The Uncertainty in Land-Atmosphere Coupling-based Drought Metrics due to Different Soil Moisture Products

Accurate assessment of drought conditions is essential for effective water resource management and mitigation. In this study, we use the triple collocation (TC) method to merge three reanalysis datasets of Convective Triggering Potential (CTP) and Humidity Index (HI), to evaluate the uncertainty in land-atmosphere coupling-based drought metrics due to soil moisture. The merged product results in improved performance and enhanced accuracy in capturing the atmospheric state based on the validation results against the Integrated Global Radiosonde Archive version 2 (IGRA2) and the Atmospheric Infrared Sounder (AIRS). By integrating the merged dataset, we enhance the evaluation of land-atmosphere coupling-based drought metrics and investigate the sensitivity of these metrics to variations in soil moisture. The analysis focuses on identifying the impact of Soil Moisture Active Passive level 4 (SMAPL4) soil moisture variations on land surface conditions and drought dynamics as compared to reanalysis soil moisture. The comprehensive evaluation sheds light on the role of SMAP soil moisture in shaping these outcomes. Results reveal consistent underestimation of drought severity by the Modern-Era Retrospective analysis for Research and Application, version 2 (MERRA2) compared to SMAPL4 soil moisture, particularly in the northern hemisphere, while a higher similarity is observed in South America with MERRA2 and other reanalysis soil moisture product from the Climate Forecast System Reanalysis (CFSR) and the European Center for Medium-Range Weather Forecast (ECMWF) Reanalysis v5 (ERA5). In future, by incorporating merged soil moisture data, we can effectively address uncertainties associated with individual datasets, enabling a more comprehensive understanding of the land-atmosphere coupling framework and facilitating informed decision-making based on the quantification of soil moisture's significance.