28 February 2019

Linear and Nonlinear Winter Atmospheric Responses to Extreme Phases of Low-Frequency Pacific Sea Surface Temperature Variability

Science

This study is to examine the linear and nonlinear atmospheric responses during the Northern Hemisphere winter (December to February) to opposite strong phases of interdecadal Pacific sea surface temperature (SST) forcing. This SST forcing resembles El Niño-Southern Oscillation (ENSO) on a longer time scale and named low frequency (LF) mode variability. The analysis includes observations and atmospheric model simulations forced by the positive and negative phases of the LF using both GFDL_AM2.1 and CAM4 models.

Impact
  • Models: GFDL_AM2.1 and CAM4
  • Simulations: climatology run forced by observed repeated annual cycle SST; idealized LF+ and LF- simulations with the climatological SST plus 2 standard deviations of LF+/LF- SST pattern
  • The linear response of the climate is represented by the addition of the LF+ simulations and LF- simulations; and the nonlinear response by the subtraction of these two sets of simulations.
Summary
  • Atmospheric models forced by SST anomalies associated with Pacific low-frequency variability are capable to reproduce the observed surface temperature and precipitation responses.
  • The observed winter surface temperature and precipitation anomalies are highly related to the low-frequency variability in the Pacific, through linear and nonlinear teleconnections.
Contact
Aixue Hu
National Center for Atmospheric Research (NCAR)
Publications
Cao, D, Q Wu, A Hu, Y Yao, S Liu, SR Schroeder, and F Yang.  2019.  "Linear and Nonlinear Winter Atmospheric Responses to Extreme Phases of Low-Frequency Pacific Sea Surface Temperature Variability."  Climate Dynamics 52(1-2): 49-68, doi:10.1007/s00382-018-4127-1.