Numerical simulations of a heavy rainfall event in the Sahelian region of Zinder in Niger

Abstract

Reliable modeling of heavy rainfall events is required for accurate flood prediction. This study evaluated the performance of the Weather Research and Forecasting (WRF) model in simulating heavy rainfall events that occurred on July 17, 2022 in the Sahelian region of Zinder in Niger. We performed a sensitivity study using various cumulus and microphysical schemes. We evaluated the reliability of the WRF model using different statistical approaches, including the probability of detection, false alarm ratio, success ratio, frequency bias, and critical success index. At the synoptic scale, atmospheric conditions were favorable for heavy precipitation in the Zinder region. Intense moisture transport from the southwest, high precipitable water values (≥ 50 kg/m²), strong wind shear (10–15 m/s) and convective instability indicators (high K index and low convective inhibition) contributed to the initiation and intensification of convection. Outgoing longwave radiation (OLR) analysis confirmed the presence of strong convective activity and an active easterly wave, which strengthened the organization of convective systems. The evaluation analysis showed that the model effectively captured the spatial pattern of heavy rainfall in all ensemble member simulations. When combined with the Purdue Lin (PL), Morrison-2 moment (M2), and New Thomson (TS) microphysical schemes, the Tiedkte (TK) cumulus scheme outperformed other convective schemes. The WRF model has the potential to improve the prediction of heavy rainfall events in Niger and to inform decision-making processes.