The influence of tropical sea surface temperatures and precipitation on north Pacific atmospheric blocking |
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Authors: | T J Hinton B J Hoskins G M Martin |
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Institution: | (1) Met Office Hadley Centre, FitzRoy Road, Exeter, EX1 3PB, UK;(2) Department of Meteorology, Reading University, Earley Gate, Reading, UK;(3) Grantham Institute, Imperial College, London, UK |
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Abstract: | Blocking is a major component of the extratropical climate and any changes in it would be a very important aspect of climate
change there. Previous studies have shown that mid-latitude variability such as blocking is sensitive to tropical sea surface
temperature (SST) anomalies and to variations in tropical precipitation. Climate models exhibit a wide range of skill in representing
blocking, with all models having deficiencies in certain respects. In addition, coupled climate models often exhibit significant
biases in both tropical precipitation and tropical and extratropical SSTs. This suggests that tropical systematic biases in
coupled climate models may influence the representation of blocking and its sensitivity to climate change. We examine the
relationship between winter north Pacific blocking and tropical precipitation and tropical SSTs through the use of idealised
SST anomaly experiments. We find that interannual variations in convection over the Maritime Continent and eastern equatorial
Pacific regions both influence the central and eastern Pacific winter blocking frequency. In addition, systematic underestimation
of tropical rainfall over the Maritime Continent region in climate models can lead to underestimation of time-mean winter
Pacific blocking. Finally, the sign, magnitude and variability of tropical SST biases in a coupled model, and their associated
effects on tropical precipitation, could influence its representation of northern hemisphere blocking, and thus affect its
ability to represent this mode of remotely-forced mid-latitude variability. These results have important implications for
model development. |
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Keywords: | Blocking Climate Model Tropical |
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