Exploring causal pathways among soil moisture, climate and ocean–atmosphere teleconnection patterns over the drought-prone Greater Horn of Africa

Drought over the Greater Horn of Africa (GHOA) is a recurring phenomenon primarily associated with precipitation deficit which leads to decreased soil moisture. Understanding the interactions among atmosphere, ocean, climate, and soil is therefore necessary for water resource management, drought monitoring, and disaster prevention. Assessing those interactions so far primarily focused on dynamic climate models and statistic models. However, the former model is proven to have well-known biases in simulating both the strength and the timing of rainfall in GHOA, and the latter model often fails to discover causal relationship due to autocorrelation and high dimensionality within time series variables. Here, we use a data driven causal graph discovery algorithm called PCMCI+ to discover causal relationships among El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) teleconnection patterns, precipitation, temperature and soil moisture (SM) during 1980–2022 over drought-prone GHOA. Additionally, we quantitatively calculated the causal effects of teleconnection patterns on SM mediated through different climate paths, and the correlation with regional drought conditions are further explored. Results suggest that IOD generally presents higher causal effects on climate variables (temperature and precipitation) or on SM through both climate pathways than ENSO over most parts of GHOA, and the strongest correlation with drought conditions are generally found during different IOD phases. Moreover, precipitation is a more vital path through which teleconnection patterns causally impact SM in GHOA. Our study provides the first attempt to quantitatively analyze the causal effects of teleconnection patterns on SM through both precipitation and temperature pathways, and it highlights the causal relationships within atmosphere–ocean-climate-soil interactions, which could help for better understanding of climate change impact on drought over GHOA.