Matthew Shupe Ola Persson

U of Colorado/NOAA

Thorsten MauritsenMax Plank Institute

Ian BrooksU of Leeds

Dynamical-Microphysical Interactions in Arctic Mixed-Phase Clouds

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.

23&31 GHzMicrowave radiometer

Ka-band Doppler Cloud Radar

449 MHzWind profiler

60 GHzRadiometer

S-band Cloud/precip Radar

Not shownCeilometer, Radiosondes

Upward-looking remote sensors

Spatial Perspective

~6 km

Measurement area

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: Multi-layer transition to single layer

25 August Case: Examining specific time periods

Upper cloud leaves and cloud starts to radiatively cool generating turbulence

Turbulent layer growth

Thermal plumes from the surface

25 August Case: Initial transition

interpolated

Turbulence near surface remains relatively constant

Shallow well-mixed layer, increases in depth over time

Peak liquid right after upper cloud goes away, with most ice later in case

Skewness decreases

In-cloud turbulence and W variance increase over time

25 August Case: ½ hour average profiles

Correlation between vertical velocity and microphysics

25 August Case:Focused view

~6 km0.7-2 km

Similar relations to those seen for stratocumulus near Barrow

25 August Case: Microphysical-dynamical relations

27-28 August Case: An example of transitionsCoupledDe-coupled De-coupled

Ice production increases with the coupling…. but doesn’t decrease after de-coupling.

Cloud top driven circulations mix down leading to coupling w/ surface

Microphysics is variable, possibly higher peak values when coupled

Thermal structure supports coupling vs. decoupling analysis

Turbulence maximized near top in “decoupled” but approximately constant w/ height for “coupled”

Skewness more negative for decoupled and more positive for coupled

interpolated

27-28 August Case: 1-hour averages

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!