Causes and predictability of persistent SST anomalies associated with the 2011-2014 California drought

Abstract:

Sea-surface temperature (SST) anomalies over the Pacific Ocean played substantial role on the 2011-14 California drought, however their drivers and predictability are not entirely clear. The first year of the drought (2011/2012) coincided with La Niña conditions in the tropical Pacific, therefore it was likely predictable. Neutral conditions returned to the central tropical Pacific during the subsequent years of the drought. The residual SST pattern, characterized by a cold eastern equatorial Pacific and a warm central north Pacific, is also conducive to drought, but its drivers and predictability are unknown (Seager et al. 2014). Using a combination of observations and climate model simulations we show that this residual SST pattern is typical of most observed La Nina events and potentially predictable. Both observations and models suggest that the physical processes causing the multi-year persistence of these SST anomalies are: 1) a positive cloud feedback over the eastern equatorial Pacific and 2) winter mixed layer reemergence over the north Pacific. We conclude with results from perfect model prediction experiments suggesting that these SST patterns could be predicted beyond the first year. Implications for translating this prediction skill to drought prediction will be discussed.

Seager, R., M. Hoerling, S. Schubert, H. Wang, B. Lyon, A. Kumar, J. Nakamura, and N. Henderson. 2014. Causes and Predictability of the 2011-14 California Drought. Page 42. NOAA.