Pacific (EP) El Niño, and central Pacific (CP) El Niño, when the AMO dominates the NH climate and contributes to the increased trend. However, the first three modes between SH GMP and global SST during boreal winter are revealed as EP El Niño, the AMO, and CP El Niño, when the EP El Niño becomes the most significant driver of the SH GMP, and the AMO-induced rainfall anomalies may cancel out each other within the SH global monsoon domain and thus result in a weak trend. The intensification of NH GMP is proposed to favor the occurrences of droughts and heat waves (HWs) in the midlatitudes through a monsoon–desert-like mechanism. That is, the diabatic heating associated with the monsoonal rainfall may drive large-scale circulation anomalies and trigger intensified subsidence in remote regions. The anomalous descending motions over the midlatitudes are usually accompanied by clear skies, which result in less precipitation and more downward solar radiation, and thus drier and hotter soil conditions that favor the occurrences of droughts and HWs. In comparison, the SH GMP may exert much smaller impacts on the NH extremes in spring and summer, probably because the winter signals associated with SH GMP cannot sufficiently persist into the following seasons.

Centennial Heat Wave Projections Over Pakistan Using Ensemble NEX GDDP Data Set

Heat waves are one of the extreme weather events affecting as many people as with other climatic hazards such as droughts and floods. Due to rise in global temperatures, the occurrences of heat waves are likely to exacerbate in many regions in future. The projections for future heat waves over Pakistan are analyzed in this study. The heat waves calculation has been done using the latest NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) data set which composed of 21 Global Climate Models (GCMs) statistically downscaled at 0.25° × 0.25° spatial resolution. The heat waves analysis is done with ensemble modelling approach and using two definitions of heat waves: the Heat waves Duration Index (HWDI) and fixed method approach. Two climate change scenarios; RCP4.5 and RCP8.5 are used for investigating future heat wave projections. The historical heat waves are calculated from 1976–2000 and future projected changes are analyzed in three 25 year time spans: 2025–2049, 2050–2074 and 2075–2099. Two metrics heat wave events and heat wave days are separately shown. The results indicate an increase in both number of heat wave events and heat wave days in Pakistan. The most vulnerable areas for future heat waves are northern areas, plains of Sindh and Punjab, the central and western parts of Baluchistan, and all regions of Khyber Pakhtunkhwa (KPK). The increased number of heat waves in northern areas of the country could result in rapid snow melting and can cause flooding downstream. The agricultural regions of the country would be highly vulnerable to increasing number of heat waves.

In this issue of Weather

We begin this issue on p. 207 with an examination of heatwaves and their occurrence in Poland since 1950. In ‘The August 2015 mega-heatwave in Poland in the context of past events’ by Agniewska Krzyźewska and Jamie Dyer, the effects of high summer temperatures and the occurrence of heatwaves in this central European country with a high degree of continentality are discussed. On p. 215, Rodney Hale gives us a fascinating brief overview of unusual electrical phenomena in ‘Rare, anomalous non-transient lights associated with cumulonimbus Clouds’. Through much of the history of meteorological observation, recording instruments produced graphical charts (and this is still the case from some instruments). Tilting syphon rain gauges have been an important method of recording rainfall rates and quantities, but they use daily, weekly or monthly charts which have to be changed at these intervals and that do not provide a digital record that can be used and stored readily. ‘Open-source tool for interactive digitisation of pluviograph strip charts’ by Nejc Sušin and Peter Peer provides a description of freely available software that can be used to extract both rainfall amounts and their rates as digital records from these charts on p. 222. Although there is a well-established observations system for hurricanes in the Atlantic and eastern Pacific Oceans, this a developing science for typhoons in the North-West Pacific, even though this area is globally most active for these storms. Recently, the Chinese government has provided an aircraft to carry out typhoon observation from Hong Kong, as described in ‘The first complete dropsonde observation of a tropical cyclone over the South China Sea by the Hong Kong Observatory’ by Pak-Wai Chan, NG Wu, CZ Zhang, WJ Deng and KK Hon on p. 227. This final paper in our July 2018 issue describes the insights they gained into Tropical Storm Aere and its structure.

Amplifying effect of ENSO on heat waves in China

This paper investigates the impacts of the El Nino Southern Oscillation (ENSO) on various aspects of heat waves (HWs), including frequency, duration, and magnitude, over China during 1961–2014. Results show that El Nino (La Nina) significantly amplifies (weakens) the HW activities in most areas of China. Such influences are particularly strong in southern China. HW activities are enhanced (weakened) during the summers following mature El Nino (La Nina) episodes, with increased (reduced) occurrence of HW events and number of HW days, as well as prolonged (shortened) duration and elevated (decreased) amplitude of such events. These amplifying effects are substantially stronger for severe HWs (i.e., hottest and longest episodes) than for those events of average duration and intensity. Diagnosis by compositing reanalysis data over ENSO events indicates that the atmospheric circulation during the summers following El Nino is characterized by anomalous rising motion over the tropical central Pacific and Indian Oceans, and sinking motion over the western North Pacific (WNP). The anomalous subsidence over the WNP is accompanied by reduced precipitation and condensational heating, as well as anomalous anticyclonic flows in the lower troposphere. El Nino also induces a stronger South Asian high, which can strengthen the WNP anticyclone and subtropical high. These changes provide a favorable environment for the occurrence and sustenance of HWs in China. Analogous arguments apply to changes with the opposite polarity in association with La Nina events.

Dependence of Present and Future European Temperature Extremes on the Location of Atmospheric Blocking.

The impact of atmospheric blocking on European heat waves (HWs) and cold spells (CSs) is investigated for present and future conditions . A 50‐member ensemble of the second generation Canadian Earth System Model is used to quantify the role of internal variability in the response to blocking. We find that the present blocking‐extreme temperature link is well represented compared to ERA‐Interim, despite a significant underestimation of blocking frequency in most ensemble members. Our results show a strong correlation of blocking with northern European HWs in summer, spring, and fall. However, we also find a strong anticorrelation between blocking and HW occurrence in southern Europe in all seasons. Blocking increases the CS frequency particularly in southern Europe in fall, winter, and spring but reduces it in summer. For the future we find that blocking will continue to play an important role in the development of both CSs and HWs in all seasons.

Modelling average maximum daily temperature using r largest order statistics: An application to South African data.

Natural hazards (events that may cause actual disasters) are established in the literature as major causes of various massive and destructive problems worldwide. The occurrences of earthquakes, floods and heat waves affect millions of people through several impacts. These include cases of hospitalisation, loss of lives and economic challenges. The focus of this study was on the risk reduction of the disasters that occur because of extremely high temperatures and heat waves. Modelling average maximum daily temperature (AMDT) guards against the disaster risk and may also help countries towards preparing for extreme heat. This study discusses the use of the r largest order statistics approach of extreme value theory towards modelling AMDT over the period of 11 years, that is, 2000–2010. A generalised extreme value distribution for r largest order statistics is fitted to the annual maxima. This is performed in an effort to study the behaviour of the r largest order statistics. The method of maximum likelihood is used in estimating the target parameters and the frequency of occurrences of the hottest days is assessed. The study presents a case study of South Africa in which the data for the non-winter season (September–April of each year) are used. The meteorological data used are the AMDT that are collected by the South African Weather Service and provided by Eskom. The estimation of the shape parameter reveals evidence of a Weibull class as an appropriate distribution for modelling AMDT in South Africa. The extreme quantiles for specified return periods are estimated using the quantile function and the best model is chosen through the use of the deviance statistic with the support of the graphical diagnostic tools. The Entropy Difference Test (EDT) is used as a specification test for diagnosing the fit of the models to the data.

Global predictability of temperature extremes

Extreme temperatures are one of the leading causes of death and disease in both developed and developing countries, and heat extremes are projected to rise in many regions. To reduce risk, heatwave plans and cold weather plans have been effectively implemented around the world. However, much of the world’s population is not yet protected by such systems, including many data-scarce but also highly vulnerable regions. In this study, we assess at a global level where such systems have the potential to be effective at reducing risk from temperature extremes, characterizing (1) long-term average occurrence of heatwaves and coldwaves, (2) seasonality of these extremes, and (3) short-term predictability of these extreme events three to ten days in advance. Using both the NOAA and ECMWF weather forecast models, we develop global maps indicating a first approximation of the locations that are likely to benefit from the development of seasonal preparedness plans and/or short-term early warning systems for extreme temperature. The extratropics generally show both short-term skill as well as strong seasonality; in the tropics, most locations do also demonstrate one or both. In fact, almost 5 billion people live in regions that have seasonality and predictability of heatwaves and/or coldwaves. Climate adaptation investments in these regions can take advantage of seasonality and predictability to reduce risks to vulnerable populations.

Early emergence of anthropogenically forced heat waves in the western United States and Great Lakes

Climate projections for the twenty-first century suggest an increase in the occurrence of heat waves. However, the time at which externally forced signals of anthropogenic climate change (ACC) emerge against background natural variability (time of emergence (ToE)) has been challenging to quantify, which makes future heat-wave projections uncertain. Here we combine observations and model simulations under present and future forcing to assess how internal variability and ACC modulate US heat waves. We show that ACC dominates heat-wave occurrence over the western United States and Great Lakes regions, with ToE that occurred as early as the 2020s and 2030s, respectively. In contrast, internal variability governs heat waves in the northern and southern Great Plains, where ToE occurs in the 2050s and 2070s; this later ToE is believed to be a result of a projected increase in circulation variability, namely the Great Plain low-level jet. Thus, greater mitigation and adaptation efforts are needed in the Great Lakes and western United States regions. Heat waves have become increasingly frequent in the United States, but their occurrence is largely linked to natural variability. Model simulations reveal anthropogenically forced signals will first emerge in the western United States and Great Lakes regions by ~2030.

Amplification of heat extremes by plant CO2 physiological forcing

Plants influence extreme heat events by regulating land-atmosphere water and energy exchanges. The contribution of plants to changes in future heat extremes will depend on the responses of vegetation growth and physiology to the direct and indirect effects of elevated CO2. Here we use a suite of earth system models to disentangle the radiative versus vegetation effects of elevated CO2 on heat wave characteristics. Vegetation responses to a quadrupling of CO2 increase summer heat wave occurrence by 20 days or more—30–50% of the radiative response alone—across tropical and mid-to-high latitude forests. These increases are caused by CO2 physiological forcing, which diminishes transpiration and its associated cooling effect, and reduces clouds and precipitation. In contrast to recent suggestions, our results indicate CO2-driven vegetation changes enhance future heat wave frequency and intensity in most vegetated regions despite transpiration-driven soil moisture savings and increases in aboveground biomass from CO2 fertilization.

Climatic change and its effects on Agri-Horti Sector (A study of the district Baramulla of J&amp;K)

The present paper will focus on effects of climatic change on agriculture and horticulture sector of Kashmir valley and will also study how it affects the socio-economic profile of framers. Climatic change is affecting all regions of the globe which not only effects the production but it also disturbs the normal life in Kashmir valley. Due to the climatic change the occurrence of floods, draughts, heat and cold waves are common across the world and have adverse impact on the livelihood of billions of people who depend on land for most of their needs. It is more important in Kashmir as the state’s economy is entirely depending on agriculture and horticulture sector. As we know the weather of Kashmir valley is entirely different from other states of India. The effects of global warming which results late snowfall and abrupt decrease in temperature in the spring season which results huge damage of crops and fruit cultivation in Kashmir valley. The need of the hour is that such problems should be undertaken seriously in the states of Jammu and Kashmir as it is the backbone of economy, if it remains same the whole nation will suffer. In this study we will analyze the whole scenario of the climatic change of Kashmir with respect to agriculture and horticulture and will summarize the issues and problems which are faced by the farmers of the Kashmir. This paper will also highlight some issues at the end which should be implemented at the ground level to overcome from such issues and problems because the state is wholly and solely dependent on the agri-horti sector. The objectives of the paper are how climatic change affects the agriculture and horticulture sector of Kashmir valley and the second objective of the study is to know how it affects the socio-economic condition of farmers in Kashmir valley.