Abstract
Precipitation in a mountainous region is highly variable due to the complex terrain. Satellite-based precipitation estimates are potential alternatives to gauge measurements in these regions, as these typical measurements are not available or are scarce in high elevation areas. However, the accuracy of these gridded precipitation datasets need to be addressed before further usage. In this study, an evaluation of the spatial precipitation pattern in satellite-based precipitation products is provided, including satellite-only (Integrated Multi satellite Retrievals for GPM IMERG-UCORR and Global Satellite Mapping of Precipitation (GSMaP-MVK) and gauge calibrated (IMERG-CORR and GSMaP-Gauge) products, with a spatial resolution of 0.1°, which is compared to 387-gauge measurements in Nepal from April 2014 to December 2016. The major results are as follows: (1) The gauge calibrated version 5 IMERG-CORR and version 6 GSMaP-Gauge are relatively better than the satellite-only datasets, although they all underestimate the observed precipitation. (2) The daily gauge calibrated GSMaP-Gauge performs fairly well in low and mid-elevation areas, whereas the monthly gauge calibrated IMERG-C performs better in high-elevation areas. (3) For the daily time scale, IMERG-CORR shows a better ability to detect the true precipitation (higher Probability of Detection (POD)) and (lowest False Alarm Ratio (FAR)) events among all datasets. However, all four satellite-based precipitation datasets accurately detect (Critical Success Index (CSI) >40%) precipitation and no-precipitation events. The results of this work provide the systematic quantification of IMERG and GSMaP of satellite precipitation products over Nepal using station observations and delivers a helpful statistical basis for the selection of these datasets for future scientific research.
Highlights
Precipitation is a fundamental component of the water cycle
It is noteworthy that Global Satellite Mapping Precipitation (GSMaP)-Gauge effectively reduces the systematic errors (30 % of RE) of GSMaP-MVK with bias-correction using the daily Climate Prediction Center (CPC) gauge-based observation, which is only 2.6 % when Global Precipitation Climatology Centre (GPCC) monthly gauge-analysis used in Integrated Multi-Satellite Retrievals for GPM (IMERG) data set
This study attempts to evaluate the spatial pattern of precipitation in version 5 IMERG and version 6 GSMaP products, including satellite‐only (IMERG-UNCORR and GSMaP-MVK) and gauge calibrated (IMERG-CORR and GSMaP-Gauge) products, against 387-gauge measurements in Nepal from April 2014 to December 2016
Summary
Precipitation is a fundamental component of the water cycle. Understanding is paramount for managing water systems under a changing climate (Daly et al, 2017; Schneider et al, 2016; Aryal et al, 2020). Mountainous regions play a significant role in regional water resource conservation and sustainable use (Viviroli and Weingartner, 2004) These important regions are vulnerable to climate change and several hydro-meteorological hazards, such as floods and landslides. Rain Gauge-based stations provide relatively accurate and actual precipitation measurements at discrete locations on the ground surface (Sun et al, 2018; Hamal et al, 2020c; Sharma et al, 2020c; Sharma et al, 2021b) These stations are inadequate for hydro-meteorological studies as their distribution is sporadic. High-resolution satellite-based precipitation (SBP) products are the potential alternatives for monitoring precipitation on regular grids nearby They represent unprecedented measurements over remote areas, especially in a mountainous region where stations are very sparse. These estimates are indirect measurements and must be calibrated or verified using gauge observations before further applications (Tian and Peters-Lidard, 2010)
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