Veronica Fall-April 24

Characteristics of the 2011-2016 California Drought

“The recent California drought persisted for five years from 2011-2016.  Previous studies have established that this drought was marked by low, but not unprecedented rainfall coupled with extremely warm temperatures that acted to exacerbate the effects of reduced precipitation.  Other studies have analyzed how snow-water equivalent during the drought compares with California’s historical records and the role that teleconnections (ENSO and the PDO) may have had to influence precipitation patterns across the state.  Since there has yet to be an analysis performed for the entire five-year period of the drought, this study analyzes maximum temperature, minimum temperature, and precipitation to compare with the findings of previous studies.  Specifically, emphasis will be placed on understanding how snowfall in the Sierra Nevada Mountains during the five years of drought compares with all other five-year groups since 1950.

Using permutation tests, it was found that 2011-2016 was the warmest five years for maximum temperature in California while minimum temperature during the drought is the seventh warmest five-year period.  In the Sierra Nevada Mountains, snowfall was the lowest on record, which was significantly different from all other five-year groups and nearly twice as low as any other five-year period.  Using one-year average snowfall during the wet season, snowfall exhibited pronounced oscillatory behavior, which was found to be significant at periods of 16 years and between 2 and 4 years.  These significant periodicities of snowfall were compared with the periods of ENSO and the PDO using wavelet analysis, where significant coherence was found with both teleconnections at periods between 3-4 years.  Understanding the relation between California snowfall and teleconnection patterns may help to achieve better prediction of yearly snowfall anomalies while providing more questions about what drives variations in snowfall from year to year, especially given the extreme precipitation and snowfall of this past winter.”