Satellite-based estimation of rainfall erosivity for Africa

Rainfall erosivity is a measure for the erosive force ofrainfall. Rainfall kinetic energy determines the erosivity and is inturn greatly dependent on rainfall intensity. Attempts for itslarge-scale mapping are rare. Most are based on interpolation oferosivity values derived from rain gauge data. For data-poor regionsthis is not an option. This study examines whether erosivity can beaccurately mapped for Africa using 3-hourly TRMM Multi-satellitePrecipitation Analysis (TMPA) precipitation data. Usingintensity-erosivity relationships and 11 years of TMPA data (1998-2008)we calculated average annual erosivity. We also calculated erosivityfrom the monthly TMPA data product using the often-applied Fournier andmodified Fournier indices. From literature 39 locations with long-termerosivity values were retrieved. Comparison showed that the modifiedFournier index attains a much stronger correlation ( r = 0.84) than theresults based on 3-hourly data ( r = 0.71). We conclude that (1) the3-hourly and 0.25-degree TMPA data provide insufficient detail torepresent high-intensity erosive events and (2) monthly satellite-basedprecipitation provides good spatial estimates of average annualerosivity.