[H-CG22] Adaptation to climate change and its social implementation

[HCG22-03] Investigating Soil Moisture Feedback on Water Availability and Drought Impacts over Africa in the Past and Projected Scenarios

*NGUYEN NGOC KIM HONG¹, KOJI DAIRAKU¹ (1. University of Tsukuba)

Keywords:Soil Moisture Feedback, Water Availability, Moisture Convergence, Drought

The study underscores the critical importance of incorporating soil moisture (SM) feedback and water availability as indicated by precipitation minus evapotranspiration (P-E) and moisture convergence (MC) in the context of prolonged drought conditions across the African continent. By using observational data, reanalysis data, satellite-based data, Regional Climate Models (RCMs) under the Coordinated Regional Climate Downscaling Experiment (CORDEX) Africa 44 (AF44) domain, and General Climate Models (GCMs) under the Sixth Phase of the Coupled Model Intercomparison Project (CMIP6), the research explores SM-(P-E) feedback with a one-month delay in soil moisture memory and MC from 1981 to 2005, along with the behavior of Vapor Pressure Deficit (VPD) in the seasonal future scenarios RCP8.5 and SSP585 within 2051-2100. The assessment uses the Standardized Precipitation-Evapotranspiration Index (SPEI) over a one-month interval to evaluate drought onset, duration, and magnitude. The study underscores the intricate relationship between SM-(P-E) by multiple linear regression model, revealing a fluctuating positive coefficient (2-6 mm) in historical and RCP8.5 projections, except for an unusually high level observed in satellite-based data. The aridity index based on FAO classifications identified hyper-arid and arid zones in the past in the North, South, and the Horn of Africa. Additionally, the research emphasizes the strong association between SM and Mean Flow Convergence (MFC), with MFC contributing 45-55% over the historical period in Africa. According to the SPEI, a transition from wet to dry is projected around 2085, and future RCP8.5 conditions indicate less intensity and frequency of "Extreme" and "Very" dry conditions compared to the historical period. Furthermore, VPD exhibits notable activity with future projections anticipating a stronger and more consistent relationship between SM and VPD in summer than in winter. We address future water scarcity issues in the study area by establishing a comprehensive understanding of land-atmospheric feedback and its responses to climate change. The insights gained from this study can serve as a valuable tool for policymakers and researchers alike, contributing to a broader understanding of climate-related challenges and facilitating informed global decision-making.