Matthew Shupe Ola Persson Paul Johnston Duane Hazen Clouds during ASCOS U. of Colorado and NOAA.

Matthew Shupe Ola Persson

Paul JohnstonDuane Hazen

Clouds during ASCOS

U. of Coloradoand NOAA

Data sets

Millimeter Cloud Radar (MMCR)•Ka-band cloud radar

•Measures Doppler spectrum, reflectivity, Doppler velocity, and spectrum width.

•“Merged” product combines the best of multiple operational modes and is now available in netCDF.

Data sets

Ceilometer•Operates at optical wavelength.

•Measures cloud base height (sometimes multiple layers) and backscatter profiles.

•Product is now available in netCDF.

Data sets

Microwave Radiometer (MWR)•2-channels at 23 and 31 GHz

•Measures sky brightness temperatures for deriving precipitable water vapor (PWV) and cloud liquid water path (LWP).

•Measurements and version#1 retrievals are available in netCDF (use retrievals with caution!)

Retrieved Products: Cloud type

Cloud type classification •Utilizes phase-specific signatures from radar, ceilometer, microwave radiometer, radiosondes•Provides a mask of cloud “phase” type •Version 1 available in netCDF

Retrieved Products: Cloud liquid properties

Liquid RetrievalsAssume “adiabatic” profile computed with active sensor cloud boundaries and temperature profile, constrained by microwave radiometer-derived LWP

Version 1 available in netCDF

Liquid droplet size

Liquid water content

Liquid water path

Retrieved Products: Cloud ice properties

Ice particle size

Ice water content

Ice water path

Ice RetrievalsIce mass is derived using a radar reflectivity power law relationship while particle size is related to radar-measured velocity

Version 1 available in netCDF

Dynamics Retrievals•Vertical velocity is derived from radar Doppler spectra using small liquid droplets as tracers of air motion

•Turbulent dissipation rate is related to the time variance of radar Doppler velocity

•Full data set not yet available, contact Matthew if interested in certain cases

Retrieved Products: Vertical velocity and turbulence

Turbulent dissipation rate

Vertical velocity

Layer-averaged vertical velocity, 5-pt smooth

Summary Statistics

Lots of low clouds, most of which were “mixed-phase” (ice crystals falling from a liquid cloud layer)

Liquid (red) and Ice (blue) water paths. Bars show daily range (5th-95th percentiles) and while symbol shows daily mean

Storm & deep cloud regime

Low-level stratiform

cloud regime

Case Study Example29 August 2008

From the Cloud Radar Perspective

1)Low-level mixed-phase stratocumulus (ice falling from liquid cloud layer)2)Brief mixed-phase strato/alto-cumulus3)Multiple high cirrus clouds and a suggestion of possible liquid water at times.

Cloud Radar Moments


Stable layer decouples cloud from surface for

first ½ of day

Strong inversion at about 800 m which

limits the vertical cloud extent

Second ½ of day appears to be well-

mixed from the surface up to the cloud at 700-

800m

60-GHz Potential Temperature and Buoyancy Profiles


Retrieval Results: Multilayer Cloud Effects

1) Upper layers from 11 – 16 inhibit cloud top radiative cooling by lower layer.

2) As a result, shallow convection, turbulence, ice production, and (probably) liquid production all decrease in lower cloud layer.

3) Circulations and turbulence are significant in upper layer because it can radiatively cool to space.


Retrieval Results: BL-Cloud Interactions

During first ½ of day (decoupledcloud and surface):1)Relatively more ice than liquid production.2)Thinner liquid layer.3)Turbulence decreases towards surface.

During second ½ of day (well-mixed):1)Less ice production and more liquid water2)Thicker liquid layer.3)Turbulence constant towards surface


Examine Profiles at 3 times1)Decoupled2)Multi-layer3)Well-mixed

1 2 3


Average profiles2) Multi-layer•Upper layer turbulence shows radiative cooling•Lower layer turbulence suggests surface forcing•Less ice production in lower layer than upper

3) Well-mixed•Turbulence profile suggests contributions from both surface and radiative cooling

1) Decoupled•Turbulence profile suggests cloud top radiative cooling•Lots of ice


Broad updrafts and narrow downdrafts on scales of 1-2 km

Focus on Circulations during “Well-Mixed” period

Higher turbulence at interfaces between up- and down-drafts

Cloud ice forms in updrafts

No clear relationship between LWP-IWP or LWP-updraft but the LWP does increase as the

liquid layer thickness increases

Please contact me: [email protected]

• Cloud interactions with boundary layer structure:How do clouds affect the boundary layer stability (and visa versa)?

• Cloud interactions with surface energy budget:What role did cloudiness play in the end of the melt season?

• Aerosol-cloud interactions, and source of particles to the cloud:Why was there more ice production when the cloud layer was decoupled from the surface (and visa versa)?

• Retrieval validation using independent measurements of vertical velocity and turbulent dissipation rate (from sodar and balloon) and cloud microphysics (from aircraft).

Research Interests & Potential Collaborations

Extra slides


Key Result1) Shallow convection, turbulence, ice production, and (probably) liquid production all decrease in lower cloud layer.

2) Upper layer inhibits cloud top radiative cooling by lower layer, which is largely responsible for driving cloud-scale circulations.

The SituationLow-level, stratiform mixed-phase cloud (ice falling from liquid). Short period with a second mixed-phase layer at 1.8 km

Case Study Example29 August 2008 Lots more liquid than ice

Case-average profiles

Raw sounding suggests low cloud decoupled from surface

Cloud layers are “well mixed”

Turbulent profiles

Matthew Shupe Ola Persson Paul Johnston Duane Hazen Clouds during ASCOS U. of Colorado and NOAA.

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