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

Case Study Example29 August 2008

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

Case Study Example29 August 2008

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.

Case Study Example29 August 2008

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

Case Study Example29 August 2008

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

1 2 3

Case Study Example29 August 2008

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

Case Study Example29 August 2008

2) Multilayer, upperSmaller scale motions

2) Multilayer, lowerSimilar size but weaker

1) Decoupled:0.5 -2 km scales

3) Well-mixed:0.5 -2 km, stronger

Case Study Example29 August 2008

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

Focus on Circulations during “Well-Mixed” period

Higher turbulence near strong 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

Well-mixed to surface? Decoupled

More ice when decoupled?

Events on satellite images

Transitions

60 GHz supports change from “well-mixed” to “decoupled”,but misses an event altogether.

And is there a stable layer right at the surface?

What does skewness reveal?

Suggests forcing from aboveSuggests forcing from below

Questions:•What factors determine whether the primary cloud at about 1 km will be effectively coupled with, or decoupled from, the surface?

•Synoptic forcing•Low level clouds and/or thermodynamic profile•Strength of radiative cooling•Surface turbulent heat fluxes

• What are the differences that occur in magnitude of circulations, scales-of-variability, phase partitioning, and microphysical properties between these two cases?

•Timeseries analysis•Skewness, variance, range of W

•How does stratification, of lack thereof, between cloud and surface impact the source of particles for cloud formation?

•Possible change in ice vs liquid•Is surface or free-troposphere source of particles•Entrainment intensity?

Questions:•How are the surface radiation budget and precipitation efficiency impacted by coupling vs. decoupling w/ surface?•What leads to periods of decreased ice production when LWP and turbulent intensity do not change significantly?