WES feedback and the Atlantic Meridional Mode: observations and CMIP5 comparisons

摘要: The Atlantic Meridional Mode (AMM) is the dominant mode of tropical SST/wind coupled variability. Modeling studies have implicated wind-evaporation-SST (WES) feedback as primary driver AMM’s evolution across basin; however, a robust coupling SST and winds has not been shown in observations. This study examines observed AMM growth, propagation, decay result WES interactions. Investigation an extended maximum covariance analysis shows that boreal wintertime atmospheric forcing generates positive anomalies (SSTA) through reduction surface evaporative cooling. When peaks magnitude during spring summer, upward latent heat flux occur over warmest SSTs act to dampen initial forcing. In contrast, on southwestern edge SSTA, SST-forced cross-equatorial flow reduces strength climatological trade provides anomalous into ocean, which causes southwestward propagation atmosphere-forced SSTA dynamics. Additionally, lead-lag relationship ocean atmosphere indicates transition from atmosphere-forcing-ocean regime northern subtropics highly tropics southern hemisphere. CMIP5 models poorly simulate latitudinal one-way interaction two-way feedback, may explain why they also struggle reproduce spatially coherent interactions between winds. valuable insight how meridional modes links extratropical variability focuses future research aimed at improving climate model simulations.