Overview schematic of the different phenomena and scales of interest in the present project. The L (Low) near the surface and at the tropopause represent the Arctic cyclone and tropopause polar vortex (TPV) respectively. The cold and warm fronts are shown in blue and red. The dashed black line denotes the axis of minimum pressure with height. In this schematic, the vertical tilt of the Arctic cyclone with height shows intense baroclinic interaction between the TPV and the Arctic cyclone. Are also shown the Arctic frontal zone (AFZ) closely related to the Arctic coastlines and the Marginal Ice Zone (MIZ) associated with lower sea ice concentration.

The project aims at studying interactions between atmospheric dynamics, cloud microphysics and sea ice near summertime Arctic cyclones. Its objectives are the following:

  1. Better understanding of Arctic cyclones dynamics. Processes contributing to the initiation, intensification and decay of Arctic cyclones are largely understudied.
  2. Better understanding of low-level moisture intrusion events. These events are often related to the presence of cold fronts but not necessarily very close to an Arctic cyclone. They can be at the origin of the more rapid Arctic warming and sea-ice decline.
  3. Better understanding of Tropopause Polar Vortex dynamics, which are often upper-level precursors of Arctic cyclones.
  4. Better understanding of the interactions between Arctic cyclones and cloud microphysics. We will investigate how cloud microphysics influence Arctic cyclones dynamics. A focus will be made on the mixed-phase clouds to address the following questions: What is the impact of large scale conditions on the mixed-phase cloud microphysical properties? How are the ice and liquid phases mixed and spatially distributed within the cloud? How do the radiative, dynamical, microphysical processes interact and control mixed-phase clouds life cycle?
  5. Better assessment of the interactions between Arctic cyclones and the underlying sea surface and sea ice. This objective will be restricted to the direct interactions between sea ice and the atmosphere without implying ocean dynamics and waves.
  6. Assessment of Numerical Weather Prediction (NWP) and climate models ability to accurately represent Arctic cyclones or tropopause polar vortices, in particular their interactions with cloud microphysics and surface heterogeneities (sea ice vs open water).
Key questions will be:
  • How do NWP models represent boundary layer and heat surface exchange above sea ice?
  • How do NWP models represent mixed-phase clouds?
  • Are radiative processes maintaining tropopause polar vortices intensity well represented in NWP models?