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PRECIPITATION MEASUREMENT MISSIONS

Data Access

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How to Access TRMM & GPM Precipitation Data

Precipitation data from the GPM and TRMM missions is made available free to the public in a variety of formats from several sources. This section outlines the different types of data available, the levels of processing, the sources to download the data, and some helpful tips for utilizing precipitation data in your research. 

 

TRMM & GPM Data Policy

TRMM and GPM data are freely available at all levels for which the particular sensor or sensor combination has been processed by GPM. For the GPM Core Observatory this is for Levels 0 through 3 products (as applicable).  For the partner satellites in the GPM constellation this is Levels 1c through 3 (as applicable).

Users are encouraged to access data from the primary TRMM and GPM archives (i.e. nasa.gov domains). When data from secondary archives are used, it is incumbent on the user to verify that the data values accessed are accurate, up-to-date, current-version copies of the original data.

The data set source should be acknowledged when the data are used.  A formal reference of the form: 

<authors>, 2012, last updated 2013:  <dataset name>.  NASA/GSFC, Greenbelt, MD, USA, NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). Accessed <enter user data access date> at <DOI> 

is suggested following Parsons et al. (2010), based on the International Polar Year (IPY) Data policy guidelines (http://www.ipy.org/images/uploads/final_ipy_data_policy-1.pdf).

In the case of data sets that have not been given DOI’s, the most persistent "landing page" should be named, for example,

http://disc.gsfc.nasa.gov/datacollection/3B42.V7.html 

Finally, dataset users are asked to report errors and difficulties in the dataset to the dataset creators using the contact form below. 

Point of Contact

 

FAQ

Q: When will GPM data be made available? 
A: GPM project data sets, including the Core Observatory and constellation partner sensor data sets, have been released to the public and are available for download now (click here to see a table of GPM data products).  The national data sets, including multi-satellite data sets, are being released in late November 2014. These initial releases will be for the GPM era (February 2014 to present).  Subsequently, in Spring 2015 a general reprocessing will extend the record back to the start of the TRMM era (January 1998) for the parts of the data record. 

NASA’s Level 3 Integrated Multi-Satellite Retrievals for GPM (IMERG) will be released in December 2014 with all available data. This gridded product will have a resolution of 0.1 degrees and updated every 30 minutes from 60⁰N-60⁰S.

Q: What is the spatial and temporal resolution of GPM data?
A: The resolution of Level 0, 1, and 2 data is determined by the footprint size and observation interval of the sensors involved.  Level 3 products are given a grid spacing that is driven by the typical footprint size of the input data sets. See the table of GPM & TRMM Data Downloads for details on the resolution of each specific product.

Q: Where can I find detailed documentation on the precipitation algorithms?
A:  Browse our tables of GPM & TRMM data downloads to locate your desired algorithm, then click on the link in the algorithm description that says “Full Documentation”.

 

Q: What is the difference between "Production" (Prod) and "Realtime" (RT) data? 
A: GPM data products can be divided into two groups (real-time and production) depending on how soon they are created after the satellite collects the observations.  For applications such as weather, flood, and crop forecasting that need precipitation estimates as soon as possible, real-time data products are most appropriate.  GPM real-time products are generally available within a few hours of observation.  For all other applications, production data products are generally best because additional or improved inputs are used to increase accuracy.  These other inputs are only made available several days, or in some cases, several months, after the satellite observations are taken, giving time to do a more thorough collection of data or to do a more careful analysis.

Q: Where can I find climatology data?
A: The TRMM FTP has a Climatology directory which contains files in the TRMM Composite Climatology developed by Wang, Adler, Huffman, and Bolvin.  A journal article on this topic is available here: http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00331.1 . Pre-generated world maps of TRMM climatology data are also available here.

 

Q: Am I allowed to use GPM data for my research?
A: Yes, please refer to the GPM Data Policy for further details.

Q: How do I give credit for using GPM data?
A: The data set source should be acknowledged when the data are used.  A formal reference of the form:

<authors>, 2012, last updated 2013:  <dataset name>.  NASA/GSFC, Greenbelt, MD, USA, NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). Accessed <enter user data access date> at <DOI> 

is suggested following Parsons et al. (2010), based on the International Polar Year (IPY) Data policy guidelines (http://www.ipy.org/images/uploads/final_ipy_data_policy-1.pdf).

In the case of data sets that have not been given DOI’s, the most persistent "landing page" should be named, for example,

http://disc.gsfc.nasa.gov/datacollection/3B42.V7.html .

As an “Acknowledgment”, one possible wording is:

"The <dataset name> data were provided by the NASA/Goddard Space Flight Center's <team's organization> and PPS, which develop and compute the <dataset name> as a contribution to <project (TRMM or GPM)>, and archived at the NASA GES DISC." 

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