Quantifying drought propagation from soil moisture to vegetation dynamics using a newly developed ecohydrological land reanalysis

Abstract

Despite the importance of the interaction between soil moisture and vegetation dynamics to understand the complex nature of drought, few land reanalyses explicitly simulate vegetation growth and senescence. In this study, I provide a new land reanalysis which explicitly simulates the interaction between sub-surface soil moisture and vegetation dynamics by the sequential assimilation of satellite microwave brightness temperature observations into a land surface model (LSM). Assimilating satellite microwave brightness temperature observations improves the skill of a LSM to simultaneously simulate soil moisture and the seasonal cycle of leaf area index (LAI). By analyzing soil moisture and LAI simulated by this new land reanalysis, I identify the drought events which significantly damage LAI on the climatological day-of-year of the LAI's seasonal peak and quantify drought propagation from soil moisture to LAI in the global snow-free region. On average, soil moisture in the shallow soil layers (0-0.45 m) quickly recovers from the drought condition before the climatological day-of-year of the LAI's seasonal peak while soil moisture in the deeper soil layer (1.05-2.05 m) and LAI recover from the drought condition approximately 100 days after the climatological day-of-year of the LAI's seasonal peak.