Ground validation: Contributing to Earth observations from space

Mar 12, 2014
The NASA NPOL (left) and D3R (right) precipitation radars deployed south of Waterloo, Iowa, for the Iowa Flood Studies ground measurement campaign. Credit: NASA/Matt Schwaller

The Global Precipitation Measurement (GPM) Core Observatory, launched on Feb. 27 from Tanegashima Space Center in Japan, will help advance our understanding of Earth's water and energy cycles, improve the forecasting of extreme events that cause natural disasters, and extend current capabilities of using satellite precipitation information to directly benefit society.

The GPM mission will provide unprecedented data on rain and snowfall. The science instruments on the GPM Core Observatory will provide data that will yield the greatest clarity on rain and snow yet gathered from orbiting spacecraft.

With GPM, scientists will gather vast amounts of data on a global scale. But, how do they know how to interpret the data? How do scientists know the data is correct?

This is where ground validation contributes to the mission. Using instruments that complement and correlate with those on the spacecraft, scientists on the ground gather similar precipitation data. These data are directly compared with that from satellites to improve the models relying on the satellite data.

Walt Petersen, GPM ground validation scientist from NASA's Wallops Flight Facility at Wallops Island, Va., said, "GPM ground validation is the process by which we identify uncertainties in satellite-based precipitation products compared to ground observations, improve satellite-based methods of estimating precipitation by better understanding precipitation physics and how this physics relate to what the instruments 'see,' and assess the utility of GPM products in monitoring the global water cycle, flood and weather prediction, and understanding climate change."

Ground validation: Contributing to Earth observations from space
This is an artist's depiction of NASA's Global Precipitation Measurement mission's Core Observatory. Credit: NASA

The GPM program uses remote campaigns and a Precipitation Science Research Facility at Wallops to supplement and correlate the data gathered by Earth-orbiting satellites.

"Ground validation is central to understanding the quality of GPM precipitation products, how the products can be improved, and evaluating the utility of the measurements in a variety of earth system science applications," Petersen said.

The remote campaigns, using instrumented aircraft and ground-based instruments, allow scientists to monitor precipitation under a variety of conditions and geographic regions.

These campaigns have included the Pre-CHUVA experiment to study rain in 2009 in Brazil; the 2010 Finland Light Precipitation Validation Experiment to study high-latitude, cold, light rain; the Mid-latitude Continental Convective Clouds Experiment in central Oklahoma in 2011 to support rainfall measurements; GPM Cold Season Precipitation Experiment in 2012 conducted over and near Ontario, Canada, to support snowfall measurements; and in 2013 scientists conducted the Iowa Flood Studies experiment over a six-week period to evaluate how well GPM rainfall data can be used for flood forecasting.

Later this year, the ground validation team will be heading to North Carolina to conduct the Integrated Precipitation and Hydrology Experiment to characterize warm season precipitation regimes and the relationship between precipitation regimes and hydrologic processes in regions of complex terrain.

According to Petersen, "Field campaigns collect targeted observations of precipitation physical properties in locations or regimes where specific precipitation types occur and can be well studied and where uncertainties either exist or are expected to exist in GPM precipitation products. This information provides a better understanding of precipitation characteristics, how those characteristics relate to uncertainties in the products, and a foundation for improving the method(s) by which we estimate precipitation from both space- and ground-based measurements."

In addition to the field campaigns, the program uses an array of gauges and radar systems on the eastern shore of Maryland and Virginia to gather precipitation data – rain or snow – year round.

Petersen said, "The Wallops Precipitation Research Facility collects multi-frequency dual-polarimetric radar observations of precipitation rates, types, sizes and shapes through the depth of the troposphere. We collect high quality, concentrated rain gauge network measurements of area-mean rainfall, and use networks of imaging instrumentation to observe the number and distributions of the size, shape and type of precipitation particles falling to ground. Collectively, these measurements enable us to describe precipitation physical properties over scales ranging from that of an individual rain drop or snowflake to that of the Delmarva and Chesapeake Bay regions."

With ground validation, scientist will be able to gauge the quality of Earth observations from space using GPM and improve combined space- and ground-based data products used to understand global precipitation.

Explore further: NASA sees Tropical Cyclone 15S meandering in Mozambique Channel

add to favorites email to friend print save as pdf

Related Stories

JPL radar treks to great white north to study snow

Jan 18, 2012

( -- Beginning Jan. 17, NASA will fly an airborne science laboratory, including a unique airborne radar built by NASA's Jet Propulsion Laboratory, Pasadena, Calif., above Canadian snowstorms to ...

US-Japan satellite to study global rain, snow

Jan 27, 2014

A new satellite built by NASA and its Japanese counterpart is poised to launch next month on a mission to study rain and snow around the world, the US space agency said Monday.

Recommended for you

Stuck-in-the-mud plankton reveal ancient temperatures

13 hours ago

New research in Nature Communications showing how tiny creatures drifted across the ocean before falling to the seafloor and being fossilised has the potential to improve our understanding of past climat ...

NASA sees Mozambique Channel's new tropical storm

13 hours ago

Tropical Cyclone 15S formed in the Mozambique Channel of the Southern Indian Ocean, and the Global Precipitation Measurement or GPM core satellite gathered data on its rainfall rates.

How rain is dependent on soil moisture

13 hours ago

It rains in summer most frequently when the ground holds a lot of moisture. However, precipitation is most likely to fall in regions where the soil is comparatively dry. This is the conclusion reached by ...

ESA image: Hungarian mosaic

14 hours ago

This image of Hungary, with the political border in white, is a mosaic of 11 scans by Sentinel-1A's radar from October to December 2014.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.