How long should the pre-existing climatic water balance be considered when capturing short-term wetness and dryness over China by using SPEI?

Xiuzhen Li, Wan Ru Huang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

Short-term, fast-developing wet and dry anomalies have gained much attention, as their suddenness brings new challenges to monitoring. It is unclear how long a pre-existing climatic water surplus/deficit (defined as the difference between precipitation and potential evapotranspiration; P-PET) should be considered when monitoring short-term wetness and dryness events over China. This study aims to answer this by evaluating the performance of the daily Standardized Precipitation Evapotranspiration Index (SPEI) for different accumulation periods of P-PET in capturing sub-surface soil moisture variation over China. Our evaluations of reanalysis soil moisture from ERA5 and ERA-Interim show that ERA5 soil moisture is superior, as it is more consistent with the variation of in situ observations. Applying ERA5 soil moisture for further examination of SPEIs, we find that pre-existing conditions should be considered for different lengths of time in different regions of China because the sensitivity of soil moisture to climatic water balance is regionally dependent. For wetness, soil moisture responds to a pre-existing climatic water surplus immediately over Southeast China, but it is more delayed over North and Northeast China. For dryness, 0.5-month pre-existing water deficit conditions over Southeast China and 1.5-month conditions over the Yangtze-Huai River valley are preferable to the frequently adopted 3 months or longer. These findings highlight the length of time for pre-existing condition is shorter over wet regions, and longer over dry regions of China.

Original languageEnglish
Article number147575
JournalScience of the Total Environment
Volume786
DOIs
Publication statusPublished - 2021 Sep 10

Keywords

  • China
  • Daily SPEIs
  • Regional dependence
  • Soil moisture
  • Wetness and dryness

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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