Evaluation of Satellite Precipitation Estimates over the South West Pacific Region

Ashley Wild,Yuriy Kuleshov,Zhi-Weng Chua

doi:10.3390/rs13193929

Abstract

Rainfall estimation over the Pacific region is difficult due to the large distances between rain gauges and the high convection nature of many rainfall events. This study evaluates space-based rainfall observations over the South West Pacific Region from the Japan Aerospace Exploration Agency’s (JAXA) Global Satellite Mapping of Precipitation (GSMaP), the USA National Oceanographic and Atmospheric Administration’s (NOAA) Climate Prediction Center morphing technique (CMORPH), the Climate Hazards group Infrared Precipitation with Stations (CHIRPS), and the National Aeronautics and Space Administration’s (NASA) Integrated Multi-Satellite Retrievals for GPM (IMERG). The technique of collocation analysis (CA) is used to compare the performance of monthly satellite precipitation estimates (SPEs). Multi-Source Weighted-Ensemble Precipitation (MSWEP) was used as a reference dataset to compare with each SPE. European Centre for Medium-range Weather Forecasts’ (ECMWF) ERA5 reanalysis was also combined with Soil Moisture-2-Rain–ASCAT (SM2RAIN–ASCAT) to perform triple CA for the six sub-regions of Fiji, New Caledonia, Papua New Guinea (PNG), the Solomon Islands, Timor, and Vanuatu. It was found that GSMaP performed best over low rain gauge density areas, including mountainous areas of PNG (the cross-correlation, CC = 0.64), and the Solomon Islands (CC = 0.74). CHIRPS had the most consistent performance (high correlations and low errors) across all six sub-regions in the study area. Based on the results, recommendations are made for the use of SPEs over the South West Pacific Region.

Highlights

Rainfall is fundamental to sustaining communities, economy, and the natural environment
SM2RAIN–ASCAT had significantly lower avAs in the comparison to Multi-Source Weighted-Ensemble Precipitation (MSWEP), we found poor performance of the satellite precipitation estimates (SPEs) over Papua New Guinea (PNG)
This research found that a key factor for SPE accuracy in the study region was topography, with more mountainous sub-regions (PNG, Timor, the Solomon Islands) consistently having weaker correlations than those characterised by less mountainous terrain (Fiji, Vanuatu, and New Caledonia)

Summary

Introduction

Rainfall is fundamental to sustaining communities, economy, and the natural environment. Numerous climate-sensitive sectors rely upon accurate precipitation measurements, and the demand for greater accuracy will increase as rainfall variability increases globally due to anthropogenic climate change [1]. Rain gauges and weather radars have been the traditional means of measuring precipitation, yet satellite remote sensing is increasingly considered as complementary to rain gauges due to its improving accuracy and spatial coverage [4,5]. Rain gauges themselves are prone to errors from evaporative losses, maintenance, and distribution issues (especially in remote areas), and the small representative area is problematic in regions with high topography and convection rainfall [6]. Weather radars can be effective for capturing the spatial extent of precipitation, but their use is limited, in developing and least developed countries, due to large upfront expense and maintenance costs [7]

Methods

Results

Discussion

Conclusion