| Summary: | Snow persistence (SP) or the snow cover index (SCI), is the fraction of time that snow is present on the ground for a defined period. No data index (NDI) is the fraction of time that there is no data, cloud, or sensor saturation for the same period. SP and NDI were calculated on a pixel by pixel basis using MODIS/Terra Snow Cover 8-Day L3 Global 500m Grid, Collection 5 obtained from the National Snow and Ice Data Center (NSIDC). We computed the 1 January – 3 July SP for each year as the fraction of 8-day MODIS images with snow present. The selected period brackets the temporal extent of peak snow accumulation to complete snow ablation in most parts of the western United States. Spatial coverage is for MODIS tiles h08v04, h08v05, h09v04, h09v05, and h10v04. The 3 July date is used because the 8-day MODIS image does not fall on the first of the month in this case. Files are provided in the \"USA Contiguous Albers Equal Area Conic USGS\" projection. File nomenclature follows the following structure: \"MOD10A2_(SCI or NDI)_(Water year the values correspond to, ex. 2001)_eq_alb.tif.\" Funding provided by NSF grant EAR-1446870.
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