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PRECIPITATION MEASUREMENT MISSIONS

GCPEx Campaign Blog

Waiting for Snow

By

Gail Skofronick-Jackson

Scientists in the CARE operations trailer In the CARE operations trailer monitoring weather conditions during the DC-8 flights on 6 February 2012 at approximately 9pm EST.

Gail Skofronick-Jackson is the Deputy Project Scientist for GPM at Goddard Space Flight Center in Greenbelt, Md. She specializes in the remote sensing of snow, and is currently the mission scientist for the campaign at the CARE ground site in Ontario, Canada. She writes to us about a night flight on February 6 and the snow that didn't show.


Models showed quickly developing snow from 9-10pm EST tonight (6 Feb 2012). We are at 9:22 and we don't yet see snow in the real time ground radar data. The DC-8 is up and flying back and forth, waiting, waiting, waiting for the snow. We aren't sending up the Citation until we see snow on the ground radars.

At 9:45pm we are so bored we are looking at pictures of snow in other parts of Canada and USA. Can we do a snow dance? We still don’t see snow developing in our real time ground radars.

The models said we’d see lake enhanced snow. But if the models/forecasts were correct we wouldn't be out here measuring the snow so we could understand it better (and then model/forecast it better).

We gave up at 10:20pm after only seeing a very small snow event in a region where we are not allowed to fly. Ending DC-8 flight. Never sent up the Citation.  We are all :(  :(  :(

Update February 7:

The CARE site did get snow early the next morning but it was only a dusting, so it was good to send the DC-8 back to it’s hanger in Bangor, Maine.

Below are a few of the ground instruments, eagerly awaiting snow:

Various ground instruments at the CARE site Three GCPEx precipitation sensors with the Environment Canada building in the background, taken 7 February 2012. Note the low snow amounts on the ground. Sensors left to right are: ADMIRARI (radiometer; U. Bonn), D3R (radar; NASA), DPR (radar; U. Koln). [This dual-precipitation radar (DRR) is not the same as to be on the GPM spacecraft.]

Credit: NASA / Gail Skofronick-Jackson


The Pluvio snow sensor The Pluvio sensor that weighs snow that falls into it. This provides a measure of how much water is in the falling snow. Note the metal “double fencing” around the instrument. This reduces inaccuracies in the measurements due to blowing snow. Photo taken 7 February 2012.

Credit: NASA / Gail Skofronick-Jackson


A hot plate sensor at GCPex The Hot Plate sensor provides a measure of the density of the snowflakes by forcing the top and bottom of the plates to be the same (hot) temperature. As snowflakes (or raindrops) fall on the plate, they cool it. The sensor reacts by applying voltage to maintain the equal temperatures. The voltage is then converted to Watts (a measure of the power taken to evaporate the precipitation). This power is divided by the heat needed to evaporate one gram of water, thus providing the total grams of water falling on the hot plate. Photo taken 7 February 2012.

Credit: NASA / Gail Skofronick-Jackson


Gail at the SkyDive Airport GCPEx instrumentation at the SkyDive Airport 11km east of the main CARE site. The antenna on the top of the trailer is a Micro Rain Radar (MRR). Note the large double fencing around additional instruments behind the trailer. The double fencing reduces errors due to blowing snow. Photo taken 7 February 2012.

Credit: NASA / Gail Skofronick-Jackson

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