Atmospheric Response to SST anomalies. Part II: Background-state dependence, teleconnections and local effects in summer
Thomson, SI; Vallis, GK
Date: 1 December 2018
Article
Journal
Journal of the Atmospheric Sciences
Publisher
American Meteorological Society
Publisher DOI
Abstract
In this paper and its companion, Part I, we explore the response of the atmosphere to sea-surface temperature
anomalies in different geographical locations and seasons. In Part 1we focussed on northern-hemisphere
winter (DJF) whereas in this paper, Part 2, we focus on summer (JJA) and inter-seasonal comparisons. We use
two different ...
In this paper and its companion, Part I, we explore the response of the atmosphere to sea-surface temperature
anomalies in different geographical locations and seasons. In Part 1we focussed on northern-hemisphere
winter (DJF) whereas in this paper, Part 2, we focus on summer (JJA) and inter-seasonal comparisons. We use
two different configurations of the same idealised atmospheric model, constructed using two different configurations
of continents and topography. These configurations give rise to slightly 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 characterise the types of responses that are found to SST anomalies in
the midlatitudes and tropics in JJA, and compare these with the corresponding responses in DJF. We find that
the responses to midlatitude SST anomalies in JJA are generally on a much smaller spatial scale than those in
DJF. Responses in the tropical Pacific are much less dependent on season, although teleconnections between
the tropical Pacific and the North Atlantic are not found in JJA as robustly as they are in DJF. Given insight
from our model results, however, we do find some summer periods in reanalysis data where there is a strong
association between the tropical Pacific and the summer North-Atlantic Oscillation. We discuss the reasons
for these effects and the implications for Northern Hemisphere seasonal prediction in summer.
Mathematics and Statistics
Faculty of Environment, Science and Economy
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