Temporal Characteristics Of Drought Research Articles

Spatial and temporal characteristics of drought in the Mu Us Sandy Land based on the Standardized Precipitation Index

The environment of the Mu Us Sandy Land, northern Shaanxi, is fragile, so the temporal and spatial evolution of drought can provide a reference for ecological construction and agricultural production. Based on the daily precipitation data of five meteorological stations from 1967 to 2020, the spatial and temporal evolution characteristics of drought in the Mu Us Sandy Land of northern Shaanxi were analyzed using the methods Standardized Precipitation Index (SPI) and run-length theory. The results show that 1) the smaller the time scale, the higher the sensitivity of the SPI to primary precipitation. 2) The annual, summer, autumn, and winter SPI showed an upward and a wetting trend, and the fastest wetting speed is observed in summer, while spring showed an increasing trend of drought. 3) In the past 54 years, the duration, degree, and intensity of drought events at SPI-3 and SPI-12 scales in the Mu Us Sandy Land of northern Shaanxi showed an insignificant decreasing trend, but the decreasing rate at the SPI-12 scale was faster than that at the SPI-3 scale. The serious periods of drought are November 2018 to May 2019 and April 1999 to July 2021. 4) The duration of drought events at two timescales in each region showed a decreasing trend. The longest durations of drought were in Yulin and Jingbian; Shenmu and Dingbian are the regions with the fastest reduction rate of drought degree at the two scales. Hengshan shows rapid reduction of drought intensity at the two scales and also the region with large average drought intensity. These results are helpful in understanding and describing drought events for drought risk management under the condition of global warming.

Study on the Response of Vegetation Water Use Efficiency to Drought in the Manas River Basin, Xinjiang, China

Ecosystem water use efficiency (WUE) is an important measure of the degree of water–hydrogen coupling and an important indicator for assessing ecosystem responses to climate change. Drought adversely affects ecosystem security, particularly in irrigated agricultural areas; therefore, understanding the relationship between WUE and drought is important. This study revealed the spatial and temporal characteristics of drought in the Manas River Basin, Xinjiang, China, from 2001 to 2020 through multi-source data using standardised anomaly indices and mutation detection. It also quantitatively analysed the hysteresis effect and resilience characteristics of drought for different vegetation types in the study area. The results showed that droughts at a severe level occurred less frequently in most of the study area on average from 2001 to 2020, and that droughts in the vegetation growing season occurred more frequently, particularly in grasslands; the frequency of droughts in woodlands was low. Furthermore, the lag in WUE to drought occurred on a 3-month scale and accounted for 64.0% of the total watershed area. Finally, 38.16% of the regional vegetation ecosystems in the Manas River Basin exhibited drought resistance. In conclusion, our results provide novel insights into the water-use strategies of plants in the study area and will help facilitate WUE optimisation.

Monitoring of long‐term vegetation dynamics and responses to droughts of various timescales in Inner Mongolia

AbstractThe characteristics of vegetation and drought for different seasons between 1982 and 2015 in Inner Mongolia were studied based on the normalized difference vegetation index (NDVI) and the standardized precipitation evapotranspiration index (SPEI). The response of vegetation to drought over various timescales for different seasons and vegetation types was investigated using the maximum Pearson correlation, allowing a discussion about the possible causes of any changes. The results indicate that the vegetation NDVI in Inner Mongolia showed an increasing trend in different seasons, with spring vegetation NDVI (April–May) having the largest significant increasing rate, followed by the growing season (April–October), autumn (September–October), and summer (June–August). Accordingly, the proportion of stations with decreasing SPEI was, in descending order, summer, growing season, autumn, and spring. Additionally, the magnitude of the SPEI decrease was greater in eastern Inner Mongolia. NDVI and SPEI were positively correlated in most regions of Inner Mongolia, indicating that changes in vegetation in most parts of this region were affected by the spatial and temporal characteristics of drought, the correlation being them being strongest in the growing season, followed by summer, then spring and autumn. Considering the different types of vegetation, forests were less affected by drought, with broadleaf forests more affected than coniferous forests. The meadow steppes and typical steppes were more affected by 12‐month droughts in the growing season and summer, 6‐month droughts in spring, and 3‐month droughts in autumn, with desert steppes mainly affected by 3‐month droughts. The shrubs, sandy vegetation, and cropland were mostly affected by droughts in summer, and show a greater response to 3‐month droughts in autumn. Finally, the water balance was found to be the most important factor affecting the response of vegetation to drought in Inner Mongolia.

Spatial and temporal characteristics of drought and its correlation with climate indices in Northeast China.

The spatial and temporal characteristics of drought in Northeast China are investigated, using monthly meteorological data from 140 stations over the period 1970–2014. The study area was divided into three regions using hierarchical cluster analysis based on the precipitation and potential evapotranspiration data. The standardized precipitation evapotranspiration index (SPEI) was calculated for each station on 3-month and 12-month time scales. The Mann-Kendall (MK) trend test and Sen’s slope method were applied to determine the trends for annual and seasonal SPEI time series. Periodic features of drought conditions in each sub-region and possible relationship with large-scale climate patterns were respectively identified using the continuous wavelet transform (CWT) and cross wavelet transform. The results show mitigations in spring and winter droughts and a significant increasing trend in autumn drought. On the annual scale, droughts became more severe and more intense in the western regions but were mitigated in the eastern region. CWT analysis showed that droughts in Northeast China occur predominantly in 14- to 42-month or 15- to 60-month cycles. Annual and seasonal droughts have 2- to 6-year cycles over the three defined regions. Cross wavelet analysis also shows that the statistically significant influence of large-scale climate patterns (the Southern Oscillation, the Atlantic Multidecadal Oscillation, the Arctic Oscillation, and the Polar–Eurasian Pattern) on drought in Northeast China is concentrated in a 16- to 50-month period, possibly causing drought variability in the different regions. The Southern Oscillation, Polar–Eurasia pattern, and Arctic Oscillation are significantly correlated with drought on decadal scales (around 120-month period). The findings of this study will provide valuable reference for regional drought mitigation and drought prediction.

Changing pattern of drought in Nepal and associated atmospheric circulation

Understanding the spatial and temporal characteristics of drought is vital for the agricultural, hydrological, ecological, and socio-economic systems. This study investigates the spatial and temporal variation of drought characteristics in Nepal using the Standardized Precipitation Evapotranspiration Index (SPEI) based on observational monthly temperature and precipitation data from 1987 to 2017. The drought variation was observed in the Western, Central, and Eastern regions of Nepal at short-term (SPEI4) and long-term (SPEI12) timescales, revealing the increased drought frequency, duration, and severity in the recent decade. The frequency of short-term drought (SPEI4 ≤ -1) has elevated by 15%, 17%, and 15% in Western, Central, and Eastern regions, respectively, during 2005–2017 compared to 1987–2004. Moreover, the interdecadal increase of drought characteristics was prominent after 2004, revealed by the SPEI12 with aggravated and prolonged drought episodes. The summer drought index (SPEI4-Sep) showed an interannual variation in the Western region at a seasonal timescale, whereas decadal variation in the Central and Eastern regions. Meanwhile, summer drought events increased five times in the Central region, two times in the Eastern Region, and did not observe any change in the Western region after 2004. The large-scale atmospheric circulations revealed the negative summer precipitation anomalies due to weakening wind anomalies with anti-cyclonic circulation and moisture divergence over the Indo-Gangetic plain and Nepal, respectively, leads to enhanced drought after 2004. Furthermore, the moisture transport from the Arabian Sea and the Bay of Bengal to the study region is weaker, resulting in more drought events, especially in the Central and Eastern regions.

Research on the Temporal and Spatial Changes Characteristics of the Drought of Natural Vegetation in the Yangtze River Source Area Based on CWSI

Under the combined effect of global climate change and local regional environmental change, drought has developed into a natural disaster with high incidence on the earth. As the Yangtze River is the mother river of Chinese civilization, the drought phenomenon in the source area in recent decades has seriously affected and restricted the development of local agriculture and economic society. With the long-term practice of remote sensing technology, researchers have improved drought monitoring methods, including crop water stress index. Crop water stress index (CWSI) is widely used in agricultural drought research based on the principle of heat balance. In this paper, the spatial and temporal characteristics of drought in the Yangtze River source area and its influencing factors were analyzed by using crop drought index method. The CWSI value of the source area of the Yangtze River featured a slightly downward trend from 2001 to 2018. With a strong spatial heterogeneity in distribution, it gradually decreases from west to east. The severest drought occurs in summer and autumn, and the regions that are mostly influenced by temperature are mainly in southwest part and the ones mostly influenced by precipitation are mainly in east part. By analyzing the temporal and spatial distribution characteristics of drought and the correlation of meteorological factors, this paper provides an effective basis for drought prevention and control in the Yangtze River source area, and then promotes the accelerated development of agriculture and economic society in the Yangtze River source area of our country.

SPATIAL-TEMPORAL CHARACTERIZATION OF METEOROLOGICAL DROUGHT USING THE STANDARDIZED PRECIPITATION INDEX.CASE STUDY IN ALGERIA

Aim of the study: In this study, the spatial and temporal characteristics of drought in the upper and middle Cheliff; a semi-arid region of northwestern Algeria was examined using the standard precipitation index [SPI] at an annual time scale as a tool for measuring the severity of meteorological drought. Material and methods: To asses of SPI annual sum of precipitation from 11 precipitation stations covering the period 1970-2009 were used. In order to identify the possible changes in the precipitation trend of the studied series, statistical tests were selected. The extent, severity and duration of the drought in the study area were obtained. Results and conclusions: Statistical tests showed that the occurrence of ruptures in the rainfall regime was detected at the end of the 1970s and the beginning of 1980s with a negative trend. The results of the SPI showed a strong existence of dry years after 1979 and 1980. The years 1993, 1999 and 2001 presented an extremely severe drought (SPI <-2). The evolution of SPI showed a dominance of the frequency of normal years (67%) and alternation of dry years (17%) and wet years (16%) over a period of 40 years. The total surface of the study area is affected by drought during severe years (1993, 1999). The study area exhibits irregularity and heterogeneity of drought due to the great variability of precipitation, it can vary from sub-basin to another and from one year to another.

Analysis of long term drought severity characteristics and trends across semiarid Botswana using two drought indices

Semiarid areas exhibit high climate variability whose frequency has increased in the recent past. This variability ultimately influences the spatial and temporal characteristics of droughts which in turn require a reliable drought index that can adequately characterize drought both in time and space. This study applied two drought indices viz.: Standardized precipitation index (SPI) and Standardized precipitation and evapotranspiration index (SPEI) at timescales of 1-, 3-, 6-, 12-, 18- and 24-months for a period of 1960–2016. The monotonic changes in drought severity were studied using Mann-Kendall Z-statistic and Sen's slope estimator. Both drought indices were able to detect the historical drought events of 1961/62–1965/66, 1980/81–1986/87, 1991/92, 2001/02–2005/06, 2009/10–2012/13 and 2014/15–2015/16. These events mainly coincided with El Niño years, hence the influence of El Niño southern oscillation (ENSO) on drought occurrence could not be ruled out. The drought evolutions were characterized by low frequency and longer durations at timescales of 12-, 18-, and 24-months. It was also observed that SPI overestimated drought severity during dry winter months while SPEI showed higher spatial coverage of drought vulnerability compared to SPI. Spatial and temporal trends of droughts showed significant wetting trends during the period 1960–1979 while during the entire period it was mostly drying tendencies after 1979/80. Pandamatenga and Shakawe showed higher vulnerability towards drying conditions during the period of analysis. The association between SPI and SPEI was also investigated using Spearman's rank correlation. Results from this analysis indicate that SPI accounts for >50% of the variations in SPEI and the association was strongest (96%) at 12-months timescale. The influence of temperature on drought evolutions was demonstrated at Francistown with SPI recording positive trends and SPEI negative ones. This study concludes that with the ongoing global warming, SPEI proves more robust in characterizing droughts in semiarid areas. It is hoped that findings from this study will augment ongoing efforts of mitigating negative impacts of increased incidences of climate variability especially in areas of agriculture and water resource management.

Spatial-temporal characteristic of drought in northern Nigeria

This paper examines the spatial and temporal characteristics of droughts during the rainy season (May-October) for 1965-2010 over northern Nigeria using monthly rainfall data from station rain gauges. The spatial distribution of rainfall is identified by  Standardized Precipitation Index (SPI), which also characterizes specific temporal drought events. Mann-Kendall trend test is applied to analyze the changes in the drought trend and also to confirm the significance of the observed trends. The results of the analysis show major changes in the drought characteristics in northern Nigeria during the major dry episodes (1973-1983) and major wet episodes (1996-2010). For the period 1965-1985, all the stations showed a decreasing trend both in 3 and 6 months time scales. In contrast, 87.5% of the stations showed an increasing trend for the period 1985-2010, with Maiduguri,  Nguru, Kano, Katsina and Yelwa showing significant increases, the prolonged dry spell in the 1970’s and 1980’s was shown clearly in some of the analyses. A large number of further  observations would be required to put some of these findings on a finer basis for the Sahelian drought characterization. It is  recommended that agricultural organizations and disaster  management parastatals should be pro-active in drought adaptation and mitigation planning. Keywords : Standardized Precipitation Index, Spatial,  Temporal, drought, Mann-Kendall, trend.

Temporal-Spatial Characteristics of Drought in Guizhou Province, China, Based on Multiple Drought Indices and Historical Disaster Records

Guizhou Province, China, experienced several severe drought events over the period from 1960 to 2013, causing great economic loss and intractable conflicts over water. In this study, the spatial and temporal characteristics of droughts are analyzed with the standard precipitation index (SPI), comprehensive meteorological drought index (CI), and reconnaissance drought index (RDI). Meanwhile, historical drought records are used to test the performance of each index at identifying droughts. All three indices show decreasing annual and autumn trends, with the latter particularly prominent. 29, 30, and 32 drought events were identified during 1960–2013 by the SPI, CI, and RDI, respectively. Continuous drought is more frequent in winter–spring and summer–autumn. There is a significant increasing trend in drought event frequency, peak, and strength since the start of the 21st century. Drought duration indicated by CI shows longer durations in the higher-elevation region of central and western Guizhou. The corresponding drought severity is high in these regions. SPI and RDI indicate longer drought durations in the lower elevation central and eastern regions of Guizhou Province, where the corresponding drought severity is also very strong. SPI shows an increasing trend in drought duration and drought severity across most of the regions of Guizhou. In general, SPI and RDI show an increasing trend in the western Guizhou Province and a decreasing trend in central and eastern Guizhou. Comparing these three drought indices with historical records, the RDI is found to be more objective and reliable than the SPI and CI when identifying the periods of drought in Guizhou.

Spatial and Temporal Characteristics of Drought and Flood in Quanzhou Based on Standardized Precipitation Index (SPI) in Recent 55 Years

To analyze the characteristics of drought and flood variations in Quanzhou during recent 55 years, the standardized precipitation index (SPI) and Empirical Orthogonal Function (EOF) and Rotated Empirical Orthogonal Function (REOF) were calculated by using the monthly precipitation data from 6 meteorological bureaus across Quanzhou for 1960-2014. Results showed that: 1) During 1960-2014, the drought and flood showed Periodic variation characteristics in Quanzhou, the specific period of frequent drought was 1963-1972, 1977-1986 and 2009-2011, and the specific period of frequent flood was 1961-1962, 1972-1975, 1990-1992 and 1997-2007; the drought and flood did not have significant tendency of variation in Spring and Summer, and the drought and flood showed a non-significant downward trend in Autumn and Winter. 2) The drought and flood variation had relatively consistent trend in Quanzhou, but there was a big difference on the northwest mountainous area, the middle semi-mountainous area and the southeast coast area in some periods. 3) The precipitation cell and distribution in every season were Nan’an and Anxi, but there was a big difference in rainfall less area: it was Yongchun and Dehua in Spring, Chongwu and Jinjiang in Summer, Chongwu in Autumn, Dehua and Chongwu in Winter.

Spatial and temporal characteristics of droughts in Central Asia during 1966–2015

In drought-prone regions like Central Asia, drought monitoring studies are paramount to provide valuable information for drought risk mitigation. In this paper, the spatiotemporal drought characteristics in Central Asia are analyzed from 1966 to 2015 using the Climatic Research Unit (CRU) dataset. Drought events, as well as their frequency, duration, severity, intensity and preferred season, are studied by using the Run theory and the Standardized Precipitation Evapotranspiration Index (SPEI) at 3-month, 6-month, and 12-month timescales. The Principle Components Analysis (PCA) and the Varimax rotation method, the Sen's slope and the Modified Mann-Kendall method (MMK), as well as the wavelet analysis are adopted to identify the sub-regional drought patterns and to study the drought trend, periodicity and the possible links between drought variation and large-scale climate patterns, respectively. Results show that the drought characteristics in Central Asia vary considerably. The Hexi Corridor region and the southeastern part suffered from more short-term drought occurrences which mostly occurred in summer while the northeastern part experienced fewer droughts with longer duration and higher severity. Central Asia showed an overall wetting trend with a switch to drying trend since 2003. Regionally, the continuous wetting trend is found in north Kazakhstan while a consistent drying in the Aral Sea and Hexi Corridor region is observed in the last half-century. For 2003–2015, a significant drying pattern is detected in most Central Asia, except the northern Kazakhstan. A common significant 16–64-month periodical oscillation can be detected over the six sub-regions. The drought changes in Central Asia are highly associated with ENSO but less related to the Tibetan Plateau pressure. The North Atlantic Oscillation has an influence on drought change in most Central Asia but less for the Hexi Corridor and the drought variation in eastern Central Asia is affected by the strength of the Siberian High.

Spatial and temporal characteristics of droughts in Luanhe River basin, China

The spatial and temporal characteristics of drought are investigated for Luanhe River basin, using monthly precipitation data from 26 stations covering the common period of 1958–2011. The spatial pattern of drought was assessed by applying principal component analysis (PCA) to the Standardized Precipitation Index (SPI) computed on 3- and 12-month time scales. In addition, annual SPI and seasonal SPIs (including spring SPI, summer SPI, autumn SPI, and winter SPI) were also defined and considered in this study to characterize seasonal and annual drought conditions, respectively. For all seven SPI cases, three distinctive sub-regions with different temporal evolutions of droughts are well identified, respectively, representing the southeast, middle, and northwest of the Luanhe River basin. The Mann-Kendall (MK) trend test with a trend-free pre-whitening (TFPW) procedure and Sen’s method were used to determine the temporal trends in the annual and seasonal SPI time series. The continuous wavelet transform (CWT) was employed for further detecting the periodical features of drought condition in each sub-region. Results of MK and Sen’s tests show a general tendency of intensification in summer drought over the entire basin, while a significant mitigating trend in spring drought. On the whole, an aggravating trend of inter-annual drought is discovered across the basin. Based on the CWT, the drought variability in the basin is generally dominated by 16- to 64-month cycles, and the 2- to 6-year cycles appear to be obvious when concerned with annual and seasonal droughts. Furthermore, a cross wavelet analysis was performed to examine the possible links between the drought conditions and large-scale climate patterns. The teleconnections of ENSO, NAO, PDO, and AMO show significant influences on the regional droughts principally concentrated in the 16- to 64-month period, maybe responsible for the physical causes of the cyclical behavior of drought occurrences. PDO and AMO also highlight a noteworthy correlation with drought variability on a decadal scale (around 128-month period). The findings of this study will provide valuable references for regional drought mitigation and water resource management.

基于SPEI指数的华北冬麦区干旱时空分布特征分析

PDF HTML阅读 XML下载 导出引用 引用提醒 基于SPEI指数的华北冬麦区干旱时空分布特征分析 DOI: 10.5846/stxb201311272825 作者: 作者单位: 中国气象科学研究院,中国气象科学研究院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家"十二五"科技支撑计划(2011BAD32B00-04) Analysis of the spatial and temporal characteristics of drought in the North China plain based on standardized precipitation evapotranspiration index Author: Affiliation: Chinese academy of meterological science,Chinese academy of meterological science 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:气候变化的背景下,华北地区干旱化趋势不断加剧。利用华北冬麦区45个气象站1961-2010逐月温度与降水数据,选取标准化降水蒸散指数SPEI(Standardized Precipitation Evapotranspiration Index)作为区域干旱指数进行华北冬麦区近50年干旱时空特征分析。研究表明:(1)近50年来华北地区平均温度明显上升,研究区整体呈现干旱化加剧趋势。华北地区平均SPEI指数对于典型干旱年份的表征准确,与历史资料相符合。(2)华北不同区域之间增温率不同,导致干旱化趋势存在差异。通过对典型站点的分析,发现增温率越大的区域干旱化趋势越严重。(3)不同等级干旱发生的站次比能够较好地反映不同年型干旱的发生特点。对SPEI指数矩阵的EOF分析结果显示出华北地区典型的干旱时空分布特征,第一模态呈现全区旱涝变化一致型的分布形式,高值区包括山东西部、河南北部、河北南部地区,表明这些地区对干旱的反应最为敏感。时间系数序列未显示出明显的变化趋势;第二模态呈现南北相反的分布型,河北及山东的大部分地区空间系数均为正值,而河南大部分地区为负值。时间系数序列整体呈下降趋势,表明研究区北部干旱化趋势加剧,南部干旱化有所缓解;第三模态呈现东西相反的分布形式,这种分布特征的变化趋势不明显。 Abstract:The North China Plain is one of the most severely drought affected areas in China, with global warming intensifying aridification in this alluvial plain. Drought may be attributed to multiple factors, among which precipitation and temperature are the most important. It is widely recognized that the Standardized Precipitation Evapotranspiration Index (SPEI) is advantageous for both spatial-and temporal-scale characteristic assessments; thus, it is a better index for evaluating the evolution of drought in the North China Plain due to climate change than other drought indices, such as the Palmer Drought Severity Index (PDSI), Standardized Precipitation Index (SPI), and Z index. In this study, monthly mean precipitation and temperature data from 45 meteorological stations in the North China Plain were used to calculate the SPEI index and investigate the spatial and temporal characteristics of drought in the North China Plain from 1961 to 2010. The analysis produced the following results. First, during the last 5 decades, a significant increase in temperature and a slight decrease in precipitation occurred in the North China Plain, resulting in a general aridification trend throughout the region. The drought time series in the North China Plain may be characterized from the analysis based on the SPEI index, and was consistent with existing publications.Second, a noticeable warming tendency with a mean warming rate that exceeds the national average level occurred in North China. Diverse aridification tendencies characterized the North China Plain because of variable warming rates. An analysis of typical stations showed that the more noticeable the warming, the deeper the intensity of aridification. Third, the drought feature may be well formulated using the ratio of weather stations with different drought intensities. Empirical orthogonal function (EOF) analysis was conducted based on a 12-month-scale SPEI index of the 45 meteorological stations from 1962 to 2010, and the top three eigenvectors were selected to explore the spatial and temporal distribution of drought occurrence in the North China Plain according to their spatial and temporal coefficients. The first mode shows consistency in the entire region, and it is the most important spatial distribution indicator of drought in the North China Plain. High values emerged in the middle of the region, including the western part of Shandong and the northern and southern parts of Henan, demonstrating that these areas are more sensitive to drought. There was no clear tendency in the time coefficient of the first mode. The second mode shows contrasts between the southern and northern parts of the North China Plain, which are consistent with the distribution of warming rate. The time coefficients show that drought in the northern part of the plain has been aggravated, whereas drought in the southern part has been alleviated, which may be due to differences in the warming rates throughout the research region. Warming rates in the northern part of the North China Plain are higher, so the aridification tendency is far more severe than that in the southern part of the North China Plain. The third mode contrasts the tendency between the eastern and western parts of the North China Plain, showing no significant tendency in the time coefficient. 参考文献 相似文献 引证文献

Spatial and temporal characteristics of droughts in the Northeast China Transect

In this study, drought trends and change magnitudes of the Northeast China Transect (NECT) were analyzed using the Mann–Kendall test and Theil–Sen’s slope estimator. Meteorological data from 20 meteorological stations of NECT region from 1957 to 2012 were used. Results demonstrated that five stations had significant negative trends in precipitation. The magnitudes of the significant negative trends at the 95 % confidence level varied from −2.41 ± 1.05 mm year−1 at Tonghe station to −1.11 ± 0.51 mm year−1 at Qianguoerluosi station. Analysis of the seasonal precipitation series showed a mix of negative and positive trends. Many stations also exhibited strong contrasting seasonal trends that counterbalanced one other at the yearly level. In addition, cluster analysis based on discrete wavelet transform (DWT) was applied to the standard precipitation index (SPI) series. Results revealed three different and spatially well-defined subregions (east, center and west regions of NECT). Due to the decrease in precipitation from the east to the west, land use varies from forest regions in the east, to agriculture in the center, to pastoral areas in the west. Characteristics of drought events for each representative station of different subregions are explored using temporal evolution of the SPI values. Results showed that severe or extreme droughts occurred in 2001, 2003 and 2008 in Tonghe, 1980 and 2007 in Tongliao and 2005–2007 in East Ujimqin Banner. Results indicate that clustering analysis based on DWT has great potential for examining spatial coherence of regional drought, which was consistent with not only the precipitation spatial distribution but also the characteristics of land use in the study area. This study not only provides important information on drought variability in the NECT, but also provides useful information for improving water management strategies and planning agricultural practices.

Spatio-temporal drought assessment in Tel river basin using Standardized Precipitation Index (SPI) and GIS

The spatial and temporal characteristics of droughts were investigated to provide a framework for agriculture practices, engineering facilities and sustainable water resources management in the Tel river basin which is about 2756 km2 and lies between 19°17′ and 20°00′N and 82°30′ and 82°59′E in Kalahandi district of Odisha, India. Using the Standardized Precipitation Index (SPI) as an indicator of drought severity for the period from 1965 to 2008, the characteristics of droughts were examined. The multiple-time scaled SPI values were evaluated for May–October months and point-wise indices were interpolated over the whole area using spatial interpolation technique in Arc GIS 9.2, in order to obtain areal extension of the drought severity. The results indicated that a dramatic and widespread drought event was recorded in the year 2002 at most of the stations and drought categories. However, regardless of the drought severity, an extraordinary dryness was experienced in the years 1966, 1972, 1979, 1987 and 2002 in the entire study area. It was observed that 10 years were successively dry during May at Jayapatna station from 1999 to 2008 in the 6-month drought category. The highest SPI value of −3.06 was observed in July 2002 in the Dharamgarh station in the 9-month drought category. The overall outcome of this study demonstrates that severe and extreme droughts were experienced from time to time across the study area leading to unfavourable results on agricultural practices and water resources in the area.

Spatial and temporal characteristics of droughts in the western part of Bangladesh

AbstractSpatial and temporal characteristics of droughts in the western part of Bangladesh have been analysed. Standardized precipitation index method is used to compute the severity of droughts from the rainfall data recorded in 12 rainfall gauge stations for the period of 1961–1999. An artificial neural network is used to estimate missing rainfall data. Geographic Information System (GIS) is used to map the spatial extent of droughts of different severities in multiple time scales. Critical analysis of rainfall is also carried to find the minimum monsoon and dry months rainfall require in different parts of the study area to avoid rainfall deficit. The study shows that the north and north‐western parts of Bangladesh are most vulnerable to droughts. A significant negative relationship between multiple ENSO index and rainfall is observed in some stations. Analysis of seasonal rainfall distribution, rainfall reliability and long‐term rainfall trend is also conducted to aid prediction of future droughts in the area. Copyright © 2007 John Wiley & Sons, Ltd.

On drought in south‐eastern United States

AbstractThe temporal characteristics of drought in Florida are compared with drought behaviour in the remainder of the southeastern United States, and are discussed in relation to previous studies by other researchers. Florida's wet/dry episodes are frequently out of phase with other south‐eastern States. Possible causes for this phenomenon are presented.