Causes of the 2011–14 California Drought*

• DOI: 10.1175/jcli-d-14-00860.1
• Publication Date: 2015-07-16T22:47:29Z
• Authors: Richard Seager; Martin Hoerling; Siegfried Schubert; Hailan Wang; Bradfield Lyon; Arun Kumar; Jennifer Nakamura; Naomi Henderson
• Keywords: Forcing (mathematics); Trough (economics)

Abstract The causes of the California drought during November–April winters 2011/12–2013/14 are analyzed using observations and ensemble simulations with seven atmosphere models forced by observed SSTs. Historically, dry most commonly associated a ridge off west coast but no obvious SST forcing. Wet trough an El Niño event. These attributes wet captured many models. According to models, forcing can explain up third winter precipitation variance. was key sustaining high pressure over suppressing three winters. In 2011/12 this response La Niña event, whereas in 2012/13 2013/14 it appears related warm west–cool east tropical Pacific pattern. All contain mode variability linking such anomalies wave train North American coast. This explains less variance than ENSO decadal variability, its importance unusual. from phase 5 CMIP (CMIP5) project rising greenhouse gases cause changes all-winter that very small compared recent anomalies. However, long-term warming trend likely contributed surface moisture deficits drought. As such, deficit dominated natural conclusion framed discussion differences between modeled trends.