The Response of Simulated Arctic Low Clouds to Sea Ice Cover Variation under Constant Large-Scale Forcing

Abstract:

The Arctic ocean-sea ice-cloud system contains processes that are crucial to the undergoing changes of Arctic climate. Low level Arctic clouds have great influence on surface radiation budget that changes the sea ice cover, and are in turn affected by the surface conditions related to sea ice coverage. This study seeks to understand the physical processes that drive the responses of Arctic low cloud properties to different sea ice cover using Large Eddy Simulations. The simulations are conducted for two different environmental conditions derived from the observational data during Surface Heat Budget of the Arctic Ocean Experiment (SHEBA) and Mixed-Phase Arctic Cloud Experiment (M-PACE) respectively. M-PACE environment is set above open ocean, in contrast to the sea ice-covered surface of SHEBA, with higher temperature and humidity in the atmosphere boundary layer than SHEBA. For either environmental condition, the simulations are conducted under constant large scale forcing with prescribed sea ice cover from 0 to 100% in 10% interval. The deviations from the reference simulations (100% sea ice for SHEBA and 0% sea ice for M-PACE) reflect the changes in boundary layer and cloud properties due to the variability in local sea ice cover. The cloud response to the increase(decrease) of surface fluxes due to the exposing(covering) of ocean surface and the changes of surface radiation are examined. The separate roles of boundary layer temperature and humidity change in the cloud response to the surface are further investigated.