May 2, 2014

Probable causes of the abnormal ridge accompanying the 2013–2014 California drought: ENSO precursor and anthropogenic warming footprint

Wang, S.‐Y., Hipps, Lawrence, Gillies, Robert R, Yoon, Jin‐Ho
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