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1.
Severe droughts have affected much of Europe over the last 40 years. A limitation to current understanding of droughts is based around drought characteristics (e.g. frequency, severity and duration) as there are limited long series (>100 years) with well documented severe droughts. This is further complicated with future climate projections, and the potential implications that these will have on drought characteristics. This paper presents reconstructed drought series from 1697, 1726 and 1767 to 2011 for three sites in southeast England. Precipitation and temperature series are reconstructed to generate long drought series using the self-calibrated Palmer Drought Severity Index, enabling determination of drought characteristics. The reconstructions identify multiple drought-rich periods, 1730–1760 and 1890-present, with an increasing tendency towards more severe droughts during the latter period. Prolonged rainfall deficiencies are found to be the primary cause of severe droughts, with rising temperatures increasing soil moisture deficit, therefore intensifying drought conditions. Cycles at the 6–10 year period identify a sub-decadal to decadal signal during drought-rich periods. Analysis of the spatial variability of droughts finds that whilst severe events are predominantly regionally coherent, there are notable variations in severity and duration between sites, which are attributed to localised rainfall variability. This study extends the temporal range of previous drought studies and places recent drought events in a longer context improving upon existing ‘benchmark’ drought analyses in southeast England; with far-reaching implications for local, national and continental scale reduction of drought vulnerability and risk.  相似文献   

2.
This study focuses on a framework of methodologies used for analyzing the frequency and spatiotemporal characteristics of agricultural droughts in Zimbabwe from a vulnerability context. By employing an empirical orthogonal analysis method, the study revealed that relatively strong spatial and temporal station drought relationships prevail, making the drought spatiotemporal characteristics of the country to be considered highly homogeneous. Thus, agricultural droughts were characterized temporarily using the Standardized Precipitation Index derived from rainfall data for the longer but sparse data period from 1901 to 2004. At the same time, higher spatial density analysis was achieved from shorter but denser database for the period 1941 to 1999. The results indicated that drought is a natural climatic feature of the region and occurs from time to time in defined periods. However, severe and extreme droughts tend to concentrate near the end of the time series, suggesting that during the earlier period of the twentieth century, droughts have been smaller or less pervasive. The extreme droughts appear to inherit the coincidence of both very high values of spatial extent and intensity in a single event. This offers a possible explanation to why extreme droughts in Zimbabwe usually have dire consequences on agriculture and the national economy. By showing that the related national drought impacts on staple maize food production can be estimated, this study has demonstrated that it is possible to anticipate future drought hazard impacts and predict periods of food insecurity. As far as the forecasting of agricultural droughts is concerned, the recently discovered Indian Ocean dipole/zonal mode seems to perform better than the traditional El Niño–Southern Oscillation as a potential drought predictor during the twentieth century.  相似文献   

3.
Using the Normalized Difference Vegetation Index (NDVI) as an indicator of vegetation growth, we explored the characteristics and differences in the response to drought of five vegetation biomes in Northeast China, including typical steppe, desert steppe, meadow steppe, deciduous coniferous forest and deciduous broad-leaved forest during the period 1982-2009. The results indicate that growing season precipitation may be the primary vegetation growth-limiting factor in grasslands. More than 70% of the temporal variations in NDVI can be explained by the amount of precipitation during the growing season in typical and desert steppes. During the same period, the mean temperature in the growing season could explain nearly 43% of the variations in the mean growing season NDVI and is therefore a dominant growth-limiting factor for forest ecosystems. Therefore, the NDVI trends differ largely due to differences in the vegetation growth-limiting factors of the different vegetation biomes. The NDVI responses to droughts vary in magnitude and direction and depend on the drought-affected areas of the five vegetation types. Specifically, the changes in NDVI are consistent with the variations in precipitation for grassland ecosystems. A lack of precipitation resulted in decreases in NDVI, thereby reducing vegetation growth in these regions. Conversely, increasing precipitation decreased the NDVI of forest ecosystems. The results also suggest that grasslands under arid and semi-arid environments may be more sensitive to drought than forests under humid environments. Among grassland ecosystems, desert steppe was most sensitive to drought, followed by typical steppe; meadow steppe was the least sensitive.  相似文献   

4.
基于TVDI的西藏地区旱情遥感监测   总被引：2，自引：0，他引：2  
西藏大部分地区属干旱或重干旱区,干旱发生较为频繁,是影响农牧业生产最严重的灾害之一。文章利用拉萨接收站的中分辨率成像光谱仪(MODIS)资料提取的归一化植被指数(NDVI)和地表温度(ST),构建ST-IND-VI特征空间,依据该特征空间设计的温度植被旱情指数作为旱情指标,找出适合该地区的旱情判别模式,以2005～2008年6～7月同时段西藏地区卫星资料、气象旱情监测结果以及土壤相对湿度观测数据为例,进行旱情对比分析。结果表明,利用温度植被旱情指数(TVDI)法对西藏地区进行夏季干旱动态监测是可行的。  相似文献   

5.
东北夏季降水的气候及异常特征分析   总被引：7，自引：2，他引：7  
采用统计分析的方法对近50 a东北夏季降水的气候及异常特征进行了分析。结果表明:东北夏季降水空间分布很不均匀,除三江平原地区外东北大部7月降水最多;夏季全区出现较重干旱的概率大于较重雨涝,旱灾更为突出,其中辽西是较重旱涝频发的地区;近50 a夏季降水没有明显变干或变湿的倾向,而是具有阶段性旱涝交替特征,存在27、11 a左右的年代际尺度周期和3~6 a左右的年际尺度周期变化;6月旱灾几率大,易形成6~7月的连续干旱,7月易形成区域性特大涝灾,6月和8月在年代际尺度上具有反位相变化的特征。  相似文献   

6.
利用鄂尔多斯市1961—2010年11个气象站的逐月降水资料,通过标准化降水指数分析鄂尔多斯市近50a来干旱的时空演化特征。结果表明:鄂尔多斯市干旱的发生在时间序列上具有阶段性特征,20世纪60年代前期和90年代末期干旱最为严重,80年代为持续性干旱阶段。用经验正交函数对鄂尔多斯市干旱的空间分布特征做进一步分析,结果表明,鄂尔多斯市干旱的空间分布既有显著的一致性,又有一定的区域性。将鄂尔多斯市具体细分为西北部、东北部、西南部、东南部4个区域,80年代之前,东北部干旱较为严重,80年代以后西部干旱化趋势加剧,西北部尤为明显,东部降水增多。  相似文献   

7.
在全球气候变暖的背景下,持续的干旱事件将对生态系统和人类社会产生不利影响。尽管存在多源卫星遥感资料及多种干旱指数,然而区域和全球尺度干旱事件的监测仍具有挑战。采用TRMM（Tropical RainfallMeasuring Mission）数据量化降水异常、MODIS（Moderate Resolution Imaging Spectroradiometer）归一化植被指数（Normalized Difference Vegetation Index,NDVI）和陆表温度（Land Surface Temperature,LST）数据表征植被生长异常,构建了一种兼顾降水异常和植被生长状况异常的多传感器陆表干旱严重程度指数（Multi-sensorsDrought Severity Index,MDSI）。结果表明:MDSI 能够准确检测准全球范围（50°S～50°N,0°～180°～0°）的气象干旱事件,如亚马逊流域2005 和2010 年干旱、中国川渝地区2006 年干旱、中国云南2010 年干旱、非洲东部2011 年干旱、2012 年美国中部干旱等;MDSI 与PDSI（Palmer Drought Severity Index）呈现出大致相同的干湿空间格局,并且MDSI 有助于湿润地区干旱程度的检测。  相似文献   

8.
Analysis of meteorological drought episodes in Paraguay   总被引：3，自引：0，他引：3  
This paper analyzes the meteorological drought events in Paraguay in the period of 1964 to 2011, using the Standardized Precipitation Index (SPI). The objective is to determine if the frequency and/or severity of droughts has increased or decreased in the last years, in response of climate change. They The southernmost parts of the country are affected by severe droughts producing damage to soybean and corn crop during the rainy season (October–March) especially during the summer of 2008–2009. The years of 1967, 1968, 1978, 1979, 2000 and 2008 was identified as severe to extreme drought events and coincides with La Niña event. However, the relationship between all drought events, especially those agricultural droughts and La Niña is not clear, suggesting the necessity of new research, focusing on new drivers to explain the cause of the droughts. The economy of Paraguay, based for good part on agriculture, is clearly vulnerable to droughts. Even though no undeniable increasing trend in drought frequency/severity was detected, contingency plans to diminish drought impacts ought to be elaborated.  相似文献   

9.
选取肇庆市6个国家基本气象站1962-2018年逐月降水资料,基于标准化降水指数SPI,利用线性回归、M-K突变检验、Morlet连续复小波分析和EOF分解等方法对肇庆市近57年干旱时空变化特征进行分析.结果表明:(1)1962-2018年肇庆市SPI12呈震荡上升趋势,但线性趋势不显著;序列存在6、11、18年的周期...  相似文献   

10.
Recent drought and precipitation tendencies in Ethiopia   总被引：3，自引：0，他引：3  
In 2011, drought in the Horn of Africa again made news headlines. This study aims to quantify the meteorological component of this and other drought episodes in Ethiopia since 1971. A monthly precipitation data set for 14 homogeneous rainfall zones was constructed based on 174 gauges, and the standardized precipitation index was calculated on seasonal, annual, and biannual time scales. The results point to 2009 as a year of exceptionally widespread drought. All zones experienced drought at the annual scale, although in most zones, previous droughts were more extreme. Nationally, 2009 was the second driest year, surpassed only by the historic year 1984. Linear regression analysis indicates a precipitation decline in southern Ethiopia, during both February–May and June–September. In central and northern Ethiopia, the analysis did not provide evidence of similar tendencies. However, spring droughts have occurred more frequently in all parts of Ethiopia during the last 10–15 years.  相似文献   

11.
2001年我国天气气候特点   总被引：2，自引：1，他引：2  
陈峪 《气象》2002,28(4):29-33
2001年我国主要天气气候特点为：全国大部地区降水偏少或接近常年，四季均出现不同程度的干旱，特别是北方地区的春夏旱或长江中下游地区的夏伏旱及我国东部地区的秋旱影响较大；汛期我国未发生大范围的暴雨洪涝灾害，但两广局地受灾较重；华西秋雨明显。全国大部气温普遍较常年偏高，东北出现异常寒冬，夏季不少地区出现高温酷热天气；新疆、内蒙古冬季发生严重雪灾；风沙和沙尘暴天气出现早、次数多；登陆我国的台风（包括热带风暴）个数偏多；风雹等强对流天气接近常年。  相似文献   

12.
Summary ?One of the most important features in analysing the climatology of any region is to study the precipitation and its periodicity of different harmonics in order to study the behavior of the observed data. In this study the amplitude of frequencies, phase angle and basic statistical parameters are calculated in order to depict spatial characteristics of precipitation over Jordan. Precipitation records of 17 stations were chosen according to climatic regions of Jordan. The first and second harmonic analyses explain more than 90% of the precipitation variation in Jordan effectively. The amplitudes of the first and second harmonic were calculated in order to describe the climatic regions in the country. The maximum amplitudes were found in the northern mountainous region. The phase angle representing the time of maximum rainfall is also used in the form of a contour chart. It is found that Jordan has its main rainfall season in winter with maximum around January. The coefficient of variation shows the high variability of rainfall of the country. Received February 4, 2002; revised August 1, 2002; accepted August 6, 2002  相似文献   

13.
Based on the Multi-Scale Standardized Precipitation Index (MSPI), extreme severe drought events in China during 1961-2010 were identified, and the seasonal, annual, and interdecadal variations of the clustering extreme drought events were investigated by using the spatial point process theory. It is found that severe droughts present a trend of gradual increase as a result of the significant increase and clustering tendency of severe droughts in autumn. The periodicity analysis of the clustering extreme droughts in different seasons suggests that there is a remarkable interdecadal change in the occurrence of clustering extreme droughts in winter. Meanwhile, it is revealed that the clustering extreme drought events exhibit greatly different annual mean spatial distributions during 1961-2010, with scattered and concentrated clustering zones alternating on the decadal timescale. Furthermore, it is found that the decadal-mean spatial distributions of extreme drought events in summer are correlated out of phase with those of the rainy bands over China in the past 50 years, and a good decadal persistence exists between the autumn and winter extreme droughts, implying a salient feature of consecutive autumn-winter droughts in this 50-yr period. Compared with other regions of China, Southwest China bears the most prominent characteristic of clustering extreme droughts.  相似文献   

14.
Contrary to assertions of widespread irreversible desertification in the African Sahel, a recent increase in seasonal greenness over large areas of the Sahel has been observed, which has been interpreted as a recovery from the great Sahelian droughts. This research investigates temporal and spatial patterns of vegetation greenness and rainfall variability in the African Sahel and their interrelationships based on analyses of Normalized Difference Vegetation Index (NDVI) time series for the period 1982–2003 and gridded satellite rainfall estimates. While rainfall emerges as the dominant causative factor for the increase in vegetation greenness, there is evidence of another causative factor, hypothetically a human-induced change superimposed on the climate trend.  相似文献   

15.
The primary focus of this study is the analysis of droughts in the Tons River Basin during the period 1969–2008. Precipitation data observed at four gauging stations are used to identify drought over the study area. The event of drought is derived from the standardized precipitation index (SPI) on a 3-month scale. Our results indicated that severe drought occurred in the Allahabad, Rewa, and Satna stations in the years 1973 and 1979. The droughts in this region had occurred mainly due to erratic behavior in monsoons, especially due to long breaks between monsoons. During the drought years, the deficiency of the annual rainfall in the analysis of annual rainfall departure had varied from ?26% in 1976 to ?60% in 1973 at Allahabad station in the basin. The maximum deficiency of annual and seasonal rainfall recorded in the basin is 60%. The maximum seasonal rainfall departure observed in the basin is in the order of ?60% at Allahabad station in 1973, while maximum annual rainfall departure had been recorded as ?60% during 1979 at the Satna station. Extreme dry events (z score <?2) were detected during July, August, and September. Moreover, severe dry events were observed in August, September, and October. The drought conditions in the Tons River Basin are dominantly driven by total rainfall throughout the period between June and November.  相似文献   

16.
近55年来云南区域性干旱事件的分布特征和变化趋势研究   总被引：1，自引：0，他引：1  
金燕  况雪源  晏红明  万云霞  王鹏 《气象》2018,44(9):1169-1178
本文利用一种简化的区域性干旱事件识别方法,对近55年来云南区域性干旱事件进行了识别,在此基础上,选取区域性干旱事件的持续天数、影响站点数、平均强度、累积强度和极端最大强度这5个单一事件评价指标,构建了云南区域性干旱的综合评估模型,确定干旱等级划分标准。进一步分析表明,云南区域性干旱的发生频次、累积强度和累积影响站次均呈现上升趋势;云南在12、1和3月干旱发生最多,7、8月干旱发生最少;干旱持续天数集中在15～45 d,最长的可达222d;云南多发全省性的干旱且旱情偏重。云南中部区域干旱偏多、偏重发生;在严重的干旱事件中,中部型发生频次最多。  相似文献   

17.
Abstract

Droughts are major natural disasters for many parts of the world. Dry areas, where the precipitation pattern is markedly seasonal, or is otherwise highly variable, are the most susceptible. The Canadian Prairies, together with the U.S. Great Plains, are one such area. While immediate loss of life is seldom a feature of most droughts, malnutrition and even starvation do follow severe droughts in some parts of the world. In Canada, economic losses, particularly in the agricultural sector, may reach several hundred millions of dollars in a drought year, with major socio‐economic repercussions affecting the entire region. Environmental damages include soil degradation and erosion, vegetation damage, slough and lake deterioration and wildlife loss. Unlike most other natural disasters, drought onset is difficult to identify. Droughts develop slowly, and until human activity begins to be affected by an on‐going reduction of precipitation, their existence is unrecognized. Development and application of specific soil moisture and drought indices based on cumulative precipitation deficits have enhanced drought monitoring programs. These in turn provide guidance on the need for mitigative measures that can be initiated early in the course of a drought. Any improvement in the timely application of these measures is, however, strongly dependent on being able to determine the drought's course, extent and likely severity at the earliest stage possible. The identification of precursor conditions for past drought has raised the possibility that the likelihood of a drought occurring in a particular year or growing season might be predictable. Teleconnections between North American precipitation patterns and ENSO events and other surface boundary conditions in the North Pacific have been detected. Forecasting seasonal temperature and perhaps precipitation anomalies appears to be potentially feasible using a suitable merging of precursor parameters and modelling methodologies. Clearly, future research must focus both on those precursors that have been identified and on a search for possible new ones. Development of better forecasting methodology is also essential. Research activity to identify and evaluate new mitigative measures should also be increased to keep pace with the prospects of drought predictability.  相似文献   

18.
In the last decade, a series of severe and extensive droughts have swept across Southwest China, resulting in tremendous economic losses, deaths, and disruption to society. Consequently, this study is motivated by the paramount importance of as- sessing future changes in drought in Southwest China. Precipitation is likely to decrease over most parts of Southwest China around the beginning of the century, followed by widespread precipitation increases; the increase in potential evapotran- spiration （PET）, due to the joint effects of increased temperature and surface net radiation and decreased relative humidity, will overwhelm the whole region throughout the entire 21st century. In comparative terms, the enhancement of PET will outweigh that of precipitation, particularly under Representative Concentration Pathway （RCP） 8.5, resulting in intensified drought. Generally, the drying tendency will be in the southeast portion, whereas the mountainous region in the northwest will become increasingly wetter owing to abundant precipitation increases. Droughts classified as moderate/severe according to historical standards will become the norm in the 2080s under RCP4.5/RCP8.5. Future drought changes will manifest different characteristics depending on the time scale： the magnitude of change at a time scale of 48 months is nearly twice as great as that at 3 months. Furthermore, we will see that not only will incidences of severe and extreme drought increase dramatically in the future, but extremely wet events will also become more probable.  相似文献   

19.
Climate extremes, particularly the droughts sustaining over a prolonged period and affecting extended area (defined as “exceptional drought events”), can have long-lasting effects on economic and social activities. Here we use the Chinese drought/flood proxy data of the past five hundred years to identify the cases of exceptional drought events over eastern China (east of 105°E), and to study their spatial patterns and temporal evolutions. The associated circulations for the contemporary case are analyzed using available meteorological data. Possible linkage of these cases to climatic forcing and natural climate events is also explored. After considering the intensity, duration, and spatial coverage, we identified three exceptional drought events, which occurred in 1586–1589, 1638–1641, and 1965–1966 in chronological order. They were the most severe droughts of last five centuries in eastern China, with more than 40% of affected area and the drought center encountered a significant summer rainfall reduction (about 50% or more). These three droughts all developed first in North China (34–40°N), and then either expanded southward or moved to the Yangtze River Valley (27–34°N) and the northern part of the southeastern coastal area (22–27°N). For the 1965–1966 case, the significant reduction of summer precipitation was caused by a weakening of summer monsoon and an anomalous westward and northward displacement of the western Pacific subtropical high. Our analyses also suggest that these three exceptional drought events might be triggered by large volcanic eruptions and amplified by both volcanic eruptions and El Niño events.  相似文献   

20.
本文基于铜仁市10个国家自动观测站1981-2020年近40a降水资料,计算多时间尺度标准化降水指数（SPI）,确定旱涝程度,分析旱涝时空分布特征,筛选典型旱、涝年进行环流分析。结果表明：(1)铜仁市20世纪80年代后期总体偏旱,90世纪后期总体偏涝。铜仁市夏季呈现出旱涝交替变化特征。(2)铜仁市中西部、东北部干旱相对频繁,并向四周逐渐减弱;市中西部、东南部发生雨涝的频率相对较高,西北部最低。夏季的干旱和雨涝均以轻、中程度为主,特重程度情况发生很少。(3)夏季偏涝年整个欧亚中高纬均为位势高度的负异常,偏旱年欧亚中高纬的乌拉尔山和中国东北的位势高度异常中心转为正异常分布。（4）赤道中东太平洋的厄尔尼诺现象与南、北太平洋海温异常分布对铜仁夏季偏涝现象的发生发展有密切关系;赤道中东太平洋拉尼娜现象、印度洋及西太平洋的海温异常分布对铜仁夏季偏旱现象的发生发展有密切关系。  相似文献   

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