CCA4: Air mass transport and transformation

Changes in anomalous moisture transport into the Arctic is important for the regional climate change. For example, anomalous strong moisture transport by atmospheric rivers can contribute to an increased Greenland ice sheet surface melt in summer. Furthermore, synoptic-scale storm events transport pulses of heat and moisture into the Arctic and can reduce radiative cooling and henceforth sea ice growth in winter. Cold air outbreaks are another facet of Arctic-mid-latitude linkage. During transport over different surfaces, e.g., sea ice and open water, air masses experience transformations, which are challenging to model due to the complexity of boundary layer processes.

• Understand spatio-temporal transport and transformation of air masses and link the related moisture transport to the precipitation efficiency,
• Verify and improve its 3D representation in climate models exploiting observations,
• Quantify its contribution to Arctic amplification.

• What is the role of anomalous moisture transport into the Arctic for precipitation and snowfall, and what is the impact on the surface energy budget and of the ice-ocean conditions along its pathway (link to CCA2)?
• How do the cloud microphysics and vertical mixing interact with the air mass transformation and thus the precipitation and snowfall and its representation in models of different resolution (link to CCA1 and CCA3)?

• Synthesising air mass related research performed in numerous (AC)³ projects,
• Results from observations and modelling across scales will be connected with respect to (a) air mass identification techniques (e.g., for atmospheric rivers, cyclones, circulation weather types, cold air outbreaks, large-scale circulation patterns), and (b) case studies for which in-situ (ground and aircraft based) and remote sensing observations (ground-based, airborne, satellite) collected during MOSAiC and HALO-(AC)³ will be synthesised,
• Generated three-dimensional assessment of air mass transport and transformation will be used to evaluate ICON-based model results on different resolutions,
• Results will be linked to (c) climatological assessment that will provide an inventory of events and their changes in time, in particular for atmospheric river in the Arctic and their effects on moisture transport, precipitation and snowfall, and surface energy budget.