Introduction to TRMM Real-Time System
Contents
What is the TRMM Real-time System
Contact Information
Obtaining or Changing Approval
Data Access Overview
What is the TRMM Real-time System
All TRMM data become available to the general science community on September 1,1998
Generally, standard TRMM products are available from the EOS Goddard
Data and Information Services Center (DISC) within 72 hours of their collection. Any user who
establishes an account with the DISC can receive the standard TRMM products.
In order to support users who wanted more timely TRMM data to determine its
usefulness in areas such as modeling, weather monitoring, disaster monitoring, etc., the TRMM
science team authorized the establishment of a real-time processing and distribution
of TRMM data. The goal is to have data available for retrieval within 3 hours of collection
of the oldest byte in the orbit. This system is obviously near real-time rather than real-time as
the data is recorded on the spacecraft and downloaded only once every 90 minutes or so. This
means that the oldest data in any download stream is already 90 minutes old before any processing
is performed. An additional 90 minutes is allocated to complete all levels of processing.
Generally, processing is completed well before the 90 minute requirement.
The products produced by the real-time system are actually parameter subsets of the standard
TRMM products. Generally, only surface rain parameters were retained from the standard
TRMM products. To achieve the time requirements the predictive ephemeris rather than
the definitive ephemeris must be used in geolocating the data. This sometimes leads to slight
geolocation errors. The specification and descriptions of the real-time products can be obtained from
other areas of this document. Each product contains data for roughly a TRMM orbit.
A major effort was made to reduce the size of near real-time so that data could more easily be
electronically retrieved. TRMM real-time data is only available via ftp from the TRMM real-time server.
All products are stored in compressed format. They were compressed using gzip.
Any user of real-time products must be approved by Dr. Erich Stocker, the PPS/TSDIS
Project Manager.
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Obtaining or Changing Approval for Access to TRMM Real-time Data
.
Users desiring to gain access to the TRMM real-time data must send a request letter to:
Dr. Erich F. Stocker
PPS/TSDIS Project Manager
GPM Deputy Project Scientist for Data
Code 610.2
NASA Goddard Space Flight Center
Greenbelt, MD. 20771
U.S.A.
The letter should indicate the name of the agency office or individual desiring access, brief
reason for the request, intended use, and the required contact information including
the email of the main contact. User should indicate that they will give the appropriate
credit to NASA and JAXA in any paper arising from the use or analysis of the data.
Users will ordinarily not be given approval to distribute the data to third parties. TRMM
Real-time data may only be used by the approved agency office or individual. The
approval letter will contain sentences similar to: Please note that the real-time TRMM data
will be made available to you for use at XXXXXXXXXX only. You should not forward this
data to a third party in any form. Any desire to modify this requirement must be approved
before access to the data is provided.
Once we have received a copy of the approval letter, we will send a letter that
explains the access requirements and the login information. The TRMM real-time
system supports only ftp transfer of data. No transfer via hard media will be provided
.
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Data Access Overview
The TRMM real-time data is available from an ftp site and the data is retained for 3
days only. After this time, the standard TRMM products would be available from the DISC.
Data is divided into 3 subdirectories on the ftp server. One contains PR data; another
contains the TMI data and the third contains the VIRS data. Generally, new data is
available every 2 hours or so. Users are encouraged to write automated ftp scripts that
check the location periodically for the arrival of new data.
Each TRMM real-time granule (approximately an orbit) is compressed. While sizes may
Vary, the average compressed sizes per granule are:
TMI 1B11- brightness temperature 7MB
TMI 2A12 - surface rain rate1.7 MB
PR 2A23 -rain type 1.4 MB
PR 2A25r1-near surface rain rate 1.7 MB
PR 2a25r2- 20 vertical levels of rainrate 2 MB
VIRS 1B01- radiances 100MB (this is really the full TRMM product)
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Real-time Contact Information
Real-time System Administrator:
Anton Stocker
.
You are invited to send any suggestions that you might have. We are collecting suggestions
to determine whether any changes to the real-time system might be useful for users. In
addition, we strive to address quickly any problems that you might encounter.
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Last Revised: October 09, 2007