Tropical Nights Research Articles

The influence of elevation, latitude and Arctic Oscillation on trends in temperature extremes over northeastern China, 1961–2011

Trend magnitudes of 14 indices of temperature extremes at 70 stations with elevations, latitude and Arctic Oscillation over northeast China during 1960–2011 are examined. There are no significant correlations between elevation and trend magnitudes with the exception of TXn (Min Tmax), TNn (Min Tmin), TR20 (tropical nights) and GSL (growing season length). Analysis of trend magnitudes by topographic type has a strong influence, which overrides that of degree of urbanization. By contrast, most of the temperature indices have stronger correlations with the latitude and Arctic Oscillation index. The correlations between the Arctic Oscillation index and percentile indices, including TX10p (cool days), TX90p (warm days), TN10p (cool nights), TN90p (warm nights), are not the same in different areas. To summarize, analysis of trend magnitudes by topographic type, the latitude and the Arctic Oscillation shows three factors to have a strong influence in this dataset, which overrides that of elevation and degree of urbanization.

The Urban Heat Island Effect in the City of Valencia: A Case Study for Hot Summer Days

Extreme heat poses significant risks to the world’s growing urban population, and the heat stress to human health is likely to escalate with the anthropogenically increased temperatures projected by climate models. Thus, the additional heat from the urban heat island (UHI) effect needs to be quantified, including the spatial pattern. This study focuses on the city of Valencia (Spain), investigating the intensity and spatial pattern of UHI during three consecutive hot summer days accompanying a heat record. For the analysis, long-term in situ measurements and remote sensing data were combined. The UHI effect was evaluated using two approaches: (a) based on air temperature (AT) time-series from two meteorological stations and (b) using land surface temperature (LST) images from MODIS products by NASA with 1 km resolution. The strongest nighttime UHI estimated from AT was 2.3 °C, while the most intense surface UHI calculated as the difference between the LST of urban and rural regions (defined by NDVI) was 2.6 °C—both measured during the night after the record hot day. To assess the human thermal comfort in the city the Discomfort Index was applied. With the increasing number of tropical nights, the mitigation of nighttime UHI is a pressing issue that should be taken into consideration in climate-resilient urban planning.

Georgian climate change under global warming conditions

Abstract Georgian Climate change has been considered comprehensively, taking into account World Meteorological Organization recommendations and recent observation data. On the basis of mean temperature and precipitation decadal trend geo-information maps for 1936–2012 years period, Georgian territory zoning has been carried out and for each areas climate indices main trends have been studied, that best characterize climate change - cold and hot days, tropical nights, vegetation period duration, diurnal maximum precipitation, maximum five-day total precipitation, precipitation intensity simple index, precipitation days number of at least 10 mm, 20 mm and 50 mm, rainy and rainless periods duration. Trends of temperature indices are statistically significant. On the Black Sea coastline and Colchis lowland at high confidence level cold and hot days and tropical nights number changes are statistically significant. On eastern Georgia plains at high level of statistical significance, the change of all considered temperature indices has been fixed except for the number of hot days. In mountainous areas only hot day number increasing is significant. Trends of most moisture indices are statistically insignificant. While keeping Georgian climate change current trends, precipitation amount on the Black Sea coastline and Colchis lowland, as well as in some parts of Western Caucasus to the end of the century will increase by 50% and amounts to 3000 and 6000 mm, respectively this will strengthen humidity of those areas. Besides increasing of rainy period duration may constitute the risk for flooding and high waters. On eastern Georgia plains, in particular Kvemo Kartli, annual precipitation amount will decrease by 50% or more, and will be only 150–200 mm and the precipitation daily maximum will decrease by about 20 mm and be only 10–15 mm, which of course will increase the intensity of desertification of steppe and semi-desert landscapes.

Prevailing trends of climatic extremes across Indus-Delta of Sindh-Pakistan

This study examines the variability and change in the patterns of climatic extremes experienced in Indus-Delta of Sindh province of Pakistan, comprising regions of Karachi, Badin, Mohenjodaro, and Rohri. The homogenized daily minimum and maximum temperature and precipitation data for a 36-year period were used to calculate 13 and 11 indices of temperature and precipitation extremes with the help of RClimDex, a program written in the statistical software package R. A non-parametric Mann–Kendall test and Sen’s slope estimates were used to determine the statistical significance and magnitude of the calculated trend. Temperatures of summer days and tropical nights increased in the region with overall significant warming trends for monthly maximum temperature as well as for warm days and nights reflecting dry conditions in the study area. The warm extremes and nighttime temperature indices showed greater trends than cold extremes and daytime indices depicting an overall warming trends in the Delta. Historic decrease in the acreage of major crops and over 33% decrease in agriculture credit for Sindh are the indicators of adverse impacts of warmer and drier weather on Sindh agriculture. Trends reported for Karachi and Badin are expected to decrease rice cultivation, hatching of fisheries, and mangroves forest surrounding these cities. Increase in the prevailing temperature trends will lead to increasingly hotter and drier summers resulting to constraints on cotton, wheat, and rice yield in Rohri and Mohenjodaro areas due to increased crop water requirements that may be met with additional groundwater pumping; nonetheless, the depleted groundwater resources would have a direct impact on the region’s economy.

长江三角洲地区极端气温事件变化特征及其与ENSO的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 长江三角洲地区极端气温事件变化特征及其与ENSO的关系 DOI: 10.5846/stxb201607091409 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41561024）；高校博士学科点专项科研基金项目（20136203110002）；山西省高等学校哲学社会科学研究项目（2015265）。 Correlation analysis of variation of extreme temperature events and El Niño Southern Oscillation(ENSO) in Yangtze River Delta region during 1960-2014 Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于1960-2014年65个气象站点逐日最高、最低气温和平均气温资料，分析了长江三角洲地区极端气温事件的变化规律和ENSO事件强度对极端气温指数变化趋势的影响。结果表明：近55年长江三角洲地区夏季日数（SU）、热夜日数（TR）、暖昼日数（TX90）、暖夜日数（TN90）、异常暖昼持续指数（WSDI）、生长期（GSL）均呈增加趋势，其中暖夜日数（TN90）增加幅度最大，增幅为8.55d/10a；极值指数也呈上升趋势，其中月最低气温极小值（TNn）上升幅度最大为（0.53℃/10a）；冰冻日数（ID）、霜冻日数（FD）、冷昼日数（TX10）、冷夜日数（TN10）、异常冷昼持续指数（CSDI）均呈减少趋势，其中冷夜日数（TN10）减少幅度最大（-6.06d/10a）；月平均日较差（DTR）以0.11℃/10a的速率呈下降趋势。空间上，所有站点SU、TXn、TNx呈增加趋势；TR、TX90、TN90、TNn、TXx、WSDI、GSL分别有97%、85%、98%、95%、78%、92%、94%的站点呈增加趋势；所有站点ID、FD、TX10、TN10呈减少趋势；CSDI、DTR分别有87%、77%的站点呈减少趋势。多数极端气温指数与纬度、经度、海拔显著相关。气候变暖突变后，极端暖指数明显增加，极端冷指数明显减少。总体上，厄尔尼诺对极端气温指数的影响大于拉尼娜的影响。 Abstract:Based on daily temperature (maximum, minimum, and average) data of 65 stations, spatial and temporal changes of extreme temperature events and the El Niño Southern Oscillation (ENSO) influence on the extreme temperature threshold over Yangtze River Delta were analyzed for the period 1960-2014. The results showed that in the last 55 years, the extreme temperature indices, i.e. summer days (SU), tropical nights (TR), warm days (TX90), warm nights (TN90), warm spell duration days (WSDI), and growing season length (GSL) have all increased significantly, and TN90 showed an increasing rate of 8.55d per decade. The extremal indices (TXn, TNn, TXx, and TNx) had increasing trends in the Yangtze River Delta region, and TNn showed an increasing rate of 0.53℃ per decade. The ice days (ID), frost days (FD), cold days (TX10), cold nights (TN10), and cold spell duration days (CSDI) have decreased significantly by 0.40 d, 4.03 d, 2.56 d, 6.06 d and 0.33 d per decade, respectively, and TN10 showed a decreasing rate of 6.06 d per decade. DTR has decreased by 0.11℃ per decade. For the spatial distribution of SU, TXn and TNx, all meteorological stations showed increasing trends during 1960-2014. TR, TX90, TN90, TNn, TXx, WSDI, and GSL showed increasing trends at 97%, 85%, 98%, 95%, 78%, 92%, and 94% of meteorological stations, respectively. ID, FD, TX10, and TN10 showed decreasing trends for all stations. For CSDI and DTR, 87% and 77% stations showed decreasing trend. Most extreme temperature indices show good correlation with latitude, longitude, and altitude. After the detected abrupt climate changes, extreme warm indices increased, and extreme cold indices decreased significantly. Overall, the effect of El Nifio on extreme temperature indices was greater than the effect of La Nina. 参考文献 相似文献 引证文献

Observed changes in temperature extremes for the Beijing–Tianjin–Hebei region of China

ABSTRACTAs one of the most significant threats facing the world, climate change has already been manifested everywhere in the form of frequent extreme climate events (e.g. heat waves, floods, droughts and wildfires) and has caused serious impacts on all aspects of the living environment. Due to the regional variability of global climate change, understanding the ongoing climatic changes at a local scale is very important for decision makers and resource managers to develop appropriate mitigation and adaptation strategies against the changing climate. In this study, recent changes in extreme temperature indices (including frost days, summer days, icy days, tropical nights, growing season length, cool nights and warm nights, cool days and warm days, and daily temperature range) over the Beijing–Tianjin–Hebei (BTH) region of China were investigated in the context of global warming. The results indicate that the historical trends of these extreme temperature indices are statistically significant in Huailai, Beijing, Leting and Shijiazhuang while no significant trends are reported in Chengde, Tianjin and Cangzhou−Potou. By comparing results between coastal and inland stations, it is found that the changes in temperature extremes in inland stations are less significant than the changes in coastal stations. The results also suggest that the indices based on minimum temperature show decreasing trends while those for maximum temperature present increasing trends. Furthermore, mutation tests were performed for all indices in order to understand when the changes were initiated. An apparent mutation point (mostly in the 1980s) is detected for most of the analysed temperature indices. This may be caused by the wide implementation of the reform and opening policy in the early 1980s to boost economic development in the BTH region.

1961-2014年中国沿海极端气温事件变化及区域差异分析

PDF HTML阅读 XML下载 导出引用 引用提醒 1961-2014年中国沿海极端气温事件变化及区域差异分析 DOI: 10.5846/stxb201609091830 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金Belmont论坛国际合作项目（NSFC-BF/IGFA，31461143032）；中国科学院战略性先导科技专项（XDA11020205） Analysis of spatiotemporal variations and regional differences in extreme temperature events in the coastal area of China during 1961-2014 Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于1961-2014年156个地面气象站日尺度的气温数据集，利用趋势分析、小波分析、Mann-Kendall检验、累积距平、Pettitt检验、主成分分析等方法分析了中国沿海地区极端气温事件的时空变化特征。结果表明：中国沿海及各子区域极端气温暖指数呈上升趋势，冷指数和气温日较差呈下降趋势，夜指数的年际倾向率明显大于昼指数的年际倾向率；除相对指数、极高值指数和冷（暖）持续日数的多年均值在各子区域之间相差不大以外，霜冻日数、冰冻日数以及气温日较差的多年均值从北至南依次递减，与之相反，夏季日数、热夜日数、极端气温极低值指数以及生长季长度的多年均值则从北至南依次增加。各子区域极端气温指数年际间的主周期介于2-8 a，均无显著的年代际震荡周期；各子区域极端气温指数的突变主要发生在1980s和1990s期间，冷指数和极低值指数的突变时间稍早于暖指数和极高值指数的突变时间，突变后，极端暖事件和气温的极值事件进入多发阶段，极端冷事件进入相对少发的阶段；主成分分析中第一主成分高载荷的极端气温指数对日均气温和日最高（低）气温均有较好的指示性，这类极端指数两两之间的相关性也较强，低载荷的极端气温指数对日均气温和日最高（低）气温的指示性相对较弱，与其他极端气温指数之间的相关性也均较弱。 Abstract:Based on the daily temperature dataset of 156 weather station records, a set of statistical methods, including trend analysis, Wavelet analysis, Mann-Kendall test, accumulative anomaly analysis, Pettitt test, and principal component analysis was employed to investigate the spatial and temporal variations of the extreme temperature events from 1961 to 2014 in the coastal area of China. Results of the trend analysis demonstrated an upward trend in warm extremes and a downward trend in cold extremes as well as diurnal temperature range (DTR). The decadal trend rates of the night extremes were obviously higher than those of the day extremes in the coastal area of China. Generally, a decrease was observed in the multi-year averages of the frost days (FD0), ice days (ID0) and diurnal temperature range (DTR), and an increase was observed in the mutil-year averages of the summer days (SU25), tropical nights (TR20), minimum value of daily maximum temperature (TNx), minimum value of daily minimum temperature (TNn) and growing season length (GSL) from north to south. However, a little variation was observed in the multi-year averages of the cool days (TX10p), cool nights (TN10p), warm days (TX90p), warm nights (TN90p), maximum value of daily maximum temperature (TXx), maximum value of daily minimum temperature (TNx), cold spell duration index (CSDI) and warm spell duration index (WSDI) between the sub-regions and the entire coastal area of China. The primary period of extreme temperature indices varied from 2 to 8 years in the sub-regions of the coastal area of China, and no significant decadal period was detected. The mutation time of extreme temperature indices occurred mainly in the 1980s and the 1990s in all sub-regions. Additionally, the cold extremes and minimum values of daily maximum (minimum) temperature mutated earlier than those of the warm extremes and maximum values of daily maximum (minimum) temperature. After mutation, the extreme warm events and extreme value events tended to occur frequently, whereas the occurrence of extreme cold events decreased gradually. The extreme temperature indices holding high load in the first principal component showed strong positive correlations with each other and exhibited high contributions to the daily average and daily maximum (minimum) temperature. On the other hand, the extreme temperature indices holding low load in the first principal component presented weak correlations with other extreme indices and showed low contributions to the daily average and daily maximum (minimum) temperature. 参考文献 相似文献 引证文献

Analysis of Potential Future Climate and Climate Extremes in the Brazos Headwaters Basin, Texas

Texas’ fast-growing economy and population, coupled with cycles of droughts due to climate change, are creating an insatiable demand for water and an increasing need to understand the potential impacts of future climates and climate extremes on the state’s water resources. The objective of this study was to determine potential future climates and climate extremes; and to assess spatial and temporal changes in precipitation (Prec), and minimum and maximum temperature (Tmin and Tmax, respectively), in the Brazos Headwaters Basin under three greenhouse gas emissions scenarios (A2, A1B, and B1) for three future periods: 2020s (2011–2030), 2055s (2046–2065), and 2090s (2080–2099). Daily gridded climate data obtained from Climate Forecast System Reanalysis (CFSR) were used to downscale outputs from 15 General Circulation Models (GCMs) using the Long Ashton Research Station–Weather Generator (LARS-WG) model. Results indicate that basin average Tmin and Tmax will increase; however, annual precipitation will decrease for all periods. Annual precipitation will decrease by up to 5.2% and 6.8% in the 2055s and 2090s, respectively. However, in some locations in the basin, up to a 14% decrease in precipitation is projected in the 2090s under the A2 (high) emissions scenario. Overall, the northwestern and southern part of the Brazos Headwaters Basin will experience greater decreases in precipitation. Moreover, precipitation indices of the number of wet days (prec ≥ 5 mm) and heavy precipitation days (prec ≥ 10 mm) are projected to slightly decrease for all future periods. On the other hand, Tmin and Tmax will increase by 2 and 3 °C on average in the 2055s and 2090s, respectively. Mostly, projected increases in Tmin and Tmax will be in the upper range in the southern and southeastern part of the basin. Temperature indices of frost (Tmin < 0 °C) and ice days (Tmax < 0 °C) are projected to decrease, while tropical nights (Tmin > 20 °C) and summer days (Tmax > 25 °C) are expected to increase. However, while the frequency distribution of metrological drought shows slight shifts towards the dry range, there was no significant difference between the baseline and projected metrological drought frequency and severity.

TO THE QUESTION OF MODERN CHANGES OF CLIMATE OF NORTHWEST BLACK SEA REGION

Purpose. In recent years, climate indices, the majority of which belongs to the category of so-called «extreme indices», widely used in international practice for assessing global and regional climate changes. The purpose of this article is to identify the characteristics of climate change, the North-Western Black Sea region since the beginning of the twentieth century through the use of climate indices. Data & Methods. For the analysis and evaluation of the changes of climate of the North-west Black Sea region have used the series of monthly, seasonal and annual values of the most informative climate indices for weather station Odessa-GMO for the period 1900-2015 from the site of European Climate Assessment & Data (ECA&D) project. In total have used 22 indexes, 12 of which are temperature, 5 – precipitation, 5 – complex. Analysis and assessment of climate change made using the comparative–geographical, graph-analytical and statistical methods of analysis. Results. During 1900-2015 years according to observations at the meteorological station of Оdessa-GMO had been an increase both air temperatures and precipitation amount. In so doing in the long-term course of most of the indices manifested the periodicity of changes with the characteristic average size equal to 62-64 years. The most intensely during this period occurred raising the minimum air temperature. While the coefficient of linear trend of average annual air temperature (TG index) equals 1,23° C / 100 years, for the absolute annual minimum of air temperature (TNn index) this coefficient equals 2.97° C / 100 years. Since the late 70-ies of the last century has been a significant increase in the intensity of warming. In particular, over the last 35 years the average annual air temperature increased by 2° C, the annual minimum air temperature increased by 4° C, more than in 2 times there was an increase the number of «summer days», in 3.5 times increased number of «tropical nights», and in 1,5 times reduced the number of «frosty nights». It should also be emphasized that in the dynamic of precipitation amount over the last 35 years the monotonicity of changes, typical for the temperature indexes, is absent. In the seasonal aspect most intensive growth both of air temperature and precipitation as a whole for period under consideration is typical for winter, the least an intensive –for the summer, which led to a decrease in annual amplitude of air temperature and equalization of distribution within the year of precipitation amount, respectively. At the same time in the last 35 years against the background of a slight increase in summer precipitation significantly increased their intensity.

Effects of Tropical Night and Light Pollution on Cicadas Calls in Urban Areas

Effects of Tropical Night and Light Pollution on Cicadas Calls in Urban Areas

Abrupt summer warming and changes in temperature extremes over Northeast Asia since the mid-1990s: Drivers and physical processes

Abstract This study investigated the drivers and physical processes for the abrupt decadal summer surface warming and increases in hot temperature extremes that occurred over Northeast Asia in the mid-1990s. Observations indicate an abrupt increase in summer mean surface air temperature (SAT) over Northeast Asia since the mid-1990s. Accompanying this abrupt surface warming, significant changes in some temperature extremes, characterized by increases in summer mean daily maximum temperature (Tmax), daily minimum temperature (Tmin), annual hottest day temperature (TXx), and annual warmest night temperature (TNx) were observed. There were also increases in the frequency of summer days (SU) and tropical nights (TR). Atmospheric general circulation model experiments forced by changes in sea surface temperature (SST)/sea ice extent (SIE), anthropogenic greenhouse gas (GHG) concentrations, and anthropogenic aerosol (AA) forcing, relative to the period 1964–93, reproduced the general patterns of observed summer mean SAT changes and associated changes in temperature extremes, although the abrupt decrease in precipitation since the mid-1990s was not simulated. Additional model experiments with different forcings indicated that changes in SST/SIE explained 76% of the area-averaged summer mean surface warming signal over Northeast Asia, while the direct impact of changes in GHG and AA explained the remaining 24% of the surface warming signal. Analysis of physical processes indicated that the direct impact of the changes in AA (through aerosol–radiation and aerosol–cloud interactions), mainly related to the reduction of AA precursor emissions over Europe, played a dominant role in the increase in TXx and a similarly important role as SST/SIE changes in the increase in the frequency of SU over Northeast Asia via AA-induced coupled atmosphere–land surface and cloud feedbacks, rather than through a direct impact of AA changes on cloud condensation nuclei. The modelling results also imply that the abrupt summer surface warming and increases in hot temperature extremes over Northeast Asia since the mid-1990s will probably sustain in the next few decades as GHG concentrations continue to increase and AA precursor emissions over both North America and Europe continue to decrease.

Analysing heat exposure in two German cities by using meteorological data from both within and outside the urban area

ABSTRACTAs many cities are increasingly affected by heat waves, knowledge regarding those parts of cities most susceptible to heat exposure is essential for the implementation of directed adaptation measures. The frequency of heat waves is projected to increase in both German cities considered for this study: Karlsruhe and Berlin. By aggregating temperature data from meteorological stations within the two cities and their hinterlands, the local temperature distribution within the administrative city boundaries was assessed. A multiple regression approach was used to reveal the regional inter‐relationship between non‐meteorological factors such as altitude, population density and land use, on the one hand, and the heat distribution, on the other. This functional relationship was then applied at the city quarter level for the two cities. A model selection process was undertaken to find the most significant models describing the heat exposure of two heat indicators: heat wave days (HWDs) and tropical nights (TRNs). While altitude and population density were found to be the most significant explanatory variables for Karlsruhe, population density had a dominating influence on the distribution of heat at the city quarter level for Berlin. In Karlsruhe, models describing the daytime temperature performed best, whereas in Berlin those describing the night time temperature distribution had the highest statistical significance. This method could be used with relatively low financial and material expense to assess heat exposure in different city quarters even if there are insufficient meteorological stations within a city.

Projection of intra-urban modification of night-time climate indices during the 21st century

The present paper evaluates the alteration of certain night-time climate indices namely warm nights (Tmin ≧ 17 °C) and tropical nights (Tmin ≧ 20 °C) during the 21st century in the city of Szeged. This examination was performed within the framework of a project founded by International Visegrad Fund, where the change of more climate indices were examined in several Central European cities. In this study the MUKLIMO_3 microclimatic model was used, which ensured the modelling of the local scale processes in the examined area. In the model for the land use we applied the Local Climate Zone (LCZ) system. In order to analyze longer periods the cuboid method was applied, which is a dynamical-statistical downscaling technique. We calculated the indices for 1981-2010 based on measurements and for 2021-2050 and 2071-2100 from the EURO-CORDEX datasets. In this study we present the results of Representative Concentration Pathways (RCP) scenarios namely RCP 4.5 and RCP 8.5. Our results show that highest values appear in the city centre and the number of the days clearly increases in the 21st century especially according to scenario RCP 8.5. The values depend on the built-up types and there are more days towards to the densely built-up LCZs. Moreover, considering the relative changes of the zones, larger values appear in sparsely built-up zones and natural surfaces.

The Effects of Climate Elements on Heat-related Illness in South Korea

The relationship between the climate and the number of heat-related patients in South Korea was analysed in this study. The number of the patients was 1,612 during the summer 2011 to 2015 according to the Heat-related Illness (HRI) surveillance system. The coefficient of determination between the number of the patients and the daily maximum temperature was higher than that between the number of them and the other elements: the daily mean/minimum temperature and relative humidity. The thresholds of daily maximum and minimum temperature in metropolitan cities (MC) were higher than those in regions except for MC (RMC). The higher the maximum and minimum temperature became, the more frequently the heat-related illness rate was observed. The regional difference of this rate was that the rate in RMC was higher than that in MC. Prolonged heat wave and tropical night tended to cause more patients, which continued for 20 days and 31 days of maximum values, respectively. On the other hand, the relative humidity was not proportional to the number of the patients which was rather decreasing at over 70% of relative humidity.

Trends of mean temperatures and warm extremes in northern tropical Africa (1961–2014) from observed and PPCA‐reconstructed time series

AbstractTrends in daily maximum (TX) and minimum (TN) temperatures and indices of warm extremes are studied in tropical North Africa, west of the eastern African highlands, from 1961 to 2014. The analysis is based on the concatenation and cross‐checking of two observed databases. Due to the large number of missing entries (~25%), a statistical infilling using probabilistic principal component analysis was applied. Averaged over 90 stations, the linear trends of annual mean TX and TN equal respectively +0.021 °C/yr and +0.028 °C/yr. The frequency of very hot days (TX > 35°C) and tropical nights (TN > 20°C), as well as the frequency of daily TX and TN above the 90th percentile (p90) (“warm days” and “warm nights”), roughly follows the variations of mean TX and TN, respectively. Heat spells of TX or TN > p90 are often short (usually <2–3 days), and the interannual variation of their mean duration is noisier than for the other indices. Nevertheless, heat spells tend to last longer, with almost constantly positive anomalies since the mid‐1990s. The trends in March–June, the warmest season across the Sahelian and Sudanian belts, show similar variations as annual means. Overall, the local‐scale warming in annual temperatures, and in March–June, may be viewed merely as a simple shift of the probability distribution function of daily TX and TN. The correlations between the thermal indices and the 2 m temperatures suggest that the low‐frequency (>8 years) variations may be viewed as a regional‐scale fingerprint of the global warming, with largest correlations in the tropical Atlantic and Indian basins, while the high‐frequency (<8 years) variations should be mostly viewed as a delayed remote impact of El Niño–Southern Oscillation (ENSO) events over the region, with warm (cold) anomalies tending to follow warm (cold) ENSO events.

Understanding the rapid summer warming and changes in temperature extremes since the mid-1990s over Western Europe

Analysis of observations indicates that there was a rapid increase in summer (June–August) mean surface air temperature (SAT) since the mid-1990s over Western Europe. Accompanying this rapid warming are significant increases in summer mean daily maximum temperature, daily minimum temperature, annual hottest day temperature and warmest night temperature, and an increase in frequency of summer days and tropical nights, while the change in the diurnal temperature range (DTR) is small. This study focuses on understanding causes of the rapid summer warming and associated temperature extreme changes. A set of experiments using the atmospheric component of the state-of-the-art HadGEM3 global climate model have been carried out to quantify relative roles of changes in sea surface temperature (SST)/sea ice extent (SIE), anthropogenic greenhouse gases (GHGs), and anthropogenic aerosols (AAer). Results indicate that the model forced by changes in all forcings reproduces many of the observed changes since the mid-1990s over Western Europe. Changes in SST/SIE explain 62.2 ± 13.0 % of the area averaged seasonal mean warming signal over Western Europe, with the remaining 37.8 ± 13.6 % of the warming explained by the direct impact of changes in GHGs and AAer. Results further indicate that the direct impact of the reduction of AAer precursor emissions over Europe, mainly through aerosol-radiation interaction with additional contributions from aerosol-cloud interaction and coupled atmosphere-land surface feedbacks, is a key factor for increases in annual hottest day temperature and in frequency of summer days. It explains 45.5 ± 17.6 % and 40.9 ± 18.4 % of area averaged signals for these temperature extremes. The direct impact of the reduction of AAer precursor emissions over Europe acts to increase DTR locally, but the change in DTR is countered by the direct impact of GHGs forcing. In the next few decades, greenhouse gas concentrations will continue to rise and AAer precursor emissions over Europe and North America will continue to decline. Our results suggest that the changes in summer seasonal mean SAT and temperature extremes over Western Europe since the mid-1990s are most likely to be sustained or amplified in the near term, unless other factors intervene.

Changes in climate extremes by the use of CMIP5 coupled climate models over eastern Himalayas

A great deal of attention has been given to analyze the trends in Himalayan climate changes due to its reflection in local and global climate variability. To study the same, the two significant meteorological parameters such as temperature and precipitation have been downscaled at various locations over the Eastern Himalayas. For the downscaling, the latest Coupled Model Intercomparison Project 5 climate models with Representative Concentration Pathways experiments were utilized. In this article, we have basically emphasized on the temperature extremity in the historical/measured (1979–2005) and twenty-first century projected (2006–2100) time series durations. The precipitation extreme indices have been computed to correlate the effect of temperature extremes. The results showed that there were substantial variations in these two factors, in terms of their rates, intensities and frequencies in intra-decadal (1979–2005, 2006–2030, 2041–2065 and 2076–2100) time durations. A multi-model climatic projection showed a significant increment in the average annual temperature rate across all the climate stations. Analysis results showed that over the period of records: (1) a diurnal variation of temperature is decreasing due to increments in the minimum temperature, especially after the 2030s; (2) extreme indices-based results showed that the frequencies increase for the summer days and tropical nights but decrease for the frost days. Likewise the intensities of warmest nights also increase; (3) a significant geographical heterogeneity was observed in the temperature as per the results from the multi-model projected temperature datasets; and (4) indeed, there were noticeable areas where these datasets differed on both the sign and significance of precipitation and temperature trends.

The heat goes on\u2014changes in indices of hot extremes in Poland

On the basis of temperature observations at 60 meteorological stations in Poland, changes in the indices associated with the presence of extremely high air temperatures were examined. Indices associated with heat waves, such as the number of hot days (Tmax ≥30 °C) in the summer months (June, July, August) and beyond the summer months (May, September), the number of extremely hot days (Tmax ≥35 °C), the duration of the longest hot spell in the year, as well as the number of tropical nights (Tmin ≤20 °C) were calculated. Spatial distribution of change rate in days per decade for the studied indices as well as the significance level of the observed trends is illustrated. Also current values of the studied indices (for 1991–2013) are examined and compared with the reference period, 1961–1990. For eight of 11 analysed indexes, increase has been detected in last decades with the help of the Mann-Kendall test at a significance level ≥0.05 or better, for a large group of stations. Statistically significant increases of the number of hot days in summer, the number of tropical nights in a year, and duration of the longest hot spell in summer were found for more than half of the stations. Distinct changes in the duration of heat waves were also noted. In 1961–1990, the longest hot spell lasted for 10 days while in 1991–2013, there were many hot spells longer than that, while the longest hot spell recorded in this period lasted for 17 days. Beyond summer, changes in the number of hot days were smaller. In May, a statistically significant increase was recorded for only three stations, while in September the downward trend was dominating and for eight stations it was statistically significant.

Changes in site‐scale temperature extremes over China during 2071–2100 in CMIP5 simulations

AbstractSite‐scale changes in probability behaviors of temperature extremes across China during 2071–2100 are studied with general circulation models (GCMs) provided by the Coupled Model Intercomparison Project Phase 5 (CMIP5). Future temperature extremes are compared to those of 1961–2005 estimated from observed daily temperatures at 498 stations. Temperature extremes are described by 15 indices recommended by the Expert Team on Climate Change Detection and Indices; quantile mapping (QM) is used to downscale the gridded GCMs outputs to site scale. The site‐scale and grid‐scale changes of temperature extremes are compared. Results indicate that during 2071–2100, increases of daily maximum and minimum temperatures are more pronounced in the Songhua River Basin, the Liao River Basin, the Hai River Basin, the north part of the Yellow River Basin, and the Northwest Rivers. The numbers of warm days are 3 times of observations, and the warm spell durations become longer. Summer days and tropical nights, which have never been observed in the Tibetan Plateau, may occur in the future. Cold spell may disappear in the Songhua River Basin and the Liao River Basin. Compared to the grid‐scale changes, appearance or disappearance of extremes at the site scale is more obvious with higher confidence. The spatial patterns of the site‐scale and grid‐scale changes are similar, but the change rates are different to a certain extent. For extremes that are more spatially homogenous, the site‐scale and grid‐scale change rates are close. But for extremes that are more spatially heterogeneous, the site‐scale changes are more remarkable.

폭염에 의한 지역별 인명피해 발생에 관한 연구

With the global temperature rises, South Korea frequently experiences heat wave, tropical nights and abnormal high temperature phenomena. Impacts of such heat wave, even if at the same intensity, can vary according to individuals' adaption to heat wave and regional climate characteristics. This study thus aims to examine the impacts on regional heat-wave frequency on heat-related disease deaths, and to propose heat-wave reduction measures for the minimization of heat wave damage. Various domestic and overseas heat-wave criteria and regional heat-wave criteria were examined. Based on the domestic heat wave criteria, guidelines for watch and warning over heat wave, the regional heat wave occurrence frequency was analyzed, and the correlation between the frequency, and heat-wave-affected deaths, and death rates was analyzed. Regional heat wave occurrence days and heat-wave-affected death rates were analyzed, revealing that regions with more occurrences of heat wave had a high heat-wave-affected death rate (about 76%), and that even regions with a low correlation between heat wave and death rate had a death rate of about 24%. In addition, heat wave reduction measures to minimize such heat wave damage were proposed, and a need to prepare differentiated heat wave countermeasures considering the aforementioned regional characteristics was indicated.