Synoptic and Spatial Dependence of Cloud Properties at Oliktok Point in Northern Alaska

Arctic clouds are a key component of the Arctic climate system. In particular, liquid-containing clouds can have a major impact on radiative transfer and budgets. Clouds interact with their environment through multiple pathways, but these can be difficult to quantify and some of the processes supporting those pathways are not well understood. The diversity of Arctic surface types (land, sea, ice) can influence cloud formation and lifetime through turbulent surface fluxes of heat and moisture and the availability of aerosols. Therefore, retreat of Arctic summer sea ice could lead to a change of cloud properties, as can changes in the magnitude of the land-sea temperature gradient. Also, modification of prevailing synoptic regimes associated with a changing Arctic climate could have impact on vertical structure of the atmosphere (e.g. stability) and moisture transport. As a consequence, also cloud formation could be modified.

To investigate some of these phenomena, we analyze one year of radar observations from the Department of Energy Atmospheric Radiation Measurement (DOE ARM) program observatory in Oliktok Point at the North Slope of Alaska. We use observations of the dual-wavelength polarimetric Ka- and W-band scanning ARM cloud radar (KaSACR & WSACR) to evaluate how surface type and synoptic regime modify cloud properties with respect to fundamental cloud properties (e.g. water content, cloud base heights and cloud phase). The impact of synoptic scale atmospheric patterns is investigated by classifying the radar observation with respect to the prevailing synoptic regime. For this, self-organizing maps (SOMs) are used to identify the prevailing synoptic types.