In-situ observation of Arctic mixed phase clouds during the ISDAC flight campaign

Measurements of mixed phase clouds from the NRC Convair 580 during the Indirect Semi-Direct Aerosol Campaign (ISDAC) are presented and analyzed. For this project, the aircraft was equipped with a suite of state-of -the-art in-situ and remote sensing instrumentation enabling accurate and highly redundant characterization of cloud microphysics. The analysis focus specifically on two days when long lived boundary layers topped with mixed phase clouds were observed over the Arctic Ocean in the Barrow region. Multiple vertical soundings show high degree of spatial and temporal homogeneity of microphysical parameters in the clouds, which extended horizontally over a distance of one hundred kilometers and a time period of several hours. The vertical profiles of basic microphysical parameters, such as ice and liquid water contents, the extinction coefficient, droplet and ice particle concentration and their characteristic sizes, are presented along with observations from the onboard X-band Doppler radar showing well defined circulation cells embedded in the cloud layers. A link between the microphysical parameters and the cloud dynamics is investigated through a comparison of microphysical characteristics of mixed phase obtained from in-situ measurements with those from a simple 1D model of dynamical maintenance of mixed phase. Results indicate that the measured microphysical and dynamical characteristics of the studied clouds satisfy the conditions required for indefinitely long maintenance of mixed phase layers.