Evaluation of five satellite products for estimation of rainfall over Uganda / Evaluation de cinq produits satellitaires pour l'estimation des précipitations en Ouganda

Abstract

Five satellite-based rainfall estimation algorithms (TRMM 3B42, CMORPH, TAMSAT, RFE 2.0 and PERSIANN) are assessed against historical monthly rainfall statistics from raingauges within four regions of Uganda. Results are discussed in terms of the accuracy of the products, the effect of climate variability, and differences between products. Products are able to reasonably reflect seasonal patterns in rainfall, and also the spatial patterns in rainfall between regions. Patterns in the occurrence of rainfall are better reflected than patterns in rainfall amounts. There is significant scope for improving the estimation of amounts by calibration to the raingauge data. TRMM 3B42, CMORPH and TAMSAT show most promise in this application followed by RFE 2.0 and the PERSIANN system. However, the relative performance of the products depends on what aspects of the rainfall regime are being considered. Differences between the products are large and the use of more than one product for any application is recommended.Key words rainfall estimation; satellites; Uganda; TRMM; CMORPH; TAMSAT; RFE; PERSIANN Evaluation de cinq produits satellitaires pour l'estimation des précipitations en OugandaRésumé Cinq algorithmes d'estimation par satellite des précipitations (TRMM 3B42, CMORPH, TAMSAT, RFE 2.0 et PERSIANN) sont confrontés aux statistiques mensuelles historiques de pluviomètres répartis dans quatre régions d'Ouganda. Les résultats sont discutés en termes de précision des estimations, de sensibilité à la variabilité climatique, et de différences entre les produits. La saisonnalité des précipitations ainsi que leur distribution géographique entre régions sont convenablement reproduites. Les structures d'occurrence sont mieux représentées que les structures de hauteur de pluie. La marge d'amélioration de l'estimation des hauteurs d'eau par calage avec les données au sol est significative. Cette application est plus prometteuse avec TRMM 3B42, CMORPH et TAMSAT qu'avec RFE 2.0 et PERSIANN. Les performances relatives des produits dépendent cependant des caractéristiques du régime pluviométrique qui sont considérées. Les résultats diffèrent largement entre les produits et une utilisation combinée est recommandée quelle que soit l'application.

The nature of rainfall in the main drainage sub-basins of Uganda

“…Generally, the seasonal pattern follows this bimodal system near the Equator and tends to a unimodal system away from the Equator (Conway 2005, Asadullah et al 2008. Inter-annual variability of rainfall correlates with SSTs in the Pacific through atmospheric teleconnections: the ENSO phenomenon.…”

Evaluation of global fine-resolution precipitation products and their uncertainty quantification in ensemble discharge simulations

“…The APHRODITE, PERSIANN, and GSMAP products are seldom evaluated in northeast China using basin-scale gauge data (Zhou et al, 2008). Owing to the high heterogeneity of rainfall across a variety of spatiotemporal scales, the uncertainty characteristics of precipitation products are variable (Asadullah et al, 2008;Dinku et al, 2008;Nikolopoulos et al, 2010;Pan et al, 2010). Thus, in northeast China, it is essential to completely evaluate the applicability of these precipitation products.…”

Where does all the water go? Partitioning water transmission losses in a data-sparse, multi-channel and low-gradient dryland river system using modelling and remote sensing

“…We found (see Table 4) that the lateral inflow between available sparse gauging stations provided the highest uncertainty in water balance estimation. However, high uncertainty of daily gridded rainfall data, especially in areas with sparse rainfall gauges (Asadullah et al, 2008;Chappell et al, 2013), is in turn a major driver of this uncertainty in lateral inflows during flood events.…”