Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole@nasa.gov
Rani Gran
Goddard Space Flight Center, Greenbelt, Md.
301-286-2483
rani.c.gran@nasa.gov
RELEASE: 12-016
NASA COLD WEATHER AIRBORNE CAMPAIGN TO MEASURE FALLING SNOW
WASHINGTON - Beginning Jan. 17, NASA will fly an airborne science
laboratory above Canadian snowstorms to tackle a difficult challenge
facing the upcoming Global Precipitation Measurement (GPM) satellite
mission -- measuring snowfall from space.
GPM is an international satellite mission that will set a new standard
for precipitation measurements from space, providing next-generation
observations of worldwide rain and snow every three hours. It is also
the first mission designed to detect falling snow from space.
"Snow is notoriously hard to measure as it falls," said Walter
Petersen, the GPM ground validation scientist at NASA's Wallops
Flight Facility in Virginia. "Snowflakes contain varying amounts of
air and water, and they flutter, wobble and drift as they leave the
clouds."
Knowing how "wet" a snowflake is allows scientists to measure overall
water content. A wet, heavy snow can shut down a city, and melted
snow is a crucial source of freshwater in many areas.
Working with Environment Canada, NASA's GPM Cold-season Precipitation
Experiment (GCPEx) will measure light rain and snow in Ontario from
Jan. 17 to Feb. 29. The field campaign is designed to improve
satellite estimates of falling snow and test ground validation
capabilities in advance of the planned launch of the GPM Core
satellite in 2014.
NASA's DC-8 airborne science laboratory will fly out of Bangor, Maine,
carrying radar and a radiometer that will simulate the measurements
to be taken from space by GPM. At an altitude of 33,000 feet (10
kilometers), the DC-8 will make multiple passes over an extensive
ground network of snow gauges and sensors at Environment Canada's
Center for Atmospheric Research Experiments north of Toronto.
The GCPEx field experiment will help scientists match measurements of
snow in the air and on the ground with the satellite's measurements.
"We will be looking at the precipitation and the physics of
precipitation, such as snowflake types, sizes, shapes, numbers and
water content," Petersen said. "These properties affect both how we
interpret and improve our measurements."
GPM's Core satellite is being built at NASA's Goddard Space Flight
Center in Greenbelt, Md., with instruments provided by NASA and its
mission partner, the Japanese Aerospace and Exploration Agency
(JAXA). The spacecraft will orbit Earth at a 65-degree inclination,
covering the world from the Antarctic Circle to the Arctic Circle.
GPM will carry a microwave radiometer and a dual-frequency
precipitation radar that distinguishes a snowflake's size and shape,
which affects how much water it holds. Knowing these microphysical
properties will lead to more accurate estimates of rain and snowfall,
especially during winter and at high latitudes where snow is the
dominant form of precipitation.
The Ontario region is prone to both lake effect snow squalls and
widespread snowstorms. If the opportunity exists, the DC-8 also will
fly over blizzards along the northeastern United States. While the
DC-8 flies above the clouds, two other aircraft, one from the
University of North Dakota and another from Canada, will fly through
the clouds, measuring the microphysical properties of the raindrops
and snowflakes inside.
Advanced ground radars will scan the entire air column from the clouds
to the Earth's surface.
"These multiple measurements of snowfall provide a complete picture, a
complete model, of the snowfall process from top to bottom," Petersen
said.
NASA's Dryden Flight Research Center in Edwards, Calif., manages the
DC-8 flights for the GCPEx mission. The aircraft is based at the
center's aircraft operations facility in Palmdale, Calif. NASA's
Marshall Space Flight Center in Huntsville, Ala., is providing
aircraft tracking and guidance through the Real Time Mission Monitor,
as well as GCPEx real-time data and personnel support for the ground
instruments in Canada.
For more information on the GCPEx ground validation, visit:
-end-
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