Atmospheric response to SST anomalies. Part 1: Background-state dependence, teleconnections and local effects in winter.
Journal of the Atmospheric Sciences
American Meteorological Society
Reason for embargo
Currently under an indefinite embargo pending publication by American Meteorological Society. On publication, author accepted manuscript to be replaced with published version under a 12 month embargo.
The atmospheric response to SST anomalies is notoriously difficult to simulate and may be sensitive to model details and biases, particularly in midlatitudes. Studies have suggested that the response is particularly sensitive to a model’s background wind field and its variability. The dependence on such factors has meant that it is difficult to know what responses, if any, are robust, and whether the system itself is sensitive or whether models themselves are failing. Our goal in this work is to better understand the geographical and seasonal dependence of the atmospheric response to SST anomalies, with particular attention to the role of the background state. We examine the response of an idealized atmospheric model to SST anomalies using two slightly different configurations of continents and topography. These configurations give rise to different background wind fields and variability within the same season, and therefore give a measure of how robust a response is to small changes in the background-state. We find that many of the midlatitude SST anomalies considered do not produce responses that are common across our model configurations, confirming that this problem is very sensitive to the background state. Local responses in the tropics, however, are much more robust. Some of the basic-state dependence seen in midlatitudes appears to be related to the structure of both the model’s modes of internal variability and the stationary-wave field. In addition, midlatitude responses involving a significant amount of vertical temperature advection produce larger-scale responses, consistent with recent studies of atmospheric responses near strong western-boundary currents.
SIT is supported by the Natural Environment Research Council (grant number NE/M006123/1), and GKV acknowledges support from the Royal Society (Wolfson Foundation), the Leverhulme Trust and the Newton Fund.
This is the author accepted manuscript.
Awaiting citation and DOI