JPL Radar Treks to Great White North to Study Snow
Measuring snow from space - it's a challenge NASA's Global Precipitation Measurement mission will tackle.
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 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.The radar on the NASA DC-8  is JPL's Airborne Precipitation Radar-2 (APR-2) dual-frequency radar. The radar  looks downward and scans its antenna across-track, acquiring a  three-dimensional image of precipitation underneath the aircraft. At each  point in this 3-D image, APR-2 measures several characteristics of the  precipitation, including its radar reflectivity, or "brightness," and its  motion. During GCPEx, APR-2 will simulate the type of measurements GPM  will make. Its data will be used to improve understanding of snowfall  microphysics and to develop and test algorithms for use with the GPM radar,  which will operate on the same 13- and 35-gigahertz frequencies.For more  information and images, visit:http://www.nasa.gov/centers/dryden/news/NewsReleases/2012/12-02.html.For more on  APR-2, visit:http://trmm.jpl.nasa.gov/apr.html.JPL is a division of the California  Institute of Technology in Pasadena.