MOSAiC

Nudged climate model runs for MOSAiC
Contact: Felix Pithan

With this project, we aim to evaluate and improve the representation of key Arctic climate processes in coupled climate models using data from the year-long central Arctic Ocean drift campaign MOSAiC. To obtain model output that is comparable to observations, we nudge the atmospheric circulation in models against reanalysis. A pilot study has demonstrated that this allows to reproduce observed weather patterns at MOSAiC in coupled climate models on a day-to-day basis (https://egusphere.copernicus.org/preprints/2022/egusphere-2022-706/).

Science questions

1. Liquid-containing and ice clouds.
   How do climate models represent the cloud liquid and ice content, cloud cover, their vertical distributions and the resulting cloud radiative effect in different seasons?
2. Stable boundary layers and inversions (Carsten Abraham, CCCma).
   Does the occurrence of stable boundary-layers, surface-based and elevated temperature and humidity inversions in models match observations? Can any mismatches be at- tributed to specific processes? Do models reproduce the observed relationship between temperature gradients, wind speeds and turbulent fluxes?
3. Air-mass transformations.
   How do temperature and humidity profiles evolve in models and observations between stations near the ice edge (e.g. Ny-Alesund) and the MOSAiC observatory over the central Arctic ocean?
4. Surface interaction.
   How quickly and strongly does surface temperature respond to changes in the surface energy balance in models and observations?
5. Aerosol Cloud Radiation Interactions (Andrew Gettelman, PNNL).
   What is the impact of aerosol species on the formation of clouds and the phase of clouds? What are the most common aerosols associated with liquid and ice clouds in the Arctic?
6. Sea ice (Valentin Ludwig, AWI ).
   How well is sea-ice deformation represented in the nudged model runs? How are sea-ice deformation and thermodynamic/dynamic ice growth linked in the model runs?
7. Upper-ocean (Marylou Athanase, AWI ).
   How well is reproduced the impact of changing atmospheric and sea-ice conditions on upper-ocean (i) stratification, (ii) dynamics, (iii) vertical heat and salt fluxes? Does constraining the precursor atmospheric conditions improve the representation of upper-ocean water mass properties?

Timeline and practicalities:
We aim to obtain model output by 1 April 2023 and discuss first results at the CFMIP/GASS meeting in July. Both coupled and atmosphere-only models can participate. If you intend to participate with your model, get involved in analyzing the data or would like to be kept updated on future steps, please get in touch with Felix Pithan.