Case Study Example 29 August 2008

1. Case Study Example 29 August 2008 Cloud Radar Moments • From the Cloud Radar Perspective • Low-level mixed-phase stratocumulus (ice falling from liquid cloud layer) • Brief mixed-phase strato/alto-cumulus • Multiple high cirrus clouds and a suggestion of possible liquid water at times.

2. Case Study Example 29 August 2008 60-GHz Potential Temperature and Buoyancy Profiles Strong inversion at about 800 m which limits the vertical cloud extent Stable layer decouples cloud from surface for first ½ of day Second ½ of day appears to be well-mixed from the surface up to the cloud at 700-800m

3. Case Study Example 29 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.

4. Case Study Example 29 August 2008 • Retrieval Results: • BL-Cloud Interactions • During first ½ of day (decoupled • cloud and surface): • Relatively more ice than liquid production. • Thinner liquid layer. • Turbulence decreases towards surface. • During second ½ of day (well-mixed): • Less ice production and more liquid water • Thicker liquid layer. • Turbulence constant towards surface

5. Case Study Example 29 August 2008 1 2 3 • Examine Profiles at 3 times • Decoupled • Multi-layer • Well-mixed

6. 1) Decoupled • Turbulence profile suggests cloud top radiative cooling • Lots of ice Case Study Example 29 August 2008 • 2) Multi-layer • Upper layer turbulence shows radiative cooling • Lower layer turbulence suggests surface forcing • Less ice production in lower layer than upper Average profiles • 3) Well-mixed • Turbulence profile suggests contributions from both surface and radiative cooling

7. Case Study Example 29 August 2008 1) Decoupled: 0.5 -2 km scales 3) Well-mixed: 0.5 -2 km, stronger 2) Multilayer, lower Similar size but weaker 2) Multilayer, upper Smaller scale motions

8. Case Study Example 29 August 2008 Focus on Circulations during “Well-Mixed” period Broad updrafts and narrow downdrafts on scales of 1-2 km 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

9. Transitions Decoupled Well-mixed to surface? Events on satellite images More ice when decoupled?

10. 60 GHz supports change from “well-mixed” to “decoupled”, but misses an event altogether. And is there a stable layer right at the surface?

11. Suggests forcing from above Suggests forcing from below What does skewness reveal?

12. 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?

13. 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?