Utilizing a Storm-Generating Hotspot to Study Convective Cloud Transitions: The CACTI Experiment

Abstract

The Cloud, Aerosol, and Complex Terrain Interactions (CACTI) field campaign was designed to improve understanding of orographic cloud life cycles in relation to surrounding atmospheric thermodynamic, flow, and aerosol conditions. The deployment to the Sierras de Córdoba range in north-central Argentina was chosen because of very frequent cumulus congestus, deep convection initiation, and mesoscale convective organization uniquely observable from a fixed site. The C-band Scanning Atmospheric Radiation Measurement (ARM) Precipitation Radar was deployed for the first time with over 50 ARM Mobile Facility atmospheric state, surface, aerosol, radiation, cloud, and precipitation instruments between October 2018 and April 2019. An intensive observing period (IOP) coincident with the RELAMPAGO field campaign was held between 1 November and 15 December during which 22 flights were performed by the ARM Gulfstream-1 aircraft.A multitude of atmospheric processes and cloud conditions were observed over the 7-month campaign, including: numerous orographic cumulus and stratocumulus events; new particle formation and growth producing high aerosol concentrations; drizzle formation in fog and shallow liquid clouds; very low aerosol conditions following wet deposition in heavy rainfall; initiation of ice in congestus clouds across a range of temperatures; extreme deep convection reaching 21-km altitudes; and organization of intense, hail-containing supercells and mesoscale convective systems. These comprehensive datasets include many of the first ever collected in this region and provide new opportunities to study orographic cloud evolution and interactions with meteorological conditions, aerosols, surface conditions, and radiation in mountainous terrain.

Ice nucleating particle connections to regional Argentinian land surface emissions and weather during the Cloud, Aerosol, and Complex Terrain Interactions experiment

“…The predominance of biological INPs at temperatures above −20°C emphasizes the need for parameterization of this INP class, which should include their short-term variation caused by precipitation (e.g., fit parameterization derived by Mignani et al, 2021) and high relative humidity. Work to investigate whether the concentrations, characteristics and dynamics of the surface-level INPs are also applicable to observations at the altitude of clouds is ongoing (DeMott & Hill, 2020;Varble et al, 2021).…”

Lightning Geolocation and Flash Rates From LF Radio Observations During the RELAMPAGO Field Campaign

“…Primarily funded by the National Science Foundation, this campaign was an international collaboration seeking to observe and investigate convective storms that produce high-impact weather (Nesbitt et al, 2021). Accompanying the RELAMPAGO campaign was the Department of Energy ARM-funded CACTI field campaign (Varble et al, 2021) which was planned and operated in coordination with RELAMPAGO to maximize the benefits of each campaign.…”

Raindrop Size Spectrum in Deep Convective Regions of the Americas

“…For example, the NASA Tropical Rainfall Measuring Mission-Large-Scale Biosphere-Atmosphere (TRMM-LBA) experiment conducted in 1999 in southwestern Amazonia [43,[50][51][52] and the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Green Ocean Amazon (GoAmazon) field campaign conducted in central Amazonia during 2014 and 2015 [53][54][55] collected DSD observations. Moreover, the DOE ARM Cloud, Aerosol, and Complex Terrain Interactions (CACTI) and Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaigns conducted during the austral warm season of 2018-2019 collected disdrometer observations in west-central Argentina near the Sierras de Córdoba (SDC) [56,57]. This north-south-oriented mountain range east of the Andes in subtropical South America is known to frequently initiate deep convection [56][57][58][59][60][61].…”

“…Moreover, the DOE ARM Cloud, Aerosol, and Complex Terrain Interactions (CACTI) and Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaigns conducted during the austral warm season of 2018-2019 collected disdrometer observations in west-central Argentina near the Sierras de Córdoba (SDC) [56,57]. This north-south-oriented mountain range east of the Andes in subtropical South America is known to frequently initiate deep convection [56][57][58][59][60][61]. In addition, measurements from the Integrated Precipitation and Hydrology Experiment (IPHEx), which was conducted in the Appalachian Mountains of North Carolina (USA), formed an extensive DSD database for midlatitude mountainous terrain [62].…”