1 University of Washington TRMM-PR Dataset

University of Washington TRMM Data Set

Regions AFC CIO EPO H01 H02 H03 H04 H05 H06 H07 H08 MSA SAM SAS TRA USA WMP WPO


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General Information

This website provides access to the database of the sixteen year University of Washington study of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) datasets. The data, methods and analysis are described in the review paper by Houze, Rasmussen, Zuluaga, and Brodzik (2015). The months of the database upon which the paper is based (December/January/February and June/July/August) are currently available. The remaining months will be gradually filled in.

The products in this data base are derived from the 2A23, 2A25 and 2H25 TRMM-PR version 7 orbital data products that are stored in HDF format in the Goddard Earth Sciences Data and Information Services Center (GES DISC).

Regions

The data are stored by regions of the globe, represented by the boxes in the map above. By clicking inside a box on the map, the user will go to the page containing the analysis products for that selected region. One can accomplish the same thing by going here and clicking on the region of interest.

Types of Data Products

The NASA PR products 2A23, 2A25 and 2H25 are provided in bins along the slant range of the antenna beam. In the University of Washington database, these data in radar coordinates are geolocated and interpolated into a three-dimensional Cartesian grid and stored for analysis. From this dataset it is possible to identify structures of reflectivity echoes that satisfy certain criteria. Six types of echo objects are identified: detectable rain areas (DRA), isolated shallow echoes (ISE), deep convective cores (DCC), wide convective cores (WCC), deep-wide convective cores (DWC), and broad stratiform rain areas (BSR).

For all the classifications except DRA, the calculations are based on two different sets of thresholds - strong (str) and moderate (mod). Each object identified by these criteria is provided in netcdf format in both gridded (dimensioned by latitude and longitude) and tabular (dimensioned by instance or case) form. These gridded and tablular netcdf files contain information of the monthly climatology and individual properties of the identified echo objects. So, for example, the broad stratiform data from January of 2000 is contained in 4 files - strong thresholds and gridded, strong thresholds and tabular, moderate thresholds and gridded, and moderate thresholds and tabular.

The following paragraphs describe the information available from this archive.

Interpolated Data Our echo feature products (DRA, SHI, DCC, WCC, DWC and BSR) and our corrected reflectivity and latent heating fields are based on an interpolated dataset that we produce from the TRMM archived data identified as 2A25 (specifially, the sub-product, attenuation corrected reflectivity) and 2H25 (latent heating). The TRMM archive provides these data in range bins along the slant range of the radar beam, i.e. in "radar coordinates." For each of the above-described regions, the 2A25 and 2H25 data in each range bin are first geolocated and then interpolated into a regular three-dimensional Cartesian grid. The interpolated grid size is 0.05° (approximately 5 km) in the horizontal at 80 vertical levels (separated by 0.25 km) for the 2A25 reflectivity factor, and 19 levels (separated by 0.5 km for the first three levels and 1 km thereafter) for 2H25 latent heating. We remapped all data from 1998 to 2013 with the same horizontal resolution despite the change in orbital altitude of the TRMM satellite from 350 to 402 km in 2001, which changed the PR pixel size from 4.3 to about 5 km. Details of the methods applied for correcting the geolocation and the interpolation of the datasets can be found in Houze et al. (2007)

Additionally, nearest neighbor interpolation is used to re-grid the 2A25 Near Surface Rain and the 2A23 Rain Type products corresponding to the selected areas into a two-dimensional 0.05° grid. The interpolated netcdf files contain all of this information with appropriate meta-data containing accurate descriptions of the stored variables. Note that the files contain two versions of the interpolated 2A23 Rain Type variable. One contains the original 2A23 values (ranging from 100 to 313 and including values of -88 for no rain and -999 for missing data). The other has a simplified version of the categories assigning values of (1) for stratiform, (2) for convective, and (3) for other.

Radar classified structures

This database contains information on six types of radar echo features.

File Naming Convention

The file naming convention is consistent throughout the website. The files are stored in directories first by region and then by data type.

For the interpolated data, the convention is: [version]_[orbit].[yyyymmdd].[hhmmss]_region.nc where

For the classified radar echo objects, the convention is: [version]_[classification]_[threshold]_[type]_[yyyymm]_[region].nc. where

So a typical filename might look like this - 'TPR7_uw1_BSR_str_tab_200012_SAM.nc'. This file would contain broad stratiform (BSR) data based on strong (str) thresholds in 'tabular' format (tab) for December of 2000 for the South America (SAM) region.

DRA is a special case since we do not use different thresholds. In that instance, threshold is set to 'xxx'.

Overlapping

Since our analyses started as a series of regional studies which eventually spanned most of the globe, the data is meant to overlap at the edges of all the global regions. It is suggested that if a user needs to combine information from two or more regions for a singular analysis, a careful 'stitching' of the data must be accomplished to avoid identifying overlapped echo elements multiple times.


References

Houze, R. A., Jr., D. C. Wilton, and B. F. Smull, 2007: Monsoon convection in the Himalayan region as seen by the TRMM Precipitation Radar. Quart. J. Roy. Meteor. Soc., 133, 1389-1411.

Houze, R. A., Jr., K. L. Rasmussen, M. D. Zuluaga, and S. R. Brodzik, 2015: The variable nature of convection in the tropics and subtropics: A legacy of 16 years of the Tropical Rainfall Measuring Mission (TRMM) satellite. Rev. Geophys., in revision.

Note of Appreciation

Erich Stocker of NASA/Goddard Spaceflight Center provided invaluable help with the processing of the data and products provided via this website.

Citation to be used for data and products obtained from this site

In all publications and presentations based on the information provided via this website, please acknowledge the University of Washington with a statement like this: "Data for this study comes from the University of Washington TRMM Data Set which was obtained from http:// trmm.atmos.washington.edu".


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