Breakout Summary Report

ARM/ASR User and PI Meeting

2 - 6 May 2016

Session Title: The Cloud, Aerosol, and Complex Terrain Interactions (CACTI) ARM field campaign
Session Date: 3 May 2016
Session Time: 7:30 PM - 9:00 PM
Number of Attendees: 0
Summary Authors: Adam Varble

Breakout Description

The Cloud, Aerosol, and Complex Terrain Interactions (CACTI) ARM field campaign (http://www.arm.gov/campaigns/amf2018cacti) will be performed between August 2018 and April 2019 covering the wet season in the Sierras de Córdoba mountain range of central Argentina with a goal of studying the interactions between environmental conditions and convective clouds from shallow cumulus through cumulonimbus for a large number of events in the hopes of addressing numerous questions related to (a) the interactions of boundary layer, free troposphere, land surface, and aerosol properties with convective clouds and precipitation, and (b) the role of different environmental conditions in predicting and regulating deep convective initiation, upscale growth, and mesoscale convective organization. The goals of this session are to:
(1) Present a broad overview of the motivation for, the experimental design of, and science questions to be addressed by the upcoming CACTI ARM field campaign,
(2) Provide background information on the potential complementary RELAMAPAGO NSF field campaign,
(3) Solicit feedback from members of the ARM and ASR community regarding measurement priorities, feasibility of measurement strategies, prioritization of science questions, and potential involvement of specific individuals,
(4) Generate plans for preparation ahead of the field campaign including possible testing of new radar scanning strategies using simulators and an SGP IOP.

Main Discussion

The purpose of this session was to introduce interested members of the ARM and ASR communities to the recently ARM-funded CACTI field campaign, which will be take place between August 2018 and April 2019 near Cordoba, Argentina. Roughly 25 people showed up for the session, which consisted of two informal presentations. The first was given by CACTI PI Adam Varble overviewing motivation for CACTI, science questions, and experimental design with intermittent questions and comments throughout the presentation, which was spread out over about 1 hour of the session. The second presentation took up the remaining session time and was given by CACTI co-I Steve Nesbitt to overview the motivation, science questions, and experimental design of the potential RELAMPAGO field campaign currently under review by NSF. This campaign would be performed in the same region as CACTI during the planned CACTI IOP period in November-December 2018, and greatly complement CACTI by providing mobile radar and sounding resources, a network of surface sites across the region, an S-band radar, and more.

Had there been extra time available after the CACTI and RELAMPAGO overview presentations and no major issues raised by the session attendees, the plan was to focus on optimal radar scanning strategies for achieving CACTI science objectives, since this is a critical component for the success of the campaign. Unfortunately, only a small portion of the session time was spent on this topic, but several radar engineers and scientists that attended the session are at least now aware of the observations that we want to make, why such observations are necessary for answering key science questions, and the preliminary strategies that are in place to make the observations. Relevant members of the CACTI science team will need to have many more discussions with the ARM radar community over the next 1-2 years to refine strategies ahead of the campaign. Several members of the radar community expressed support for a SGP radar scanning strategies IOP in 2017 (also suggested in the recent ASR Workshop on Convection) that tests the ability of the cloud and precipitation radars to perform unique scan sequences that target specific cloud and precipitation processes; however, such an IOP may depend on the operational status of C-SAPR2 and other SGP radars in mid-late 2017.

Issues

One concern is the current state of C-SAPR2 and the probability that it will be ready for deployment given the overwhelmingly long list of tasks planned for completion by the ARM radar engineers, technicians, and scientists over the next couple years. A significant fraction of the proposed CACTI research depends on a research precipitation radar being deployed. Another concern is the availability of the Gulfstream-1 aircraft in late 2018 for in situ measurements of the evolving free troposphere that will be only discretely measured in space or time from the ground, free tropospheric aerosol properties being ingested and detrained from clouds that cannot be measured from the ground, and cloud properties that will be crucial for validating and tuning radar retrievals of cloud dynamics and microphysics. The next year will hopefully include discussions between ARM personnel and CACTI scientists to address these concerns.

Concerns were also raised by radar engineers about the potential for severe wind or hail at the AMF-1 deployment site. While most severe weather is expected downstream of the site because of initiation of systems very close to the site, quickly developing systems or mature systems initiated on the Andes propagating overhead at night that produce strong winds or hail are possible just as they are at the SGP site. Therefore, CACTI scientists will need to have future discussions with the AMF-1 team and ARM radar engineers to assess whether radomes are necessary for any of the radars.

Future Plans

Additional potential requests to ARM or other agencies for supplementary surface meteorological and flux stations as well as aerosol instrumentation not covered by the AMF-1 that are deemed crucial to science questions will depend on whether the RELAMPAGO NSF proposal is funded and which instruments will be part of the reconfigured AMF-1 that will include much of the instrumentation previously in the MAOS.

A more important CACTI session discussing updated and more firm CACTI plans that solicits feedback and involvement from the ARM/ASR community will be planned for the 2017 ARM/ASR PI Meeting, which will take place 12-18 months ahead of the CACTI deployment.