1193 / 2024-09-20 16:33:27
Joint influences of the PDO and AMV on the linkage between tropical SST and Hadley Circulation
Hadley circulation, AMV, PDO, tropical SST, meridional structures, equatorially asymmetrical variation, equatorially symmetrical variation
Session 20 - Decadal Climate Variability: Key Processes of Air-Sea Interaction, Mechanisms and Predictability
Abstract Accepted
The Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Variability (AMV) represent the most significant interdecadal variabilities within the ocean-atmosphere system, exerting prominent interdecadal impacts on global and regional climates. Their joint interdecadal modulation on the linkage between Hadley circulation (HC) and tropical sea surface temperatures (SST) in different meridional structures during their opposite phase combinations (PDO−&AMV+ and PDO+&AMV− phases) is explored using various datasets. The PDO−&AMV+ and PDO+&AMV− phases demonstrate asymmetrical impacts on the relationship of HC−SST. During PDO−&AMV+ phase, increased variations in the equatorially asymmetrical components of HC are observed, and the response of the HC to tropical SST significantly decreases. However, this is not the case during the PDO+&AMV− phase, showing insignificant change in the response of the HC to tropical SST. These results have been consistently corroborated by multiple datasets and further validated in another PDO−&AMV+ phase. The underlying process of the decreased response of HC to tropical SST during the PDO−&AMV+ phase is explored, indicating that the anomalous meridional SST gradient in the tropical central-eastern Pacific is the main contributor. The meridional SST gradient in this region induces equatorially asymmetric cyclonic circulation, which significantly reduces the variation of the equatorially asymmetrical component of HC, leading to a reduced response of HC to the different meridional structures of SST during PDO−&AMV+ phase. The result elucidates the co-influence of both PDO and AMV on tropical ocean-atmosphere interactions, particularly when the two are in opposite phases. The phase combinations of the two can modify the intensity of the tropical ocean-atmosphere response by altering the meridional structure of SST in the central and eastern tropical Pacific. This provides insights for understanding the impact of extratropical interdecadal variability on tropical ocean-atmosphere processes, offering a new perspective for predicting variations in both global and regional HC.