TRMM Level 1B Product Precipitation Radar (PR) Power 1B21

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TRMM Level 1B Product Precipitation Radar (PR) Power 1B21

Data Access:

1B21: http://disc.sci.gsfc.nasa.gov/data/datapool/TRMM_DP/01_Data_Products/01_Orbital/03_Pr_Power_1B_21/

Summary

This document provides basic information on 1B21, the TRMM Precipitation Radar (PR) Power data product.
The TRMM PR, the first of its kind in space, is an electronically scanning radar, operating at 13.8 GHz that measures the 3-D rainfall distribution over both land and ocean, and defines the layer depth of the precipitation.

The PR calibration algorithm (1B21) converts the counts of radar echoes and noise levels into engineering values (power) and outputs the radar echo power and noise power separately. The algorithm also detects and flags the range bin with return power that exceeds a pre-determined threshold value.

TRMM Satellite Operating Altitude Change

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.

Sponsor and Acknowledgement

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.

Future Updates

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.

Data Flow Description

PR Level 1A ==> 1B21 PR Power
The data flow of all products are shown in Satellite Algorithm Flow Diagram.

Data Set Description

Data Characteristics

TRMM 1B21 (PR) Data Characteristics
	Pre-boost (before 2001-08-07)	Post-boost (after 2001-08-24)
Temporal Coverage	Start Date: 1997-12-08 Stop Date: 2001-08-07	Start Date: 2001-08-24 Stop Date: -
Geographic Coverage	Latitude: 38°S - 38°N Longitude:180°W - 180°E	Latitude: 38°S - 38°N Longitude:180°W - 180°E
Temporal Resolution	About 91.5 minutes per orbit About 16 orbits per day More information about revisit frequency	About 92.5 minutes per orbit About 16 orbits per day More information about revisit frequency
Horizontal Resolution	4.3 km	5.0 km
Scan Characteristics	Swath Width: 215 km Rays/Scan: nray = 49 Scans/Second (SS): 1/0.6 Seconds/Orbit (SO): 5490 Average Scans/Orbit: nscan = SS*SO = 9150	Swath Width: 247 km Rays/Scan: nray = 49 Scans/Second (SS): 1/0.6 Seconds/Orbit (SO): 5550 Average Scans/Orbit: nscan = SS*SO= 9250
Average File Size	Compressed: ~66 MB Original: ~157 MB	Compressed: ~77 MB Original: ~158 MB
File Type	HDF	HDF

Data Format Structure

Further information on the contents and structure of the 1B21, PR Surface Cross Section product can be found in Volume 3 of the "File Specifications for TSDIS Products - Level 1" .

Data Format Structure for 1B21, PR Power
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
PR Cal Coef	Vdata Table	4	18	-	-	-	Calibration coefficients for the PR. The records consist of: Transmission coefficient (unitless, 1 record), Reception coefficient (unitless, 1 record), and FCIF I/O Characteristics (unitless, 16 records). Descriptions are TBD by NASDA.
Ray Header	Vdata Table	60	49	-	-	-	Information about each ray (angle bin) that is constant for every scan. The record number represents the angle bin number. Each record describes one ray and is defined in Ray Header Table.
Swath Structure	Char Attribute	5,000	-	-	-	-	Specification of the swath geometry
Scan Time	Vdata Table	8	nscan	-	-	-	Time associated with the scan, expressed as 8-byte float UTC second of the day.
Geolocation	Float SDS	4	2nraynscan	-	-	degree	Earth location of the center of the IFOV at the altitude of the earth ellipsoid. The first dimension is latitude and longitude, in that order. The next dimensions are numbers of pixels and scans.
Scan Status	Vdata Table	15	nscan	-	-	-	Status of each scan.
Navigation	Vdata Table	88	nscan	-	-	-	Spacecraft geocentric information
Powers	Vdata Table	6	nscan	-	-	-	Powers: Radar Transmission Power and Transmitted Pulse Width.
System Noise	Integer SDS	2	nray*nscan	100	-120 ~ -20	dBm	System Noise (dBm) is an average of the 4 measured system noise values. Missing data are given the value of -32,734.
System Noise Warning Flag	Integer SDS	1	nray*nscan	-	-	-	System Noise Warning Flag indicates possible contamination of lower window noise by high towers of rain. 1 means possible contamination; 0 means no possible contamination.
Minimum Echo Flag	Integer SDS	1	nray*nscan	-	-	-	Minimum Echo Flag indicates the presence of rain in the ray (angle bin).
Bin Storm Height	Integer SDS	2	2nraynscan	-	-	-	Bin Storm Height is Range Bin Number of the storm top.
Satellite Local Zenith Angle	Float SDS	4	nray*nscan	-	-	-	Angle, in degrees, between the local zenith and the beam's center line. The local (geodetic) zenith at the intersection of the ray and the earth ellipsoid is used.
Spacecraft Range	Integer SDS	4	nray*nscan	-	-	m	Distance (m) between the spacecraft and the center of the footprint of the beam on the earth ellipsoid.
Bin Start of Oversample	Integer SDS	2	229nscan	-	-	-	Bin Start of Oversample is the starting range bin number of the oversample (either surface or rain) data, counting from the top down.
Land/Ocean Flag	Integer SDS	2	nray*nscan	-	-	-	Land or ocean information. The values of the flag are: 0 = Water, 1 = Land, 2 = Coast, 3 = Water (w/large attenuation), 4 = Land/Coast (w/large attenuation).
Surface Detect Warning Flag	Integer SDS	2	nray*nscan	-	-	-	Definition TBD by NASDA.
Bin Surface Peak	Integer SDS	2	nray*nscan	-	-	-	Range bin number of the peak surface echo. This peak is determined by the post observation ground processing, not by the on board surface detection. The range bin number is defined in this volume in the section on Precipitation Radar, Instrument and Scan Geometry.
Bin Ellipsoid	Float SDS	2	nray*nscan	-	-	-	Range bin number of the earth ellipsoid. The range bin number is defined in this volume in the section on Precipitation Radar, Instrument and Scan Geometry. This field will not be used until product version #4 products are available. Until that time this field contains zero (0) and should be ignored.
Bin Clutter Free Bottom	Integer SDS	2	2nraynscan	-	-	-	Range bin number of the lowest clutter free bin. Clutter free bin numbers are given for clutter free certain and possible, respectively. The clutter free certain bin is always less than or equal to the clutter free possible bin number. This field will not be used until product version #4 products are available. Until that time this field contains zero (0) and should be ignored.
Bin DID Average	Integer SDS	2	nray*nscan	-	-	-	Mean range bin number of the DID surface elevation in a 5 km x 5 km box centered on the IFOV. The range bin number is defined in this volume in the section on Precipitation Radar, Instrument and Scan Geometry. This field will not be used until product version #4 products are available. Until that time this field contains zero (0) and should be ignored.
Bin DID Top	Integer SDS	2	2nraynscan	-	-	-	Range bin number of the maximum DID surface elevation in a box centered on the IFOV. The first dimension is the box size, with sizes of 5 km x 5 km and 11 km x 11 km. The range bin number is defined in this volume in the section on Precipitation Radar, Instrument and Scan Geometry. This field will not be used until product version #4 products are available. Until that time this field contains zero (0) and should be ignored.
Bin DID Bottom	Integer SDS	2	2nraynscan	-	-	-	Range bin number of the minimum DID surface elevation in a box centered on the IFOV. The first dimension is the box size, with sizes of 5 km x 5 km and 11 km x 11 km. The range bin number is defined in this volume in the section on Precipitation Radar, Instrument and Scan Geometry. This field will not be used until product version #4 products are available. Until that time this field contains zero (0) and should be ignored.
Normal Sample	Integer SDS	2	140nraynscan	100	-120 ~ -20	dBm	Return power (dBm) of the normal sample. Since each ray has a different size, the elements after the end of each ray are filled with a value of -32767. Other bins where data is not written due to a transmission, calibration, or other problem, including an entire scan of missing bins, have the value of -32734. The size of each ray is specified in Ray Header, with an accuracy of 0.9 dBm.
Surface Oversample	Integer SDS	2	529nscan	100	-120 ~ -20	dBm	Return power (dBm) of the surface echo oversample for the central 29 rays (rays #11-39), with an accuracy of 0.9 dBm. Bins where data is not written due to a transmission, calibration, or other problem, including an entire scan of missing bins, have the value of -32734. In the CrossTrack dimension, Offset = -10 and Increment = 1.
Rain Oversample	Integer SDS	2	2811nscan	100	-120 ~ -20	dBm	Return power (dBm) of the rain echo oversample for the central 11 rays (rays #20-30), with an accuracy of 0.9 dBm. Bins where data is not written due to a transmission, calibration, or other problem, including an entire scan of missing bins, have the value of -32734. In the CrossTrack dimension, Offset = -19 and Increment = 1.

Tools for Visualizing Data

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.

Sample Software

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.

Data Access Information

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 1B21 can be accessed and ordered using the Goddard DISC's TRMM Data Search and Order System at http://disc.sci.gsfc.nasa.gov/data/datapool/TRMM_DP/01_Data_Products/01_Orbital/03_Pr_Power_1B_21/ .

Points of Contact

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)

References

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 Navigation
Name	Format	Description
Spacecraft Geocentric Position [3]	3 X 4-byte float	The position (m) of the spacecraft in Geocentric Inertial Coordinates at the Scan mid-Time (i.e., time at the middle pixel/IFOV of the active scan period). The order of components is: x, y, and z. Geocentric Inertial Coordinates are also commonly known as Earth Centered Inertial coordinates. These coordinates will be True of Date (rather than Epoch 2000 which are also commonly used), as interpolated from the data in the Flight Dynamics Facility ephemeris files generated for TRMM.
Spacecraft Geocentric Velocity [3]	3 X 4-byte float	The velocity (ms ^-1) of the spacecraft in Geocentric Inertial Coordinates at the Scan mid-Time. The order of components is: x, y, and z.
Spacecraft Geodetic Latitude	4-byte float	The geodetic latitude (decimal degrees) of the spacecraft at the Scan mid-Time.
Spacecraft Geodetic Longitude	4-byte float	The geodetic longitude (decimal degrees) of the spacecraft at the Scan mid-Time. Range is -180 to 179.999999.
Spacecraft Geodetic Altitude	4-byte float	The altitude (m) of the spacecraft above the Earth Ellipsoid at the Scan mid-Time.
Spacecraft Attitude [3]	3 X 4-byte float	The satellite attitude Euler angles at the Scan mid-Time. The order of the components in the file is roll, pitch, and yaw. However, the angles are computed using a 3-2-1 Euler rotation sequence representing the rotation order yaw, pitch, and roll for the rotation from Orbital Coordinates to the spacecraft body coordinates. Orbital Coordinates represent an orthogonal triad in Geocentric Inertial Coordinates where the Z-axis is toward the geocentric nadir, the Y-axis is perpendicular to the spacecraft velocity opposite the orbit normal direction, and the X-axis is approximately in the velocity direction for a near circular orbit. Note this is geocentric, not geodetic, referenced, so that pitch and roll will have twice orbital frequency components due to the onboard control system following the oblate geodetic Earth horizon. Note also that the yaw value will show an orbital frequency component relative to the Earth fixed ground track due to the Earth rotation relative to inertial coordinates.
Sensor Orientation Matrix [3 X 3]	3 X 3 X 4-byte float	The rotation matrix from the instrument coordinate frame to Geocentric Inertial Coordinates at the Scan mid-Time.
Greenwich Hour Angle	4-byte float	The rotation angle (degrees) from Geocentric Inertial Coordinates to Earth Fixed Coordinates.

TRMM PR Scan Status
Name	Format	Values	Description
Missing	1-byte integer	Value and meaning	Indicates whether information is contained in the scan.
Validity	1-byte integer	Bit and meaning	A summary of status modes.
QAC	1-byte integer	0: No decoding error occurred.	The Quality and Accounting Capsule of the Science packet as it appears in Level-0 data.
Geolocation Quality	1-byte integer	Bit and Meaning	A summary of geolocation quality in the scan.
Data Quality	1-byte integer	Bit and Meaning	A summary of data quality in the scan.
Current Spacecraft Orientation	1-byte integer	Value and Meaning	Current spacecraft orientation.
Current ACS Mode	1-byte integer	Value and Meaning	Current ACS mode.
Yaw Update Status	1-byte integer	0: Inaccurate 1: Indeterminate 2: Accurate	Yaw update status.
PR Mode	1-byte integer	1: Observation Mode 2: Other Mode	PR mode.
PR Status 1	1-byte integer	0: Normal 1: A little questionable	A warning for scan data. This field is used only for NASDA's data analysis.
PR Status 2	1-byte integer	0: Not initialized 1: Initialized	Initialization in Onboard Surface Algorithm.
Fractional Orbital Number	4-byte float		The orbit number and fractional part of the orbit at Scan Time. The orbit fraction part is calculated as: (Time-Orbit Start Time)/(Orbit End Time-Orbit Start Time)

Value and Meaning of Missing
Value	Meaning
0	Scan data elements contains information
1	Scan was missing in the telemetry data
2	Scan data contains no elements with rain

Bit and Meaning of Validity
Bit	Meaning if bit=1
0	Spare (always 0)
1	Non routine spacecraft orientation (2 or 3)
2	Non routine ACS mode (other than 4)
3	Non routine yaw update status (0 or 1)
4	Non routine instrument status (other than 1)
5	Non routine QAC (non-zero)
6	Spare (always 0)
7	Spare (always 0)

Bit and Meaning of Geolocation Quality
Bit	Meaning if bit=1 for Non-routine Situation	Routine Situation
0	Latitude limit error	If all status modes are routine, all bits in Validity = 0. Routine means that scan data has been measured in the normal operational situation as far as the status modes are concerned. Validity does not assess data or geolocation quality. Validity is broken into 8 bit flags. Each bit=0 if the status is routine but the bit = 1 if the status is not routine. Bit 0 is the least significant bit (i.e., if bit i=1 and other bits = 0, the unsigned integer value is 2**i).
1	Geolocation discontinuity
2	Attitude change rate limit error
3	Attitude limit error
4	Satellite undergoing maneuvers
5	Using predictive orbit data
6	Geolocation calculation error
7	not used

Bit and Meaning of Data Quality
Bit	Meaning if bit=1	Note
0	Missing	Unless this is 0 (normal), the scan data is meaningless to higher processing. Bit 0 is the least significant bit (i.e., if bit i=1 and other bit = 0, the unsigned integer value is 2**i).
5	Geolocation quality is not normal
6	Validity is not normal

Value and Meaning of Current Spacecraft Orientation
Value	Meaning
0	+x forward
1	-x forward
2	-y forward
3	Inertial -- CERES Calibration
4	Unknown Orientation

Value and Meaning of Current ACS Mode
Value	Meaning
0	Standby
1	Sun Acquire
2	Earth Acquire
3	Yaw Acquire
4	Nominal
5	Yaw Maneuver
6	Delta-H (Thruster)
7	Delta-V (Thruster)
8	CERES Calibration

PR Power Ray Header
Name	Format	Description
Ray Start	2-byte integer	Starting range bin number of Normal sample
Ray Size	2-byte integer	Number of Normal samples in the ray
Angle	4-byte float	Angle (degrees) of the ray from nadir. The sign of the angle is consistent with the sensor y-axis, i.e., the angle is positive to the right of the direction of travel if the spacecraft is in normal mode.
Starting Bin Distance	4-byte float	Distance (m) between the satellite and the starting bin number of the Normal sample for the ray
Rain Threshold 1	4-byte float	Threshold used in minimum echo test (unitless). Value set by NASDA
Rain Threshold 2	4-byte float	Threshold used in minimum echo test (unitless). Value set by NASDA
Transmitter Antenna Gain	4-byte float	Transmitted radar antenna effectiveness (dB)
Receiver Antenna Gain	4-byte float	Received radar antenna effectiveness (dB)
One-way 3dB Along-track Beamwidth	4-byte float	Radar beamwidth (radians) at the point transmitted power reaches one half of peak power in the along-track direction.
One-way 3dB Cross-track Beamwidth	4-byte float	Radar beamwidth (radians) at the point transmitted power reaches one half of peak power along the cross-track.
Equivalent wavelength	4-byte float	Equivalent wavelength (m).
Radar Constant	4-byte float	Radar constant dC (units are dB), which relates Received Power to Radar Reflectivity. dC depends on angle.
PR Internal delayed time	4-byte float	The time (seconds) between when echo returns at antenna and when echo is recorded in onboard processor.
Range Bin Size	4-byte float	The vertical resolution of Normal sample bin (250 m).
Logarithmic Averaging Offset	4-byte float	The offset value (dB) between logarithmic average and normal average (+2.507dB).
Mainlobe Clutter Edge	1-byte integer	Absolute value of the difference in Range Bin Numbers between the detected surface and the edge of the clutter from the mainlobe.
Sidelobe Clutter Range [3]	3 X 1-byte integer	Absolute value of the difference in Range Bin Numbers between the detected surface and the clutter position from the sidelobe. A zero means no clutter indicated in this field since less than 3 bins contained significant clutter.

PR Powers
Name	Format	Description
Radar Transmission Power	2-byte Integer	Total (sum) power of 128 SSPA elements corrected with SSPA temperature in orbit, based on temperature test data of SSPA transmission power. The units are dBm * 100. For this variable, the TSDIS Toolkit does not provide scaling.
Transmitted Pulse Width	4-byte float	Transmitted pulse width (s) corrected with FCIF temperature in orbit, based on temperature test data of FCIF.

Minimum Echo Flag
Value	Mean
0	no rain
10	rain possible
11	rain possible (Echo greater than rain threshold #1 in clutter range)
12	rain possible (Echo greater than rain threshold #2 in clutter range)
20	rain certain

1B21 Bin Storm Height Description

Bin Storm Height is Range Bin Number of the storm top.
The first dimension is threshold, with values of possible rain threshold and 
certain rain threshold in that order. The Bin Storm Heights are generated in 
the procedure to determine the Minimum Echo Flag. The Bin Storm Height is the
top range bin of the portion of consecutive range bins that flagged the ray as 
rain possible or rain certain. The range bin number is defined in this volume 
in the section on Precipitation Radar, Instrument and Scan Geometry.

1B21 Bin Start of Oversample Description

The first dimension is the Bin Start of Oversample and Surface Tracker Status. 
The second dimension is the ray. The number of rays is 29 because this 
information only applies to the rays that have oversample data (rays #11 to #39). 
The third dimension is the scan. 
The Surface Tracker Status has the value of 0 (Lock) or 1 (Unlock), where Lock 
means that 
(1) the on board surface detection detected the surface and 
(2) the surface detected later by processing on the ground fell within the 
oversample bins. 
Unlock means that Lock was not achieved. The range bin number is defined in 
this volume in the section on Precipitation Radar, Instrument and Scan Geometry.

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.

NASA Official: Steve Kempler
Website Curator: Stephen W Berrick

Last updated: April 14, 2008 15:54:47 GMT

Additional Features

TRMM Level 1B Product Precipitation Radar (PR) Power 1B21

Data Access:

Contents:

Appendix