SNODAS-PRISM
SNODAS-PRISM is a derived dataset that uses both SNODAS and PRISM together. SNODAS provides modeled snow data at daily, 1km resolution grid cells from 2003 to present, whereas PRISM provides modeled weather data at daily, 4km resolution grid cells from 1981 to present.
Winter Severity Index (winter-severity)
The Winter Severity Index is a derived variable combining SNODAS snow days (snowdays; snow depth greater than 38 mm (1.5 inches)) and PRISM mean temperature tempdays (tmean-tempdays; number of days the mean daily temperature was below -17.78 C° (0 F°)) and represents the cumulative effects of harsh winter conditions.
- Daily data represent the summation of the two datasets (0 equals not deep snow and not severely cold temperatures, 1 equals either deep snow or severely cold temperatures, and 2 equals both deep now and cold temperatures).
\(\text{(Daily snowdays)}_i + \text{(Daily tmean-tempdays)}_i =\) 0: Not deep snow & not severely cold
\(\text{(Daily snowdays)}_i + \text{(Daily tmean-tempdays)}_i =\) 1: Deep snow or severely cold
\(\text{(Daily snowdays)}_i + \text{(Daily tmean-tempdays)}_i =\) 2: Both deep snow & severely cold
\(i\): current day
- Monthly data are the summation of each day’s Winter Severity Index within the month
\[\text{Monthly winter-severity} = \sum_{i=1}^{d} \text{(Daily winter-severity)}_i \]
\(d\): # of days in the month | \(i\): Current day (iterator) | A month with 30 days would have a maximum winter-severity value of 60
- Annual data are the summation of each day’s Winter Severity Index within the water year (Oct 1 - Sep 30 of the given year, e.g. 10/01/2003 - 09/30/2004 would be labeled as 01/01/2004).
\[\text{Annual winter-severity} = \sum_{i=1}^{d} \text{(Daily winter-severity)}_i \]
\(d\): # of days in the water year | \(i\): Current day (iterator)
Source
Snow Data Assimilation System (SNODAS) Data Products at NSIDC