Abstract
In March 2019, Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG)-Final v6 (hereafter IMERG6) was released, with data concerning precipitation dating back to June 2000. The National Aeronautics and Space Administration (NASA) has suggested that researchers use IMERG6 to replace the frequently used Tropical Rainfall Measuring Mission (TRMM)-3B42 v7 (hereafter TRMM7), which is expected to cease operation in December 2019. This study aims to evaluate the performance of IMERG6 and TRMM7 in depicting the variations of summer (June, July, and August) precipitation over Taiwan during the period 2000–2017. Data used for the comparison also includes IMERG-Final v5 (hereafter IMERG5) and Global Satellite Mapping of Precipitation for Global Precipitation Measurement (GSMaP)-Gauge v7 (hereafter GSMaP7) during the summers of 2014–2017. Capabilities to apply the four satellite precipitation products (SPPs) in studying summer connective afternoon rainfall (CAR) events, which are the most frequently observed weather patterns in Taiwan, are also examined. Our analyses show that when using more than 400 local rain-gauge observations as a reference base for comparison, IMERG6 outperforms TRMM7 quantitatively and qualitatively, more accurately depicting the variations of the summer precipitation over Taiwan at multiple timescales (including mean status, daily, interannual, and diurnal). IMERG6 also performs better than TRMM7 in capturing the characteristics of CAR activities in Taiwan. These findings highlight that using IMERG6 to replace TRMM7 adds value in studying the spatial-temporal variations of summer precipitation over Taiwan. Furthermore, the analyses also indicated that IMERG6 outperforms IMERG5 and GSMaP7 in the examination of most of the features of summer precipitation over Taiwan during 2014–2017.
Highlights
The Tropical Rainfall Measuring Mission (TRMM) was launched in November 1997 [1], and its most frequently used product, TRMM-3B42 v7, is expected to cease in December 2019
The analysis mainly focuses on the time periods that overlap in all data investigated, that is, the summers of 2014–2017 (Table 1), with an additional comparison between TRMM7 and IMERG6 for the summers of 2000–2017
Where O is the area of precipitation depicted by the CWB data that exceeds a given precipitation threshold, F is the area of precipitation depicted by the selected satellite precipitation products (SPPs) that exceeds the given precipitation threshold, and H is the intersection of O and F over a period of accumulation
Summary
The Tropical Rainfall Measuring Mission (TRMM) was launched in November 1997 [1], and its most frequently used product, TRMM-3B42 v7 (hereafter TRMM7), is expected to cease in December 2019 (https://pmm.nasa.gov/data-access/downloads/trmm). The satellite precipitation products (hereafter SPPs) of the GPM mission, including Integrated Multi-satellitE Retrievals for GPM (IMERG) [3] and Global Satellite Mapping of Precipitation for GPM (GSMaP) [4], were provided by the National Aeronautics and Space Administration (NASA) and the Japan Aerospace Exploration Agency (JAXA), respectively. It is important to clarify which SPP (e.g., IMERG or GSMaP) is the most suitable product to replace TRMM7 for studies of precipitation changes over various regions and during various seasons [13,14,15]. Huang et al [24] showed that
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