Abstract
The regional and national scales variation and propagation characteristics of different types of droughts are critical for improving drought resilience, while information is limited in China. The objective of this research was to investigate the evolution and propagation characteristics of three types of droughts using standardized indices at multi-timescales in different sub-regions of China. The indices included Standardized Precipitation/Soil Moisture/Runoff Index (SPI/SSI/SRI) using the optimal probability density function, representing meteorological, agricultural, and hydrological droughts based on precipitation, soil water storage, and baseflow-groundwater runoff, respectively. Wavelet analysis was used to reveal their periodical characteristics. Modified Mann-Kendall trend test was used to compare the trend among drought indices. Correlation coefficients between SPI and SSI/SRI were calculated to identify the time-lags of SPI with SSI and SRI. In general, droughts indicated by SPI agreed well with the historical drought events at different sub-regions. The main periods of SSI were closer to SPI than SRI, indicating stronger connections of agricultural drought with meteorological drought. A weaker connection between meteorological and agricultural/hydrological droughts at shorter timescales was observed in northwestern arid and semi-arid regions. The propagation from meteorological to agricultural or hydrological droughts were well denoted by the lagged time (months) from SPI to SSI or SRI at a timescale ranged from 0 (mostly located in south China) to 5 months (mostly located in northeastern China) for 1-, 3-, 6-, 12-, or 24-month timescale; this was a new finding for China. The methods of wavelet combining trend test and Pearson coefficient showed meaningful power for revealing the drought propagation characteristics and the obtained results can be a good reference for other regions of the world since this study compared different climate zones from arid to humid conditions. The study provides crucial information and guidance to develop drought management strategies at regional to national scale and their critical time of action.
Highlights
Drought, a globally common natural hazard and one of the most damaging environmental disasters resulting from climate variations, has threatened human life, property safety, and ecosystem at large [1,2,3]
The interconnection between different types of droughts, their spatiotemporal distribution and propagation characteristics at multiple scales, and the dominant time lag are critical for developing policies and strategies for responding to drought hazards
Standardized Precipitation Index (SPI), soil moisture index (SSI), and Soil Runoff Index (SRI) representing meteorological, agricultural, and hydrological droughts were calculated based on PPT, soil water storage (SWS), and baseflow-groundwater runoff (BGR) characteristics
Summary
A globally common natural hazard and one of the most damaging environmental disasters resulting from climate variations, has threatened human life, property safety, and ecosystem at large [1,2,3]. Against the background of global warming, severe drought events have occurred throughout China, the damages through crop yield reduction, economic loss, safety of our society and others caused by drought cannot be neglected [4]. There are several types of droughts depending on the water deficit patterns including meteorological, agricultural, hydrological, and socio-economic [5]. Agricultural drought refers to soil moisture that cannot meet the water demand of plants at different growth stages [7]. Hydrological drought refers to a period with inadequate surface and subsurface water resources for established water uses of a given water resources management system [6]. Continuation of meteorological to agricultural or hydrological drought involves a suite of processes including occurrence, development, and propagation
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