Breakout Summary Report

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• Discussion about requirements for measurements of turbulent fluxes at the top of the clear convective PBL (entrainment fluxes). This can be done in principle with remote sensing (e.g., pairing Doppler lidar with DIAL water vapor profiles) but the require high time resolution makes it challenging to resolve the flux-carrying scales. Drones and tethered balloons are other options. There are some plans for an ARM DIAL lidar.

• Participants are starting to discuss potential follow-on field campaigns at ENA to build on what was learned during ACE-ENA. Will need clear and distinct scientific focus. Has sufficient analysis been done with existing ACE-ENA data? Are there useful closure studies (e.g. CDNC, or CCN, or precipitation closure) that have not yet been carried out?

• Shaocheng Xie presented on the data products that are available or will shortly be available for WBLP-focused studies. There was some discussion about the PBL height VAP, for which there is a new ML estimate now available (Damao Zhang). Participants suggested not only providing a single ML version but also the other definitions that are used, as each provides info about some different aspect of the PBL (e.g. residual layers).

• Stable Isotopes of atmospheric water vapor from the SCILLA Airborne Campaign can help constrain vertical mixing processes, especially those enhanced by channel island circulations (Lisa Welp, Purdue)

• WRF simulations and satellite observations are being used to evaluate the correlation between cloud droplet concentration and liquid water path (LWP adjustment metric) in comparison with ARM ground-based observations. Simulations yield stronger precipitation rates for effective radii from 10-15 micron than appear to occur in the observations, indicating drizzle is forming too early in the simulations, and its suppression yields an incorrectly strong positive LWP adjustment (Shaoyue Qiu, LLNL).

• Studies of cloud top entrainment are now possible with the Pi Convection-Cloud Chamber (Will Cantrell, Michigan Tech). Responses of clouds are locally heterogeneous (mixing preferentially results in evaporation of all the drops from some regions and none from others), but each entrainment event will change the amount of vapor, affecting the global condensate amount, which appears as a "homogeneous" mixing event. It is possible to create a cloudy boundary layer top in the PI chamber in order to study entrainment effects on microphysics.

• A new 4D observational dataset of atmospheric boundary-layer properties in Houston as part of the TRACER campaign has been produced by Katia Lamer (Brookhaven) and released to the ARM/ASR community. The dataset combines different remote sensing and in-situ (sonde) metrics of PBL depth from 14 different sites in the Houston area, together with Doppler lidar to provide vertical and horizontal wind estimates.

• Kenneth Davis (Penn State) presented science questions, deployment plan, possible activities/efforts with WBLP involvement from the Coast-Urban-Rural Atmospheric Gradient Experiment (CoURAGE) campaign in Baltimore. The Baltimore Social-Environmental Collaborative (BSEC) is a Department of Energy Urban Integrated Field Lab program designed to generate the science needed for informed energy investments and extreme weather resilience in Baltimore. CoURAGE measures the coupled land-ABL-cloud-radiation-atmospheric composition-precipitation system in the city of Baltimore and explores how Baltimore’s atmospheric environment depends on its complex surroundings. The presentation highlighted the multiple sites being used, along with the core facility/supersite. Early results are showing important local features such as sea-land breezes, coastal low level jets, which affect many processes including pollutant transports and dispersion.

• Jay Mace (University of Utah) presented some of the CAPE-k preliminary findings, possible activities/efforts with WBLP involvement. Time series comparing CCN and UHSAS accumulation mode aerosol concentrations reveal that there is a systematic seasonal shift in the hygroscopicity of submicron aerosol at CAPE-k, with higher hygroscopicity in winter, possibly reflecting fewer sulfates and organics (and more sea salt) in winter. The data are being designated as "baseline" conditions when the prevailing winds are from the remote Southern Ocean. Mace highlighted several other interesting datasets from the campaign, and highlighted the frequent cases of both open and closed mesoscale cellular convection over the annual cycle.

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