Enhancing Rainfall Estimates in East Africa by Merging TAHMO Precipitation Gauge Data with Remote Sensing Rainfall Products

Sub-Saharan Africa heavily relies on remotely-sensed rainfall measurements due to a lack of in-situ rainfall data. While a high number of satellite-based rainfall products do exist, they are typically developed and tested in regions with a high density of ground data. The Trans-African Hydro-Meteorological Observatory (TAHMO) aims to tackle the ground data gap by installing and operating a dense network of weather stations in Sub-Saharan Africa. As part of the TEMBO Africa project, TAHMO data were used to make a new regional rainfall product in East Africa based on the SM2Rain algorithm.  Subsequently, this regional product was merged with a reanalysis product (ERA5) and two MW/IR-based rainfall products (IMERG-L and CHIRPS) based on the Statistical Uncertainty analysis-based Precipitation mERging framework (SUPER). Within this framework, merging weights are based on error variances of the rainfall products determined from quadruple collocation on a pixel-to-pixel basis. The merged product and the individual products are evaluated using data of the individual TAHMO stations. Our findings indicate that the merged product outperforms the individual products in most selected evaluation metrics.  ERA5 has the highest contribution in the merged product, followed by SM2Rain. Both IMERG and CHIRPS have limited contribution in the merged product due to a high error variance. The ultimate goal of this study was to develop a workflow to enhance the accuracy of rainfall measurements in Sub-Saharan Africa by leveraging information from TAHMO data and different existing products, contributing to the improvement of remotely-sensed rainfall measurements in Sub-Saharan Africa.

We welcome suggestions on possible improvements and operational implementation, as well as ideas on how to use this merged product to understand the sources of error in satellite-based rainfall measurements in Sub-Saharan Africa.

 

TEMBO Africa: The work leading to these results has received funding from the European Horizon Europe Programme (2021-2027) under grant agreement n° 101086209. The opinions expressed in the document are of the authors only and no way reflect the European Commission’s opinions. The European Union is not liable for any use that may be made of the information