A one-dimensional simulation of the stratocumulus-capped ...
Case Study Example 29 August 2008 From the Cloud Radar Perspective 1)Low-level mixed- phase...
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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?