Validation and intercomparison of satellite-based rainfall products over
Africa using TAHMO in-situ rainfall observations
Abstract
Sparse rain gauge networks and declining observations in Africa limit
climate research in the region. However, the proliferation of
satellite-rainfall products (SRPs) and the growth of
citizen-science-driven in-situ observations driven by cheaper data
collection technologies have provided a pathway to overcoming the data
scarcity problem. In this paper, we used rain gauge data from 596
stations operated by the Trans-African Hydro-Meteorological Observatory
(TAHMO) across Africa to evaluate the performance of two widely-utilized
satellite-based rainfall products: the Climate Hazards InfraRed
Precipitation with Stations (CHIRPS) and the Tropical Applications of
Meteorology using Satellite data (TAMSAT), and two under-validated and
underutilized products: the satellite-only Global Satellite Mapping of
Precipitation (GSMaP) and the gauge-corrected GSMaP version
(GSMaP_Gauge). We also inter-compared the performance of the four
products over Africa, East Africa, Southern Africa and West Africa at
daily, pentadal, and monthly timescales. Our findings indicated that the
GSMaP products had better performances at daily timescales whereas
CHIRPS and TAMSAT matched or outperformed the GSMaP products at pentadal
and monthly timescales. GSMaP_Gauge daily rainfall detection was almost
1.5 times the CHIRPS detection scores at the same temporal scale. The
Pearson correlation coefficient increased with temporal aggregation but
the volumetric errors increased for all products. Additionally, all the
products overestimated (underestimated) low (high) intensity rainfall
events. Our analysis adds to a growing number of validation studies in
Africa and presents an opportunity for developers of satellite-rainfall
products to integrate the new TAHMO observations in bias-correction
algorithms to improve the accuracy of SRPs in the region.