Atmospheric response to SST anomalies. Part 1: Background-state dependence, teleconnections and local effects in winter
Thomson, S; Vallis, G
Date: 9 November 2018
Journal
Journal of the Atmospheric Sciences
Publisher
American Meteorological Society
Publisher DOI
Abstract
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 ...
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.
Mathematics and Statistics
Faculty of Environment, Science and Economy
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