Evaluation of TRMM 3B42 (TMPA) precipitation estimates and WRF retrospective precipitation simulation over the Pacific-Andean basin into Ecuador and Peru

Resumen

Abstract. An important issue for the Pacific-Andean basin in western South-America is whether the latest satellite-based and Numerical Weather Prediction (NWP) model outputs, provide the potential to compensate data scarcity. Based on a comprehensive dataset of ground precipitation, the performance of the Tropical Rainfall Measuring Mission (TRMM) 3B42V7 and its predecessor version the 3B42V6, and the Weather Research Forecast (WRF) precipitation product (OA-NOSA30) are evaluated over 21 sub-catchments situated in the westernmost N-S axis of South America: the Pacific-Andean Basin in Ecuador and Peru (PAEP). In general, precipitation estimates from TRMM and OA-NOSA30 capture the seasonal features of precipitation in the study area. Quantitatively, only the Southern sub-catchments of Ecuador and Northern Peru (3.6–6° S) are relatively well estimated by both methods. The accuracy of both approaches is considerably less in the northern and central basins of Ecuador (0–3.6° S). It is shown that the detection probability is better for light precipitation (less than 5 mm day−1). Compared to its predecessor 3B42V7 shows modest basin-wide improvements in reducing biases. The improvement is specific to the coastal and open ocean sub-catchments. In view of hydrological applications, the correlation of TMPA's and OA-NOSA30 estimates with observations increases with time aggregation. The correlation is higher for the monthly time aggregation in comparison with the daily, weekly and 15-daily time scales. Furthermore, it is found that TMPA performs better than OA-NOSA30 in generating the spatial distribution of mean annual precipitation.