Spatio-temporal assessment of Gridded precipitation products across topographic and climatic gradients in Colombia

Abstract

Gridded precipitation products (GPPs) represent an alternative to and a complement to gauge-based observations of precipitation, improving the representation of spatio-temporal precipitation variability in regions with scarce gauge networks. However, GPPs' accuracy varies among products, temporal resolution, and regions, indicating the need for particular regional performance assessments. In this study, we evaluate the performance of eight state-of-the-art GPPs (CHIRPSv2, CMORPHv1, ERA5, ERA5-Land, IMERG, MSWEPv2.8, PERSIANN-CCS, and PERSIANN-CDR) over the steep topographic and climatic gradients of Colombia, in northwestern South America. We use a point-to-pixel comparison between ground-based observations from 1334 gauges with the corresponding grid cell of each GPP at 3-day, monthly, seasonal (DJF, MAM, JJA, SON), and annual scales over 2005–2014. Five categorical indices are used to assess the ability of each GPP to capture different 3-day precipitation intensity events correctly. The Kling-Gupta efficiency and its components are used to assess the GPPs' performance over Colombia and its five natural regions. Our results show that, at the 3-day scale, GPPs can correctly identify the occurrence of no-precipitation events (< 1 mm/day), but their capacity to classify precipitation events (≥ 1 mm/day) is low. The best performance is observed at the monthly scale, particularly at low elevation zones (0–1000 m.a.s.l), compared to 3-day and annual scales. Seasonally, GPPs tend to perform better during the dry season compared to the wet season in all regions. Overall, CHIRPSv2 outperforms other GPPs throughout the country and its five natural regions for all elevation zones and temporal scales, followed closely by MSWEPv2.8 and IMERG. PERSIANN-CCS and ERA5 products had the lowest performance, mainly over the driest and higher-altitude regions, respectively. This study provides insights into the performance of GPPs in complex climatic and topographic settings and, importantly, suggests the most suitable products for climate, hydrological, or ecological studies in a climatic, hydrological, and ecologically-strategic region.