Key points are not available for this paper at this time.
• Utilization of remote-sensing-based water balance assessment tool (RWBAT) model. • An optimized PDSI index based on the RWBAT model is constructed, namely RW-PDSI. • Tree-ring data were used to evaluate the performance of the drought index. • RW-PDSI has a better correlation with the tree-ring data than SC-PDSI and SPEI. • The drought of the Loess Plateau has weakened over the past 30 years. Palmer Drought Severity Index (PDSI) is a widely used indicator to assess the intensity of drought based on a similar two-layer bucket (TLB) model, especially in arid and semi-arid regions. However, the TLB model cannot quantify surface water balance, effectively, which may lead to the mis-assessment of drought. Therefore, an optimized PDSI indicator named RW-PDSI based on the water balance is constructed. RW-PDSI is developed using the output of a newly proposed remote-sensing-based water balance assessment tool (RWBAT) model. The RWBAT model is constructed to depict the detailed hydrological processes on a fine spatial scale using high-resolution remote sensing data. To test its performance, we collected tree-ring data on the Loess Plateau (LP) to show the drought conditions in past decades (1991–2020). Tree-ring data provide a useful continuous multi-year data archive for drought assessment. Our results showed that the correlation between RW-PDSI and tree-ring data was statistically significant (p < 0.01) at Kongtong and Hengshan sites with 0.65 and 0.64 respectively. Meanwhile, RW-PDSI showed a greater overall correlation with the tree-ring data than the self-calibrating PDSI(SC-PDSI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Results also illustrated that RW-PDSI of the LP region increased in the past three decades, indicating weakening drought frequency and intensity. The area with a significant weakening trend of drought in the investigated region accounts for 71 %. Overall, drought characteristics in LP were well represented by our drought indicators, which could provide research support for the sustainable development of the ecosystem and social economy in drought areas.
Yang et al. (Tue,) studied this question.