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Abstract:
This study investigates whether the representation of explicit and parameterized convection influences the response to the Atlantic Meridional Mode (AMM). The main focus is on the precipitation response to the AMM-SST pattern, but possible implications for the atmospheric feedback on SST are also examined by considering differences in the circulation response between explicit and parameterized convection. Based on analysis from observations, SST composites are built to represent the positive and negative AMM. These SST patterns, in addition to the March-May climatology, are prescribed to the atmospheric ICON model. High-resolution simulations with explicit (E-CON) and coarse-resolution simulations with parameterized (P-CON) convection are used over a nested tropical Atlantic and a global domain, respectively. Our results show that a meridional shift of about 1° in the precipitation climatology explains most of the response to the AMM-SST pattern, both in simulations with explicit and with parameterized convection. Our results also indicate a linearity in the precipitation response to the positive and negative AMM in E-CON, in contrast to P-CON. Further analysis of the atmospheric response to the AMM reveals that anomalies in the wind-driven enthalpy fluxes are generally stronger in E-CON than in P-CON. This suggests that SST anomalies would be amplified more strongly in coupled simulations using an explicit representation of convection.
