Data Access for
3B31:
TRMM Monthly Combined Rainfall
Contents:
[Skip Contents]
- Summary
- TRMM Satellite Operating Altitude
Change
- Sponsor and
Acknowledgement
- Future Updates
- Data Flow Description
- Data Set Description
-
- Tools for Visualizing Data
-
- Sample Software
-
- Data Access
- Points of Contact
- References
This document provides basic information on 3B31, TRMM Monthly 5 x 5 Degree
Combined Rainfall Data. The purpose of 3B31 is to compare and accumulate the
instantaneous rainfall products from the TMI (2A12) and Combined (2B31) algorithms.
This is done because the combined algorithm should, in principle, produce better
rainfall estimates than would the TMI alone. Its swath, however, is only 220 km
compared to the 760 km swath of the TMI. Thus, for monthly accumulations, the best
possible solution was thought to be the use of the TMI product (for sampling), but
normalized by its ratio to 2B31. 3B31 contains these accumulations and ratio. The
algorithm also provides the ratio rain water contents for 14 vertical layers as
well.
Output data of 2A12 and 2B31 are input to the 3B31 and then accumulated for
each month at 0.5 grid elements. Monthly surface rainfall totals are derived by
multiplying the mean rainfall rate by the total number of hours in each month.
Because the rain water content profile of 2A12 and rain rate profile of 2B31 are
output at different vertical resolutions, averaging the outputs of 2B-31 over
several radar range gates to match the 14 layers of 2A12 is necessary. Also, the
rain rate (mm/hr) at each radar gate in 2B-31 is converted into rain water content
(g/m3) to match that in 2A-12. The relationship between rain rate and rain water
content can be found in Haddad et al., (1996).
The average operating altitude for TRMM was changed from 350 to 403 km
during the period of August 7-24, 2001. This orbit boost maneuver
extended the mission life significantly. All post-boost data products had
been released by the TRMM Science Project, as of early December 2001. All
TRMM data products (post- and pre-boost) are available via the TRMM data
search-and-order system at http://disc.sci.gsfc.nasa.gov/data/datapool/TRMM_DP/.
The time period before August 7, 2001 is referred to as
pre-boost, and the time period after August 24, 2001 is
referred to as post-boost.
The characteristics of the three rain instruments for pre- and post-boost
are shown in following table:
| Characteristics of TRMM Instruments |
| |
Swath Width (km) |
Ground Resolution (km) |
| Pre-boost |
Post-boost |
Pre-boost |
Post-boost |
| VIRS |
720 |
833 |
2.2 |
2.4 |
| TMI |
760 |
878 |
4.4* |
5.1* |
| PR |
215 |
247 |
4.3 |
5.0 |
| * Ground resolutions of TMI
are those at 85.5 GHz (highest resolution). |
The pre- and post-boost characteristics of TRMM data are different; their
details are listed in the Data Characteristics table for each orbital
product. Some caveats associated with post-boost TRMM Precipitation Radar
(PR) products have been released by the PR algorithm scientists and are
available at
ftp://disc2.nascom.nasa.gov/data/TRMM/Documentation/TRMM_Boost_PR_Caveats.html.
For TRMM version 5 products, the post-boost filenames all have a "5A"
in the product version part of the name, compared with a "5" in pre-boost
filenames. For version 6, the filenames have no differences for pre-boost
and post-boost.
The distribution of this data set is funded by NASA's Earth Science Enterprise
(ESE). The data are not copyrighted; however, we request
that when you publish data or results using these data, please
acknowledge as follows:
The data used in this study were acquired as part of the Tropical
Rainfall Measuring Mission (TRMM). The algorithms were developed by the
TRMM Science Team. The data were processed by the TRMM Science Data and
Information System (TSDIS) and the TRMM Office; they are archived and
distributed by the Goddard Distributed Active Archive Center. TRMM is
an international project jointly sponsored by the Japan National Space
Development Agency (NASDA) and the U.S. National Aeronautics and Space
Administration (NASA) Office of Earth Sciences.
Please send a copy of your publication to Help Desk, Goddard
DAAC, Code 610.2, NASA GSFC, Greenbelt, MD 20771 or email the
reference of your publication to help-disc@listserv.gsfc.nasa.gov.
It is expected that some of the TRMM algorithms will be refined or
improved as new measurements are gathered and analyzed by the TRMM
Science Team. The data products are expected to be periodically
reprocessed by TSDIS in order to provide the scientific and other user
communities with the most current and best available rainfall products.
The exact reprocessing schedule will be set by a team designated by the
TRMM Project Scientist. This document will be updated in coordination
with the TRMM reprocessing schedule and whenever appropriate as
determined by the Goddard DAAC Hydrology Data Support Team.
The data flow of all products are shown in Satellite Algorithm Flow Diagram.
Data Characteristics
| Temporal Coverage |
Start Date: 1997-12-08; Stop Date: - |
| Geographic Coverage |
Latitude: 40°S - 40°N; Longitude:180°W - 180°E |
| Temporal Resolution |
Monthly |
| Horizontal Resolution |
5° x 5°; nlat = 16, nlon = 72 |
| Average File Size |
Compressed: ~380 KB; Original: ~440 KB |
| File Type |
HDF |
Data Format Structure
The following table summarizes the contents and structure of the TRMM Monthly 5 x
5 Degree Combined Rainfall Data (3B31) product. Further information can be found in
Volume 4 of the "File Specifications for TSDIS Products - Level 2 and Level 3" .
| Data Format Structure for
3B31, TRMM Monthly 5 x 5 Degree Combined Rainfall Data |
| Name |
Type |
Record
Size
(byte) |
Dim Size
(# of Records) |
Scaled
by |
Range |
Unit |
Description |
| ECS Core Metadata |
Char Attribute |
10,000 |
- |
- |
- |
- |
ECS Core Metadata |
| PS Metadata |
Char Attribute |
10,000 |
- |
- |
- |
- |
Product Specific Metadata |
| GridStructure |
Char Attribute |
5,000 |
- |
- |
- |
- |
GridStructure gives the specification of the geometry of the grids. |
| sfcrainTMI |
Float SDS |
4 |
nlat*nlon |
- |
0.0 ~ 3000.0 |
mm |
Surface rain from 2A12 accumulated in each 5° x 5° box |
| convect Rain |
Float SDS |
4 |
nlat*nlon |
- |
0.0 ~ 3000.0 |
mm |
Convective surface rain from 2A12 accumulated in each 5° x 5°
box |
| cloudWater |
Float SDS |
4 |
nlat*nlon*nlayer |
- |
0.0 ~ 10.0 |
g m-3 |
Monthly mean cloud water from 2A12 at each vertical layer in each 5° x
5° box |
| rainWaterTMI |
Float SDS |
4 |
nlat*nlon*nlayer |
- |
0.0 ~ 10.0 |
g m-3 |
Monthly mean rain water from 2A12 at each vertical layer in each 5° x
5° box |
| cloudIce |
Float SDS |
4 |
nlat*nlon*nlayer |
- |
0.0 ~ 10.0 |
g m-3 |
Monthly mean cloud ice from 2A12 at each vertical layer in each 5° x
5° box |
| graupel |
Float SDS |
4 |
nlat*nlon*nlayer |
- |
0.0 ~ 10.0 |
g m-3 |
Monthly mean graupel from 2A12 at each vertical layer in each 5° x
5° box |
| latentHeat |
Float SDS |
4 |
nlat*nlon*nlayer |
- |
-256.0 ~ 256.0 |
deg hr-1 |
Monthly mean latent heating from 2A12 at each vertical layer in each 5°
x 5° box |
| sfcrainCOMB |
Float SDS |
4 |
nlat*nlon |
- |
0.0 ~ 3000.0 |
mm |
Surface rain from 2B31 accumulated in each 5° x 5° box |
| rainWaterCOMB |
Float SDS |
4 |
nlat*nlon*nlayer |
- |
0.0 ~ 10.0 |
g m-3 |
Rain water at each vertical layer from 2B31 accumulated in each 5° x
5° box |
| sfcrainTMIoverlap |
Float SDS |
4 |
nlat*nlon |
- |
0.0 ~ 3000.0 |
mm |
Surface rain from 2A12 where 2A12 and 2B31 overlap accumulated in each
5° x 5° box |
| convectRainoverlap |
Float SDS |
4 |
nlat*nlon |
- |
0.0 ~ 3000.0 |
mm |
Convective surface rain from 2A12 where 2A12 and 2B31 overlap accumulated
in each 5° x 5° box |
| sfcrainCOMBoverlap |
Float SDS |
4 |
nlat*nlon |
- |
0.0 ~ 3000.0 |
mm |
Surface rain from 2B31 where 2A12 and 2B31 overlap accumulated in each
5° x 5° box |
| surfAdjRatio |
Float SDS |
4 |
nlat*nlon |
- |
- |
- |
The ratio of 2B31 to 2A12 surface rainfall, calculated from the swath
overlap region for each 5° x 5° box |
| surfAdjRatiooverlap |
Float SDS |
4 |
nlat*nlon |
- |
- |
- |
The ratio of 2B31 to 2A12 surface rainfall, calculated from the swath
overlap region for each 5° x 5° box |
Parameters used in above table:
| Name |
Value |
Definition |
| nlat |
16 |
the number of 5° grid intervals of latitude from 40° N to 40° S |
| nlon |
72 |
the number of 5° grid intervals of longitude from 180° W to
180° E |
| nlayer |
14 |
the number of profiling layers |
| 14
Vertical Layers |
| Layer Index |
Layer Height |
| 1 |
surface - 0.5 km |
| 2 |
0.5 - 1.0 km |
| 3 |
1.0 - 1.5 km |
| 4 |
1.5 - 2.0 km |
| 5 |
2.0 - 2.5 km |
| 6 |
2.5 - 3.0 km |
| 7 |
3.0 - 3.5 km |
| 8 |
3.5 - 4.0 km |
| 9 |
4.0 - 5.0 km |
| 10 |
5.0 - 6.0 km |
| 11 |
6.0 - 8.0 km |
| 12 |
8.0 -10.0 km |
| 13 |
10.0 -14.0 km |
| 14 |
14.0 - 18.0 km |
The Goddard DAAC provides the following tools to help users visualize
data in the Hierarchical Data Format (HDF).
TSDIS Orbit Viewer
The TSDIS Orbit Viewer is a menu-driven graphical interface for
dynamically generating images from TRMM HDF files. The viewer can
display, at the full instrument resolution, TRMM satellite, Ground
Validation, browse, and Coincidence Subsetted Intermediate (CSI)
products, as well as other derived products.
The software runs on Microsoft Windows and UNIX.
The source code and installation instructions for the Orbit Viewer are
available from the Goddard DAAC's TRMM ftp site (ftp://disc2.nascom.nasa.gov/software/trmm_software/Orbit_Viewer).
Please note: TSDIS can provide technical support for
the Orbit Viewer only to certain members of the TRMM Science Team. Other
users should contact the DAAC's Hydrology Data Support
Team (hydrology-disc@listserv.gsfc.nasa.gov).
EOSView
EOSView is a standalone X-based data visualization tool that displays
HDF files. It can be used to view data ordered from the Goddard DAAC. In
addition, it provides a secondary mechanism for previewing browse files
before ordering data. (The primary mechanism is the preview feature of
the TRMM Data
Search and Order System.) EOSView serves as a file verification tool.
The contents of HDF files are displayed and individual objects can be
selected for display. Displayable objects include raster images, data
sets in tables, pseudocolor images of data sets, attributes, and
annotations. Simple animations can be performed for a file with multiple
raster images.
A unique interface has been provided for handling HDF-EOS data
structures. The Swath/Point/Grid interface uses only HDF-EOS library
calls. EOSView users will not see the underlying HDF structures but will
be prompted for what parts of the HDF-EOS object they wish to view. The
EOSView requires at least 4 megabytes of memory and a larger than 24-bit
graphics board.
Download Instructions for the
Software:
-
These tools can be downloaded via anonymous ftp using a command
line ftp client, available on all Unix machines.
The source code, installation instructions, and documentation for
EOSView and Orbit Viewer are available from the Goddard DAAC's
TRMM ftp site
(ftp://disc2.nascom.nasa.gov/software/trmm_software).
The following files should be downloaded for EOSView:
- EOSView (executable)
- eosview.csc (help)
- eosview.uid (user interface description file)
- eosview.dat (IDL commands file)
- How to start EOSView:
-
Start EOSView by typing 'EOSView' at the command prompt. The
current working directory must contain the four EOSView files.
TRMM HDF Data File Read Software
The Goddard DAAC Hydrology Team has developed the TRMM HDF Data File
Read Software, first released in February 1999. The software reads TRMM
HDF data files and writes out to flat binary files. The software has been
tested with most of the TRMM standard products, as well as with some
derived subset products. Both C and Fortran versions are available from
ftp://disc2.nascom.nasa.gov/software/trmm_software/Read_HDF/.
TSDIS Toolkit
TSDIS developed the TSDIS Science Algorithm Toolkit to assist the TRMM
Science Team's algorithm developers. The toolkit provides a library of
commonly used routines, constants, and macros. It also allows seamless
integration of TRMM algorithms into the TSDIS environment.
The toolkit provides routines for reading and writing data to and from
the HDF files; routines are provided for Levels 1-3 products and for both
satellite and GV. Each of the routines in the toolkit are callable in
either C or Fortran. The toolkit also includes routines for reading
land/sea data and topographical data.
The Goddard DAAC maintains archives of all TRMM data products and many
other Hydrology data sets. The archived data can be ordered via FTP network transfer.
| Data Volume Limits By Media |
| CDR |
FTP-Pull |
| Min. |
Max. |
Min. |
Max. |
Min. |
Max. |
Min. |
Max. |
| 0 GB |
3.17 GB |
0 GB |
2 GB |
1 GB |
50 GB |
1 GB |
50 GB |
TRMM 3B31 can be accessed and ordered from the Goddard DAAC's TRMM Data
Search and Order System at
http://disc.sci.gsfc.nasa.gov/data/datapool/TRMM_DP/01_Data_Products/02_Gridded/04_Monthly_Combined_Rain_3B_31/
.
- For information about or assistance in using any Goddard DAAC data,
contact the DAAC Help Desk at:
-
GES Distributed Active Archive Center (DAAC)
Code 610.2
NASA Goddard Space Flight Center
Greenbelt, Maryland 20771
Email: help-disc@listserv.gsfc.nasa.gov.
301-614-5224 (voice)
301-614-5268 (fax)
Tropical Rainfall Measuring Mission Science Data and Information System
(TSDIS) Interface Control Specification Between the TSDIS and the TSDIS
Science User (TSU)
Volume 3: File Specifications for TRMM Products - Level 1.
Volume 4: File Specifications for TRMM Products - Level 2 and Level 3.
Appendix
TRMM Frequency Analysis Result*
(Number of visits for a 30-day period) |
| Radar Site |
Latitude (°) |
PR (~215 km) |
VIRS (~720 km) |
TMI (~760 km) |
| Kwajalein Atoll |
8.72 |
9 |
29 |
31 |
| Darwin, Australia |
-12.45 |
10 |
31 |
32 |
| Guam |
13.50 |
9 |
32 |
32 |
| Om Koi, Thailand |
17.80 |
9 |
31 |
33 |
| Kauai, HI |
22.17 |
13 |
36 |
38 |
| Sao Paolo, Brazil |
-23.58 |
12 |
41 |
42 |
| Taiwan |
23.92 |
11 |
40 |
42 |
| Key West, FL |
24.67 |
13 |
41 |
42 |
| Miami, FL |
25.75 |
13 |
45 |
45 |
| Brownsville, TX |
25.97 |
13 |
43 |
47 |
| Corpus Christi, TX |
27.85 |
15 |
49 |
51 |
| Tampa, FL |
28.03 |
13 |
51 |
52 |
| Melbourne, FL |
28.10 |
15 |
49 |
53 |
| San Antonio, TX |
29.53 |
16 |
57 |
59 |
| Jacksonville, FL |
30.33 |
19 |
63 |
65 |
| Texas A&M, TX |
30.58 |
18 |
67 |
68 |
| Jerusalem, Israel |
31.87 |
20 |
92 |
102 |
PR:
Precipitation Radar
VIRS: Visible/InfraRed Scanner
TMI: TRMM Microwave Imager
* This analysis result was derived based on TRMM
pre-boost orbital information.
The revisit frequency should be slightly higher after TRMM boost
(August 24, 2001).
If you have questions regarding this table, please send email to:
helpdesk@tsdis02.nascom.nasa.gov. |
|
Atmos Composition
