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1.
Rainfall is one of the pivotal climatic variables, which influence spatio-temporal patterns of water availability. In this study, we have attempted to understand the interannual long-term trend analysis of the daily rainfall events of ≥?2.5 mm and rainfall events of extreme threshold, over the Western Ghats and coastal region of Karnataka. High spatial resolution (0.25°?×?0.25°) daily gridded rainfall data set of Indian Meteorological Department was used for this study. Thirty-eight grid points in the study area was selected to analyze the daily precipitation for 113 years (1901–2013). Grid points were divided into two zones: low land (exposed to the sea and low elevated area/coastal region) and high land (interior from the sea and high elevated area/Western Ghats). The indices were selected from the list of climate change indices recommended by ETCCDI and are based on annual rainfall total (RR), yearly 1-day maximum rainfall, consecutive wet days (≥?2.5 mm), Simple Daily Intensity Index (SDII), annual frequency of very heavy rainfall (≥?100 mm), frequency of very heavy rainfall (≥?65–100 mm), moderate rainfall (≥?2.5–65 mm), frequency of medium rainfall (≥?40–65 mm), and frequency of low rainfall (≥?20–40 mm). Mann-Kendall test was applied to the nine rainfall indices, and Theil-Sen estimator perceived the nature and the magnitude of slope in rainfall indices. The results show contrasting trends in the extreme rainfall indices in low land and high land regions. The changes in daily rainfall events in the low land region primarily indicate statistically significant positive trends in the annual total rainfall, yearly 1-day maximum rainfall, SDII, frequency of very heavy rainfall, and heavy rainfall as well as medium rainfall events. Furthermore, the overall annual rainfall strongly correlated with all the rainfall indices in both regions, especially with indices that represent heavy rainfall events which is responsible for the total increase of rainfall.  相似文献   

2.
Daily data of minimum and maximum temperature from 76 meteorological stations for 1960–2010 are used to detect the annual and seasonal variations of temperature extremes in the arid region, China. The Mann–Kendall test and Sen estimator are used to assess the significance of the trend and amount of change, respectively. Fifteen temperature indices are examined. The temperature extremes show patterns consistent with warming, with a large proportion of stations showing statistically significant trends. Warming trends in indices derived from daily minimum temperature are of greater magnitudes than those from maximum temperature, and stations along the Tianshan Mountains have larger trend magnitudes. The decreases in frequency for cold extremes mainly occur in summer and autumn, while warm extremes show significant increases in frequency in autumn and winter. For the arid region as a whole, the occurrence of cold nights and cold days has decreased by ?1.89 and ?0.89 days/decade, respectively, and warm nights and warm days has increased by 2.85 and 1.37 days/decade, respectively. The number of frost days and ice days exhibit significant decreasing trends at the rates of ?3.84 and ?2.07 days/decade. The threshold indices also show statistically significant increasing trends, with the extreme lowest temperatures faster than highest temperatures. The diurnal temperature range has decreased by 0.23 °C/decade, which is in accordance with the more rapid increases in minimum temperature than in maximum temperature. The results of this study will be useful for local human mitigation to alterations in water resources and ecological environment in the arid region of China due to the changes of temperature extremes.  相似文献   

3.
Surface air temperature is one of the main factors that can be used to denote climate change. Its variation in the westerly and monsoon-influenced part of China (i.e., North-West and East China) were analyzed by using monthly data during 1961–2006 from 139 and 375 meteorological stations over these two regions, respectively. The method of trend coefficient and variability was utilized to study the consistency and discrepancy of temperature change over North-West and East China. The results suggest that whether for the annual or the seasonal mean variations of temperature, there were consistent striking warming trends based on the background of global warming over North-West and East China. The most obvious warming trends all appeared in winter over the two regions. Except for the period in spring, the annual and seasonal mean warming trends in North-West China are more obvious than those in East China. The annual mean temperature warming rates are 0.34°C per decade and 0.22°C per decade over North-West and East China, respectively. The average seasonal increasing rates in spring, summer, autumn, and winter are 0.22°C per decade, 0.24°C per decade, 0.35°C per decade, and 0.55°C per decade in North-West China, respectively. At the same time, they are 0.25°C per decade, 0.11°C per decade, 0.22°C per decade, and 0.39°C per decade in East China, respectively. The temperature discrepancies of two adjacent decades are positive over the westerlies and monsoonal region, and they are bigger in the westerlies region than those in the monsoonal region. The most significant warming rate is from the North-East Xinjiang Uygur Autonomous Region of China to West Qinghai Province of China in all seasons and annually over the westerlies region. The North and North-East China are the main prominent warming areas over the monsoonal region. The warming rate increases with latitude in the monsoonal region, but this is not the case in the westerlies region.  相似文献   

4.
The objective of the present study was to reconstruct a short-term (12–14 years) trend of surface temperature and precipitation patterns using their surrogates as provided by satellite images for selected locations along the Red Sea mountains in Saudi Arabia. Time series land surface temperature (LST) and normalized difference vegetation index (NDVI) data acquired from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite were temporally plotted to delineate the trend and the decadal rates of change of both parameters. Results showed that real climate change is reported in the study area during the study period. There is a net increasing in the surface temperatures by 0.45 to 1.2 °C/decade and a net decrease in annual rainfall between 2001 and 2014. Findings of the present study show that the region is under a warming of the climate and a declining of wetness, which coincide with the air temperature and rainfall trends obtained from meteorological stations.  相似文献   

5.
Water management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. The rainfall and temperature records of the Saudi meteorological data for more than three decades were analyzed for policy suggestions in water sectors based on the changing rainfall patterns. The trends in the annual aridity and rain indices were also examined to define the changing climate conditions and for determining the dry months in different cities of the Kingdom. An increased annual and maximum rainfall was observed for six cities while a decreasing trend in both annual and maximum rainfall was observed for the same number of cities highlighting the variability of rainfall in the whole region. An increasing maximum rainfall with decreasing annual rainfall was observed for the rest of the cities signifying the more extreme rainfall evens and resulting floods of short durations. The changing rainfall trends were also observed for different months during 31 years of the recorded period in addition to the varying climate pattern for different cities within the same district. Finally, these preliminary assessments of any systematic changes in view of the increased rain intensities and extreme climate events are viewed to demonstrate the value rainwater harvesting and management as a local adaptation to the climate variability and extreme in the Kingdom.  相似文献   

6.
Ozone trends in the Upper Troposphere and Lower Stratosphere over the Indian region are investigated using three satellite data sets namely Halogen Occultation Experiment (1993–2005), Stratospheric Aerosol and Gas Experiment (1993–2005) II, and Aura Microwave Limb Sounder (MLS, 2005–2011). Estimated ozone trends using multi-variate regression analysis are compared with trends at two Indian ozonesonde stations (Delhi, 28°N, 77°E and Pune, 18°N, 73°E), and a 3-D Chemical Transport Model (CTM, SLIMCAT) for the 1993–2005 time period. Overall, all the observational data sets and model simulations indicate significant increasing trend in the upper troposphere (0–2.5 %/year). In the lower stratosphere, estimated trends are slightly positive up to 30 mb and are negative between 30 and 10 mb. Increasing trends in the upper troposphere is probably due to increasing trends in the tropospheric ozone precursor gases (e.g. CO, NO x , NMHCs). Here, we argue that these contrasting ozone-trend profiles might be partially responsible for insignificant long-term trends in the tropical total column ozone. On seasonal scale, positive trends are observed during all the seasons in the upper troposphere while structure of trend profile varies in lower stratosphere. Seasonal variations of ozone trends and its linkages with stratospheric intrusions and increasing trends in lightning flashes in the troposphere are also discussed.  相似文献   

7.
The aim of this study was to investigate temporal variation in seasonal and annual rainfall trend over Ranchi district of Jharkhand, India for the period (1901–2014: 113 years). Mean monthly rainfall data series were used to determine the significance and magnitude of the trend using non-parametric Mann–Kendall and Sen’s slope estimator. The analysis showed a significant decreased in rainfall during annual, winter and southwest monsoon rainfall while increased in pre-monsoon and post-monsoon rainfall over the Ranchi district. A positive trend is detected in pre-monsoon and post-monsoon rainfall data series while annual, winter and southwest monsoon rainfall showed a negative trend. The maximum decrease in rainfall was found for monsoon (? 1.348 mm year?1) and minimum (? 0.098 mm year?1) during winter rainfall. The trend of post-monsoon rainfall was found upward (0.068 mm year?1). The positive and negative trends of annual and seasonal rainfall were found statistically non-significant except monsoon rainfall at 5% level of significance. Rainfall variability pattern was calculated using coefficient of variation CV, %. Post-monsoon rainfall showed the maximum value of CV (70.80%), whereas annual rainfall exhibited the minimum value of CV (17.09%), respectively. In general, high variation of CV was found which showed that the entire region is very vulnerable to droughts and floods.  相似文献   

8.
The Tarim River lies in the inland area of Northwest China, which has a semiarid or arid climate. Because of relatively scarce precipitation in this area, the main water resource is runoff from a mountainous drainage basin. It is very important to ascertain variations of regular hydrologic and meteorological time series data. Through the use of monthly precipitation and hydrologic data in the three headstream mountain areas of the Tarim River over the past 50 years, this work analyzes the variation of a drought–flood index and annual runoff volume, along with spatio-temporal structures of the index related to runoff at multiple time scales, via non-parametric testing and a wavelet transform method. Wavelet transform can clearly demonstrate many characteristics of the time series, including trend, shift, and major periods. Based on the analysis, the following conclusions can be drawn: (1) the drought–flood indices showed increasing trends for the Aksu and Yarkand rivers, and rose non-significantly for Hotan River. The indices of the three headstreams changed remarkably (p < 0.05) in 1986. The curves of wavelet variance show that significant periods of the indices are 4 and 8 years for Aksu and Hotan rivers, and 8 and 10 years for Yarkand River; (2) runoff of the Aksu and Hotan rivers had significant periods of 6 and 8 years, plus 3 and 9 years for Hotan River; (3) there was significant correlation between the drought–flood indices and annual runoff volume in the three headstreams. The results provide important information toward achieving predictability of flood and drought in Northwest China.  相似文献   

9.
In recent years in Mexico and around the world, the scientific community has shown great interest in acquiring knowledge regarding the behavior of extreme climate events due to their increasing number and intensity. The objective of this research was to analyze variations in extreme temperature events using extreme climate indices. We conducted a case study for the municipality of Apizaco, Tlaxcala, Mexico, using data sets of the daily maximum and minimum temperatures for the period from 1952 to 2003. Six indices related to maximum and minimum temperatures were calculated: frost days, summer days, warm days, cool days, warm nights and cool nights. All of the index results were evaluated annually and only four of the indices were analyzed according to the seasons. A trend based on a linear least squares regression model was fit to the indices to determine their behavior. The index results showed that extreme events related to maximum temperatures corresponded to greater changes and an increased number of summer days and decreased cool days. Additionally, there was an increase of frost days, associated with a greater number of days with minimum temperatures below 0 °C. In general, the results indicated that warmer and colder extreme temperatures are occurring. The detection of those trends in the extreme events can be seen as a first step in any study of the attribution of those observed changes (e.g., land use change, regional climate change, etc.). This attribution aspect will not be discussed in the present study.  相似文献   

10.
The increased rate of annual temperature in the Qinghai-Tibetan Plateau exceeded all other areas of the same latitude in recent decades. The influence of the warming climate on the alpine ecosystem of the plateau was distinct. An analysis of alpine vegetation under changes in climatic conditions was conducted in this study. This was done through an examination of vegetation greenness and its relationship with climate variability using the Advanced Very High Resolution Radiometer satellite imagery and climate datasets. Vegetation in the plateau experienced a positive trend in greenness, with 18.0 % of the vegetated areas exhibiting significantly positive trends, which were primarily located in the eastern and southwestern parts of the plateau. In grasslands, 25.8 % of meadows and 14.1 % of steppes exhibited significant upward trends. In contrast, the broadleaf forests experienced a trend of degradation. Temperature, particularly summer temperature, was the primary factor promoting the vegetation growth in the plateau. The wetter and warmer climate in the east contributed to the favorable conditions for vegetation. The alpine meadow was mostly sensitive to temperature, while the steppes were sensitive to both temperature and precipitation. Although a warming climate was expected to be beneficial to vegetation growth in the alpine region, the rising temperature coupled with reduced precipitation in the south did not favor vegetation growth due to low humidity and poor soil moisture conditions.  相似文献   

11.

A 22-member ensemble from CMIP6 is used to analyze the projected changes and seasonal behavior in surface air temperature over South America during the twenty-first century. In the future projections, CMIP6 models shown a high dependency to the socioeconomic pathway over each country of South America. The multimodel ensemble projects a continuous increase in the annual mean temperature over South America during the twenty-first century under the three future scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5). Besides, it was possible to identify consistent positive trends across all the models, with values between 0.45 ± 0.05 and 2.05 ± 0.31 °C cy−1 under the historical experiment, however largest trends occurs for the projection periods (near, mid and far future), with values between − 0.87 ± 0.84 to 2.88 ± 0.60 °C cy−1 (SSP1-2.6), 1.41 ± 0.88 to 5.32 ± 0.81 °C cy−1 (SSP2-4.5) and 4.75 ± 0.58 to 8.76 ± 0.74 °C cy−1 (SSP5-8.5) with maximum values at Bolivia, Brasil, Paraguay and Venezuela whilst minimum values for Argentina and Uruguay, regardless of the SSP scenario used. From the seasonal behavior analysis was possible to identify maximum values between January and March whilst minimum between June and July, except in Brasil, Venezuela and Guyana–Surinam–French Guayana, with annual range decreasing as the latidude decreases. By the end of the twenty-first century the annual mean temperature over South america is projected to increase between 0.92–2.11 °C, 0.97–3.37 °C and 1.27–6.14 °C under SSP1-2.6, SSP2-4.5 and SSP5-8.5 projection scenarios respectively. This projected increase of temperature across the continent will produce negative repercussions in the social, economic and political spheres. The results obtained in this study provide insights about the CMIP6 performance over this region, which can be used to develop adaptation strategies and might be useful for the adaptation to the climate change.

  相似文献   

12.
In this study, the hydro-climatic trends (1964–2006) of Tangwang River basin (TRB) were examined using the Kendall’s test. Moreover, the impacts of climate variability and land use change on streamflow in each sub-basin were assessed using the Soil and Water Assessment Tools (SWAT) model. The results indicated that annual mean flow and peak flow showed insignificant decreasing trends (?0.14 m3 s?1 year?1, 1 %; ?8.67 m3 s?1 year?1, 40 %), while annual low flow exhibited a slightly increasing trend (0.02 m3 s?1 year?1, 11 %). Correspondingly, the annual precipitation for the entire basin decreased by 0.02 mm year?2, while the annual means of daily mean, maximum and minimum temperature increased significantly by 0.07, 0.10 and 0.02 °C year?1, respectively. On the other hand, with the implementation of “Natural Forest Protection Project” and “Grain for Green Project”, the forests in TRB totally increased by 744.5 km2 (4.00 %) from 1980 to 2000. Meanwhile, the grasslands and the farmlands decreased by 378.0 km2 (?1.98 %) and 311.9 km2 (?1.63 %), respectively. Overall, land use changes played a more important role for the streamflow reduction than climate change for SUB1, SUB2 and SUB3, in which the primary conversions were from grassland, farmland and bare land to forests. Conversely, in SUB4, the influence of climate variability was predominant. The results obtained could be a reference for water resources planning and management under changing environment.  相似文献   

13.
One of the most important scientific concerns of the last few decades is climate change, which is the result of a great many factors like global warming. Although a number of studies have been dedicated to understand the phenomenon of climate change, more attention is required to understand the potential effects of global warming on the ecosystems as well as on human life. The present study was designed to survey the trends of minimum, maximum and mean temperatures, relative humidity, and the time series of annual precipitation and 10-year moving average low-pass filter in the 13 synoptic weather stations of Iran’s arid and semi-arid regions during the last 55 years by using τ Kendall test. The analyses indicate a significantly increasing trend for the minimum and mean temperatures while a decreasing trend for the mean relative humidity in the arid and semi-arid regions, especially during the last few years up to the year 2000. Any clear increasing or decreasing trend was not found for the maximum temperature, while the precipitation did not show any increasing/decreasing trend for most of the surveyed stations. Further studies, with long-term programming, are recommended to be carried out to evaluate the climate change and its effects on such regions.  相似文献   

14.
路红亚  杜军  袁雷  廖健 《冰川冻土》2014,36(3):563-572
利用西藏珠穆朗玛峰地区5个气象站点1971-2012年逐日降水量资料,采用滑动平均、线性回归、Mann-Kendall非参数检验和Morlet小波分析等方法,分析了珠穆朗玛峰地区极端降水事件的时空变化特征. 结果表明：1971-2012年42 a来,珠穆朗玛峰地区大部分极端降水指数呈现出自东向西逐渐增大的空间分布格局, 连续干旱日数、连续湿日和降水强度表现为增加趋势,其他极端降水指数趋于减少. 其中,强降水量、极强降水量和年降水总量减幅较大,分别为-5.74 mm·（10a）-1、-1.20 mm·（10a）-1和-5.32 mm·（10a）-1,在喜马拉雅山南坡的聂拉木站表现的最为明显. 大部分极端降水指数在21世纪最初的10 a减幅最大,在30 a际尺度上也表现为减少趋势. 除连续干旱日数外,极端降水与年降水总量关系密切. 各项极端降水指数都存在3～4 a显著周期,也存在10 a、12 a和15 a的周期. 在时间转折上,各项极端降水指数均未发生气候突变.  相似文献   

15.
青海省极端气温事件的气候变化特征研究   总被引：9，自引：3，他引：6  
申红艳  马明亮  王冀  王力  李江英 《冰川冻土》2012,34(6):1371-1379
选用青海省37个气象站点1961-2011年近51 a, 逐日气温(最高、 最低、 平均)资料, 采用国际通用的极端气温指数定义计算了9种极端气温指数, 并分析其主要气候特征.结果表明: 近51 a青海省极端气温呈明显上升趋势, 极端冷指标(霜冻、 结冰日数、 冷夜、 冷昼指数)呈下降趋势, 而极端暖指标(夏天日数、 暖夜、 暖昼指数)呈上升趋势, 且极端冷指标的减少幅度高于极端暖指标的增加幅度.空间分布上, 极端气温指数在全省呈一致的上升(下降)趋势分布.在近51 a的时间尺度上各种极端气温指数都存在多个较明显的周期, 如较短的3~8 a的准周期, 以及13 a、 17 a、 27 a的年代际周期特征.青海省年平均气温与极端气温指数有很高的相关性, 气候变暖突变前后极端气温指数表现出明显差异: 在变暖突变发生后, 霜冻日数、 冷夜指数、 冷昼指数、 结冰日数明显减少, 夏天日数、 暖夜指数及暖昼指数明显增加, 其中相对指数几乎呈倍数显著变化, 表明极端气温指数对气候变暖有很好的响应.  相似文献   

16.
Horizontal surface visibility range, one of the simplest measures of local atmospheric pollution, is critical for aviation, surface transport besides long-term impact on human health and climate. Long-term observations from multiple stations (including airports) across the world show statistically significant decline in visibility. We have studied climatology and trends of morning poor visibility days (PVD, visibility <4 km) and afternoon good visibility days (GVD, visibility >10 km) based on 279 surface meteorological stations well distributed over India for the period 1961–2008. During last 5 decades, all India averaged range of annual morning PVD has increased from 6.7 to 27.3 % days, while the range of afternoon GVD has decreased from 76.1 to 30.6 % days. Annually, the morning PVD increased significantly at 3.3 % days per decade, and the afternoon GVD declined significantly at ?8.6 % days per decade. Seasonally, the highest increase in morning PVD has occurred in winter (+4.3 % days per decade), while post-monsoon has the highest decrease in afternoon GVD (?9.2 % days per decade). In spatial distribution, visibility has decreased nationwide especially over Indo-Gangetic (IG) plains, central, east and northeast India which is due to increased wintertime fog, water vapor and aerosol loading. The IG plains suffer from increased fog or smog and aerosol loading during wintertime. Long-term visibility impairment over India is visible through increasing morning PVD (decreasing GVD) and decreasing afternoon GVD (increasing PVD) which are spatially well correlated with increasing relative humidity and decreasing wind speed (seasonal).  相似文献   

17.
Rapid warming in mid-latitude central Asia for the past 100 years   总被引：5，自引：0，他引：5  
Surface air temperature variations during the last 100 years (1901–2003) in mid-latitude central Asia were analyzed using Empirical Orthogonal Functions (EOFs). The results suggest that temperature variations in four major sub-regions, i.e. the eastern monsoonal area, central Asia, the Mongolian Plateau and the Tarim Basin, respectively, are coherent and characterized by a striking warming trend during the last 100 years. The annual mean temperature increasing rates at each sub-region (representative station) are 0.19°C per decade, 0.16°C per decade, 0.23°C per decade and 0.15°C per decade, respectively. The average annual mean temperature increasing rate of the four sub-regions is 0.18°C per decade, with a greater increasing rate in winter (0.21°C per decade). In Asian mid-latitude areas, surface air temperature increased relatively slowly from the 1900s to 1970s, and it has increased rapidly since 1970s. This pattern of temperature variation differs from that in the other areas of China. Notably, there was no obvious warming between the 1920s and 1940s, with temperature fluctuating between warming and cooling trends (e.g. 1920s, 1940s, 1960s, 1980s, 1990s). However, the warming trends are of a greater magnitude and their durations are longer than that of the cooling periods, which leads to an overall warming. The amplitude of temperature variations in the study region is also larger than that in eastern China during different periods.  相似文献   

18.
Spatio-temporal variations in precipitation are affecting agricultural production in China in the context of climate change. Based on daily precipitation data from 63 national meteorological stations on the Huang-Huai-Hai Plain from 1963 to 2012, this paper analysed the spatio-temporal variations in precipitation in terms of precipitation days and intensity, using spatial interpolation, linear trend estimation and wavelet analysis. The results indicated that: (i) from 1963 to 2012, the number of annual precipitation days and intensity decreased gradually from the southeast to the northwest. Additionally, the distribution of the extreme precipitation index was similar to that of the annual precipitation index; (ii) the number of annual precipitation days and heavy precipitation days gradually decreased, while precipitation intensity and extreme precipitation days and extreme rainfall intensity remained relatively stable or decreased. The spatial patterns of annual variation trends were considerably different. The annual precipitation days and intensity trends are consistent with the overall trend, while that of the extreme rainfall index in some regions differs from the overall trend; (iii) the precipitation index displayed different periodic oscillations during the period, and the precipitation index values differed at different time scales. However, all the precipitation index values exhibited a 28-yr oscillation.  相似文献   

19.
一个降水再循环模型的建立及分析   总被引：3，自引：1，他引：3       下载免费PDF全文
伊兰  陶诗兰 《水科学进展》1997,8(3):205-211
陆-气相互作用是当今水文科学界和大气科学界共同瞩目的一个前沿课题。为寻求陆-气相互作用的某些信号,在长江流域的主体区域上建立了一个降水再循环模型,并分析了这一区域降水的不同水汽来源。依据再循环降水率这个反映陆面过程对当地气候影响的定量指标,得出了一些很有实际意义的结论。  相似文献   

20.
Climate extreme and its linkage to regional drought over Idaho, USA   总被引：2，自引：0，他引：2  
To investigate consequences of climate extreme and variability on agriculture and regional water resource, twenty-seven climatic indices of temperature and precipitation over Idaho, USA, were computed. Precipitation, mean temperature and maximum temperature, self-calibrated Palmer Drought Index and Standardized Precipitation Index for 1-, 3-, 6- and 12-month time scales were used to identify spatial and temporal distribution of climatic extreme and variability as well as drought frequency and magnitude. Seven oceanic indices were also used to detect teleconnections between climatic indices and regional droughts. The analyses were conducted for 56 meteorological stations, during 1962?C2008, characterized by a long-term and high-quality data set. The result indicates that decreasing trends and increasing trends are identified for precipitation and temperature, respectively. Consequently, it appears that frost and ice days dwindle as growing season (May?CAugust) length, tropical nights and summer days increase. Given current climate conditions, the results also imply that these trends will continue in the future possibly driven by uncertain climate variability. We anticipate that these indices explained by teleconnections will improve drought-forecasting capability in this region.  相似文献   

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