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NMQ: National Mosaic and Multi-Sensor QPE

Comparisons of rainrates from 3B42, IMERG and MRMS

3B42

TMPA 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:
    (1) the microwave precipitation estimates are calibrated and combined;
    (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.
Click here to download 3B42_web-description.doc (Word.Document) by algorithm developer Dr. George Huffman.

IMERG

Integrated 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 90S to 90N.

For more information about IMERG, downlad IMERG_ATBD_V4.4.pdf

Thanks to George Huffman and David T. Bolvin for providing the pre-launch "test-version" of IMERG data (03-28 Jun 2012) and IMERG Final Run research product (V03D, from Apr 2014).

Comparisons with MRMS

The comparisons are conducted over the CONUS (20N-50N, 125W-65W) using 3B42, IMERG and MRMS data.

Last updated on 23 Sep 2016, and checked again on 07 Nov 2016,
IMERG available: 03 Jun 2012 - 28 Jun 2012; 01 Apr 2014 - 31 Jan 2016.
3B42 available: 01 Jan 1998 - 31 Aug 2016.

  • Area-averaged daily rainfall
    All data (rain and no rain) from each product at its native resolution (MRMS: 0.01o,1h; 3B42: 0.25o, 3h; IMERG: 0.1o, 0.5h) are accumulated to daily rainfall, and resampled to 3B42's resolution ( 0.25o, 3h), then averaged over all matched 0.25o pixels.
    The daily rainfall cutoff time is 2300Z for MRMS, 2230Z for 3B42 and IMERG. There is a 30-minute offset.

  • Scatter plot for area-averaged 3-hourly rainrates (RQI=100)

  • PDF by 3-hourly rain occurrence and volume for different rain and RQI thresholds


  • Daily rainfall [mm] contours
    Daily rainfall for each product is accumulated from its native temporal resolutions (1h for MRMS, 3h for 3B42, 0.5h for IMERG) at 0.25o spatial resolution. 0- and non-0 rain rates are all included.
    The daily rainfall cutoff time is 2300Z for MRMS, 2230Z for 3B42 and IMERG. There is a 30-minute offset.

  • 3-hourly rainrate [mm/h] contours
    Three-hourly rainrate for each product is accumulated from its native temporal resolutions (1h for MRMS, 3h for 3B42, 0.5h for IMERG) at 0.25o spatial resolution. 0- and non-0 rain rates are all included.
    The 3-hourly rainrate cutoff time is 0200, 0500,..., 2300Z for MRMS, 0130, 0430, ..., 2230Z for 3B42 and IMERG. There is a 30-minute offset.


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