12 February 2007: Canada (C. Derksen)

Satellites and Snow

A major objective of our traverse is to measure snow to validate measurements made by satellites (see the AMSR-E satellite above). These spaceborne sensors that measure naturally emitted microwave energy are well suited to monitoring snow cover because the snowpack scatters the microwaves. Deep snow scatters more energy than shallow snow. Unfortunately, the satellite sensors measure large areas of the earth’s surface at a time, so the data have a very coarse resolution. It can therefore be helpful for research purposes to have very focused sensor to identify the microwave “signatures” of different surface types.

We are planning on having ground based microwave sensors at Daring Lake this April. The microwave radiometers measure energy at the same wavelengths as the satellite sensors, but over a very small area. Before sending all the equipment up to Daring Lake, we are presently doing some testing, and acquiring some measurements near North Bay, Ontario. It’s been quite cold there this week (minus 30 Celsius) so these conditions are great for cold weather testing.

We need to use liquid nitrogen to calibrate the microwave sensors (liquid nitrogen has a very stable temperature). In the first photo, liquid nitrogen is being poured into a container lined with microwave absorbing material. The second photo shows the microwave sensors set up and measuring microwave energy emitted by snow covered lake ice. It doesn’t look too exciting, but that’s science at work!






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