NASA's DC-8 airborne science laboratory soars over the Sierra Nevadas and the Owens Valley near Lone Pine, Calif., during a checkout flight in the winter of 1998. The aircraft is validating several specialized instruments for the future Global Precipitation Measurement satellite during the six-week GCPEx airborne campaign over Ontario, Canada from late January through February 2012. (NASA / Jim Ross) › View Larger Image
GCPEx Snowfall Study Resumes Over Ontario, Canada
After a couple of no-fly days due to weather conditions and media outreach, NASA’s DC-8 flying laboratory resumed flying Jan. 26 in NASA's Global Precipitation Measurement Cold-season Precipitation Experiment, or GCPEx, snow study.
The goal of the more than six-hour night flight was to collect precipitation bands over the Environment Centre for Atmospheric Research Experiments, or CARE, located in Egbert, Ontario, Canada. About 35 passes were made over the CARE site in inclement weather, with freezing rain and strong winds forcing the flight crew to change the flight patterns to increase data collection.
The GCPEx field experiment will help scientists match measurements of snow in the air and on the ground with the satellite's measurements.
"We are looking at the precipitation and the physics of precipitation, such as snowflake types, sizes, shapes, numbers and water content," said Walter Petersen, the GPM ground validation scientist at NASA's Wallops Flight Facility in Virginia. "These properties affect both how we interpret and improve our measurements."
The Airborne Precipitation Radar-2 (APR-2) developed by NASA's Jet Propulsion Laboratory and the Conical Scanning Millimeter-wave Imaging Radiometer (CoSMIR) developed by NASA’s Goddard Space Flight Center were operated during the first science flight Jan. 19. As a small low-pressure system moved across the area, the DC-8 flew an orbiting pattern over the CARE site. A Cessna Citation operated by the University of North Dakota joined the aerial orbit that included repeated spiral descents and climbs. Sites around CARE are heavily instrumented to collect snow and water measurements.
In addition to the CARE ground network of snow gauges and sensors and measurements from aircraft, advanced ground radars will scan the entire air column from the clouds to the Earth's surface.
Among scientists aboard a second science flight Jan. 21 was Gail Skofronick-Jackson, GPM deputy project scientist at NASA Goddard in Greenbelt, Md.
"We took a short flight to measure surface information over our GCPEx field campaign region. It is important to know what our surface 'looks like' with our instruments for clear-air conditions because we can 'subtract' the surface signal when we are observing falling snow," said Skofronick-Jackson.
"It's like trying to weigh your luggage to make sure that it is under 50 pounds so you don't get charged extra at the airport," she added. "First you weigh yourself (like clear-air surfaces), then you weigh yourself holding the luggage (snow falling over the surfaces), finally you subtract the two leaving just the luggage weight (only the falling snow signal)."
During GCPEx the DC-8 is flying above the clouds while the Citation and a Canadian National Research Council Convair 580 fly through the clouds and measure the microphysical properties of the raindrops and snowflakes inside.
If the opportunity exists during the mission, now scheduled to end Feb. 29, the DC-8 also will fly over blizzards along the northeastern United States.
For more information about GCPEx, visit:
NASA Dryden public affairs