Precipitation Processing System (PPS) servers will be down for extended maintenance from Tuesday, September 22nd through Thursday September 24th. During this time the PPS websites, the PMM Publisher API, and the GPM research data server (arthurhou) will be unavailable. The GPM near real-time server (jsimpson) and satellite data collection will not be affected. Click here to learn more.


Content which is not specifically affiliated with GPM or TRMM, but which is about the Precipitation Measurement Missions in general.

Wall of Dust, by Meggan Wood

A huge dust storm approaching
Image Caption
A huge dust storm approaches Maricopa, Arizona.

Date and Location:
July 5, 2011
Maricopa, Arizona

How this Photo was Taken:
“This photo was taken in a wash that runs through my neighborhood in Maricopa, AZ. The wash runs north/south through the neighborhood and the haboob (type of intense dust storm) was rolling in from the east.

It was taken on 7/5/11 in the afternoon, not long before sunset.

Thunderstorm, by Grant Petty

A huge thunderstorm cloud
Image Caption
A huge thundercloud in Dane County, Wisconsin.

Date and Location:
May 22, 2011
Dane County, Wisconsin

How this Photo was Taken:
“I was out on a farm with a photography club for the purpose of photographing farm life -- animals, barns, etc. I saw this impressive thunderstorm building several miles to the east of where we were and ended up focusing on that while the others in the group continued to follow the goats and horses around. This is one of many examples of how a completely unplanned photo wound up being among my best photos.

MicroRain Radar in the Smokies

MicroRain Radar in the Smokies
Image Caption
MicroRain Radar at Purchase Knob in the Great Smoky Mountains National Park.

This instrument is a vertical profiler radar that delivers information about structure in the atmospheric column and enables scientists to estimate the vertical distribution of rainfall. At all times of the day, light rainfall is the dominant type of precipitation. 

Light Rain in the Smokies

A misty mountaintop in the Smokies
Image Caption
Mid-morning peak in light rainfall appears as clouds and fog at Purchase Knob in the Great Smoky Mountains National Park.

Light rainfall is the most reliable and most frequent form of rainfall in the region, contributing 50 to 60 percent of the total precipitation over a year. Light rain is no less than the lifeline of freshwater resources for the landscape’s ecosystems. 

Document Description

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.

GPM flying over Earth with a data swath visualized.
Precipitation Measurement Mission Science NASA’s Precipitation Measurement Missions (PMM) develop and deploy advanced space-borne sensors to gain physical insights into precipitation processes and to enable improved monitoring and forecasting of climate, weather and precipitation-related natural hazards. PMM includes the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM) mission. TRMM and GPM pursue a unique and innovative approach to measuring precipitation from space through the collection of observations by both active and passive sensors, which are...

Active and Passive Remote Sensing Diagram

Diagram illustrating the differences between active and passive remote sensing.
Image Caption
This diagram illustrates the differences between active and passive remote sensing.

TRMM and GPM rely on active and passive instruments to measure the properties of precipitation from space.

Active radars, such as the TRMM Precipitation Radar, transmit and receive signals reflected back to the radar. The signal returned to the radar receiver (called radar reflectivity) provides a measure of the size and number of rain/snow drops at multiple vertical layers in the cloud (Left figure).

GPM flying over Earth with a data swath visualized.
In addition to the PMM satellites, TRMM and GPM, roughly a dozen other satellites carry precipitation-relevant sensors. The goal of multi-satellite algorithms is to use “all” of the available quasi-global precipitation estimates computed from this international constellation of satellites to create a High-Resolution Precipitation Product with complete coverage over the chosen domain and period of record (currently 50°N-50°S, 1998-present). Estimates based on microwave and combined radar/radiometer input data have higher quality due to the physically direct relationships that exist between...