Abstract
The Yarlung Zangbo River (YZR) basin occupies a crucial position in the formation and development of atmospheric circulation and climate change in the Tibetan Plateau, where is the potential trigger and amplifier in global climate fluctuations. Previous studies mainly focused on meteorological drought induced by variations of precipitation and temperature. In this study, a multi-index evaluation of drought characteristics from the perspective of meteorology and agriculture was implemented. GLDAS (Global Land Data Assimilation System) precipitation, surface air temperature and soil moisture data from 1982 to 2015 were used to calculate the meteorological drought index (Standardized Precipitation Evapotranspiration Index) and agricultural drought index (Soil Water Deficit Index), respectively. Meanwhile, the scPDSI (self-calibrating Palmer Drought Severity Index) dataset provided by CRU (Climate Research Unit) was also utilized to represent the meteorological drought, with the aim of comprehensively investigating the spatiotemporal evolution characteristics of drought in the YZR basin. Results indicated that although there was a slightly wetting tendency of the whole basin from 1982 to 2015, drought condition from the perspective of meteorology and agriculture at both annual and growing seasonal scales showed a transition from alleviation to aggravation during 1982–2015, with an abrupt change from wetting to drying occurring at the year of 2000 detected by multiple statistical tests including Mann-Kendall test, Moving t-test and Yamamoto test. Specifically, since the 21st century, the meteorological drought in the YZR basin has changed from moderate wet to moderate dry, while the agricultural drought relieved to moderate dry from severe dry with a much more complicated fluctuation. From the perspective of spatial pattern, the annual and growing season variation trends of all three drought indices were identically consistent during 1982–2015. Areas with extremely significant decreasing trend (2.24%~21.09%) were mostly distributed in the west upstream and southwest downstream dominating the overall wetting trend of the YZR basin during the period of 1982–2015, while the transition from wet to dry after 2000 was attributed to the aggravating drought of the western upstream and southeastern downstream. Results of this study have important implications for drought monitoring and eco-environmental sustainability in alpine regions.
Highlights
Drought is a natural hazard developed slowly that would initiate considerable losses (Kelly et al, 2015; Schwalm et al, 2017; Jiang et al, 2019) which is regarded as an elusive phenomenon with the indeterminate onset and demise (Greve et al, 2014; Bachmair et al, 2016a)
Growing season drought was investigated along with annual drought in this study, and the growing season in the Yarlung Zangbo River (YZR) basin was defined as the period from May to September within a year according to the variation characteristic of vegetation growth, precipitation, and temperature
It can be seen that values of Self-Calibrated Palmer Drought Severity Index (scPDSI), Standard Precipitation Evapotranspiration Index (SPEI), and Soil Water Deficit Index (SWDI) at both annual and growing season scales all showed a change from increasing to declining in the later 1990s, inferring that the drought condition in the YZR basin during the period of 1982–2015 was firstly alleviated and gradually aggravated from both the meteorological and agricultural perspectives
Summary
Drought is a natural hazard developed slowly that would initiate considerable losses (Kelly et al, 2015; Schwalm et al, 2017; Jiang et al, 2019) which is regarded as an elusive phenomenon with the indeterminate onset and demise (Greve et al, 2014; Bachmair et al, 2016a). In order to overcome the poor applicability of PDSI in arid and semi-arid regions, scPDSI (self-calibrating Palmer Drought Severity Index) was put forward by Wells et al (2004), which has been proven to be a suitable index for detecting and monitoring the effects of global warming on drought conditions (Wang et al, 2016; Herrera and Ault, 2017; Zhu et al, 2018) It improves PDSI by adopting a self-calibration procedure that automatically adjusts the PDSI standardization coefficient to suit the local climate (Bai et al, 2020). With the combination of the sensitivity of the PDSI to changes in evaporation demand and robustness of the multi-temporal nature of the SPI, SPEI at various timescales has been developed and employed in an increasing number of climatological and hydrological studies (Vicente-Serrano et al, 2010; Yu et al, 2014; Spinoni et al, 2018; Li et al, 2019c). Li X. et al (2015)
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