Intercomparison of improved satellite rainfall estimation with CHIRPS gridded product and rain gauge data over Venezuela

Satellite-dericed rainfall products are useful for both drought and environmental monitoring, and they also allow for tackling the problems of sparse, unevenly distributed and arratic rain gauge observations provided their accuracy is well known. Venezuela is a country highly vulnerable to extreme weather events such as extensive droughts and flash floods; therefore, an understanding of the strengths and weaknesses of satellite-based rainfall products is useful for the planning of water resources. Using numerical metrics in order to evaluate performance, monthly rainfall estimates, from the Climate Hazards Group InfraRed Precipitation and Stations (CHIRPS v.2) product, are compared to gauge data from the 1981-2007 interval and categorical metrics for assessing rain-detection skills. The analysis was performed considering different rainfall categories, seasonality, and spatial context. The results show that the satellite product CHIRPS v.2 overestimates (underestimates) low (high) monthly rainfall values; although on the majority of numerical metrics of skill shows a good performance. This product, on the other hand, achieves better performance during the rainy season (April-September), significantly overestimating, however, the rainfall-events frequency. The product also shows best overall performance over flat and open regions (e.g., Los Llanos), where precipitation is influenced by the Intertropical Convergence Zone activity and local convective systems.Original Abstract: Los productos que proveen estimaciones de lluvia derivadas de satelites son utiles para el monitoreo tanto ambiental como de sequias, y permiten ademas afrontar el problema de las observaciones derivadas de estaciones pluviometricas mal distribuidas, siempre y cuando su precision sea conocida. Venezuela es altamente vulnerable a eventos climaticos extremos como sequias extensivas y crecientes rapidas, por lo tanto conocer las debilidades y fortalezas de las estimaciones de lluvias derivadas de satelites resulta util para la planificacion de los recursos hidricos. Las estimaciones mensuales de lluvia derivadas del producto Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS v.2) son contrastadas con los registros proveniente de estaciones climaticas (1981-2007), empleando metricas numericas para evaluar su desempeno en la estimacion de la cantidad de lluvia, y metricas categoricas para evaluar su capacidad de deteccion de eventos de lluvia. Los analisis aplicados considera