Explicit versus Parameterized Convection in Response to the Atlantic Meridional Mode

  • - This study investigates the sensitivity of the coupling between precipitation and SST to the representation of convection, being explicit or parameterized, in the context of the Atlantic Meridional Mode (AMM).
  • - We use the ICON atmospheric model over the tropical Atlantic, wherein we impose SST patterns representative of the climatology, positive and negative AMM during March-April-May. Two configurations are applied: one with convective parameterization (P-CON) at a grid spacing of 40 km on a global domain; and one with the convective parameterization switched off (E-CON) at a grid spacing of 5 km over a nested tropical Atlantic domain.
  • - We find that the precipitation response to an AMM-SST pattern is robust to the representation of convection despite E-CON and P-CON display a distinct precipitation climatology. Both experiments shift the mean position of the ITCZ about one degree toward the warmer tropical Atlantic as a result of the related gradient of SST anomalies, which induces cross-equatorial surface winds.
  • - Analysis of surface flux anomalies lead us to expect a stronger amplification of SST anomalies in simulations with explicit rather than parameterized convection. Our argument is based on the wind speed anomalies in response to an AMM-SST pattern. Changes in the wind-driven heat fluxes are more strongly enhanced when convection is explicitly resolved.
  • Read the full article here: https://journals.ametsoc.org/view/journals/clim/34/9/JCLI-D-20-0224.1.xml