Kenny Bae, Graduate Student

In-situ observations on the size and shape of particles in arctic cirrus are less common than those in mid-latitude and tropical cirrus with considerable uncertainty about the contributions of small ice crystals (maximum dimension D<50 µm) to the mass and radiative properties of cirrus that impact radiative forcing. In situ measurements of small ice crystals in arctic cirrus were made during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in April 2008 during transits of the National Research Council of Canada Convair-580 between Fairbanks and Barrow, Alaska. Concentrations of small ice crystals with D < 50 μm from a Cloud and Aerosol Spectrometer (CAS), a Cloud Droplet Probe (CDP), a Forward Scattering Spectrometer Probe (FSSP), and a two-dimensional stereo probe (2DS) are compared as functions of  the concentrations of crystals with D > 100 μm measured by a Cloud Imaging Probe (CIP) and 2DS in order to assess whether the shattering of large ice crystals on protruding components of different probes artificially amplified measurements of small ice crystal concentrations. The performances of these probes are compared against the data collected by a CAS, CDP and CIP during the Tropical Warm Pool-International Cloud Experiment. The size distributions, crystal shapes and other bulk parameters are compared against values observed in mid-latitude and tropical cirrus.