Deliverable No. 2.4 Report on the application of the fully coupled SCM to test cases based on Arctic YOPP IOPs

The new tool, the Atmosphere-Ocean Single-Column Model (AOSCM), developed within APPLICATE and demonstrated in D2.1, is further developed to become an even more versatile tool for understanding model behaviour and aid model development. The enhancements of the model are mostly on the technical side with the goal to be able to run well-defined cases that can be compared with process observations. Procedures on how to set up cases have been defined and are described in a document appended to this deliverable.

Observational process level data from the Arctic Ocean obtained in expeditions with the ice- breaker Oden is described and merged into files designed with the purpose of being easily accessible for model development. These observations are from three summer expeditions and provide data in the vertical column that is represented by the AOSCM. The methodology is developed in an international setting and will be utilized for data from the ongoing expedition MOSAiC that will provide data for a whole year October 2019 – October 2020.

An experimental protocol is developed for the AOSCM and tested for a warm air advection case observed during the Oden expedition ACAS in 2014. The protocol covers perturbations of model setup and forcing and consists of 480 simulations of the three-day period. The perturbation analysis reveals that the net energy available at the surface during this period vary between 30 and 130 Wm-2. The results are most sensitive to the advection of moisture but substantial changes are seen when using all forcing and modifying other parameters such as the sea-ice properties, time step, model version etc. The methodology of using the AOSCM and combining it with observations are now mature enough to be expanded to cover the whole set of observational periods.

This work contributes to Objective #2 of WP2 “Develop innovative methods, using observations and a variety of model configurations, to facilitate parameter optimization for physical processes in coupled model systems for NWP and climate”.