1962-2011年长江流域极端气温事件分析

根据1962-2011 年长江流域115 个气象站点的逐日最高气温、日最低气温资料,利用线性倾向估计法、主成分分析及相关分析法,并根据选取的16 个极端气温指标,分析了该地区极端气温的时间变化趋势和空间分布规律。结果表明:(1) 冷昼日数、冷夜日数、冰冻日数、霜冻日数、冷持续日数分别以-0.84、-2.78、-0.48、-3.29、-0.67 d·(10a)^-1的趋势减小,而暖昼日数、暖夜日数、夏季日数、热夜日数、暖持续日数、生物生长季以2.24、2.86、2.93、1.80、0.83 、2.30 d·(10a)^-1的趋势增加,日最高(低) 气温的极低值、日最高(低) 气温的极高值和极端气温日较差的倾向率分别为0.33、0.47、0.16、0.19、-0.07 ℃·(10a)^-1;(2) 冷指数(冷夜日数、日最高气温的极低值、日最低气温的极低值)的变暖幅度明显大于暖指数(暖夜日数、日最高气温的极高值、日最低气温的极高值),夜指数(暖夜日数、冷夜日数) 的变暖幅度明显大于昼指数(暖昼日数、冷昼日数);(3) 空间分布上,长江上游区域冷指数的平均值大于其中下游区域,而暖指数和生物生长季则是中下游多年平均值大于上游区域(暖持续日数除外);(4) 因子分析的结果表明,除了极端气温日较差之外,各极端气温指数之间均呈现很好的相关性。     

1980–2011年中国农作物种植结构时空变化（英文）

Understanding the spatial and temporal variations of cropping systems is very important for agricultural policymaking and food security assessment,and can provide a basis for national policies regarding cropping systems adjustment and agricultural adaptation to climate change.With rapid development of society and the economy,China's cropping structure has profoundly changed since the reform and opening up in 1978,but there has been no systematic investigation of the pattern,process and characteristics of these changes.In view of this,a crop area database for China was acquired and compiled at the county level for the period 1980–2011,and linear regression and spatial analysis were employed to investigate the cropping structure type and cropping proportion changes at the national level.This research had three main findings:(1) China's cropping structure has undergone significant changes since 2002;the richness of cropping structure types has increased significantly and a diversified-type structure has gradually replaced the single types.The single-crop types—dominated by rice,wheat or maize—declined,affected by the combination of these three major food crops in mixed plantings and conversion of some of their planting area to other crops.(2) In the top 10 types,82.7% of the county-level cropping structure was rice,wheat,maize and their combinations in 1980;however,this proportion decreased to 50.7% in 2011,indicating an adjustment period of China's cropping structure.Spatial analysis showed that 63.8% of China's counties adjusted their cropping structure,with the general change toward reducing the main food types and increasing fruits and vegetables during 1980–2011.(3) At the national level,the grain-planting pattern dominated by rice shifted to coexistence of rice,wheat and maize during this period.There were significant decreasing trends for 47% of rice,61% of wheat and 29.6% of maize cropping counties.The pattern of maize cropping had the most significant change,with the maize proportion decreasing in the zone from northeastern to southwestern China during this period.Cities and their surroundings were hotspots for cropping structural adjustment.Urbanization has significantly changed cropping structure,with most of these regions showing rapid increases in the proportion of fruit and vegetables.Our research suggests that the policy of cropping structural adjustment needs to consider geographical characteristics and spatial planning of cropping systems.In this way,the future direction of cropping structural adjustment will be appropriate and scientifically based,such as where there is a need to maintain or increase rice and wheat cropping,increase soybean and decrease maize,and increase the supply of fruit and vegetables.     

1961–2011年中国南方地区极端降水事件变化(英文)

Based on the daily precipitation from a 0.5°×0.5° gridded dataset and meteorological stations during 1961–2011 released by National Meteorological Information Center, the reliability of this gridded precipitation dataset in South China was evaluated. Five precipitation indices recommended by the World Meteorological Organization(WMO) were selected to investigate the changes in precipitation extremes of South China. The results indicated that the bias between gridded data interpolated to given stations and the corresponding observed data is limited, and the proportion of the number of stations with bias between –10% and 0 is 50.64%. The correlation coefficients between gridded data and observed data are generally above 0.80 in most parts. The average of precipitation indices shows a significant spatial difference with drier northwest section and wetter southeast section. The trend magnitudes of the maximum 5-day precipitation(RX5day), very wet day precipitation(R95), very heavy precipitation days(R20mm) and simple daily intensity index(SDII) are 0.17 mm·a–1, 1.14 mm·a–1, 0.02 d·a–1 and 0.01 mm·d–1·a–1, respectively, while consecutive wet days(CWD) decrease by –0.05 d·a–1 during 1961–2011. There is spatial disparity in trend magnitudes of precipitation indices, and approximate 60.85%, 75.32% and 75.74% of the grid boxes show increasing trends for RX5 day, SDII and R95, respectively. There are high correlations between precipitation indices and total precipitation, which is statistically significant at the 0.01 level.     

哈萨克斯坦1982–2015年植被时空变化（英文）

归一化植被指数(NDVI)作为表征植被生长状况的关键性指标,能够有效的提供植被生长状况的信息。本研究基于1982–2015年哈萨克斯坦时间序列的GIMMS/NDVI数据,分析植被)生长的空间格局及变化趋势,研究结果表明:哈萨克斯坦自北向南分布着农田、草地、灌丛这三类主要的植被类型,呈明晰的地带性分布特征;植被指数由北到南逐渐降低,农田、草地和灌丛三类主要植被类型的NDVI均值水平依次为农田草地灌丛;1982–2015年间,NDVI呈现出先增长(1982–1992年)、再降低(1993–2007年)、然后又增长(2008–2015年)的变化趋势。NDVI显著下降的区域占土地总面积的24.0%,主要分布在西北部的农田与草地交错地带以及南部边缘的农田,草地退化面积占草地总面积的23.5%、农田退化面积占农田总面积的48.4%、灌丛退化面积占灌丛总面积的13.7%,植被改善的区域分布在中东部的农田以及农田与草地的交错带,显著提升的面积占土地总面积的11.8%。     

1976–2010年波兰湖泊水位变化（英文）

The paper presents the analysis of tendencies in water level changes in 32 lakes in Poland during 1976–2010.Series of monthly,seasonal,and annual precipitation and air temperature for 9 meteorological stations were also studied.The trend analysis for all of the studied series of water levels in lakes showed high spatial and temporal variability.Series of annual water levels in the case of 6 lakes showed statistically significant increasing tendencies,and in 7 lakes,significant decreasing trends.Series of annual amplitudes in the majority of lakes(22) showed a decreasing trend,but they were statistically significant only in three cases.The tendencies for air temperature fluctuations are more statistically significant than precipitation.The key role in determining water level changes is played by local factors,particularly including human economic activity,obscuring the effect of natural factors on water level changes.The paper describes cases of changes in water levels in lakes under anthropopressure related to among others: agricultural irrigations,hydropower infrastructure,water transfers,navigation,or mining.     

1960–2012年青藏高原极端气候时空动态与变异研究（英文）

极端气候事件是全球长期气候变化研究中的重要内容。作为世界第三极,青藏高原对气候变化和变异的响应非常敏感。本文基于青藏高原98个气象站(大部分位于海拔4000 m以上)的日值观测数据,包括日气温最大值、最小值和日降水量,计算了1960–2012年间的极端气候指数并分析了其时空变化格局。首先,根据国际气象组织的标准计算了15个核心气温极端指数和8个核心降水极端指数,然后从高原整体、生态区和台站尺度分析了极端指数的时空变化趋势。气温极端指数表明青藏高原整体表现为显著升温趋势,高原的冷日和冷夜时间序列呈下降趋势,每10年分别减少8.9天和17.3天。相应的暖日和暧夜增长趋势分别为7.6 d (10 yr)-1和12.5 d (10 yr)-1。生长季长度以5.3 d (10 yr)-1的速率增加。在站点尺度,大部分台站的气温极端指数存在显著趋势,但是空间分异性显著。生态区的气温极端指数与高原整体的发展趋势一致。高原整体的降水极端指数波动性较大,增长趋势微弱。年总降水增长趋势为2.8mm(10yr)-1。时序变化点分析表明极端气候指数的突变主要发生在1980和1990年代。赫斯特指数表明未来各种极端气候指数都将保持研究时间段内的发展趋势。另外,探索了极端气候指数与海拔高度的关系,发现各指数的变化趋势与高程并无显著相关性。总体上高原升温呈现显著的不对称特征,即气温冷指数的上升幅度明显大于暖指数的上升幅度,日最低气温的增长趋势也很显著。大多数降水极端指数表现为微弱的增加趋势(不显著)。本研究综合分析了青藏高原极端气候的时空分布格局,可以为高原气候变化研究提供参考。     

2000–2012年中国北方海岸线时空变化（英文）

This study examined the spatial distribution of the continent coastline in northern China using remote sensing and GIS techniques,and calculated the fractal dimension of the coastline by box-counting method,with a time span from 2000 to 2012.Moreover,we analyzed the characteristics of spatial-temporal changes in the coastline's length and fractal dimension,the relationship between the length change and fractal dimension change,and the driving forces of coastline changes in northern China.During the research period,the coastline of the study area increased by 637.95 km,at a rate of 53.16 km per year.On the regional level,the most significant change in coastline length was observed in Tianjin and Hebei.Temporally,the northern China coastline grew faster after 2008.The most dramatic growth was found between 2010 and 2011,with an increasing rate of 2.49% per year.The fractal dimension of the coastline in northern China was increasing during the research period,and the most dramatic increase occurred in Bohai Rim.There is a strong-positive linear relationship between the historical coastline length and fractal dimension(the correlation coefficient was 0.9962).Through statistical analysis of a large number of local coastline changes,it can be found that the increase(or decrease) of local coastline length will,in most cases,lead to the increase(or decrease) of the whole coastline fractal dimension.Civil-coastal engineering construction was the most important factor driving the coastline change in northern China.Port construction,fisheries facilities and salt factories were the top three construction activities.Compared to human activities,the influence of natural processes such as estuarine deposit and erosion were relatively small.     

陕西榆林地区1954-2013年极端气温变化特征

对1954-2013年横山站、榆林站、绥德站的每日气象资料,运用线性拟合及累积距平、Mann-Kendall突变检验、主成分分析和Morlet复数小波等方法对WMO发布的10种极端气温指数进行了计算和分析。结果表明：榆林地区近60年极端最高气温、极端最低气温都呈上升趋势,冰日天数、霜日天数、冷夜天数、冷日天数呈下降趋势,夏日天数、热夜天数、暖夜天数、暖日天数呈现稳步上升趋势。近60年,榆林市极端气温的变化存在明显的阶段特征,并有突变现象发生。各指数的突变主要发生在20世纪90年代。暖指数的变化是榆林地区近60年气温呈上升趋势的主要原因。榆林地区冬春季气温升高是年平均气温上升的主要原因。33 a左右的周期是10个指数比较稳定的周期,共同反映榆林地区极端天气的周期规律。极端暖指标在未来持续上升,极端冷指标则持续下降。研究区极端高温天气增加,会导致旱灾等极端天气增加的概率,并对森林防火产生一定的压力。极端低温天数的减少导致易发生森林和草原的病虫灾害,应做好预防工作。     

中国气温变化对全球变暖停滞的响应（英文）

The 1998–2012 global warming hiatus has aroused great public interest over the past several years. Based on the air temperature measurements from 622 meteorological stations in China, the temperature response to the global warming hiatus was analyzed at national and regional scales. We found that air temperature changed –0.221℃/10 a during 1998–2012, which was lower than the long-term trend for 1960–1998 by 0.427℃/10 a. Therefore, the warming hiatus in China was more pronounced than the global mean. Winter played a dominant role in the nationwide warming hiatus, contributing 74.13%, while summer contributed the least among the four seasons. Furthermore, the warming hiatus was spatial heterogeneous across different climate conditions in China. Comparing the three geographic zones, the monsoon region of eastern China, arid region of northwestern China, and high frigid region of the Tibetan Plateau, there was significant cooling in eastern and northwestern China. In eastern China, which contributed 53.79%, the trend magnitudes were 0.896℃/10 a in winter and 0.134℃/10 a in summer. In the Tibetan Plateau, air temperature increased by 0.204℃/10 a, indicating a lack of a significant warming hiatus. More broadly, the warming hiatus in China may have been associated with the negative phase of PDO and reduction in sunspot numbers and total solar radiation. Finally, although a warming hiatus occurred in China from 1998 to 2012, air temperature rapidly increased after 2012 and will likely to continuously warm in the next few years.     

2004–2011年中国省域生态补偿差异分析（英文）

In this study, we developed a theoretical framework to analyze the provincial differences in eco-compensation and selected appropriate measurement methods to investigate these differences in the operation of the eco-compensation framework. Via the use of the coefficient of variation, Atkinson index, and Gini coefficient, we investigated the overall differences in Chinese provincial eco-compensation time series data from 2004 to 2014 and studied the driving mechanism underlying these differences. The results showed that:(1) The provincial eco-compensation standard has geographical features. For example, the provinces crossed by the "HU Huanyong Line", or located to its northwestern side, have obtained extensive eco-compensation.(2) There was a trend for differences in eco-compensation to increase over time, but with some fluctuations in 2006, 2009, and 2014 as shown by the coefficient of variation, in 2005, 2007, 2011, 2013, and 2014 as shown by the Gini coefficient, and in 2007, 2008, 2011, and 2012 as shown by the Atkinson index.(3) Time series curves indicated that while the signals from the three metrics(coefficient of variation, Atkinson index, and Gini coefficient) differ in a short-term analysis, they show the same tendency in the longer term. The results indicate that it is necessary to evaluate the differences in eco-compensation at the provincial level over a long period of time.(4) Via the calculation of the virtual Gini coefficient, we found that among the factors that influence provincial differences in eco-compensation, the economic value of eco-resources played the decisive role, explaining more than 73% of the difference. The cost of environmental pollution abatement was the second most important factor, accounting for more than 19% of the difference. The input to environmental pollution abatement had the least influence, accounting for less than 8% of the difference. The results agreed with those obtained from other studies, and could be used as a reference by policy makers.     

2000-2011年可可西里地区主要湖泊冰情时空变化（英文）

Lake ice phenology,i.e.the timing of freeze-up and break-up and the duration of the ice cover,is regarded as an important indicator of changes in regional climate.Based on the boundary data of lakes,some moderate-high resolution remote sensing datasets including MODIS and Landsat TM/ETM+ images and the meteorological data,the spatial-temporal variations of lake ice phenology in the Hoh Xil region during the period 2000–2011 were analyzed by using RS and GIS technology.And the factors affecting the lake ice phenology were also identified.Some conclusions can be drawn as follows.(1) The time of freeze-up start(FUS) and freeze-up end(FUE) of lake ice appeared in the late October–early November,mid-November – early December,respectively.The duration of lake ice freeze-up was about half a month.The time of break-up start(BUS) and break-up end(BUE) of lake ice were relatively dispersed,and appeared in the early February – early June,early May – early June,respectively.The average ice duration(ID) and the complete ice duration(CID) of lakes were 196 days and 181 days,respectively.(2) The phenology of lake ice in the Hoh Xil region changed dramatically in the last 10 years.Specifically,the FUS and FUE time of lake ice showed an increasingly delaying trend.In contrast,the BUS and BUE time of lake ice presented an advance.This led to the reduction of the ID and CID of lake.The average rates of ID and CID were –2.21 d/a and –1.91 d/a,respectively.(3) The variations of phenology and evolution of lake ice were a result of local and climatic factors.The temperature,lake area,salinity and shape of the shoreline were the main factors affecting the phenology of lake ice.However,the other factors such as the thermal capacity and the geological structure of lake should not be ignored as well.(4) The spatial process of lake ice freeze-up was contrary to its break-up process.The type of lake ice extending from one side of lakeshore to the opposite side was the most in the Hoh Xil region.     

1910-2014年湖南省均一化气温序列构建及其变化特征（英文）

Based on the statistical method and the historical evolution of meteorological stations,the temperature time series for each station in Hunan Province during 1910–2014 are tested for their homogeneity and then corrected.The missing data caused by war and other reasons at the 8 meteorological stations which had records before 1950 is filled by interpolation using adjacent observations,and complete temperature time series since the establishment of stations are constructed.After that,according to the representative analysis of each station in different time periods,the temperature series of Hunan Province during 1910–2014 are built and their changes are analyzed.The results indicate that the annual mean temperature has a significant warming trend during 1910–2014 and the seasonal mean temperature has the largest rising amplitude in winter and spring,followed by autumn,but no significant change in summer.Temperature variation over Hunan Province has several significant warm-cold alternations and more frequent than that in whole China.Annual and seasonal mean temperatures except summer and autumn have abrupt warming changes in the recent 100 years.The wavelet analysis suggests that the annual and four seasonal mean temperatures in recent 100 years have experienced two climatic shifts from cold to warm.     

1992–2015全球耕地时空变化（英文）

人口和人均食物需求的增加对全球耕地产生了显著的影响。利用欧空局提供的精度为300m的最新土地覆被产品,文章分析了1992-2015年全球耕地的时空变化趋势和耕地转化特征。结果显示:1)在1992-2004年间全球耕地面积增长迅速,而在2004-2012年间耕地增长缓慢,2012年后耕地有缓慢减少的趋势。2)在洲尺度上,非洲耕地有一直增长的态势,而其他洲耕地都经历了耕地转型,有先增长后下降的趋势;在收入较高的国家,耕地多有下降的趋势。3)全球耕地增长的热点区域主要分布在亚马逊林地、欧亚大草原和撒哈拉沙漠边缘。全球耕地减少的中心从欧洲转移到亚洲。由于迅速的城市化,亚洲耕地扩张侵占了大量农田。     

毛乌素沙地1960-2013年极端气温变化

毛乌素沙地处于多层次生态地理景观过渡带,拥有丰富的自然及人文资源.研究该生态脆弱区极端气温变化,有利于揭示全球气温变化与局地气温响应之间的复杂关系,为当地的可持续发展和气象灾害预防提供参考。通过线性趋势分析、累计距平、Mann-Kendall法、因子分析、R/S分析等方法,分析了该地极端气温指数的变化特征\,突变特点、相互关系,探讨了该地区气温变化的空间差异和极端气温未来的变化趋势。结果表明:(1)极端最低气温、极端最高气温、夏日日数、热夜日数、暖夜日数、暖日日数分别以不同的速率上升;冰日日数、霜冻日数、冷夜日数、冷日日数分别以不同的速率下降。(2)除极端最高气温、极端最低气温外,其余8项极端气温指数均发生突变,突变年份集中在20世纪90年代。(3)冷指数大幅下降是毛乌素沙地极端气温变化的主要特点,并且各冷指数间、各暖指数间相关关系显著。(4)毛乌素沙地极端气温在空间上表现出不同的变化特点,东北方向(榆林及鄂托克旗)冷指数呈现大幅减少,西南方向(横山及盐池)暖指数呈现大幅增加。(5)ENSO事件具有使毛乌素沙地极端最高气温降低的作用以及使极端最低气温升高的作用。(6)10项极端气温指数的Hurst指数均大于0.5,表明未来毛乌素沙地极端气温仍将呈现冷指数下降、暖指数上升的变化趋势。     

1960～2014年北京极端气温事件变化特征

基于北京1960~2014年逐日最高温、最低温、平均气温实测数据,采取RHtest方法对气温序列进行均一性检验和修订。在此基础上选取16个极端气温指标,分析了北京市极端气温变化趋势和突变特征,探讨了冷暖极端气温指数对北京气候暖化的贡献。结果表明:1 1960~2014年北京气温暖化趋势明显,最低温增温速率远快于最高温,修订后增长速率为:最高温(0.17℃/10a)平均温(0.30℃/10a)最低温(0.51℃/10a);2冷昼日数、冷夜日数、霜冻日数、冰冻日数、冷持续日数分别以-1.43 d/10a、-6.56 d/10a、-3.95 d/10a、-1.18 d/10a、-4.83 d/10a的趋势减小;3暖昼日数、暖夜日数、夏季日数、热夜日数、暖持续日数、生物生长季以2.12 d/10a、5.27 d/10a、1.22 d/10a、5.43 d/10a、0.84 d/10a、1.96 d/10a的趋势增加;4日最高(低)气温极高值、日最高(低)气温极低值和气温日较差的倾向率分别为0.21℃/10a、0.34℃/10a、0.31℃/10a、0.73℃/10a、-0.33℃/10a;5极端最低气温的变暖幅度大于极端最高气温,夜指数的变暖幅度大于昼指数,冷指数的变幅大于暖指数。极端气温冷指数、夜指数、低温指数的快速变化是近年来北京市气候暖化的最直接体现。     

1990–2015年横断山区国土空间时空变化研究（英文）

Hengduan Mountains offer land space for a variety of ecological services. However, the sustainable development and management of land space has been challenged by increased human activities in recent years. This paper performs the spatial pattern analysis of the quantitative and structural changes of various landscapes at different altitudes, and uses the land use data in 1990, 2000, 2010 and 2015 to reveal how various land patterns have changed. The results show that, within the production-living-ecological space schema, the ecological space dominates Hengduan Mountains, while the production and living space was mainly distributed in south region. During 1990–2015, the production-living-ecological spatial changes had been gradually accelerated and the regional differences had become more prominent. The agricultural production space had continuously decreased by 1132.31 km~2, and the industrial and mining production space had rapidly increased by 281.4 km~2 during 1990–2015. The living space had steadily increased, and the ecological space had increased with fluctuations. The land space pattern in Hengduan Mountains was greatly restricted by the terrain, such as altitude and slope. The implementations of China Western Development Strategy and the Returning Farmland to Forest Program had favorably promoted the changes of land spatial pattern in Hengduan Mountains.     

1960–2016年中国北方寒潮事件时空变化分析（英文）

Among the most devastating extreme weather events, cold surge(CS) events frequently impact northern China. It has been reported that extreme weather events will increase in the global warming context. However, the direct evidence of this hypothesis is limited. Here, we investigated the changes in frequency, number, duration, and temperature of CS events in northern China using the daily minimum temperature dataset of 331 stations from 1960 to 2016. The results indicate that the annual CS events in terms of frequency and number decreased, and the duration shortened as the starting date was later and the ending date earlier. Meanwhile, the annual CS temperature increased. In addition, spatial trends in the CS events in terms of frequency, number, and duration decreased while the CS temperature increased in most regions of northern China. We interpreted these variations as a response to global warming. However, the extreme CS events in terms of frequency, number and the earliest starting date and the latest ending date showed little change though the extreme CS temperature increased, implying climate warming had not limited extreme CS events. The adverse effect of CS events on agriculture and human health remain concerning.     

北疆地区1961~2010年极端气温事件变化特征

根据1961~2010年北疆地区34个气象台站逐日平均气温、最高气温和最低气温资料,定义高温和低温的阈值、频率及其强度,并采用线性趋势、EOF等方法对其研究分析。研究表明：① 北疆地区的高温阈值研究发现空间分布变化特征基本呈现从东南向西北规律变化趋势。时间变化趋势分析发现该地区高温阈值呈现上升趋势。其中,夏季上升幅度最小,冬季上升幅度最大。频数分析发现天山山区极端高温频数变化要高于其他地区变化频数。② 北疆地区的低温阈值研究发现空间分布变化特征基本也呈现从东南向西北规律变化趋势。频数分析发现夏季频数总体呈现下降趋势。③ 通过线性趋势和EOF分析表明北疆地区高温和低温事件强度、频数呈现增加的趋势。由于北疆属于干旱与半干旱地区,生态环境较为脆弱。极端气温趋势的增加会影响到该地区的水文、工业和农业管理。     

1961-2010 年西藏极端气温事件的时空变化

利用18 个气象站点1961-2010 年逐日最高、最低气温和平均气温资料,分析了西藏极端气温事件的变化规律。结果表明:近50a 西藏霜冻日数和结冰日数明显减少,结冰日数减少显著的区域集中在藏北,霜冻日数则在整个区域都显著减少;生长季长度以4.71 d/10a 的速度明显延长,以拉萨、泽当最显著。极端最低气温在全区范围均呈显著升高,尤其是近30a 升幅更大,达1.06 oC/10a;最高气温的极大值在沿雅鲁藏布江一线东段和那曲地区上升较明显,而在南部边缘地区有下降的趋势。冷夜(昼) 日数普遍明显减少,减幅为9.38 d/10a (4.96 d/10a);暖夜(昼) 日数显著增加,增幅为10.99 d/10a (6.72 d/10a)。大部分极端气温指数的变化趋势与海拔高度有较高的相关性,其中极端最低气温与海拔高度呈正相关,极端最高气温、结冰日数、暖昼(夜) 日数和生长季长度呈负相关。极端最高、最低气温和气温暖指数呈逐年代增加趋势,极端气温冷指数和生长季长度表现为下降的年代际变化特征。在时间转折上,极端最低气温、冷(暖) 夜指数和生长季长度的突变点发生在20 世纪90 年代中期前,霜冻、结冰日数和冷(暖) 昼指数的突变点则推迟到21 世纪初期。多数情况下,西藏极端气温指数的变幅比全国、青藏高原及其周边地区偏大,说明西藏极端气温变化对区域增温的响应更为敏感。     

1961-2015年中国极端干旱时间演变特征（英文）

Understanding the past variations in extreme drought is especially beneficial to the improvement of drought resistance planning and drought risk management in China. Based on the monitoring data of meteorological stations from 1961 to 2015 and a meteorological drought index, the Standardized Precipitation Evapotranspiration Index(SPEI), the spatio-temporal variations in extreme drought at inter-decadal, inter-annual and seasonal scales in China were analyzed. The results revealed that 12 months cumulative precipitation with 1/2 to 5/8 of average annual precipitation will trigger extreme drought. From the period 1961–1987 to the period 1988–2015, the mean annual frequency of extreme drought(FED) increased along a strip extending from southwest China(SWC) to the western part of northeast China(NEC). The increased FED showed the highest value in spring, followed by winter, autumn and summer. There was a continuous increase in the decadal-FED from the 1990 s to the 2010 s on the Tibetan Plateau(TP), the southeast China(SEC) and the SW. During the period 1961–2015, the number of continuous drought stations was almost the same among 4 to 6 months and among 10 to 12 months of continuous drought, respectively. It can be inferred that drought lasting 6 or 12 months may lead to more severe drought disasters due to longer duration. The range of the longest continuous drought occurred in the 21 st century had widely increased compared with that in the 1980 s and the 1990 s. Our findings may be helpful for water resources management and reducing the risk of drought disasters in China.