Apr 10, 2017

Multi-century evaluation of recovery from strong precipitation deficits in California

Eugene. R. Wahl, Henry F. Diaz, Russell S. Vose, and Wendy S. Gross
American Meteorological Society

The odds of the state completely recovering from its extreme dryness within two years are estimated at less than 1 percent.

Eugene R. Wahl, NCEI paleoclimatologist and lead author of the study

  • Employs spatially-explicit precipitation reconstructions for California in combination with instrumental data to provide perspective on this event since 1571
  • Finds that 2012-2015 stands out as particularly extreme in the southern Central Valley and South Coast regions, which likely experienced unprecedented precipitation deficits over this time, apart from considerations of increasing temperatures and drought metrics that combine temperature and moisture information
  • Finds some areas lost more than two years’ average moisture delivery during these four years, and full recovery to long-term average moisture delivery could typically take up to several decades in the hardest-hit areas
  • These results highlight the value of the additional centuries of information provided by the paleo-record, which indicates the shorter instrumental record may underestimate the statewide recovery time by over thirty percent
  • Finds the extreme El Niño that occurred in 2015-2016 ameliorated recovery in much of the northern half of the state, and since 1571 very strong-to-extreme El Niño’s during the first year after a 2012-2015 type event reduce statewide recovery times by approximately half
  • Finds the southern part of California did not experience the high precipitation anticipated, and the multi-century analysis suggests the north-wet/south-dry pattern for such an El Niño was a low-likelihood anomaly
  • States that recent wetness in California motivated evaluation of recovery times when the first two years are relatively wet, suggesting the state is benefiting from a one-in-five (or lower) likelihood situation: the likelihood of recovery in just two years is less than ~0.5% in the instrumental data and even lower in the reconstruction data