A modelling and observational study of the relationship between sea surface temperature in the North‐West atlantic and the atmospheric general circulation

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Authors: Palmer, T. N., Zhaobo, Sun
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1985
• Subjects: North Atlantic; North West Atlantic; Northwest Atlantic
• Online Access: http://dx.doi.org/10.1002/qj.49711147003; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqj.49711147003; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.49711147003

Abstract Results from four pairs of 50‐day wintertime integrations of the Meteorological Office's 5‐level general circulation model, with warm and cold sea surface temperature (s.s.t.) anomalies of about 3 K in the northwest Atlantic, are described. Difference fields between the warm and cold integrations are statistically significant at the 1% level with positive geopotential height over the central north Atlantic, and weaker negative height over Europe. the storm track over the Atlantic is displaced from its normal position. Results from four further pairs of integrations with halved s.s.t. anomalies are also described. the response is approximately linear, with systematic differences in 500 mb geopotential height over the Atlantic, parts of which are just significant at the 10% level with half the full s.s.t. anomaly. Overall, however, the model's response is weaker than could be obtained with tropical s.s.t. anomalies of the same magnitude. Results from the model integrations are compared with results from an observational study of the relationship between wintertime s.s.t. in the north‐west Atlantic, and mean sea level pressure and 500mb height. Two independent 30‐year periods were chosen for study, thus minimizing the influence of long‐term trends in s.s.t. Over the Atlantic and Europe the model results compared well with the observations. With s.s.t. data lagging the atmosphere by one month, the observational study appears to show that the s.s.t. anomalies are initially forced by perturbations in the atmospheric circulation. With s.s.t. data leading the atmosphere by one month results show that atmospheric and s.s.t. anomalies are most persistent in the period October to December. Throughout the winter these lagged relationships are much weaker and not statistically significant. Diagnostics of E ‐vector divergence from the GCM experiments are used to suggest that anomalous baroclinic wave activity over the Atlantic is important as a momentum forcing for the anomalous time‐mean flow pattern. On the other ...