The Simulated Atmospheric Response to Western North Pacific Sea Surface Temperature Anomalies

Observations reveal two distinct patterns of atmospheric variability associated with wintertime variations in midlatitude sea surface temperatures (SSTs) in the North Pacific sector: 1) a pattern of atmospheric circulation anomalies that peaks 2-3 weeks prior to large SST anomalies in the western North Pacific that is consistent with atmospheric forcing of the SST field, and 2) a pattern that lags SST anomalies in the western North Pacific by several weeks that is consistent with the atmospheric response to the SST field. Here we explore analogous lead-lag relations between the atmospheric circulation and western North Pacific SST anomalies in two sets of simulations run on the NCAR Community Earth System Model version 1 (CESM1): 1) a simulation run on a fully coupled version of CESM1 and 2) a simulation forced with prescribed, time-evolving SST anomalies over the western North Pacific region. Together, the simulations support the interpretation that the observed lead-lag relationships between western North Pacific SST anomalies and the atmospheric circulation reveal the patterns of atmospheric variability that both force and respond to midlatitude SST anomalies. The results provide numerical evidence that SST variability over the western North Pacific has a demonstrable effect on the large-scale atmospheric circulation throughout the North Pacific sector.

Automated summary

Observations reveal two distinct patterns of atmospheric variability associated with wintertime variations in midlatitude sea surface temperatures (SSTs) in the North Pacific sector. One pattern is characterized by peak atmospheric circulation anomalies 2-3 weeks prior to large SST anomalies in the western North Pacific, consistent with atmospheric forcing of the SST field. The other pattern shows atmospheric circulation anomalies lagging behind SST anomalies in the western North Pacific by several weeks, consistent with the atmospheric response to the SST field. Numerical simulations support the interpretation of these lead-lag relationships, providing evidence for the influence of SST variability on the large-scale atmospheric circulation.