Diagnosing Product Variability in the Soil Moisture Response to Precipitation on the Tibetan Plateau

Previous studies show that some soil moisture products have a good agreement with in situ measurements on the Tibetan Plateau (TP). However, the soil moisture response to precipitation variability in different products is yet to be assessed. In this study, we focus on the soil moisture response to precipitation variability across weekly to decadal time scales in satellite observations and reanalyses. The response of soil moisture to precipitation variability differs between products, with large uncertainties observed for variations in weekly accumulated precipitation. Using June 2009 as an ex-ample, weekly mean anomalous soil moisture varies by up to 25% between products. Across decadal time scales, soil mois-ture trends vary spatially and across different products. In light of the soil moisture response to precipitation at different time scales, we conclude that remote sensing products developed as part of the European Space Agency's (ESA) Water Cycle Multimission Observation Strategy and Soil Moisture Climate Change Initiative (CCI) projects are the most reliable, followed by the Global Land Evaporation Amsterdam Model (GLEAM) dataset. Even products that strongly agree with in situ observations on daily time scales, such as the Global Land Data Assimilation System (GLDAS), show inconsistent soil moisture responses to decadal precipitation trends. European Centre for Medium-Range Weather Forecasts (ECWMF) reanalysis products have a relatively poor agreement with in situ observations compared to satellite observa-tions and land-only reanalysis datasets. Unsurprisingly, products which show a consistent soil moisture response to precipi-tation variability are those mostly aligned to observations or describe the physical relationship between soil moisture and precipitation well.

Automated summary

Previous studies have found that some soil moisture products show good agreement with in situ measurements on the Tibetan Plateau. However, the response of soil moisture to precipitation variability in different products has not been assessed. This study examines the soil moisture response to precipitation variability across different time scales in satellite observations and reanalyses. The results show that different products have varying uncertainties and spatial variations in their soil moisture response to precipitation.