Prevalence, microphysics, and radiative properties of diamond dust, fog, and blowing snow over the central Greenland Ice Sheet
Monday, 15 December 2014
The surface mass balance of the Greenland ice sheet is modulated in part by clouds through their interactions with the hydrologic cycle and influence on the surface energy budget. Furthermore, precipitation and post-depositional processes influence the isotopic composition of the ice, which is used for paleoclimatic reconstructions. Despite these important roles, relatively little is known of the properties of clouds over Greenland. Therefore, detailed observations are needed to constrain the influence that clouds have on the ice sheet and to support climate and weather modeling. This work focuses on observations of surface-based clouds from Summit, Greenland (72N 38W 3200m), including supercooled liquid radiation fogs, diamond dust, and blowing snow. Co-located measurements from a variety of sensors are combined to report on the prevalence of these clouds, their microphysical and radiative properties, the influence they have on the isotopic ratio of surface accumulation, and the meteorological conditions under which they occur. Observations include in situ measurements from particle imaging and scattering probes as well as meteorology at 2m and 10m and remotely sensed observations made at the surface from a cloud radar, an infrared spectrometer, and a suite of broadband radiation sensors. The period of study is June 2012 through October 2013. Surface-based clouds (Nd > 1 cm-3) occur between 20% and 60% of the time, more often in winter and less in summer. Supercooled liquid is identified throughout the year and at temperatures as low as -40 C. These types of clouds exhibit a range of radiative, dynamic, and hydrologic interactions with the surface and therefore are sensitive to changes in aerosols, the presence of other cloud types, temperature, humidity, and near-surface stability.