Comparisons of rainrates from 3B42, IMERG (V03D) and Korean QPE
TMPA 3B42TMPA 3B42 files are avaliable from the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). These gridded estimates are on a 3-hour temporal resolution and a 0.25-degree by 0.25-degree spatial resolution in a global belt extending from 50S to 50N. The 3B42 estimates are produced in four stages:
(2) infrared precipitation estimates are created using the calibrated microwave precipitation;
(3) the microwave and IR estimates are combined;
(4) rescaling to monthly data is applied. Each precipitation field is best interpreted as the precipitation rate effective at the nominal observation time.
IMERGIntegrated Multi-Satellite Retrievals for GPM (IMERG) Algorithm is intended to intercalibrate, merge, and interpolate "all" satellite microwave precipitation estimates, together with microwave-calibrated infrared (IR) satellite estimates, precipitation gauge analyses, and potentially other precipitation estimators at fine time and space scales for the TRMM and GPM eras over the entire globe. The system is run several times for each observation time, first giving a quick estimate and successively providing better estimates as more data arrive. The final step uses monthly gauge data to create research-level products. Background information and references are provided to describe the context and the relation to other similar missions. Issues involved in understanding the accuracies obtained from the calculations are discussed. Throughout, a baseline Day-1 product is described, together with options and planned improvements that might be instituted before or after launch depending on maturity and project constraints. The IMERG gridded estimates are on a 30-minute temporal resolution and a 0.1-degree by 0.1-degree spatial resolution extending from 180W to 180E and 60S to 60N. For more information about IMERG, download IMERG_ATBD_V4.1.pdf Thanks to George Huffman and David T. Bolvin for providing nearly one-month (03-28 Jun 2012) pre-launch "test-version" of IMERG data and IMERG Early-Run, Late-Run, and Final-Run products.
Korean QPEKorea Meteorological Administration(KMA) has developed a Real-time ADjusted Radar-AWS (Automatic Weather Station) Rainrate (RAD-RAR) system using eleven radars over the South Korea. The Korean QPE data are on a 1-hour temporal resolution and a 1-km by 1-km spatial resolution extending from 119.883E to 136.316E and 29.1906N to 45.7572N. Thanks to Geunhyoerk Ryu at KMA for providing Korean QPE data for this study.
Comparisons among 3B42, IMERG and Korean QPEKorean QPE available: Jun 01 - Dec 31, 2012; Mar 01, 2014- Dec 31, 2016 (as of May 5, 2017).
IMERG Early-Run and Late-Run Products available: Apr 1, 2015 - present (V03); Mar 12, 2014 - present (V04A)
IMERG Final-Run Product available: Jun 03 - Jun 28, 2012 (pre-launch test-version); Mar 12, 2014 - Jan 31, 2016 (V03), Mar 12, 2014 - Nov31, 2016 (V04) (as of this update on Jan 6, 2017).
3B42 available: Jan 1, 1998 - Oct 31, 2016.
The comparisons are conducted over the area (124.5E-130.5E, 32.5N-39N) for Jun 2012 and Mar 2014- Jan 2016. At 3-hourly scale, 3B42, IMERG (Final Run) and Korean QPE data are used. At hourly scale, only IMERG and Korean QPE data are used as 3B42 is at 3-hour resolution.