Abstract
Abstract. The Global Precipitation Measurement (GPM) Integrated Multi-satellite Retrievals for GPM (IMERG) products provide quasi-global (60° N–60° S) precipitation estimates, beginning March 2014, from the combined use of passive microwave (PMW) and infrared (IR) satellites comprising the GPM constellation. The IMERG products are available in the form of near-real-time data, i.e., IMERG Early and Late, and in the form of post-real-time research data, i.e., IMERG Final, after monthly rain gauge analysis is received and taken into account. In this study, IMERG version 3 Early, Late, and Final (IMERG-E,IMERG-L, and IMERG-F) half-hourly rainfall estimates are compared with gauge-based gridded rainfall data from the WegenerNet Feldbach region (WEGN) high-density climate station network in southeastern Austria. The comparison is conducted over two IMERG 0.1° × 0.1° grid cells, entirely covered by 40 and 39 WEGN stations each, using data from the extended summer season (April–October) for the first two years of the GPM mission. The entire data are divided into two rainfall intensity ranges (low and high) and two seasons (warm and hot), and we evaluate the performance of IMERG, using both statistical and graphical methods. Results show that IMERG-F rainfall estimates are in the best overall agreement with the WEGN data, followed by IMERG-L and IMERG-E estimates, particularly for the hot season. We also illustrate, through rainfall event cases, how insufficient PMW sources and errors in motion vectors can lead to wide discrepancies in the IMERG estimates. Finally, by applying the method of Villarini and Krajewski (2007), we find that IMERG-F half-hourly rainfall estimates can be regarded as a 25 min gauge accumulation, with an offset of +40 min relative to its nominal time.
Highlights
The Global Precipitation Measurement (GPM) mission was launched in February 2014
Once observation data are received from the passive microwave (PMW) and IR platforms, they are combined into half-hourly gridded fields through the Integrated Multi-satellite Retrievals for GPM (IMERG) system (Huffman et al, 2015a, b)
We evaluate and compare the rainfall data generated by all three IMERG runs using rain-gauge-based gridded data from the WegenerNet Feldbach region (WEGN) high-density climate station network in southeastern Austria (Kirchengast et al, 2014)
Summary
The Global Precipitation Measurement (GPM) mission was launched in February 2014. This international mission is led by the National Aeronautics and Space Administration (NASA) and the Japan Aerospace and Exploration Agency (JAXA), as a successor to the Tropical Rainfall Measuring Mission (TRMM), to continue and improve satellite-based rainfall and snowfall observations on a global scale (Tapiador et al, 2012; Hou et al, 2014; Yong et al, 2015). The GPM mission consists of a core observatory satellite and a constellation of partner satellites to collect information from as many passive microwave (PMW) and infrared (IR) satellite platforms as available. Processed differently based on user requirements in terms of data latency and accuracy (see Sect. 2.1 for details), the IMERG computes Early, Late, and Final runs (hereafter IMERG-E, IMERG-L, and IMERG-F runs)
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