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Lidar characterization of the Arctic atmosphere during ASTAR 2007: four cases studies of boundary layer, mixed-phase and multi-layer clouds

by A. Lampert, C. Ritter, A. Hoffmann, J.-F. Gayet, G. Mioche, A. Ehrlich, A. Dörnbrack, M. Wendisch, M. Shiobara show all authors
Atmospheric Chemistry and Physics ()

Abstract

During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation\n(ASTAR), which was conducted in Svalbard in March and April 2007,\ntropospheric Arctic clouds were observed with two ground-based\nbackscatter lidar systems (micro pulse lidar and Raman lidar) and with\nan airborne elastic lidar. In the time period of the ASTAR 2007\ncampaign, an increase in low-level cloud cover (cloud tops below 2.5 km)\nfrom 51% to 65% was observed above Ny-Alesund. Four different case\nstudies of lidar cloud observations are analyzed: With the ground-based\nRaman lidar, a layer of spherical particles was observed at an altitude\nof 2 km after the dissolution of a cloud. The layer probably consisted\nof small hydrated aerosol (radius of 280 nm) with a high number\nconcentration (around 300 cm(-3)) at low temperatures (-30 degrees C).\nObservations of a boundary layer mixed-phase cloud by airborne lidar and\nconcurrent airborne in situ and spectral solar radiation sensors\nrevealed the localized process of total glaciation at the boundary of\ndifferent air masses. In the free troposphere, a cloud composed of\nvarious ice layers with very different optical properties was detected\nby the Raman lidar, suggesting large differences of ice crystal size,\nshape and habit. Further, a mixed-phase double layer cloud was observed\nby airborne lidar in the free troposphere. Local orography influenced\nthe evolution of this cloud. The four case studies revealed relations of\ncloud properties and specific atmospheric conditions, which we plan to\nuse as the base for numerical simulations of these clouds.

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