SNOTEL Stations

Ratio of SWE to Winter Precipitation

Drought type Min Max Median
dry 0.26 0.96 0.75
warm 0.23 0.76 0.62
nodrought 0.45 0.97 0.77

Take home: Using criteria from Harpold et al. (2017) (drought if peak is less than long-term mean) results in drought (warm or dry) for 55% of station-years. The ratio of SWE to winter precipitation alone cannot be used to determine type or occurrence of drought. This method excludes high snow years

Percentiles

Palmer Drought Severity Index

Surface Water Supply Index

WRF-SM for Upper Colorado

year ctl pgw delta perc.diff
2001 8.9 7.0 -1.8 -20.7
2002 6.4 5.8 -0.5 -8.3
2003 10.0 8.3 -1.7 -17.3
2004 12.3 11.3 -1.0 -7.8
2005 15.2 12.1 -3.1 -20.7
2006 10.9 7.8 -3.1 -28.4
2007 10.1 6.8 -3.4 -33.1
2008 15.6 14.7 -1.0 -6.1
2009 12.6 11.6 -1.0 -7.8
2010 13.4 13.1 -0.3 -2.4
2011 17.6 14.1 -3.5 -19.9
2012 6.6 6.1 -0.4 -6.8
2013 9.4 7.1 -2.3 -24.2

Temperature, total precipitation, and solid precipitation

For each year at every cell, I found onset of accumulation, day of peak SWE, and snow all gone. I then calculated (this was again for each year at every cell) mean temperature, sum of precipitation, and sum of solid precipitation for accumulation (defined between onset and peak SWE), snowmelt (peak SWE and SAG), and SAG (SAG to rest of the WY). I used the zonal statistics tool for each elevation band (mean for temperature and median for precipitation).