Breakout Summary Report
ARM/ASR User and PI Meeting
10 - 13 June 2019
13 June 2019
1:30 PM - 4:00 PM
70
Yunyan Zhang and Rob Wood
Breakout Description
The overarching theme for this breakout session was focused on warm boundary-layer processes, which include boundary-layer turbulence, clouds and precipitation, their interaction with the underlying surface, the associated radiative and microphysical processes, and the interaction with aerosols. We are interested in improving our understanding of these processes using ARM observations and improving the representation of these processes in models.Main Discussion
This breakout consists of four parts. The agenda was:
Science Talks (1:30 to 2:20)
- LAFE and DIAL updates, Dave Turner
- Stereophotogrammetry and COGS, David Romps
ARM Infrastructure Updates (2:20 to 2:50, Shaocheng Xie)
Breakout Summaries (2:50 to 3:40, ~5 minutes each)
- ACE-ENA (Jian Wang)
- Marine cloud-topped boundary-layer processes: cloud, aerosol, drizzle and turbulence (Xue Zheng)
- MICRE/MARCUS and Southern Ocean Activities (Roger Marchand)
- Shortwave-absorbing aerosols and their interactions with clouds (Paquita Zuidema)
- Land-Atmosphere-Cloud Interaction (Larry Berg and Yunyan Zhang)
- Lidar (Larry Berg)
- LASSO (Bill Gustafson)
- ARM Cloud and Precipitation Measurements and Science Group (Ann Fridlind)
Discussion (3:40 to 4:00)
Key Findings
The two scientific talks focused on new instruments that ARM has deployed in recent years, and provided snapshots of derived scientific results. Dave Turner showed a novel evaluation of surface similarity theory using remote-sensing observations from the LAFE field campaign and emerging observational capabilities to measure higher moments of water vapor, temperature, and wind distribution functions using lidars. David Romps showed the latest results from the new installation of six stereo cameras including observations of the geometry of shallow cumulus fields, together with data development of COGS and potential applications and limitations. The COGS observations show considerable promise for evaluating LES cloud fields and for creating constraining lateral entrainment parameterizations used in large-scale models.
Shaocheng Xie and Jennifer Comstock provided updates on ARM data developments most relevant to the WBLP WG and described ongoing efforts to address data issues. After their talk, there was a discussion on data uncertainties, which measurements we need them most, and how to use these uncertainties. Shaocheng provided some findings from a very brief survey of WG members on instrument priorities. MWRs are not being supported by the manufacturers in a few years. What is the ARM plan for replacement?
We had eight brief breakout summaries on studies and discussions most relevant to WBLP. Following the summaries, we had a discussion on the group need of ARM data, e.g. profiles of fluxes, precipitation data products, and so on.
Issues
WG Members voiced some concerns about the long-term viability of the ARM LWP sensing systems. Existing MWRs are not being supported by the manufacturers in a few years. What is the ARM plan for replacement?Needs
The group discussion on flux profiles mentioned the need for current data filtering to deal with sampling errors and examine missing physics and suggested a pilot study using LAFE data evaluated against LES and hopefully leading to some routine data products with error or uncertainties estimate too.
The group discussed the issues in precipitation data development. There are a few algorithms on effective radius, CDNC, column-averaged number concentration, and so on; however, structural differences exist in the assumptions in retrieval algorithms.
There is a general and long-standing divergence of opinion on the approach to liquid cloud microphysics retrievals in stratiform clouds that applies to both ground-based and satellite remote sensing. Some feel that attempts to retrieve cloud droplet concentration (Nd) is not well posed because remote sensing is primarily providing information about the second moment (visible transmission) and the third moment, i.e., liquid water content (LWP from MWR). These moments lend themselves to estimations of their ratio, i.e., the effective radius. However, the effective radius varies significantly with height (in contrast to Nd, which is typically does not show a systematic vertical gradient), so effective radius retrievals pose their own set of challenges. The recent ACE-ENA aircraft deployments and associated ground-based ARM remote sensing provide a wealth of data to test new and existing retrievals and group members are encouraged to document and compare these data products and also compare with flight data. Selection of a few good test cases from the deployment will be useful in providing focus for such comparisons.
Decisions
No specific decisions were made.Future Plans
See Action ItemsAction Items
We conducted a survey among the WBLP WG before the PI meeting on the most urgent need and issues on ARM data most relevant to a few research areas in WBLP. Although there were not many responses, they are pretty consistent with each other and with the discussion items listed above: on the surface and PBL profiling and cloud and precipitation measurements. We plan to design a more detailed survey during this year and try to collect more thoughts and ideas on this and continue some discussion before the next PI meeting: hopefully this may lead to some group activities.
A few breakout sessions also have organized AGU sessions on similar topics.
Rob Wood is volunteering to hold a teleconference to bring together observational and remote-sensing scientists working on microphysical retrievals, with a view to identifying test cases from ACE-ENA for intercomparison.