Abstract

A physically-based parameterization of atmospheric surface drag over the marginal-ice-zone has recently been validated and tuned based on a large set of observations of surface stress from the ACCACIA project (Elvidge et al. 2016, Atmos. Chem. and Physics). This parameterization has now been implemented in the Met Office Unified Model (MetUM) and is available for both weather and climate applications. Here we present test results for a case study of a cold-air outbreak over and downstream of the MIZ , and for a collection of cases from the ACCACIA field campaign. Our focus is on the response of the atmosphere to the changes in surface drag. Preliminary results show that the new parameterization has a significant impact on simulated boundary layer conditions. For example, boundary layer temperatures over the MIZ during cold air outbreaks are generally reduced by 2-3 K in the model, in response to markedly reduced surface heat fluxes. Comparisons with aircraft observations reveal the changes to generally be beneficial. The implications of these changes for the climate system will be discussed.