The atmospheric response to Oyashio front shifts in atmospheric GCMs

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Wednesday, 5 February 2014: 5:00 PM
Room C101 (The Georgia World Congress Center )
Dimitry Smirnov, CIRES/Univ. of Colorado, Boulder, CO; and M. A. Alexander, M. Newman, Y. O. Kwon, and C. Frankignoul

We investigate the atmospheric response to Oyashio SST front variability by forcing a high-resolution (0.25) GCM with SST anomalies seen during typical north/south shifts of the Oyashio front during the boreal winter. The local response is an anomalous, thermally direct vertical circulation extending through most of the troposphere, accompanied by a weak negative sea-level pressure (SLP) anomaly. Meanwhile, the downstream response is a significant weakening of the Aleutian Low associated with a northward shifted Oyashio front, which is remarkably persistent across individual months. An analogous simulation using the 1 version of the same GCM reveals no downstream response. The 0.25 GCM appears more consistent with observations in two regards: the relatively weak local SLP response, and the deeper extent of the anomalous vertical circulation. Consequently, the larger emphasis on anomalous vertical heat transport in the 0.25 GCM, as opposed to horizontal heat transport in the 1 GCM, may be more efficient in forcing changes in the storm track.