Spring soil moisture as potential source of West African summer rainfall predictability

Soil moisture plays a key role in the water and energy cycle through radiation and persists to further induce wet or dry climate. In this study, we analyzed the lead-lag relationship between soil moisture and the precipitation over the West African region during boreal summer season. The Soil moisture data from European Space Agency-Climate Change Initiative (ESA-CCI) version 4.4 global dataset is adapted for the period 1979 to 2017, while precipitation dataset was taken from Climatic Research Unit (CRU). Linear regression shows that April-May area-averaged soil moisture index over West Africa are able to predict the lead-1 seasonal mean (June-September) rainfall anomalies over the region. It is noticed that wet soil moisture anomalies can induce more rainfall in their subsequent (lead-1) season and vice-versa. Furthermore, we utilized the Saudi-King Abdulaziz University (KAU) Atmospheric Global Climate Model (AGCM) to assess simulated soil moisture with the lead rainfall simulated by the model by using 25-ensemble members. It is noticed that model were able to reproduce the observed pattern quite well. The potential predictability of soil moisture and precipitation over the West Africa was analyzed by using Signal to noise ratio, which shows that soil moisture can be used potentially as a regional rainfall predictor over West Africa.