May 2, 2014
Probable causes of the abnormal ridge accompanying the 2013–2014 California drought: ENSO precursor and anthropogenic warming footprint
by
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Geophysical Research Letters
- States the 2013–2014 California drought was initiated by an anomalous high-amplitude ridge system
- Investigates this anomalous ridge using reanalysis data and the Community Earth System Model (CESM)
- Finds the ridge emerged from continual sources of Rossby wave energy in the western North Pacific that started in late summer and intensified into winter
- Finds the ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole
- Says that 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
- Finds 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
- Holds that there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013–2014 and the associated drought