Combined impacts of temperature, sea ice coverage, and mixing ratios of
sea spray and dust on cloud phase over the Arctic and Southern Oceans
Abstract
We analyze the importance of cloud top temperature, dust aerosol, sea
salt aerosol, and sea ice cover for the thermodynamic phase of
low-level, mid-level, and mid to low-level clouds observed by
CloudSat/CALIPSO over the Arctic and the Southern Ocean using an
explainable machine learning technique.
As expected, the cloud top temperature is found to be the most important
parameter for determining cloud phase. The results show also a
predictive power of sea salt and sea ice on the phase of low-level
clouds, while in mid-level clouds dust shows predictive power. Over the
Southern Ocean, strong zonal winds coincide with the aerosol
distribution. While they can produce high mixing ratios of sea spray at
lower levels, the strong zonal winds may prevent the pole-ward transport
of dust. Sea ice may prevent the release of sea salt aerosols and marine
organic aerosols leading to higher liquid fractions in clouds over sea
ice.