yellowstoneThe area surrounding Yellowstone and Teton national parks is one of the largest ecosystems in the Earth’s northern temperate zone. It is diverse in land types, flora and fauna. It possesses mountains, subalpine forests, geothermal features and a large fresh water high-altitude lake. Snow covers much of the park from early winter through spring. Better evaluation of snow cover variability will contribute to better understanding of climate change. While there are a number of snow stations in and around the park, the area is difficult to access during the winter. Instead, snow cover can be studied using snow maps from the NASA MODIS instrument. These maps, however, are limited in forested regions where trees occlude snow cover. To determine snow in these regions, the NASA snow algorithm uses information from multiple MODIS bands. Designed for both MODIS/Terra and MODIS/Aqua, the algorithm depends critically on band 6. Unfortunately, ¾ of Aqua’s band 6 detectors are unusable. Therefore, the algorithm has been modified to use band 7, producing different results.

To improve the MODIS/Aqua snow mask, we have developed a quantitative restoration technique for band 6. Since the band 6 dependent algorithm can now be used on both Aqua and Terra, two views can be created per-day to help mitigate occlusion and lighting differences. In order to evaluate the benefits of band 6 restoration, we have created a database containing information from the restored Aqua band 6 over the Yellowstone region for the 2010-2011 snow season. Database includes restored radiances, NDVI, thermal data, NDSI and band 6 based snow mask products. The restored Aqua has also been re-gridded and combined with Terra data to produce a Cloud-Gap-Filled snow cover map. Such information may be used to evaluate how changes in snow cover affect the hydrologic cycle and ecosystem of the Yellowstone region.


© 2010, NOAA-CREST CSDIRS, CCNY-Glasslab/Michael Grossberg/Irina Gladkova/Paul Alabi

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