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Study interactions among atmospheric structure, clouds, aerosols, gases, ocean, and energy budget in Arctic mixed-phase clouds. Research conducted during the Arctic Summer Cloud-Ocean Study (ASCOS) in 2008. Detailed analysis of cloud transitions, microphysical-dynamical relations, turbulence patterns, and thermal structures. Future directions include expanding analyses to Barrow and Eureka to understand cloud-atmosphere impact.
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Dynamical-Microphysical Interactions in Arctic Mixed-Phase Clouds Matthew Shupe Ola Persson U of Colorado/NOAA Thorsten Mauritsen Max Plank Institute Ian Brooks U of Leeds
The Arctic Summer Cloud – Ocean Study (ASCOS) • Objective: Study the interactions among the atmospheric structure, clouds, aerosols, gases, ocean, and surface energy budget. • Late summer 2008, 5 weeks for full cruise including 3 week ice station. • Aboard Swedish icebreaker Oden • Large suite of instruments deployed on the icebreaker, on the sea-ice, from a tethered balloon, and adjacent to an open lead.
Upward-looking remote sensors 60 GHz Radiometer Ka-band Doppler Cloud Radar 23&31 GHz Microwave radiometer S-band Cloud/precip Radar 449 MHz Wind profiler Not shown Ceilometer, Radiosondes
Spatial Perspective ~6 km Measurement area
25 August Case: Multi-layer transition to single layer When the upper cloud leaves….. vertical motions become more active in lower layer, W skewness begins to show contributions from the cloud top, in-cloud turbulence increases, the atmospheric depth prone to vertical mixing increases in depth, and ice production begins.
25 August Case: Initial transition Upper cloud leaves and cloud starts to radiatively cool generating turbulence Thermal plumes from the surface Turbulent layer growth
25 August Case: ½ hour average profiles Turbulence near surface remains relatively constant In-cloud turbulence and W variance increase over time Skewness decreases Shallow well-mixed layer, increases in depth over time Peak liquid right after upper cloud goes away, with most ice later in case interpolated
25 August Case: Focused view Correlation between vertical velocity and microphysics
25 August Case: Microphysical-dynamical relations ~6 km 0.7-2 km Similar relations to those seen for stratocumulus near Barrow
27-28 August Case: An example of transitions De-coupled Coupled De-coupled Cloud top driven circulations mix down leading to coupling w/ surface Ice production increases with the coupling…. but doesn’t decrease after de-coupling.
27-28 August Case: 1-hour averages Turbulence maximized near top in “decoupled” but approximately constant w/ height for “coupled” Skewness more negative for decoupled and more positive for coupled interpolated Thermal structure supports coupling vs. decoupling analysis Microphysics is variable, possibly higher peak values when coupled
Summary and Future Directions • Multi-instrument, remote-sensor suite can provide a coordinated perspective on cloud microphysics and dynamics. • Dynamic and thermodynamic signatures reveal the interactions between clouds and the atmosphere (boundary layer). • Want to further understand the impact of the cloud-atmosphere state (coupled vs. uncoupled) on the dynamical and microphysical properties (scales-of-motion, phase partitioning, ice production) Expand analyses to Barrow and Eureka. Thanks!