Associations Between Summer Circulation Anomalies and Sea Surface Temperature Forcing

摘要

Observational studies have associated a 3-cell pattern of anomalous 700 mb anticyclones with drought. These three strong anticyclones are located over the eastern North Pacific, the central United States, and the eastern North Atlantic. The present study utilizes a two-level global spectral model to test the hypothesis that sea surface temperature anomaly (SSTA) forcing is initiating the 3-cell, drought-producing anticyclone pattern. It is proposed that the two anomalous oceanic anticyclones develop over the barotropic eastern ocean basins in response to abnormally cold surface water in this region, as observed in June of 1980. Teleconnection patterns for summer reveal the tendency for a similar anomalous anticyclone to develop over the central United States once the oceanic anomaly has formed. Based on this empirical evidence, the initial experiments investigate the association between SSTA forcing and anomalous drought-producing circulations. Additional experiments are undertaken to examine the effects of changes in the magnitude and latitude of the SSTAs on the model response, and to investigate the possibility of an interhemispheric energy transfer within the model integration. The magnitude and location of the SSTA greatly influences the resultant model response, demonstrating the atmosphere's sensitivity to this type of forcing. The large interhemispheric response discovered in the model is attributed to the difficulties in the simulation of the tropical wind field, which allows for the transfer of meridionally propagating energy between the Northern and Southern Hemispheres through westerly wind ducts. 34 refs. (ERA citation 11:011863)