Latest Documents

  • Validation Network Data Product User’s Guide - Volume 2 (GPM)
    Publication Date:
    11/16/2015
    Abstract / Summary:

    This document provides a basic set of documentation for the data products available from the GPM Ground Validation System (GVS) Validation Network (VN). In the GPM era the VN performs a direct match-up of GPM’s space-based Dual-frequency Precipitation Radar (DPR) data with ground radar data from the U.S. network of NOAA Weather Surveillance Radar-1988 Doppler (WSR-88D, or “NEXRAD”). Ground radar networks from international partners are also part of the VN. The VN match-up will help evaluate the reflectance attenuation correction algorithms of the DPR and will identify biases between ground observations and satellite retrievals as they occur in different meteorological regimes. Volume 2 of the Validation Network Data User’s Guide describes the GPM core and constellation VN data set. 

    An earlier version  of the VN capability performed a match-up of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data with ground-based radar (GR) measurements from a subset of the WSR-88D sites now included in the GPM-era VN operational radar data network. Legacy TRMM data and their matching GR observations will continue to be part of the VN operations in the GPM era.  Refer to Volume 1 of the Validation Network Data User’s Guide for a description of the legacy TRMM-specific VN data set.

     

  • 2014 PMM Science Team Meeting Summary from the Earth Observer, November 2014
    Author(s):
    Publication Date:
    11/01/2014
    Abstract / Summary:

    This excerpt from the November 2014 edition of The Earth Observer provides a summary of the activities at the PMM Science Team Meeting which took place from August 4 - 7, 2014. The PMM program supports scientific research, algorithm development, and ground-based validation activities for the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM) Core Observatory that launched on February 27, 2014. The meeting opened with a special memorial session dedicated to Arthur Hou, the former GPM Project Scientist, who passed away November 20, 2013. Hou’s friends and colleagues remembered him as an exceptional scientist and leader who was able to build and navigate the international relationships that got the GPM mission off the ground.

  • The Transition in Multi-Satellite Products from TRMM to GPM (TMPA to IMERG)
    Author(s):
    Keywords:
    Publication Date:
    11/01/2019
    Abstract / Summary:

    The transition from the Tropical Rainfall Measuring Mission (TRMM) data products to the Global Precipitation Measurement (GPM) mission products is well underway. This document specifically addresses the multi-satellite products, the TRMM Multi-satellite Precipitation Analysis (TMPA), the real-time TMPA (TMPA-RT), and the Integrated Multi-satellitE Retrievals for GPM (IMERG).

    The TRMM satellite ran out of altitude-keeping fuel in July 2014. On 7 November 2014 the satellite descended to an altitude that precluded useful TRMM Precipitation Radar data, although the TRMM Microwave Imager (TMI) functioned alone, with slowly changing characteristics until the decommissioning in April 2015.

  • GPM Science Implementation Plan
    Publication Date:
    04/02/2013
    Abstract / Summary:

    The Global Precipitation Measurement Mission is an international space network of satellites designed to provide the next generation precipitation observations around the world every 2 to 4 hours. It is a science mission with integrated applications goals. The GPM concept centers on the deployment of a Core Spacecraft carrying advanced active and passive microwave sensors to function as a physics observatory to gain physical insights into precipitating systems and to serve as a reference standard to improve global precipitation estimates from a constellation of research and operational microwave sensors capable of precipitation measurements. The GPM constellation buildup follows a progressive strategy to take advantage of partner satellites that carry microwave sensors such as a conical-scanning imager or a cross-track-scanning sounder. 

  • Download File:
    GPM Mission Brochure
    Publication Date:
    11/01/2013
    Abstract / Summary:

    This 17 page flyer provides an overview of the GPM Mission. It describes the technologies used to measure precipitation and the missions scientific goals and societal applications.

    Excerpt:

    "The Global Precipitation Measurement (GPM) mission is an international partnership co-led by NASA and the Japan Aerospace Exploration Agency (JAXA). The mission centers on the deployment of the GPM Core Observatory and consists of a network, or constellation, of additional satellites that together will provide next-generation global observations of precipitation from space. The GPM Core Observatory will carry an advanced radar/radiometer system and serve as a reference standard to unify precipitation measurements from all satellites that fly within the constellation."

    Table of Contents:

    • Precipitation Measurement Science
    • Global Precipitation Measurement Mission
    • GPM Core Observatory
    • GMI: GPM Microwave Imager
    • DPR: Dual-frequency Precipitation Radar
    • Spacecraft Design
    • Ground System and Data
    • GPM Mission Applications: A Global Understanding for a Better Future
  • 2011 PMM Science Team Meeting Summary from the Earth Observer, March 2012
    Author(s):
    Publication Date:
    03/01/2012
    Abstract / Summary:

    This excerpt from the March-April 2012 edition of The Earth Observer provides a summary of the activities at the PMM Science Team Meeting which took place from November 7 - 10 2011. The meeting brought together over 150 participants from 10 countries, and included representatives from NASA, JAXA, the National Oceanic and Atmospheric Administration (NOAA), universities, industry, and other international partner agencies. During the first three days of the meeting, participants focused on TRMM/ GPM programmatic summaries, international activities, ground validation summaries, and science reports from science team members. In addition to 12 oral presentations, two afternoon poster sessions were held to facilitate discussion of research results in an interactive forum. The final day was devoted to GPM algorithm team meetings. Working groups that focused on hydrology, algorithm development, latent heating, and land-surface characterization met throughout the week.

  • MC3E Summary from The Earth Observer, January 2012
    Publication Date:
    02/01/2012
    Abstract / Summary:

    This excerpt from the NASA Earth Observer publication provides and in-depth summary of the Midlatitude Continental Convective Clouds Experiment (MC3E), which took place from April 22nd - June 6th 2011 in central Oklahoma. The overarching goals of the field effort were to provide a complete three-dimensional characterization of precipitation microphysics in the context of improving the reliability of GPM precipitation retrievals over land, and to advance understanding of the primary physical components that form the basis for models that simulate convection and clouds.

  • A Ground Validation Network for the Global Precipitation Measurement Mission
    Publication Date:
    03/01/2011
    Abstract / Summary:

    A prototype Validation Network (VN) is currently operating as part of the Ground Validation System for NASA’s Global Precipitation Measurement (GPM) mission. The VN supports precipitation retrieval algorithm development in the GPM prelaunch era. Postlaunch, the VN will be used to validate GPM spacecraft instrument measurements and retrieved precipitation data products.

    The period of record for the VN prototype starts on 8 August 2006 and runs to the present day. The VN database includes spacecraft data from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and coincident ground radar (GR) data from operational meteorological networks in the United States, Australia, Korea, and the Kwajalein Atoll in the Marshall Islands. Satellite and ground radar data products are collected whenever the PR satellite track crosses within 200 km of a VN ground radar, and these data are stored permanently in the VN database. VN products are generated from coincident PR and GR observations when a significant rain event occurs.

    The VN algorithm matches PR and GR radar data (including retrieved precipitation data in the case of the PR) by calculating averages of PR reflectivity (both raw and attenuation corrected) and rain rate, and GR reflectivity at the geometric intersection of the PR rays with the individual GR elevation sweeps. The algorithm thus averages the minimum PR and GR sample volumes needed to “matchup” the spatially coincident PR and GR data types. The result of this technique is a set of vertical profiles for a given rainfall event, with coincident PR and GR samples matched at specified heights throughout the profile.

    VN data can be used to validate satellite measurements and to track ground radar calibration over time. A comparison of matched TRMM PR and GR radar reflectivity factor data found a remarkably small difference between the PR and GR radar reflectivity factor averaged over this period of record in stratiform and convective rain cases when samples were taken from high in the atmosphere. A significant difference in PR and GR reflectivity was found in convective cases, particularly in convective samples from the lower part of the atmosphere. In this case, the mean difference between PR and corrected GR reflectivity was −1.88 dBZ. The PR–GR bias was found to increase with the amount of PR attenuation correction applied, with the PR–GR bias reaching −3.07 dBZ in cases where the attenuation correction applied is >6 dBZ. Additional analysis indicated that the version 6 TRMM PR retrieval algorithm underestimates rainfall in case of convective rain in the lower part of the atmosphere by 30%–40%.

  • Download File:
    TRMM Senior Review Proposal 2011
    Author(s):
    Publication Date:
    09/01/2011
    Abstract / Summary:

    Excerpt:

    "Although TRMM started as an experimental mission to study tropical rainfall, and was originally expected to last only 3-5 years, it has evolved into the primary satellite in a system of research and operational satellites monitoring precipitation on time scales from 3-hr to inter-annually and beyond. TRMM’s role as the primary satellite in this system is because of the high-quality precipitation information available from its combination of active-passive instruments and the inclined orbit visiting the entire diurnal cycle with frequent intersections with polar-orbiting satellites. Today TRMM data are used to calibrate and integrate precipitation information from multiple polar orbiting satellites/instruments (AMSR on Aqua, SSM/Is on DoD/DMSP and AMSU on NOAA platforms) and geosynchronous satellites into merged precipitation analyses being used both for research and applications. The real-time availability of TRMM products has also resulted in the use of TRMM data by operational weather agencies in the U.S. and around the world for monitoring and forecasting of tropical cyclones, floods and other hazardous weather."

  • GCPEX Science Plan
    Publication Date:
    09/02/2011
    Abstract / Summary:

    During the GPM pre-launch period physically-based snowfall retrieval algorithms are in an active phase of development. Further refinement and testing of these emerging algorithms requires the collection of targeted ground-validation datasets in snowing environments. This document describes a field campaign effort designed to provide both new datasets and physical insights related to the snowfall process- especially as they relate to the incorporation of appropriate physics into GPM snowfall retrieval algorithms. The referenced field campaign effort is the GPM Cold Season Precipitation Experiment (GCPEx), a collaboration between the NASA GPM Ground Validation (GV) program and its international partner Environment Canada (EC).

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