Assessing the variability of satellite and reanalysis rainfall products over a semiarid catchment in Tunisia

Abstract

Precipitation is a key component in hydrologic processes. It plays an important role in hydrological modeling and water resource management. However, many regions suffered from limited and data scarcity due to the lack of ground-based rain gauge networks. The main objective of this study is to evaluate and compare three different satellite-based precipitation products (CHIRPS, PERSIANN and GPM) and a reanalysis (ERA5) in semi-arid catchment of Tunisia (Haffouz catchment) against rain-gauge stations records for the period between September 2000 and August 2018. Twelve rain-gauges and two different interpolation methods (Inverse Distance Weight and ordinary kriging) were used to compute a set of interpolated precipitation reference elds. The evaluation was performed at daily, monthly, and yearly time scales and at spatial scales, using different statistical metrics. The results showed that the two interpolation methods give similar and valid precipitation estimates at the catchment scale.According to the different statistical metrics, CHRIPS showed the most satisfactory results followed by PERSIANN which performed well in terms of correlation but overestimated precipitations spatially over the catchment. GPM underestimate the precipitation considerably, but it gives a satisfactory performance temporally. ERA5 shows a very good performance at daily, monthly, and yearly timescale, but it is unable to present the spatial variability distribution of precipitation for this catchment. This study concluded that satellite-based precipitation products can be useful in semi-arid regions and data-scarce catchments, and it may provide less costly alternatives for data-poor regions.