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Jerome D. Fast
,
Larry K. Berg
,
Lizbeth Alexander
,
David Bell
,
Emma D’Ambro
,
John Hubbe
,
Chongai Kuang
,
Jiumeng Liu
,
Chuck Long
,
Alyssa Matthews
,
Fan Mei
,
Rob Newsom
,
Mikhail Pekour
,
Tamara Pinterich
,
Beat Schmid
,
Siegfried Schobesberger
,
John Shilling
,
James N. Smith
,
Stephen Springston
,
Kaitlyn Suski
,
Joel A. Thornton
,
Jason Tomlinson
,
Jian Wang
,
Heng Xiao
, and
Alla Zelenyuk

Abstract

Shallow convective clouds are common, occurring over many areas of the world, and are an important component in the atmospheric radiation budget. In addition to synoptic and mesoscale meteorological conditions, land–atmosphere interactions and aerosol–radiation–cloud interactions can influence the formation of shallow clouds and their properties. These processes exhibit large spatial and temporal variability and occur at the subgrid scale for all current climate, operational forecast, and cloud-system-resolving models; therefore, they must be represented by parameterizations. Uncertainties in shallow cloud parameterization predictions arise from many sources, including insufficient coincident data needed to adequately represent the coupling of cloud macrophysical and microphysical properties with inhomogeneity in the surface-layer, boundary layer, and aerosol properties. Predictions of the transition of shallow to deep convection and the onset of precipitation are also affected by errors in simulated shallow clouds. Coincident data are a key factor needed to achieve a more complete understanding of the life cycle of shallow convective clouds and to develop improved model parameterizations. To address these issues, the Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems (HI-SCALE) campaign was conducted near the Atmospheric Radiation Measurement (ARM) Southern Great Plains site in north-central Oklahoma during the spring and summer of 2016. We describe the scientific objectives of HI-SCALE as well as the experimental approach, overall weather conditions during the campaign, and preliminary findings from the measurements. Finally, we discuss scientific gaps in our understanding of shallow clouds that can be addressed by analysis and modeling studies that use HI-SCALE data.

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Adam C. Varble
,
Stephen W. Nesbitt
,
Paola Salio
,
Joseph C. Hardin
,
Nitin Bharadwaj
,
Paloma Borque
,
Paul J. DeMott
,
Zhe Feng
,
Thomas C. J. Hill
,
James N. Marquis
,
Alyssa Matthews
,
Fan Mei
,
Rusen Öktem
,
Vagner Castro
,
Lexie Goldberger
,
Alexis Hunzinger
,
Kevin R. Barry
,
Sonia M. Kreidenweis
,
Greg M. McFarquhar
,
Lynn A. McMurdie
,
Mikhail Pekour
,
Heath Powers
,
David M. Romps
,
Celeste Saulo
,
Beat Schmid
,
Jason M. Tomlinson
,
Susan C. van den Heever
,
Alla Zelenyuk
,
Zhixiao Zhang
, and
Edward J. Zipser

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.

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Bart Geerts
,
Scott E. Giangrande
,
Greg M. McFarquhar
,
Lulin Xue
,
Steven J. Abel
,
Jennifer M. Comstock
,
Susanne Crewell
,
Paul J. DeMott
,
Kerstin Ebell
,
Paul Field
,
Thomas C. J. Hill
,
Alexis Hunzinger
,
Michael P. Jensen
,
Karen L. Johnson
,
Timothy W. Juliano
,
Pavlos Kollias
,
Branko Kosovic
,
Christian Lackner
,
Ed Luke
,
Christof Lüpkes
,
Alyssa A. Matthews
,
Roel Neggers
,
Mikhail Ovchinnikov
,
Heath Powers
,
Matthew D. Shupe
,
Thomas Spengler
,
Benjamin E. Swanson
,
Michael Tjernström
,
Adam K. Theisen
,
Nathan A. Wales
,
Yonggang Wang
,
Manfred Wendisch
, and
Peng Wu

Abstract

One of the most intense air mass transformations on Earth happens when cold air flows from frozen surfaces to much warmer open water in cold-air outbreaks (CAOs), a process captured beautifully in satellite imagery. Despite the ubiquity of the CAO cloud regime over high-latitude oceans, we have a rather poor understanding of its properties, its role in energy and water cycles, and its treatment in weather and climate models. The Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) was conducted to better understand this regime and its representation in models. COMBLE aimed to examine the relations between surface fluxes, boundary layer structure, aerosol, cloud, and precipitation properties, and mesoscale circulations in marine CAOs. Processes affecting these properties largely fall in a range of scales where boundary layer processes, convection, and precipitation are tightly coupled, which makes accurate representation of the CAO cloud regime in numerical weather prediction and global climate models most challenging. COMBLE deployed an Atmospheric Radiation Measurement Mobile Facility at a coastal site in northern Scandinavia (69°N), with additional instruments on Bear Island (75°N), from December 2019 to May 2020. CAO conditions were experienced 19% (21%) of the time at the main site (on Bear Island). A comprehensive suite of continuous in situ and remote sensing observations of atmospheric conditions, clouds, precipitation, and aerosol were collected. Because of the clouds’ well-defined origin, their shallow depth, and the broad range of observed temperature and aerosol concentrations, the COMBLE dataset provides a powerful modeling testbed for improving the representation of mixed-phase cloud processes in large-eddy simulations and large-scale models.

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Jian Wang
,
Rob Wood
,
Michael P. Jensen
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J. Christine Chiu
,
Yangang Liu
,
Katia Lamer
,
Neel Desai
,
Scott E. Giangrande
,
Daniel A. Knopf
,
Pavlos Kollias
,
Alexander Laskin
,
Xiaohong Liu
,
Chunsong Lu
,
David Mechem
,
Fan Mei
,
Mariusz Starzec
,
Jason Tomlinson
,
Yang Wang
,
Seong Soo Yum
,
Guangjie Zheng
,
Allison C. Aiken
,
Eduardo B. Azevedo
,
Yann Blanchard
,
Swarup China
,
Xiquan Dong
,
Francesca Gallo
,
Sinan Gao
,
Virendra P. Ghate
,
Susanne Glienke
,
Lexie Goldberger
,
Joseph C. Hardin
,
Chongai Kuang
,
Edward P. Luke
,
Alyssa A. Matthews
,
Mark A. Miller
,
Ryan Moffet
,
Mikhail Pekour
,
Beat Schmid
,
Arthur J. Sedlacek
,
Raymond A. Shaw
,
John E. Shilling
,
Amy Sullivan
,
Kaitlyn Suski
,
Daniel P. Veghte
,
Rodney Weber
,
Matt Wyant
,
Jaemin Yeom
,
Maria Zawadowicz
, and
Zhibo Zhang

Abstract

With their extensive coverage, marine low clouds greatly impact global climate. Presently, marine low clouds are poorly represented in global climate models, and the response of marine low clouds to changes in atmospheric greenhouse gases and aerosols remains the major source of uncertainty in climate simulations. The eastern North Atlantic (ENA) is a region of persistent but diverse subtropical marine boundary layer clouds, whose albedo and precipitation are highly susceptible to perturbations in aerosol properties. In addition, the ENA is periodically impacted by continental aerosols, making it an excellent location to study the cloud condensation nuclei (CCN) budget in a remote marine region periodically perturbed by anthropogenic emissions, and to investigate the impacts of long-range transport of aerosols on remote marine clouds. The Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA) campaign was motivated by the need of comprehensive in situ measurements for improving the understanding of marine boundary layer CCN budget, cloud and drizzle microphysics, and the impact of aerosol on marine low cloud and precipitation. The airborne deployments took place from 21 June to 20 July 2017 and from 15 January to 18 February 2018 in the Azores. The flights were designed to maximize the synergy between in situ airborne measurements and ongoing long-term observations at a ground site. Here we present measurements, observation strategy, meteorological conditions during the campaign, and preliminary findings. Finally, we discuss future analyses and modeling studies that improve the understanding and representation of marine boundary layer aerosols, clouds, precipitation, and the interactions among them.

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