Jun 21, 2016

Characterizing the extreme 2015 snowpack deficit in the Sierra Nevada (USA) and the implications for drought recovery

Margulis, Steven A., Cortés, Gonzalo, Girotto, Manuela, Huning, Laurie S., Li, Dongyue, Durand, Michael
Geophysical Research Letters

“The main take-home is thinking about drought over longer time scales. The first wet year doesn’t necessarily solve the longer-term problem.”

Steve Margulis, principal investigator, UCLA’s Henry Samueli School of Engineering and Applied Science

  • Uses a new spatially distributed snow reanalysis data set in combination with longer term in situ data to analyze the Sierra Nevada (USA) snowpack
  • Analysis indicates that water year 2015 was a truly extreme (dry) year
  • Finds the range-wide peak snow volume was characterized by a return period of over 600 years (95% confidence interval between 100 and 4400 years) having a strong elevational gradient with a return period at lower elevations over an order of magnitude larger than those at higher elevations
  • Finds that the 2015 conditions, occurring on top of three previous drought years, led to an accumulated (multiyear) snowpack deficit of ~ 22 km3, the highest over the 65 years analyzed
  • Early estimates based on 1 April snow course data indicate that the snowpack drought deficit will not be overcome in 2016, despite historically strong El Niño conditions
  • Results based on a probabilistic Monte Carlo simulation show that recovery from the snowpack drought will likely take about 4 years