Quantifying the local and remote impacts of sub‐grid physical processes on the Southeast Pacific sea surface fluxes in the Community Atmosphere Model version 5 by a limited‐area parameter perturbation approach

Abstract

AbstractThe Southeast Pacific (SEP) has distinct climate features that are governed by interactions among processes at multiple spatial scales and thus are hard to represent in climate models. This study investigates the local and remote impacts of various physical processes on surface fluxes over SEP in the Community Atmosphere Model version 5 by using a limited‐area parameter perturbation approach. In this approach, physical parameters from the Zhang‐McFarlane (ZM) convection scheme and the turbulence parameterization scheme of Cloud Layers Unified by Binormals (CLUBB) are perturbed in specific regions, but fixed outside. Three limited‐area perturbed parameter ensembles are performed over SEP, the Intertropical Convergence Zone (ITCZ) and the South Pacific convergence zone (SPCZ), respectively, with the simulations over SEP the primary focus that can respond to both local impacts and remote impacts from ITCZ and SPCZ. Results show that most of the variability of surface radiative fluxes is explained by the local impacts of sub‐grid physical processes and those related to shallow convection are most important. By contrast, a considerable portion of the variability of the surface latent heat flux is attributed to the remote effects from ITCZ and SPCZ, which are mainly contributed by the ZM parameters that can affect the large‐scale circulation by modulating the diabatic heating related to precipitation. Both the latent heat flux and shortwave radiative flux over SEP increase with the eastern‐ITCZ precipitation due to the stronger surface wind and less clouds, respectively. Overall, our results help better understand the sources of uncertainties in the simulated SEP climate.