Fig. 7. Comparison of Landsat-derived and MODIS-derived snow-cover depletion curves for 2000 for the Fremont Lake basin. Both the Landsat and MODIS curves, modeled using cubic polynomial curve fitting, are shown. The blue diamonds represent the 13 points used to derive the curve for Landsat and the solid black line shows each daily value from MODIS. Confidence intervals at the 95% confidence level for the modeled MODIS and Landsat curves are shown as red and blue dashed lines, respectively.Figure optionsDownload full-size imageDownload high-quality image (169 K)Download as PowerPoint slide
4.2.2. Snowmelt completion
Because of cloud cover, it MK 571 is not possible to obtain a usable MODIS or Landsat scene every time that one is acquired. To overcome this limitation using MODIS data, we used cloud-gap filled data but for Landsat, with only one scene acquired from TM, ETM + or OLI every 16 days, the limitation is even greater.
Using the MODIS CGF maps the day from which the observation was made can be determined. For example, if vaccination was clear on DOY 75 then the DOY 75 fractional snow cover observation was used. If it was cloudy on DOY 75 then the DOY 74 observation was used, and so on. The average on which a measurement was obtained was 1.3 days prior to the actual day of melt (melt completion is defined herein as when MODIS reported five percent or less snow cover in the Fremont Lake basin), so the accuracy of the technique of measuring snowmelt completion is ± 1.3 days for the present MODIS CGF dataset. (The year 2001 is excluded because of missing MODIS data in the spring melt period.)