85th AMS Annual Meeting

Monday, 10 January 2005: 1:30 PM
Model simulations of the impact of SST conditions on atmospheric variability
Ngar-Cheung Lau, NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, NJ
A brief review is given on the influences of anomalous sea surface temperature (SST) conditions on the atmospheric circulation, as inferred from a series of experiments based on GFDL general circulation models (GCMs) developed under the leadership of Syukuro Manabe during the past three decades. These experiments range in complexity from simulations of atmospheric responses to prescribed SST anomalies in different parts of the World Oceans, to incorporation of feedbacks between the atmosphere and simplified oceanic mixed layers, and to fully coupled atmosphere-ocean GCMs. The cumulative evidence from this succession of model integrations highlights the prominent role of El Nino-Southern Oscillation (ENSO) phenomena in modulating the variablity of the atmosphere-ocean system on a broad range of time scales.

As illustration of the utility of the above modeling approach in diagnosing various facets of atmosphere-ocean interactions, results are presented from a recent simulation study on the anomalous zonally symmetric upper-level pressure ridges in the midlatitude belts of both hemispheres during the year after warm ENSO events. It is demonstrated that these atmospheric changes are primarily responses to SST perturbations in the Indo-western Pacific sector, which are in turn linked to ENSO variability in the equatorial Pacific by the `atmospheric bridge' mechanism. The model results further indicate that the zonally extended atmospheric signal spanning the East Asian-North Pacific-North American sector could serve as a conduit linking Asian summer monsoon activity to the seasonal climate in North America. The latter connection could be a contributing factor to the occurrence of summertime droughts and heat waves in the North American region.

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