Benefits of the Successive GPM Based Satellite Precipitation Estimates IMERG–V03, –V04, –V05 and GSMaP–V06, –V07 Over Diverse Geomorphic and Meteorological Regions of Pakistan

Abstract

Launched in 2014, the Global Precipitation Measurement (GPM) mission aimed at ensuring the continuity with the Tropical Rainfall Measuring Mission (TRMM) launched in 1997 that has provided unprecedented accuracy in Satellite Precipitation Estimates (SPEs) on the near-global scale. Since then, various SPE versions have been successively made available from the GPM mission. The present study assesses the potential benefits of the successive GPM based SPEs product versions that include the Integrated Multi-Satellite Retrievals for GPM (IMERG) version 3 to 5 (-v03, -v04, -v05) and the Global Satellite Mapping of Precipitation (GSMaP) version 6 to 7 (-v06, -v07). Additionally, the most effective TRMM based SPEs products are also considered to provide a first insight into the GPM effectiveness in ensuring TRMM continuity. The analysis is conducted over different geomorphic and meteorological regions of Pakistan while using 88 precipitations gauges as the reference. Results show a clear enhancement in precipitation estimates that were derived from the very last IMERG-v05 in comparison to its two previous versions IMERG-v03 and -v04. Interestingly, based on the considered statistical metrics, IMERG-v03 provides more consistent precipitation estimate than IMERG-v04, which should be considered as a transition IMERG version. As expected, GSMaP-v07 precipitation estimates are more accurate than the previous GSMaP-v06. However, the enhancement from the old to the new version is very low. More generally, the transition from TRMM to GPM is successful with an overall better performance of GPM based SPEs than TRMM ones. Finally, all of the considered SPEs have presented a strong spatial variability in terms of accuracy with none of them outperforming the others, for all of the gauges locations over the considered regions. to ensure the continuity of the TRMM mission. From the GPM mission, two new SPEs were made available: the Integrated Multi-Satellite Retrievals for GPM (IMERG) [14] and a new version of GSMaP product. Available at a 0.1 • and half-hourly and hourly temporal scales, respectively, they offer the opportunity of capturing finer local precipitation variations in space and time [15]. Due to their recent release, few studies report on GPM based SPEs.A first attempt was made by, [16] while comparing IMERG to its predecessor TMPA at the monthly timescale. The study highlighted the differences in both precipitation datasets, which vary according to surfaces and precipitations rates. Since then, numerous studies were dedicated to provide more insights into this discrepancy and highlighted the potential IMERG benefits over its predecessor TMPA at a more local scale. For example, in India, IMERG was found more accurate in the estimation of mean monsoon precipitation than TMPA [17]. In China, IMERG precipitation estimates were compared with the gauges observation at the national level considering daily [18] and monthly temporal scales [19], and a local level study reported on IMERG precipitation estimates over the Chinese Bei...

Validation of GPM IMERG V05 and V06 Precipitation Products over Iran

“…Zhao et al (2018) and Wei et al (2018b) showed that V03 outperforms V04 over China. Satgé et al (2018), who compared IPPs V03, V04, and V05 over Pakistan, indicated V04 works worse than V03. However, V05, with a real enhancement, estimates precipitation with more accuracy in comparison with V03 and V04.…”

“…Considering the high resolution of IPPs and significant uncertainties arising from interpolation of the daily data of 76 synoptic stations across Iran (due to the lowdensity of stations), we applied a point-to-pixel approach for evaluations in this study like many previous studies, for example, Xu et al (2017), Rivera et al (2018), Wei et al (2018a), and Satgé et al (2018). To assess the validity of IMERG products over Iran, we considered continuous validation metrics such as modified Kling-Gupta efficiency (KGE), relative bias (RBias), correlation coefficient (CC), and root-mean-square error (RMSE); as well as categorical validation metrics such as probability of detection (POD), false alarm ratio (FAR), critical success index (CSI), and Heidke skill score (HSS).…”

“…validation metrics, since the tiny precipitation events are not important from a meteorological and hydrological point of view, it is common to consider a threshold to eliminate their effect on the results of assessments. Therefore, the rain/no-rain threshold was assumed to be 1 mm day 21 , as reported by Alijanian et al (2017) and Satgé et al (2018). We also decomposed mean squared error (MSE) of IPPs to their systematic and random error components, following the method of AghaKouchak et al (2012).…”

A Preliminary Assessment of the Gauge-Adjusted Near-Real-Time GSMaP Precipitation Estimate over Mainland China

“…The gauge-calibrated product of standard GSMaP_MVK is GSMaP_Gauge, which adjusted by daily CPC gauge data. Many studies have assessed and compared the performances of GSMaP_Gauge over the last few years and have shown that GSMaP_Gauge is a satisfactory gauge-adjusted satellite precipitation estimation around the world, especially over East Asia [34][35][36][37][38].Recently, in the GSMaP project, the GSMaP_Gauge_NRT was produced by a GSMaP algorithm team, aiming to improve the accuracy of near-real-time product of GSMaP (i.e., GSMaP_NRT) and maintain its timeliness. Section 2.2 describes the calibration procedure of GSMaP_Gauge_NRT in detail.…”

Editorial for Special Issue “Remote Sensing of Precipitation”

“…Satgé et al [25] present an assessment of the potential benefits of the successive GPM-based SPEs product versions that include the Integrated Multi-Satellite Retrievals for GPM (IMERG) version 3 to 5 (-v03, -v04, -v05) and the Global Satellite Mapping of Precipitation (GSMaP) version 6 to 7 (-v06, -v07). The analysis is conducted over different geomorphic and meteorological regions of Pakistan while using 88 precipitation gauges as a reference.…”