Rain on snow (ROS) events in the high latitudes have been shown to have a significant impact on the permafrost and rangifer populations in the circumpolar arctic (Putkonen and Roe, 2002), and can also impact the frequency of avalanches in mountainous regions. We're attempting to understand these events more thoroughly, and use that understanding to quantify their past and projected future impacts.

The diverse set of impacts of rain on snow, from permafrost and snow to caribou and the native populations that depend on them, mean that it requires a multi-disciplinary approach to study them. Our team consists of

• Gerard Roe, Associate Professor, Earth and Space Sciences, University of Washington
• Jaakko Putkonen, Research Assistant Professor, Quaternary Research Center, University of Washington
• Cecilia Bitz, Physicist at the Polar Science Center and affiliate professor of Atmospheric Sciences at the UW
• Don Russell, leading rangifer expert and researcher with Environment Canada

To this point in the project, we've been using the recently released European 40 Year Reanalysis in conjunction with meteorological station data provided by Amir Shabbar of Environment Canada to quantify the frequency and amplitude of past ROS events.

For a more detailed presentation of our work, please take a look here for the powerpoint of my poster presented at the 2004 AGU Fall conference in San Francisco.

Basic climatologies using these data sets are available here.

The fairly coarse resolution (2.5 x 2.5 degrees) of the ERA 40 data set has led us to do a bit of downscaling to get an idea of if a higher resolution would give us more or less ROS. A very rough cut at this gives us the impression that the resolution of the ERA 40 is causing it to give less ROS than a higher resolution (.5 x .5 deg) by about 10-12%.

Analysis

• Refreeze Events by Month : Russell Criterion
• ROS vs Melt from Positive Degree Days (side by side comparison)
  • 1 cm minimum snow depth [One page] [Animation] [trend]
  • 3 cm minimum snow depth [One page] [Animation] [trend]
  • 5 cm minimum snow depth [One page] [Animation] [trend]
  • 10 cm minimum snow depth [One page] [Animation] [trend]
• ROS vs PDD difference maps
  • 1 cm minimum snow depth [One page] [Animation]
  • 3 cm minimum snow depth [One page] [Animation]
  • 5 cm minimum snow depth [One page] [Animation]
  • 10 cm minimum snow depth [One page] [Animation]
• TRENDS in ERA40 SAT
  • [ By Month]
  • [ By Season]
  • [ old NCEP for comparison]