骤发干旱前期气象驱动条件及可模拟性分析

Precedent meteorological driving forces of flash drought and their feasibility for flash drought simulation

骤发干旱(简称骤旱)是一种以短历时、高强度、快速度为特征的极端事件,其形成速度已超出现有干旱监测工具的能力范围,监测模拟难度大。基于欧洲中心再分析产品(ERA)土壤含水量数据,构建考虑旱情开始速度的骤旱识别方法,提取中国1979—2018年骤旱事件,剖析旱情初期气象要素异常值的变化规律,探讨利用气象条件模拟骤旱的可行性。结果表明:①开始速度在空间上呈现显著的南北差异,长江以南地区较快,西北地区较慢;②骤旱比缓慢干旱具有更强的气象驱动力,骤旱各气象要素异常值的均值、峰值及变化幅度比缓慢干旱变化更为显著,尤其是峰值,约超过缓慢干旱0.5个标准差;③综合考虑骤旱爆发前后不同时段多个气象要素异常,能够较好地模拟开始速度,可用于监测与模拟骤旱。

Flash droughts are extreme events characterized by a short duration,strong intensity,and rapid onset.Owing to their unusually rapid occurrence,the use of current drought monitoring tools to capture them is still challenging.In this study,using ERA-Interim soil moisture reanalysis products from the European Center for Medium-Range Weather Forecast,an approach that considers the rate of decrease in soil moisture content during the onset stage of flash droughts was proposed for the identification of the flash droughts that occurred during the 1979—2018 period.Further,the anomalies associated with meteorological variables during the drought onset stage of these events were analyzed,and the feasibility of using precedent meteorological driving forces to realize flash drought simulation based on a multivariate linear regression model was investigated.The results obtained showed that the rate of soil moisture intensification during the onset state of flash droughts showed significant spatial discrepancy.Specifically,during this stage,soil moisture content declined much faster in the south of the Yangtze River than in Northwestern China.Additionally,the mean,peak,and variation ranges of the anomalies of the different meteorological variables exhibited more significant spatial discrepancies during this stage.Particularly,the peak values showed the most significant variation,and were half the standard deviation higher than the slowly-evolving drought.Furthermore,by integrating the anomalies associated with multiple meteorological variables during the early and onset stages of the flash drought events,the regression model provided satisfying simulations of the soil moisture intensification rate,suggesting that it is possible to simulate flash droughts from a meteorological perspective.