Assessing the Reliability of Satellite and Reanalysis Estimates of Rainfall in Equatorial Africa

Abstract

This article examines the reliability of satellite and reanalysis estimates of rainfall in the Congo Basin and over Lake Victoria and its catchment. Nine satellite products and five reanalysis products are considered. They are assessed by way of inter-comparison and by comparison with observational data sets. The three locations considered include a region with little observational gauge data (the Congo), a region with extensive gauge data (Lake Victoria catchment), and an inland water body. Several important results emerge: for one, the diversity of estimates is generally very large, except for the Lake Victoria catchment. Reanalysis products show little relationship with observed rainfall or with the satellite estimates, and thus should not be used to assess rainfall in these regions. Most of the products either overestimate or underestimate rainfall over the lake. The diversity of estimates makes it difficult to assess the factors governing the interannual variability of rainfall in these regions. This is shown by way of correlation with sea-surface temperatures, particularly with the Niño 3.4 temperatures and with the Dipole Mode Index over the Indian Ocean. Some guidance is given as to the best products to utilize. Overall, any user must establish that the is product reliable in the region studied.

Rainfall Variability and Trends over the African Continent Using TAMSAT Data (1983–2020): Towards Climate Change Resilience and Adaptation

“…Many studies have emphasized that rainfall products produced by the TAMSAT team at the University of Reading in the UK are more suitable than their surrogates for study in Africa, given the availability of the above rainfall estimates, TAMSAT's level of accuracy, its spatial resolution, and its widespread use for trend analysis [30,[64][65][66]. The gridded TAMSAT rainfall products are based on high-resolution Meteosat thermal infrared (TIR) observations and data gathered through rainfall stations [67].…”

“…West African Sahel became known as having the region's most devastating drought because of changes in WAM conditions during the 1970s and 1980s [28,29]. During the EAM seasons, the ITCZ is located south of the equator, with long-duration rain from March to May and short duration rain from October to December in the central, southern, and eastern parts of Africa [24,30].…”

Topoclimate and diurnal cycle of summer rain over the Ethiopian highlands in a convection‐permitting simulation

“…Through its enhanced resolution and orographic details and improved representation of surface processes as compared to ERA5, temperature, wind speed and humidity is expected to be better represented in mountainous areas. The rainfall of ERA5, on the other hand, is known to be strongly biased which is the reason why IMERG is preferred (Nicholson & Klotter, 2021; Van den Hende et al, 2021).…”

Verification of operational numerical weather prediction model forecasts of precipitation using satellite rainfall estimates over Africa

“…RFE2 has been shown to perform well across Africa (Thiemig et al, 2012), as well as in regional specific validations from Egypt (Abd Elhamid et al, 2020), Burkina Faso (Dembélé & Zwart, 2016), Ethiopia (Gebremicael et al, 2017), Mozambique (Toté et al, 2015), Sudan (Abd Elhamid et al, 2020) and Zimbabwe (Dinku et al, 2018). However, there is evidence to suggest that RFE2 captures rainfall less skillfully than several other products over East and Central Africa (Camberlin et al, 2019; Diem et al, 2014; Dinku et al, 2018; Nicholson & Klotter, 2021).…”