NORTH SLOPE SITE SCIENTIST TEAM

Significant and interrelated atmospheric, oceanic and terrestrial changes have been occurring in the Arctic in recent decades. Arctic temperatures have risen at almost twice the rate compared to the rest of the world for the last few decades, resulting in broad-ranging changes. Of particular concern is the reduction in perennial sea-ice and summer sea-ice extent. As a result, there has been a sustained interest in studying processes that might contribute to these accelerated changes in the Arctic. Various contributing factors have been identified, but in all likelihood multiple factors contribute in a complicated, nonlinear way to changes in perennial and summer sea ice. As a consequence, the variability in the prediction of climate trends is much greater in the Arctic than anywhere else on Earth. This uncertainty derives from the important contribution of ice and snow at higher latitudes to climate trends through the ice-albedo feedback. The magnitude of this feedback remains uncertain because the ice-albedo feedback is strongly coupled to Arctic cloud processes and ocean heat transport. Climate model projections of summer sea-ice declines range from ice-free Arctic summers within 30 years to the end of the twenty-first century. These projections must be viewed in light of most models significantly underestimating the observed trend in Arctic sea-ice seasonal decline.The coming years are going to be exciting years at all of the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) sites, including the North Slope of Alaska (NSA). The addition of the scanning cloud and precipitation radars, operating at multiple frequencies, to the NSA suite of instruments represents a new era in Arctic cloud research. We propose a coupled observational/modeling approach to advance the process-level understanding of the key interactions among aerosols, clouds, precipitation, radiation, dynamics (small- and large-scale), and thermodynamics in Arctic clouds. Cloud extent and lifetime, as well as precipitation amount and intensity, are complex functions of the environment in which they form. The radiation budget and hydrological cycle are intimately tied to the properties of clouds, and in the Arctic, where mixed-phase stratiform clouds are frequently observed, are particularly sensitive to the phase partitioning of the condensed water. We will exploit the new radar systems to develop a new retrieval to characterize ice phase processes in Arctic clouds and to constrain a model of the same processes via improved forward models that better link to novel model outputs. This combined observational/modeling approach is anticipated to lead to improvements in our understanding of the precipitation production processes in Arctic clouds.