Jul 1, 2010

Observed Climate–Snowpack Relationships in California and their Implications for the Future

Sarah Kapnick and Alex Hall
American Meteorological Society
  • Studies the California Sierra Nevada snowpack using snow station observations and reanalysis surface temperature data
  • Combines monthly snow water equivalent (SWE) measurements from two datasets to provide sufficient data from 1930 to 2008
  • Uses the monthly snapshots to calculate peak snow mass timing for each snow season
  • Finds there has been an overall trend toward earlier snow mass peak timing by 0.6 days per decade since 1930
  • Finds the trend toward earlier timing occurs at nearly all individual stations—even stations showing an increase in 1 April SWE exhibit the trend toward earlier timing, indicating that enhanced melting is occurring at nearly all stations
  • Analysis of individual years and stations reveals that warm daily maximum temperatures averaged over March and April are associated with earlier snow mass peak timing for all spatial and temporal scales included in the dataset
  • Finds the early spring temperature influence is particularly pronounced for low accumulation years indicating the potential importance of albedo feedback for the melting of shallow snow
  • Finds the robustness of the early spring temperature influence on peak timing suggests the trend toward earlier peak timing is attributable to the simultaneous warming trend (0.1°C decade^sup -1^ since 1930, with an acceleration in warming in later time periods)
  • States that given future scenarios of warming in California, one can expect acceleration in the trend toward earlier peak timing—which will reduce the warm season storage capacity of the California snowpack