A set of deterministic and stochastic model improvements for the AWI-CM3 climate model

We present intermediate results as well as ongoing work on improving the post-CMIP6 climate model of the Alfred Wegener Institute, AWI-CM3. A baseline version of the model was completed in 2021 with an above average performance when compared to other CMIP6 models. Close investigation of surfaces fluxes revealed that v3.0 can be further improved in a number of ways which will also benefit other climate models.

As a first step we reevaluated old coupling simplifications and assumptions made years ago. At the air-sea ice interface we corrected the gradient of surface sensible heat flux / wind speed vs. (2m air temp - sea ice surf temp), by using a nudged version of AWI-CM3 and evaluating against in situ data from the MOSAiC-Expedition. We added the coupling of ocean current feedback, as well as new latent and sensible heat fluxes resulting from precipitation entering the ocean with a different temperature and state than the ocean surface. As a precursor to subsequent Earth System Model (ESM) development we included the coupling of mass and heat fluxes of snow falling on ice-sheets. The resulting AWI-CM3 v3.1 shows increased ability to represent the current climate and historic climate change.

Furthermore we present ongoing work towards AWI-CM3 v3.2, where among other improvements we will include the coupling of sub atmospheric gridscale information from the higher resolution ocean grid, via a stochastic method. Finally we give a brief outlook on our efforts to link up with the EC-Earth climate and earth system model community for common cryosphere, vegetation and isotope developments towards two comprehensive ESMs.