Breakout Summary Report

The Clouds And Precipitation Experiment at kennaook (CAPE-k) is generating an extensive record of aerosols, clouds, and precipitation from pristine Southern Ocean air masses at the Kennaook/Cape Grim observatory on the Island of Tasmania since May, 2024. CAPE-k is adding to ARM’s investment in Southern Ocean data collection and science focus that includes the MARCUS, MICRE and AWARE campaigns. With CAPE-k nearly two-thirds complete, we invite discussion of early science from CAPE-k as well as observational and modeling studies the mid and high latitude Southern Ocean more generally.

The purpose of this breakout was to provide ARM/ASR meeting attendees an overview of ongoing operations at CAPE-k and provide a forum for talks on ongoing Southern Ocean science activities.

Session began with an overview of ongoing operations at CAPE-k given jointly by John Bilberry, Jay Mace and Roj Marchand.

John Bilberry provided a brief overview of instruments deployed by both ARM and visiting/guest scientists, as well as those operated by Kennaook Cape Grim (KCG) Station. Visiting scientist instrument/studies include:

• Southern Ocean Sulfur Dioxide Study (AFC10182) Peter Edwards

• Water Vapor Isotopic Measurements During CAPE-k (AFC10183) Joe Galewsky

• EarthCARE validation at CAPE-k (AFC10191) Matthew Lebsock

• CAPE-k Summertime Single-Particle and INP Campaign (AFC10215) Kerri Pratt

• CAPE-k-CHEM: Aerosol composition and precursors (AFC10217) Branka Miljevic

Jay Mace briefly examined monthly variations in aerosols (UHSAS & CCN) and cloud liquid water path (LWP) to date, during baseline conditions (conditions under which measurements at the site are expected to be representative of SO conditions).  Jay also talked briefly about plans for the associated COAST-k experiment, during which the Austrailian RV investigator will be positioned upwind of CAPE-k to provide for “lagrangian” studies.

Roj Marchand then provided a bit more information on the High Resolution Time of Flight Aerosol Mass Spectrometer, Nitrate-Chemical Ionisation Mass Spectrometer, and Neutral cluster and Air Ion Spectrometer being deployed by Branka Miljevic. He also discussed further the concept of baseline conditions and gave some examples of how the “standard” definition being used by the KCG stations was not entirely sufficient for cloud studies. Mace and Marchand are planning to produce a refined baseline index for cloud and precipitation studies.

Next Scott Collis gave an overview of the recent ARM-supported Student Workshop at CAPE-k and status on productions / plans of ARM VAP products for CAPE-k. The workshop hosted twenty-seven students (with four students financially supported by ARM). The participants learned much, giving the workshop strongly positive reviews and completing four small hands on projects.

The remainder of the session was devoted to individual science presentations, all of which focused on opportunities for collaborations

Matt Lebsock gave an overview of the G-band (240 GHz) radar that NASA JPL has deployed to CAPE-k. This is the first extensive dataset where Ka-, W-, and G-Band radar have been deployed together. The G-band data will provide information on air motions during precipitating conditions (when drop size is > ~0.7 mm) and contribute to multi-frequency radar retrievals for rain, cloud liquid, and snow.

Paytsar Muradyan gave an overview of MPL and mini-MPL operations. The mini-MPL is being run at 3 times the vertical resolutions of the MPL (5 vs. 15 m). The data appear to be of high-quality allowing tracking of fine scale structures. Paystar plans to recommend ARM move to using the higher resolution for future campaigns (as the current data show the 5 m data can be averaged down to 15 m, as needed).

Zeqian (Hazel) Xia showed results of some preliminary comparison of COMBLE, MARCUS, and CAPE-k observations. Key findings are that (i) COMBLE sampled more intense cold-air-outbreaks than MARCUS and CAPE-k have, (ii) COMBLE sampled conditions with higher concentration of moisture in the mid-level atmosphere (free-troposphere), while (iii) CAPE-k dataset contains more samples with very strong BL inversions and has generally higher winds. How the differences impact cloud properties will be the focus of future work.

Litai Kang gave a brief overview on SO aerosol–cloud–precipitation interactions (ACI), the importance of mesoscale cellular convection to ACI, and touched on the seasonal cycle of both clouds and aerosols. She has examined a number of case studies that shows strong co-variability among aerosol, cloud, precipitation, and cold pools, motivating further LES simulations.

Johnathan Gero reported on Observations of the Marine Boundary Layer being made by the M-AERI at CAPE-k. The M-AERI is situation on the cliff overlooking the ocean to the west of the site.  It is looking both upward (collecting data to support the AERIoe VAP – profiling of BL temperature and moisture) as well as scanning down from the cliff at several elevation angles (to enable running MAERI-based retrievals for SST and potentially extending AERIoe down to the ocean surface). Initial results from scanning look promising but will need calibration/validation data collected during COAST-k.

Christina McCluskey talked about ongoing collection of aerosol particulates at CAPE-k. She and Kerry Pratt are funded to examine size resolved single particle composition. These data will be combined with INP filter collections with offline treatments (DOE ARM Ice Spectrometer) to study the chemical composition and concentrations of sea spray aerosol and secondary marine-derived sulfate aerosol, as well as episodic contribution from dust.

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