. Spatial dependence of cloud properties at the North Slope of Alaska

Abstract
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. Also, anthropogenic activity at the North Slope of Alaska, which is mostly focused to the Prudhoe Bay oilfield, can be a local source for emissions. If these emissions contain cloud condensation nuclei or ice nucleating particles, this might also cause spatial patterns in cloud properties. To investigate some of these phenomena, we analyze two different datasets: First, we use 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 the polarimetric Ka-band scanning ARM cloud radar (KaSACR) to evaluate how surface type (land, sea, ice) modifies fundamental cloud properties on a scale of 20 km. For this, we focus on properties which can be observed (e.g. cloud cover, cloud base heights) or retrieved (e.g. water content and precipitation) with the radar. Second, we use 10 years of regridded MODIS satellite products to investigate spatial gradients of cloud properties such as effective radius, liquid water path and optical thickness for the whole North Slope of Alaska region. These gradients are related to surface properties and sources of anthropogenic emissions.