Evaluating the IMERG precipitation satellite product to derive intensity-duration-frequency curves in Colombia

Abstract

This article explores the potentialities of the IMERG V06B FINAL product for estimating Intensity-Duration-Frequency curves in Colombia, using the in-situ data available for 110 rain gauges. From observed data for 76 of these stations, we validated the satellite IMERG precipitation data for the period 2001-2019, at daily, monthly, and annual resolutions. For 60 stations, better results were obtained for the monthly time aggregation, followed by the yearly and daily scales, suggesting that seasonality is the main rainfall characteristic captured by the product. Concerning the occurrence of daily precipitation, results indicate that both the probability of detection and the probability of false detection are high. In general terms, the comparison between intensities from existing IDF curves and those derived from IMERG showed underestimations of the rainfall intensities for the short durations studied (0.5 and 1 h), with mean relative errors in the range [-69%,+56%], and overestimations for the large durations of 2 and 6 h, with mean relative errors in the range [-61%,+171%]. Results also suggest that the IMERG product at this moment is not able to capture the daily rainfall distribution in most of the stations. Nevertheless, for almost 20% of the rain gauges, located mainly in the Amazon, Orinoco, and Pacific Regions, the analysis showed that the maximum intensities derived from IMERG are within +/-25% relative error, compared with the ones calculated using the traditional approach.