The BOREAS Information System
Hydrology (HYD)

HYD-2: Validation of a Passive Microwave Snow Water Equivalent Algorithm Using an Energy Balance Model

P.I.(s): Al T.C. Chang -- NASA/Goddard Space Flight Center
Co-I(s): James L. Foster and Dorothy K. Hall -- NASA/GSFC

Objectives: The surface meteorological data collected at the tower and ancillary sites is being used as inputs to an energy balance model to monitor the amount of snow storage in the boreal forest region. Snow Water Equivalent (SWE) derived from an energy balance model and insitu observed SWE are being used to compare the SWE inferred from airborne and spaceborne microwave data, and to assess the accuracy of microwave retrieval algorithms. The major external measurements that are needed are snowpack temperature profiles, and in situ snow areal exent and snow water equivalent data.

HYD-2 Data Sets

  • Microwave Measurements
  • Snow Water Equivalent from microwave

  • Get some HYD-2 data using FTP (BOREAS Investigators only, password required). [FTP Help]

    HYD-2 BOREAS Operations in 1994

    Passive microwave data have been used to infer the areal snow water equivalent (SWE) over forested areas, but the accuracy of these retrieved SWE values cannot be easily validated for heterogeneous vegetated regions. Energy balance models have been used to account for the amount of snow storage in snowpacks. We are proposing to utilize the extensive meteorological data to be collected by the BOREAS project, as inputs to an energy balance model in order to measure and monitor snow parameters in the boreal forest region. In-situ observed SWE and SWE derived from an energy model will be compared to the SWE inferred from air-borne and space-borne microwave data and the accuracy of microwave retrieval algorithms will be evaluated.

    Types of Data Collected, Equipment Used:
    Microwave radiometers (18, 37 and 92 GHz) were successfully integrated onto the Canadian National Research Council's Twin Otter aircraft for BOREAS-94. Brightness temperatures were measured during the experiment.

    Summary of Places and Times of Measurements:
    The plane started the deployment on January 30 and arrived at Prince Albert on February 1. On February 3, a local test flight was flown to make sure the overall system functioned properly. A liquid nitrogen calibration was performed inside the RCMP hanger. The first data flight was on February 6 from Prince Albert. A total of fourteen flights were flown from February 6 to 13. Flight lines for the south site and the north site were covered by these flights. On February 14, the Twin Otter returned to Ottawa via Thunder Bay and Sault Ste. Marie.

    Known Problems and Caveats:
    The calibrated brightness temperature is believed to be accurate to about 2 K. A minor problem uncovered during this mission, that the calibration of the 92 GHz was noisier than expected. This is due to the fact that the radiometer uses outside ambient air temperature as the cold calibration reference. For targets with low brightness temperatures, the signal to noise ratio is not optimal

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    Last Updated: October 21, 1997