Water Resource Associates


Since 2010, WRA has been actively using TRMM data for water resource and flood defence projects, particularly in areas of sparse data. David Plinston is leading this initiative and has further enhanced the TRMM-sys software and database configuration to provide continuous rainfall time-series and rainfall intensity-duration-frequency [IDF] curves for any point on the globe between the 50 degree latitudes. The software analyses TRMM rainfall by quarter degree grid cell for any duration between 3 and 72 hours for the 1998-2014 period, a record of 192 months of short-duration rainfall data.

This global database and software system can provide a rapid response to project requirements anywhere in the Earth’s tropical and sub-tropical regions. An IDF relationship can be derived or specific storm events can be investigated for any location with relative ease.

So far, the data have been used and tested by WRA in Sabah, Brunei, Sarawak, Indonesia, UAE, Yemen, Somaliland, Kenya and Angola.. The data have been validated by comparison of statistics with ground stations, and the software is undergoing further development.
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Comparison of Monthly Rainfall and CV at Two sites
TRMM data were acquired as part of the activities of NASA's Science Mission Directorate, and are archived and distributed by the Goddard Earth Sciences Data and Information Services Center
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TRMM Grid cells across a large river basin
The Tropical Rainfall Measuring Mission (TRMM) is a joint NASA-JAXA [Japanese] satellite mission to monitor tropical and subtropical precipitation and to estimate its associated latent heating. TRMM was launched in November 1997, and provides Real-Time Multi-Satellite Precipitation Analysis.

TRMM data represent an areal rainfall averaged across the grid cell, as opposed to a point-rainfall, measured at a rainfall station. The areal measure of rainfall in each cell varies with latitude, and grid-cells are 28 by 28 km at the equator, which represent an area of 784 km2. [http://pmm.nasa.gov/node/158]
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Distribution of TRMM rainfall across a river basin in four different rainfall events
TRMM data were acquired as part of the activities of NASA's Science Mission Directorate, and are archived and distributed by the Goddard Earth Sciences Data and Information Services Centre.

TRMMsys - Current program segments
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Blocks: Rectangular arrays of TRMM cells (current limiting size 40 x40 cells)
Locations: Individual cells eg raingauge locations (current limit 10 locations)
Sub-basins: Defined by array from GIS intersection of sub-basins with TRMM cells (current limit 10 sub-basins)
GRID: Ascii GRID files
TXT: Text file
IDF: Intensity-Duration-Frequency

GPM New Directions

The TRMM satellite ended data collection in April 2015 (see http://pmm.nasa.gov/trmm/mission-end ). Launched in November 1997, the TRMM satellite delivered a unique 17-year dataset of global tropical rainfall and lightning. The data collection started by TRMM continues with the joint NASA/JAXA Global Precipitation Measurement (GPM) mission, which launched in February 2014.

WRA is currently working on a systematic procedure for linking the TRMM data-set with the GPM data, and thereby providing a global data-set starting in 1998 and extending into the future over the working life of the new satellite.

GPM offers two options: the raw data (GPM V03E RT) and the calibrated data (GPM V03D). Historically, WRA has always used the TRMM data calibrated against reference ground stations. Thus I initially looked only at the calibrated GPM, which is always a month or two delayed as the calibration and adjustment is done monthly in arrears.

The GPM data have a higher resolution, available at 0.5 hourly intervals and with an aerial coverage of only 0.1 degree squares. The latitudinal range has also been extended to 60 degN - 60degS. However, the Mirador site continues to adopt the TRMM style coverage of 3-hourly over 0.5 degree squares by using some kind of spatial and temporal merging procedure, possibly part of the "imerge" process described by NASA. These merged data files are in HDF-EOS format and can be downloaded, but not directly as with the TRMM data, and is no longer available in binary format.

Initially at least, WRA work is focusing on the 3-hourly and 24-hour options so that it is possible to extend the original TRMM series. There could be benefits of also having access to the more detailed data provided by the GPM series, especially for short duration flood analyses, but the available data-set is still relatively short [two years].

New posts will be placed here as the processed GPM data-sets become available.
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