Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Probable Causes of the Abnormal Ridge Accompanying the 2013-2014 California Drought: ENSO Precursor and Anthropogenic Warming Footprint

TitleProbable Causes of the Abnormal Ridge Accompanying the 2013-2014 California Drought: ENSO Precursor and Anthropogenic Warming Footprint
Publication TypeJournal Article
Year of Publication2014
AuthorsWang, S-Y, Hipps Lawrence, Gillies Robert R., and Yoon Jin-Ho
JournalGeophysical Research Letters
Volume41
Number9
Pages3220-3226
Abstract / Summary

The 2013–2014 California drought was initiated by an anomalous high‐amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either El Niño–Southern Oscillation (ENSO) or Pacific Decadal Oscillation; instead, it is correlated with a type of ENSO precursor. The connection between the dipole and ENSO precursor has become stronger since the 1970s, and this is attributed to increased greenhouse gas loading as simulated by the CESM. Therefore, there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013–2014 and the associated drought.

URLhttps://doi.org/10.1002/2014GL059748
DOI10.1002/2014GL059748
Journal: Geophysical Research Letters
Year of Publication: 2014
Volume: 41
Number: 9
Pages: 3220-3226
Publication Date: 05/2014

The 2013–2014 California drought was initiated by an anomalous high‐amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either El Niño–Southern Oscillation (ENSO) or Pacific Decadal Oscillation; instead, it is correlated with a type of ENSO precursor. The connection between the dipole and ENSO precursor has become stronger since the 1970s, and this is attributed to increased greenhouse gas loading as simulated by the CESM. Therefore, there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013–2014 and the associated drought.

DOI: 10.1002/2014GL059748
Citation:
Wang, S, L Hipps, RR Gillies, and J Yoon.  2014.  "Probable Causes of the Abnormal Ridge Accompanying the 2013-2014 California Drought: ENSO Precursor and Anthropogenic Warming Footprint."  Geophysical Research Letters 41(9): 3220-3226.  https://doi.org/10.1002/2014GL059748.