Breakout Summary Report
ARM/ASR User and PI Meeting
2 - 6 May 2016
3 May 2016
7:30 PM - 9:00 PM
0
Greg McFarquhar
Breakout Description
Greg McFarquhar overviewed the planned MARCUS campaign, describing its motivation (climate model biases and observational knowledge gaps, lack of knowledge on seasonal cycle of cloud and aerosol properties), its observational and modeling requirements, and four science themes under which specific hypotheses will be tested. He also described the Aurora Australis (AA) on which the AMF2 would be installed, the likely ship tracks (based on the 2012/13 campaign), and the prioritization of instruments given there is likely not sufficient space for all of the instruments on board. Paul DeMott described the ice nucleation measurements to be made through filter samples, and slides from Patricia Quinn described proposed aerosol chemical composition measurements using automated collection of filters and heated and unheated size distributions. Subsequent discussion centered around merits of the proposed instrument suite and anticipated difficulties in making observations over the Southern Oceans.Main Discussion
Specific discussion items are as follows:
1) There probably is sufficient room on the AA for EITHER the KAZR and wind profiler or the HSRL. The HSRL would provide better vertical profiles of cloud properties and free tropospheric aerosols (when not attenuated) than can be obtained by the current suite (e.g., MPL), but would require a lot of work to well detect the properties of the boundary-layer aerosols. The KAZR and wind profiler are advantageous by giving some redundancy in and multi-frequency radar measurements, additional information on clouds and winds (given possibility of losing sondes under heavy winds) and enhanced drizzle retrievals, but the size of the KAZR might make it harder to fit. The MARCUS steering committee needs to identify which of these options is preferable.
2) It appears that ARM can supply an automated sonde launcher for about 200 sondes per cruise. This will allow for the needed 4 launches per day (including additional launches in event of failures) for an entire cruise to Antarctic and back to Hobart. It may be possible to reduce the launches to 2 per day when in port at the Antarctic. It is also necessary to ensure there is sufficient room for a sonde launching cart that would need to be affixed to the deck to assist in operating under high winds (is it also possible to affix to helideck?).
3) Although information was presented on probable sea surface temperatures, no information was presented on air temperatures. A question was raised about the potential for icing on the ship given the spray in high winds (and the spray itself could also have an impact on instrument performance). The MARCUS steering committee will obtain climatologies of expected air temperatures over the Southern Ocean for the times of the cruises.
4) There is a good possibility that there may be room on the monkey deck for the MAERI. However, this needs to be assessed on a site visit.
5) There was agreement that the chemical composition measurements proposed by Patricia Quinn would be a good addition to MARCUS. A site visit will determine if there is sufficient space on the monkey deck, and a decision will also have to be made whether the ARM technicians have sufficient time to make these measurements.
6) A question was raised about how many berths were available on the ship for ARM personnel. A follow-up inquiry will be made.
7) A question was raised about whether the aerosol measurements would be above the noise floor of the instruments given the anticipated pristine conditions. It is fully expected that the measurements will be above the noise threshold (though concentrations will be low).
8) There is a need to get some information on the degree of roll that might be expected on the ship, as the stabilized platform for the 95 GHz radar can only handle about 10 degrees of roll. Discussions after the session suggested that the degree of roll on the ship discussed in the section may have been exaggerated, with only 1 day of bad weather per leg expected where the roll might be too large to operate the instruments.
9) It was mentioned that given the absence of clear skies, there would not be a pressing reason to have observations of aerosol optical depth from sun photometers.
10) It was mentioned that in addition to having supercooled water in the cold, dry areas of cyclones, there is also lots of supercooled water in the stratiform clouds that also needs to be sampled.
11) A question was asked whether the MARCUS ship tracks would be oriented with NASA satellite overpasses. Given that we have minimal control of the ship tracks, this will probably not happen. However, a list of times/locations should be available for minor deviations in track in case the overpasses are close to the ship location.
12) It should be explored what data will be available during the cruises so that data (or plots) can be downloaded during the cruise, or at a minimum, when the ship is docked in Antarctica. It will be explored to what degree downloading of the plots can be automated.
13) A site survey by Kim Nitschke, possibly accompanied by Greg McFarquhar and Roj Marchand, is planned for late boreal summer 2016.
Action Items
Action items are summarized as follows:1) Decide whether HSRL vs. KAZR/wind profiler scientifically preferable
2) Get data on pitch/roll from past cruises of the AA
3) Determine number of berths available on AA
4) Get climatology of expected air temperatures
5) Determine degree of communications available for downloading data; what satellite links will be available to get data during voyages.
6) Complete site survey to identify final suite of instruments that will be available (also will need to record their exact locations which may be helpful for pitch/roll corrections.