Regionalization of Precipitation and Identification of the Onset and Cessation of the Rainy Season in Angola Using Satellite-Based Precipitation Estimates

de Sousa Afonso J.M.; Pareja-Quispe D.; Aparco-Lara J.; Ihadua I.M.T.J.; Almeida A.P.; Pedra G.U.; Gaspar A.M.L.; da Silva Caetano M.; Lins M.C.C.; Segunda E.C.T.; Vasco N.D.A.A. · Earth Systems and Environment (2026) · DOI: 10.1007/s41748-025-00872-z

Resumen

This study presents the first comprehensive regionalization of Angola’s rainfall and estimates onset and cessation of the rainy season using Satellite-based Precipitation Estimates (SPEs). During 2021 to 2023, data from stations of the National Institute of Meteorology and Geophysics of Angola (INAMET) were used to evaluate the performance of two SPE products: Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) and Integrated Multi-satellite Retrievals for GPM (IMERG). Rainfall in Angola is better represented by SPE products in higher-altitude regions than in coastal areas. Among them, CHIRPS outperforms IMERG in terms of correlation, statistical distribution, and temporal consistency. Importantly, CHIRPS also provides a longer record (1981–2023). Using K-means clustering on 43 years of CHIRPS data, we identified seven distinct precipitation regimes across Angola. Most regions show austral summer rainfall peaks, while the Northwest uniquely peaks in autumn. Using Gaussian fits to daily precipitation, three regions (Central-East, Central-South, Southeast) exhibit a unimodal regime with a summer maximum. Four regions (Northwest, Northeast, Central-West, Southwest) show a transitional regime with two peaks, one between spring–summer and another in autumn, and a higher likelihood of extreme events in autumn. The rainy-season onset ranges from August 1 (Northeast) to October 7 (Southwest), and the end ranges from May 9 (Southwest) to June 3 (Northeast). The Northeast has the longest rainy season, starting in winter; 68 days later, the Southeast, the shortest, starts in spring. An opposite pattern is observed in autumn: rainfall ends first in the Southeast, and 25 days later it ends in the Northeast. Future work should compare onset and cessation estimates at the grid-point scale using multiple methods across the seven regions. © The Author(s) 2025.

Instituciones: Universidad Nacional Mayor de San Marcos