Temporal Variation Of Drought Research Articles

Trivariate copula functions for constructing a comprehensive atmosphere-land surface-hydrology drought index: A case study in the Yellow River basin

The current univariate and multivariate drought indices cannot fully reflect the multiple processes of meteorological-hydrological-agricultural drought. So it is important to construct a comprehensive drought index for drought monitoring in a changing environment from the perspective of the whole process of the natural water cycle “atmosphere-land surface-hydrology”. In this study, based on the standardized indices (SCI) framework and trivariate Copula functions, a multi-scale comprehensive drought index (SPERSI) integrating rainfall, temperature, runoff and soil moisture is proposed, which can synthetically reflect meteorological, hydrological and agricultural droughts. The spatial and temporal variations of drought in the Yellow River Basin (YRB) from 1961 to 2019 were investigated, and then the links between SPERSI and some remotely correlated factors were revealed by using the multiple cross wavelet transform technique. Results show that: (1) the SPERSI constructed by fusing rainfall-temperature-runoff-soil moisture information can sensitively and effectively capture the onset, persistence and termination of drought; (2) the SPERSI exhibits good performance in detecting integrated drought events in the YRB with probability of detection (POD) > 0.75, false alarm rate (FAR) < 0.04 and critical success index (CSI) > 0.73; (3) From 1961 to 2019, drought in different time scales of above Longyangxia (AL) and Longyangxia to Lanzhou (LL) zones in the YRB both show a slight mitigation trend, while the drought in remaining subzones show a trend of intensification; (4) Multiple cross-wavelet results indicate that AO is the dominant factor of drought in the Yellow River Basin, followed by ENSO. In general, SPERSI results are reliable and can provide basis for drought decision-making.

The Effects of Drought in the Huaibei Plain of China Due to Climate Change

Damage from climate change is widespread throughout the world. This change has brought about calamities, the most prevalent of which is the emergence of numerous droughts which are increasingly threatening human lives. In this paper, we studied the spatial and temporal variations of drought under the effect of climate change in the Huaibei Plain, which is a very important agricultural zone in China. Drought has attracted increasing attention in research due to its heavy impact on agriculture, the environment, livelihood, and food security. The SPEI (Standardized Precipitation Evapotranspiration Index) has been used in this study to express and identify drought events in the Huaibei Plain due to climate change. A general circulation model (GCM), HadGEM2-AO, which was the most appropriate for the study area’s precipitation simulation, and three Representative Concentration Pathways (RCP), RCP 2.6, RCP 4.5, and RCP 8.5, were used to analyze and compare the drought effect for the baseline (1985–2017) and the future climate scenarios (2025–2090). At 3 and 6 months, the SPEI successfully detects agricultural drought in temporal and spatial variation. However, according to the analysis, more severe agricultural drought events are foreseen in the future than in the baseline because of climate change. SPEI performed better than SPI in detecting drought in the baseline and simulated data due to increased evapotranspiration. Between the SPEI-3 and SPEI-6, the Pearson coefficient correlation reveals a positive association. The Mann-Kendall test was used to cover the two studied periods in order to establish the drought trend. Both decreasing and increasing trends, in different timescales, were detected by Sen’s Slope in the baseline and future periods with all RCPs.

Spatiotemporal Variations of Drought and the Related Mitigation Effects of Artificial Precipitation Enhancement in Hengyang-Shaoyang Drought Corridor, Hunan Province, China

It is important to reveal the spatial and temporal variations of drought and evaluate the alleviating effects of artificial precipitation on drought severity, as it will contribute immensely to the formulation of drought prevention and mitigation measures and the provision of guidance to artificial precipitation enhancement operation. Based on the monthly precipitation data of 28 meteorological stations in Hengyang-Shaoyang Drought Corridor (HSDC) from 1960 to 2019, the standardized precipitation index (SPI) at multiple time scales were calculated to estimate drought frequency, drought station ratio, and drought intensity. Then the spatiotemporal variations of drought in the study area were unveiled, and the effects of artificial precipitation enhancement were evaluated in line with the relevant data from 2005 to 2019. The results show that at the annual scale, drought occurred in 3/4 of past sixty years in the study area, where almost 1/3 of such years experienced area-wide droughts. Drought coverage in HSDC exhibited a decreasing trend, but drought intensity, as well as the number of area-wide droughts and regional droughts showed an increasing one. Mild and moderate droughts occurred in an extensive part of the HSDC, whereas severe and extreme droughts were mainly found in a few stations. At the seasonal scale, winter drought occurred most frequently, followed by summer and autumn droughts, while spring drought events had the lowest frequency. Overall, drought is more serious in spring, autumn, and winter, but less severe in summer; although drought intensity decreased slightly in summer, both its intensity and coverage showed an increasing trend in other seasons. At the monthly scale, the ratio of positive to negative SPI values in HSDC was basically balanced in the past six decades, exhibiting no distinct variation characteristics. In addition, artificial precipitation enhancement effectively eased monthly and even seasonal drought in HSDC. These findings, which fully reflect the characteristics of drought in the study area, can also raise awareness of the contribution that artificial precipitation could make to drought mitigation, which in turn will contribute to the formulation of appropriate strategies for climate change mitigation and adaptation.

Spatial and temporal variations of drought in Sichuan Province from 2001 to 2020 based on modified temperature vegetation dryness index (TVDI)

Investigating the drought response to evapotranspiration and climate change was key to understanding the dynamics of drought changes and the mechanism of drought changes in the future. In this study, a modified Temperature Vegetation Drought Index was constructed based on the correction of elevation and incorporating air temperature and also based on climate indices recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI) the effects of evaporation and vegetation cover on the drought in Sichuan Province were investigated. The results showed that: the degree of drought in the northwestern Sichuan Plateau (0.57 < TVDI < 0.86) was weaker than in other regions (the Chengdu Plain, the Eastern Sichuan Basin Plain, and southwestern Sichuan's mountainous region) with TVDI ≤ 0.86. Agricultural land and construction land had a relatively high degree of drought (0.76 < TVDI < 0.86), the decreasing trend was insignificant in the whole province. The drought degree in spring was the least, and the main trend was insignificant; 0–0.01/a in summer. The drought in autumn and winter was more severe, and most areas of the province were extremely dry, showing an increasing trend. The minimum and maximum value of ET was concentrated in the northwestern Sichuan Plateau (ET < 130 mm) and the Sichuan Basin (ET ≤ 170 mm), respectively. ET of water bodies (ET ≥ 170 mm) was the highest, and lowest in construction land (90 < ET < 130 mm). The increase rate of ET was highest in spring and lowest in winter. TVDI was negatively correlated with annual precipitation in the northwestern Sichuan Plateau, Jinsha River Valley, and eastern Chengdu Plain, positively correlated with annual temperature and positively correlated with the yearly minimum value of daily minimum temperature (TNn), the yearly minimum value of daily maximum temperature (TXn), and the yearly maximum value of daily minimum temperature (TNx), and negatively correlated with the yearly maximum value of daily maximum temperature (TXx) and the yearly maximum consecutive five-day precipitation (PX5). The results are useful for the understanding of drought and policy making of climate change.

Spatio-temporal evolution and non-stationary characteristics of meteorological drought in inland arid areas

The climate system has both non-stationary and nonlinear characteristics. The non-stationary processes such as climate change and human activities have brought severe challenges to life, agriculture and ecology in arid areas. It is of great practical significance to study the spatiotemporal variation and non-stationary characteristics of drought in arid region for adopting the countermeasures to adapt to climate change. The traditional trend change and variation analysis method was used to study the drought change characteristics, which could not effectively identify the clustering phenomenon of drought and the spatial and temporal variation of drought in different time intervals. Therefore, the method of breaks for additive seasonal and trend (BFAST) was introduced to determine the non-stationary characteristics and spatial variation of drought. In this study, a typical inland arid area was taken as the study area, and the drought was quantified by standardized precipitation evapotranspiration index (SPEI). The results show that: (1) the study area was prone to light drought and moderate drought, and the duration and intensity of drought events increased significantly after 1996; (2) The spatial distribution of drought frequency and drought intensity in different seasons were significantly different; (3) The results of BFAST analysis showed that there were four discontinuities in SPEI12 time series, which indicated that the drought in the study area had obvious non-stationary characteristics. Through the analysis of the breakpoint and drought change characteristics in the study area, the occurrence time of the breakpoint in the northern region had a certain periodicity, and the climate was in a state of aridity. The results of this study have important guiding significance for further understanding the non-stationary characteristics of drought in inland arid areas, and will promote the management of water resources and the protection of ecological environment.

Spatial and Temporal Variations of Drought in Inner Mongolia, China

Drought has become an important natural disaster, affecting the development of Inner Mongolia, as an important animal husbandry region in China. In this study, the characteristics and trends of the Inner Mongolia drought are thoroughly analysed by calculating the standardised precipitation evapotranspiration index (SPEI) at different time scales, based on monthly precipitation and temperature data from 40 national meteorological stations in Inner Mongolia from 1958 to 2019. Subsequently, the area drought intensity (ADI), which is a comprehensive evaluation indicator for evaluating drought intensity within the region, is proposed, taking into account the effects of the persistent drought on drought intensity. The results show that drought has increased during this period, with a remarkable increase in the frequency and the area of drought. The areas with stronger drought intensity are mainly located in the west, north central, and the western area of the east. Since 2000, March to October are identified as drought-prone months and April is characterised as the month with the highest frequency of drought. The inflection points of SPEI and climate conditions both appeared in 1990s and it is speculated that the increase in drought may have been caused by excessive temperature rise. The frequency, coverage area, and continuous duration of drought have increased greatly after climate mutation in this region. According to the changes in the spatial distribution of the ADI and frequency of drought occurrence, the drought-stricken areas shifted from the southeast to the northwest after climate mutations. The findings from this study provide a theoretical basis for the drought management of Inner Mongolia.

Integration of Microwave and Optical/Infrared Derived Datasets from Multi-Satellite Products for Drought Monitoring

Drought is among the most common natural disasters in North China. In order to monitor the drought of the typically arid areas in North China, this study proposes an innovative multi-source remote sensing drought index called the improved Temperature–Vegetation–Soil Moisture Dryness Index (iTVMDI), which is based on passive microwave remote sensing data from the FengYun (FY)3B-Microwave Radiation Imager (MWRI) and optical and infrared data from the Moderate Resolution Imaging Spectroradiometer (MODIS), and takes the Shandong Province of China as the research area. The iTVMDI integrated the advantages of microwave and optical remote sensing data to improve the original Temperature–Vegetation–Soil Moisture Dryness Index (TVMDI) model, and was constructed based on the Modified Soil-Adjusted Vegetation Index (MSAVI), land surface temperature (LST), and downscaled soil moisture (SM) as the three-dimensional axes. The global land data assimilation system (GLDAS) SM, meteorological data and surface water were used to evaluate and verify the monitoring results. The results showed that iTVMDI had a higher negative correlation with GLDAS SM (R = −0.73) than TVMDI (R = −0.55). Additionally, the iTVMDI was well correlated with both precipitation and surface water, with mean correlation coefficients (R) of 0.65 and 0.81, respectively. Overall, the accuracy of drought estimation can be significantly improved by using multi-source satellite data to measure the required surface variables, and the iTVMDI is an effective method for monitoring the spatial and temporal variations of drought.

Spatial distribution and temporal variation of drought in Inner Mongolia during 1901–2014 using Standardized Precipitation Evapotranspiration Index

With intensification of climate change and human activities, warming and drying trend has brought severe challenges to pastoral areas in arid and semi-arid regions. Consequently, it becomes imperative to explore non-stationarity features of drought in such regions. In this research, the SPEIbase v2.4 datasets with a 0.5 degree spatial resolution was employed to extract Standardized Precipitation Evapotranspiration Index (SPEI) in Inner Mongolia, China. We explored non-stationarity characteristics of drought using Breaks For Additive Seasonal and Trend (BFAST) method, investigated the variation characteristics of drought intensity in each time interval using intensity analysis method, and finally assessed the spatial and temporal gathering characteristics of drought with Empirical Orthogonal Function (EOF). The results showed that trend of regional drought had a tendency towards drought conditions, which is particularly significant from the year 1945 onwards in the overall Inner Mongolia. We have explored a long behavior of drought in semiarid and central regions of cold semihumid climate zone throughout the whole study period, and detected a drying trend in northeastern regions of Inner Mongolia at the latter decades. The overall drought intensity displayed an increasing trend first, which was followed by a decreasing trend, among which the extreme drought was dominant in period of 1960–1970. EOF mode1 showed that variation intensity of drought showed a not significantly increasing trend in the entire region, and the drought with high amplitude was likely to occur in the central region. EOF mode2 showed that variation intensity of drought displayed the opposite phases between the eastern and the western regions. The northeastern regions were prone to display a high amplitude of drought.

Variation of Thornthwaite moisture index in Hengduan Mountains, China

The Thornthwaite moisture index, an index of the supply of water (precipitation) in an area relative to the climatic demand for water (potential evapotranspiration), was used to examine the spatial and temporal variation of drought and to verify the influence of environmental factors on the drought in the Hengduan Mountains, China. Results indicate that the Thornthwaite moisture index in the Hengduan Mountains had been increasing since 1960 with a rate of 0.1938/yr. Annual Thornthwaite moisture index in Hengduan Mountains was between –97.47 and 67.43 and the spatial heterogeneity was obvious in different seasons. Thornthwaite moisture index was high in the north and low in the south, and the monsoon rainfall had a significant impact on its spatial distribution. The tendency rate of Thornthwaite moisture index variation varied in different seasons, and the increasing trends in spring were greater than that in summer and autumn. However, the Thornthwaite moisture index decreased in winter. Thornthwaite moisture index increased greatly in the north and there was a small growth in the south of Hengduan Mountains. The increase of precipitation and decrease of evaporation lead to the increase of Thornthwaite moisture index. Thornthwaite moisture index has strong correlation with vegetation coverage. It can be seen that the correlation between Normalized Difference Vegetation Index (NDVI) and Thornthwaite moisture index was positive in spring and summer, but negative in autumn and winter. Correlation between Thornthwaite moisture index and relative soil relative moisture content was positive in spring, summer and autumn, but negative in winter. The typical mountainous terrain affect the distribution of temperature, precipitation, wind speed and other meteorological factors in this region, and then affect the spatial distribution of Thornthwaite moisture index. The unique ridge-gorge terrain caused the continuity of water-heat distribution from the north to south, and the water-heat was stronger than that from the east to west part, and thus determined the spatial distribution of Thornthwaite moisture index. The drought in the Hengduan Mountains area is mainly due to the unstable South Asian monsoon rainfall time.

Assessing spatiotemporal variation of drought in China and its impact on agriculture during 1982–2011 by using PDSI indices and agriculture drought survey data

AbstractInspired by concerns of the effects of a warming climate, drought variation and its impacts have gained much attention in China. Arguments about China's drought persist and little work has utilized agricultural drought survey area to evaluate the impact of natural drought on agriculture. Based on a newly revised self‐calibrating Palmer Drought Severity Index (PDSI) model driven with air‐relative‐humidity‐based two‐source (ARTS) E0 (PDSIARTS; Yan et al., 2014), spatial and temporal variations of drought were analyzed for 1982–2011 in China, which indicates that there was nonsignificant change of drought over this interval but with an extreme drought event happened in 2000–2001. However, using air temperature (Ta)‐based Thornthwaite potential evaporation (EP_Th) and Penman‐Monteith potential evaporation (EP_PM) to drive the PDSI model, their corresponding PDSITh and PDSIPM all gave a significant drying trend for 1982–2011. This suggests that PDSI model was sensitive to EP parameterization in China. Annual drought‐covered area from agriculture survey was initially adopted to evaluate impact of PDSI drought on agriculture in China during 1982–2011. The results indicate that PDSIARTS drought area (defined as PDSIARTS &lt; −0.5) correlated well with the agriculture drought‐covered area and PDSIARTS successfully detected the extreme agriculture drought in 2000–2001 during 1982–2011, i.e., climate factors dominated the interannual changes of agriculture drought area, while PDSITh and PDSIPM drought areas had no relationship with the agriculture drought‐covered area and overestimated the uptrend of agriculture drought This study highlights the importance of coupling PDSI with drought survey data in evaluating the impact of natural drought on agriculture.

Spatial and temporal variations of drought in Henan province over a 53-year period based on standardized precipitation evapotranspiration index

Drought, one of the most complex natural hazards, affects agriculture, water resources, natural ecosystems, and society. The negative societal consequences of drought include severe economic losses, famine, epidemics, and land degradation. However, there are few studies on the complexity of drought characteristics, both at multiple time scales and with variations in evapotranspiration. In this study, drought occurrences were quantified using a new drought index, the standardized precipitation evapotranspiration index(SPEI), based on observed meteorological data of monthly mean temperature and precipitation from 1961 to2013 in Henan province, central China. This can help decision- makers improve their level of preparedness and adopt appropriate policies for agricultural management. Based on the SPEI values of each weather station in the study, the frequency and severity of meteorological droughts were computed, and the monthly, seasonal, and annual drought frequency and intensity over a 53- year period were analyzed. The spatial and temporal evolution, intensity,and the primary causes of drought occurrence in Henan were revealed. The results showed that the SPEI values effectively reflected the spatial and temporal pattern of drought occurrence. As the time scale decreased, the amplitude of the SPEI increased and droughts became more frequent. Since 1961, drought has occurred at the annual, seasonal, and monthly scales, and the occurrence of drought has increased. However, regional distribution has been uneven. The highest drought frequency, 35%, was observed in the Zhoukou region, while the lowest value,26%, was measured in the central and western parts of Henan. The most severe seasonal droughts occurred in the spring and summer months, followed by autumn. Annually, wideranging droughts occurred in 1966- 1968, 1998- 2000, and 2011- 2013. The drought intensity distribution showed higher values in northern and western Henan, and lower values in its east and south. The maximum drought intensity value was recorded in Anyang, and the minimum occurred in Zhumadian, at 22.18% and 16.60%, respectively. The factors with the greatest influence on drought occurrence are increasing temperatures, the Eurasian atmospheric circulation patterns, and the El Ni?o effect.

Spatial and Temporal Variation of Drought in Far and Mid Western Regions of Nepal: Time Series Analysis (1982-2012)

Recent and potential future increases in global temperature are likely to be associated with impacts on the hydrological cycle, including changes to precipitation and increases in extreme events such as droughts. This study has investigated the spatial and temporal changes in drought occurrence in far and mid-western regions of Nepal. Quantification of the severity and frequency of drought within different physiographical regions have been worked out with the help of Standardized Reconnaissance Drought Index (RDIst). Time series analyses of mean annual rainfall and annual temperature datasets of 16 meteorological stations covering far and mid western development regions from 1982-2012 have been used. It has been revealed that all the three kinds (moderate, severe and extreme) of droughts occurred in the study area. Extreme drought was recorded in four stations (Dadeldhura, Patan, Tikapur and Silgadhi) of far west region and five stations (Musikot, Dailekh, Surkhet, Tulsipur and Khajura) of mid western region. These events occurred when precipitation recorded its lowest range. Most frequent droughts were observed in Dhangadhi, Dadeldhura and Jumla. There were higher number of droughts in far western region but more extreme events occurred in mid western region. No clear correlation was found between temperature and precipitation trends in five selected stations except in Dhangadi that lies in Terai region.DOI: http://dx.doi.org/njst.v15i2.12118Nepal Journal of Science and Technology Vol. 15, No.2 (2014) 65-76

Spatio-Temporal Variation of Drought Characteristics in Bearma Basin of Bundelkhand Region in Madhya Pradesh

Long-term drought forecasts can provide valuable information to help in mitigation of the consequences of drought. The study has been carried out for Bearma basin of Bundelkhand region in Madhya Pradesh which is regularly suffered from frequent droughts due to large variation of rainfall. Rainfall data of 5 stations located in Bearma basin over the period of 1976–2005 were used. Efforts have been made to identify the drought characteristics through the modern technique using the Standardized Precipitation Index (SPI). The drought severities as well as the drought intensity have been evaluated for all the rain gauge stations in Bearma basin. The result showed that Damoh faced drought of 5 months in 1979 with the highest drought severity of -11.95 and intensity of -2.39 whereas a drought of severity -11.12 occurred during June to November 1979 at Jabera for a period of 6 months. It is also indicated that the maximum intensity of -5.50 was observed between onset and termination of drought of 1984 at Hatta. The drought of 4 months duration was recorded at Deori during June-September 1992 and at Rehli during August-November 1986. The spatial and temporal variations of drought and its progression into more areas in subsequent months and its withdrawal after the initiation of sufficient rainfall has been studied in detail for drought year 2002 as well as normal year 2004. The analysis indicated that each drought had unique phenomenon and area under its influence varied from one drought event to the other. In July 2002, 100% of the basin was reeling under extreme and severe drought whereas by October 2002, over 71% of the basin area was back to normal condition due to favourable rainfall scenario. During 2004, the drought situation varied rapidly between successive months. About 86% of the area was affected with moderate drought in June 2004 but in July and August, the situation was near normal in the entire basin.

Spatio-temporal variation of drought in China during 1961–2012: A climatic perspective

Summary Understanding the spatial and temporal variation of drought is essentially important in drought assessment. In most previous studies, drought event is usually identified in space and time separately, ignoring the nature of the dynamic processes. In order to better understand how drought changes have taken place in China during the past half-century, we carried out a comprehensive analysis of their spatio-temporal variation based on multiple drought indices from a climatic perspective. A 3-dimensional clustering method is developed to identify drought events in China from 1961 to 2012 based on the 0.25° gridded indices of SPI3 (3 months Standardized Precipitation Index), RDI3 (3 months Reconnaissance Drought Index) and SPEI3 (3 months Standardized Precipitation Evapotranspiration Index). Drought events are further characterized by five parameters: duration, affected area, severity, intensity, and centroid. Remotely sensed soil moisture data were used to validate the rationality of identified drought events. The results show that the two most severe drought events in the past half century which occurred in the periods 1962–1963 and 2010–2011 swept more than half of the non-arid regions in China. Large magnitude droughts were usually centered in the region from North China Plain to the downstream of Yangtze River. The western part of North China Plain, Loess Plateau, Sichuan Basin and Yunnan-Guizhou Plateau had a significant drying trend, which is mainly caused by the significant decrease of precipitation. The three drought indices have almost the same performance in the humid regions, while SPI and RDI were found to be more appropriate than SPEI in the arid regions.

Dynamic monitoring of drought using HJ-1 and MODIS time series data in northern China

From early November 2008 to February 2009, lack of rainfall led to severe drought in northern China. More than 9.3 million ha of wheat in six major crop production provinces, including Henan, Anhui, Shandong, Shanxi, Gansu, and Shaanxi, were hit by drought. Supported by Chinese HJ-1 satellite images together with NASA Moderate Resolution Imaging Spectroradiometer (MODIS) data, dynamic monitoring of the drought was conducted. HJ-1 CCD data with 30-m resolution were used to identify cropland information. Spatial–temporal variation of drought was detected using Vegetation Index and Water Index time series data derived from MODIS visible, infrared, and short-wave infrared bands. The influences of drought were classified into five levels based on MODIS-derived 8-day composite Anomaly Water Index (AWI) and field survey data. The results indicated that the drought deteriorated beginning in November 2008 and became most serious in late January 2009. HJ-1 data together with MODIS data proved to be valuable data sources for monitoring soil moisture and drought at a both regional and national scale.