Breakout Summary Report


ARM/ASR User and PI Meeting

High-Latitude Working Group Breakout Session
27 October 2022
2:00 PM - 5:00 PM
Gijs de Boer, Greg McFarquhar

Breakout Description

The High-Latitude Processes Working Group focuses on understanding and model representation of physical processes controlling the surface energy budgets in northern and southern high-latitude regions. This includes work to understand: 1) cloud microphysical and macrophysical properties, with emphasis on hydrometeor (rain, snow, etc.) phase division and ice crystal properties; 2) aerosol particle properties, including sources and transport, chemical and optical properties, and the role of the particles in cloud structure; 3) tropospheric states (pertaining to the lowest atmospheric layer, where most weather occurs), including the role of clouds in atmospheric mixing, development of convective boundary layers in regions with diverse surface conditions, and the role of microscale and mesoscale meteorological circulation patterns on thermodynamic evolution; and 4) surface-atmosphere interactions, including elements affecting radiative and turbulent surface energy exchange.

Main Discussion

This breakout session included an initial 10-minute window for WG members to socially connect with new faces in the room and get to know one another.  We find this exercise to be tremendously helpful with allowing new members to integrate, and giving people an opportunity to develop community.  Following the socializing, we briefly discussed the avenues that ARM has available for communicating community needs, and Jim Mather gave a quick overview of this process.  Specifically, he gave an overview of online resources for identifying needs.  After this, we transitioned to a series of 11 short presentations (~5-10 minutes) as outlined on the WG session agenda.  Speakers were encouraged to highlight the main points and save room for discussion.  Some shorthand notes on the topical areas presented are included below.  In general, the presentations were short and sweet and fostered some lively questions and discussion.

Overview of presentations:

Kerri Pratt:  Individual aerosol sources and composition in the Arctic: measuring composition of individual aerosol particles; looking at sea spray aerosol from leads gives information about how aerosols being produced by exopolymeric substances secreted by sea ice algae and bacteria; blowing snow falsely predicted; secondary aerosol formation in regional fog at Oliktok Point; solid organic coated ammounium sulfate particles, surprising observation linked to marine gas and bird emission that may have applications for CCN and INP.

Jessie Creamean: long-term measurements of INPs at several arctic stations: important to capture full, highly contrasting annual cycle; (QR code for scanning available data); aerosols collected from many sources (filters, seawater, melted sea ice, melted snow), then they freeze and compute how many INPs as function of temperature; INPs generally colder during fall/winter (e.g., dust) and warmer in summer (e.g., local biology); COMBLE INPs with CAOs indicated to see correlation; Oliktok Point very variable INPs, but need to explain wiggles—feel free to use in next profile, branching into long-term measurements in Antartica in next couple of years.

Zhien Wang: Seasonal variation of dust aerosol vertrical distribution in Arctic based on polarized micropulse lidar measurements: MPL processing (overlap corrections, afterpulse correction, clear-sky identification, and use of Fernald method for backscattering retrievals); shows MPL measurements capture aerosol structures detected by HSRL; long-term MPL retrievals are consistent with collocated HSRL observations; dust aerosols occur in entire troposphere in winter and spring, in low (0-2) and middle (2-5 km) tropsosphere during summer and autumn; out-of-phase annual cycles of mid-level dust concentration and westerly wind over source regions control seasonal upper-tropospheric dust loading variations.

Xiaohong Liu: Importance of SIP for high-latitude cloud properties; SIP increases ice concentration D > 100 um at cloud bottom; SIP  more mixed-phase clouds; moderately cold cloud, T > -20C, SIP contributes 80%, enhances SIP by 4 orders of magnitude.

Aaron Kennedy: Identifying blowing snow with in situ and remote-sensing observations: retrieval of height of blowing snow problematic from ceilometer alone using Gossart et al. (2017) algorithm and AWARE algorithm; now combine with MPL/HSRL/KAZR to come up with these heights; surface PSDs had some strange events and were dependent on wind speed (PSDs wonky during blowing snow, so many particles going through things, there is just one particle); what is missing, microphysics observations above surface; AWARE data available, NSA/MOSAIC tweaking height-detection algorithm; will have SAIL available soon; tweaking maching learning detection algorithm for NSA/MOSAIC.

Sergey Matrosov: Observationally based relations between precipitation and atmospheric moisture parameters during rain at NSA: wind speed optical sensor at ground overestimates rainfall rate; shows a lot of scatter plots of snowfall rates versus quantitites like integrated water vapor, etc.; no significant correlation between columnar LWP and near-surface snowfall rate from several independent data sets and sensors; but correlation between IWP and snowfall rate, which may indicate snow/cold processes dominate the relation; correlation between IWV and snowfall rate and also between IWC and TWP = LWP + IWP is moderate.

Matt Shupe: MOSAiC, lots of VAPs and growing, working on merged observatory data files, PI products of snowfall, microphysics, trajectories, data available at ARM Data Center, NSF Arctic Data Center, PANGAEA Archive; science possibilities – surface energy budget processes; dynamical drivers of ice motion; ABL structure and processes; gas concentrations, fluxes and cycles; aerosols, sources, and cloud processes; precipitation and snow on sea ice; warm air advection and atmospheric rivers; light transmission through sea ice; ocean heat budgets and fluxes to the ice; physical system constraints on ecosystem; process-based, multi-scale model assessment; high-res cloud modeling; satellite-ground comparisons.

Pavlos Kollias: Zach looking at COMBLE data, 34 CAOs during COMBLE, picked 13 of days, characteristic size of updrafts showing small depths, widths, and magnitudes as histograms; shallow, narrow, and strong; model simulation with horizontal resolutions less than 250 m begin to lose valuable information on dynamical characteristics of CAO events resolution matters when looking at features; most of turbulence concentrated near surface and two modes appear; magnitudes exceed those typically found in stratocumulus environments; found evidence of SIP; Eulerian perspective looking at 2D view of atmosphere, can’t speak of evolution of 3D geometry.

Tim Juliano:  Mesoscale simulations of arctic mixed-phase clouds during COMBLE; how does representation of CBL turbulence affect simulated MPC properties and mesoscale organization? What are microscale characteristics of convective CAO cloud systems, including role of coherent turbulent structures? Identifying roll and cell regions (in north can’t see roll structures, but closer to Andenes are simulating cell structures); modeled roll cloud tops are too cold with EDMF; what happens along coast of Andenes?  Confirms EDMF likely outlier where clouds are too deep/cold and contain too much liquid, will examine SW/LW radiation measurements; turbulence closure approach has strong influence on arctic mixed-phase clouds (and radiation) properties under convective CAO conditions; EDMP performing poorly; explore strong CAO case of 28 March case to see if findings consistent; looking quite similar; setting up mesoscale-> microscale couped online real simulations underway.

Florian Tornow: Cold-air outbreak cases during COMBLE selected for LES and SCM intercomparison.

Key Findings

The presentations provided interesting insights into a variety of processes and new data products.  Please see the uploaded slides for additional information and insight. There was a significant amount of discussion and support for potential UAS/TBS-based work at high latitudes. This included discussions related to possible deployment of UAS to Southern Ocean regimes (e.g., Cape-K) and attempting to re-develop UAS and TBS activities on the North Slope (e.g., NSA). The group was reminded that the TBS is often available for proposed deployments. There was also discussion about attempting to use the unique triple-frequency radar overlap that is available at NSA.


Discussions were held on the need for smaller group meetings to discuss potential field deployments and other observational activities.  Specifically, there was mention of insufficient understanding within the working group of smaller IOPs and observing activities, and it was mentioned that it would be helpful if there was better communication about such events.  WG members were reminded that the WG leads do their best to solicit information for a quarterly newsletter and that this newsletter would be a terrific avenue for making the community aware of smaller activities that might be of broad interest.





Future Plans

There was some discussion about highlighting needs for upcoming field campaigns (e.g., Cape-K AMF deployment).  There was additional discussion about attempting to expand on vertical profiling of the atmosphere using ARM capabilities and those of partner institutes, particularly at the NSA facility.

Action Items