Modelling Study of the Summer Time Arctic Liquid Clouds

Investigation of the cloud microphysics is carried out by using a fully coupled version of GEM-MACH, the Environment and Climate Change Canada’s (ECCC) online air quality forecast model, (Global Environmental Multiscale–Modelling Air quality and Chemistry) for the Arctic domain during summer 2014. Simulation results indicate that model is capable of simulating the low clouds prevailing in summertime Arctic, particularly thin water clouds (or clouds with liquid water path < 50 g m^-2), which have a significant effect on cloud radiative forcing in the Arctic.

Model simulations are also compared with the July 2014 NETCARE field campaign aircraft observations based from Resolute NU. The field campaign consisted of two periods with distinct metrological conditions: relatively pristine and relatively polluted Arctic atmosphere with the influence of transport from lower latitudes. For the relatively polluted period, simulations of cloud’s microphysics suggested more and smaller droplets with higher liquid water content (LWC), and hence lower precipitation and longer cloud lifetime. The model agrees well with the observation results showing that aerosols in the size range of 50-100 nm are commonly activated in the summer Arctic, with even smaller aerosols (< 50 nm) being activated during the pristine period.