Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS)

1 October 2017 - 1 April 2018

Lead Scientist: Greg McFarquhar

Observatory: amf, mar

The Southern Ocean (SO) is the stormiest place on Earth, buffeted by winds and waves that circle the ice of Antarctica, sheathed in clouds that mantle a dynamic ocean with rich ecosystems. The remote and usually pristine environment, typically removed from anthropogenic and natural continental aerosol sources, makes the SO unique for examining cloud‐aerosol interactions for liquid and ice clouds, and the role of marine biogenic aerosols, their precursors, and sea salt. There is strong seasonality in aerosol sources and sinks over the SO that are poorly understood. Weather and climate models are challenged by uncertainties and biases in the simulation of SO clouds, aerosols, and air‐sea exchanges that trace to poor physical understanding of these processes, and by cloud feedbacks (e.g., phase changes) in response to warming. Models almost universally underestimate sunlight reflected by near surface clouds, particularly in the cold sector of cyclonic storm systems, and this might be due to difficulties in representing pervasive supercooled and mixed‐phase boundary layer clouds. Motivated by these issues, a large international multi-agency effort called the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) has been proposed to improve understanding of clouds, aerosols, air‐sea exchanges and their interactions over the SO. Researchers propose to acquire comprehensive observations of aerosols including cloud condensation nuclei (CCN) and ice nucleating particles (INP) in the boundary layer, vertical distributions of macrophysical and microphysical properties of liquid and mixed‐phase clouds, and downwelling radiative fluxes over the SO during a seven‐month period centered upon the austral summer. In particular, researchers propose the Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) field campaign. The second ARM Mobile Facility (AMF2) will be installed on the Australian Antarctic supply vessel Aurora Australis (AA) as it routinely travels between Hobart, Australia, and the Antarctic, visiting the Australian Antarctic stations Mawson, Davis, and Casey. The MARCUS observations will be self‐standing and unique within SOCRATES in that they will capture the variability in aerosol and cloud properties across the SO from spring to autumn, especially in cold waters at latitudes poleward of 60 degrees south, where supercooled and mixed‐phase boundary layer clouds in the cold sector of cyclones are frequent and where past and planned SOCRATES observations are most sparse. The data to be obtained during MARCUS under a range of synoptic settings will document how temperature‐dependent distributions of cloud properties and frequency of supercooled water vary with concentrations of CCN and INPs, synoptic regime, latitude, and season (spring, summer, fall). MARCUS data will also help in understanding the sources, sinks, and variability of CCN and INPs, the increased bias of absorbed shortwave radiation in summer in models, and conditions conducive to extensive supercooled water. Specific hypotheses will be tested under four SOCRATES themes to understand:

  • the synoptically varying vertical structure of SO boundary layer clouds and aerosols
  • sources and sinks of the ocean's CCN and INPs, including the role of local biogenic sources over spring, summer, and fall
  • mechanisms controlling supercooled liquid and mixed‐phase clouds
  • advances in retrievals of clouds, precipitation, and aerosols over the SO.

Parameterization development and testing needs are integrated in MARCUS' design and in the design of the multi-agency SOCRATES project so that systematic confrontation and improvement of leading climate models with data will be possible. In addition to measurements from the Aerosol Observing System, weather balloons with sondes, micropulse lidar, microwave radiometer, marine W‐band (95 GHz) stabilized cloud radar, ceilometer, sun photometer, downwelling radiometers, and inertial navigation system, user‐supplied filter samples will be collected and subsequently processed in order to determine immersion freezing INP concentrations as a function of temperature.


Simon Alexander Roger Marchand Steven Siems
Christopher Bretherton Alain Protat Robert Weller
Paul DeMott Patricia Quinn Robert Wood


  • Child Campaign


Zhang M, S Xie, X Liu, W Lin, X Zheng, J Golaz, and Y Zhang. 2022. "Cloud Phase Simulation at High Latitudes in EAMv2: Evaluation using CALIPSO Observations and Comparison with EAMv1." Journal of Geophysical Research: Atmospheres, 1 27(22), e2022JD037100, 10.1029/2022JD037100.

Theisen A, Y Feng, A Matthews, K Johnson, E Schuman, A Lindenmaier, T Wendler, V Castro, S Giangrande, S Collis, D Zhang, J Mather, and J Comstock. 2022. ARM FY2023 Radar Plan. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-TR-282. 10.2172/1888480.

Giangrande S, J Comstock, S Collis, J Shilling, K Gaustad, K Kehoe, S Xie, and D Zhang. 2022. Translator Plan: A Coordinated Vision for Fiscal Years 2023-2025. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-22-003. 10.2172/1893730.

ZHU Z, P Kollias, E Luke, and F Yang. 2022. "New insights on the prevalence of drizzle in marine stratocumulus clouds based on a machine learning algorithm applied to radar Doppler spectra." Atmospheric Chemistry and Physics, 22(11), 10.5194/acp-22-7405-2022.
Research Highlight

Xi B, X Dong, X Zheng, and P Wu. 2022. "Cloud phase and macrophysical properties over the Southern Ocean during the MARCUS field campaign." Atmospheric Measurement Techniques, 15(12), 10.5194/amt-15-3761-2022.

Tang S, J Fast, K Zhang, J Hardin, A Varble, J Shilling, F Mei, M Zawadowicz, and P Ma. 2022. "Earth System Model Aerosol–Cloud Diagnostics (ESMAC Diags) package, version 1: assessing E3SM aerosol predictions using aircraft, ship, and surface measurements." Geoscientific Model Development, 15(10), 10.5194/gmd-15-4055-2022.
Research Highlight


Humphries R, M Keywood, S Gribben, I McRobert, J Ward, P Selleck, S Taylor, J Harnwell, C Flynn, G Kulkarni, G Mace, A Protat, S Alexander, and G McFarquhar. 2021. "Southern Ocean latitudinal gradients of cloud condensation nuclei." Atmospheric Chemistry and Physics, 21(16), 10.5194/acp-21-12757-2021.

Mace G, A Protat, and S Benson. 2021. "Mixed‐phase clouds over the Southern Ocean as observed from satellite and surface based lidar and radar." Journal of Geophysical Research: Atmospheres, , e2021JD034569, 10.1029/2021JD034569.

Vignon E, S Alexander, P DeMott, G Sotiropoulou, F Gerber, T Hill, R Marchand, A Nenes, and A Berne. 2021. "Challenging and improving the simulation of mid‐level mixed‐phase clouds over the high‐latitude Southern Ocean." Journal of Geophysical Research: Atmospheres, 126(7), e2020JD033490, 10.1029/2020JD033490.

Alexander S, G McFarquhar, R Marchand, A Protat, É Vignon, G Mace, and A Klekociuk. 2021. "Mixed‐phase clouds and precipitation in Southern Ocean cyclones and cloud systems observed poleward of 64°S by ship‐based cloud radar and lidar." Journal of Geophysical Research: Atmospheres, 126(8), e2020JD033626, 10.1029/2020JD033626.

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Campaign Data Sets

IOP Participant Data Source Name Final Data
Paul DeMott Ice Spectrometer Order Data
Ruhi Humphries Cloud Condensation Nuclei Counter Order Data
Martin Schnaiter Waveband Integrated Bioaerosol Sensor mark 4 Order Data

MAR Data Sources

Name Full Name Browse Data
AERI Atmospheric Emitted Radiance Interferometer Browse Data
AERINF AERI Noise Filtered Browse Data
AERIOE AERIoe Thermodynamic Profile and Cloud Retrieval Browse Data
AOP Aerosol Optical Properties Browse Data
AOS Aerosol Observing System Browse Data
AOSMET Meteorological Measurements associated with the Aerosol Observing System Browse Data
CAMSITE camera that monitors a site area Browse Data
CCN Cloud Condensation Nuclei Particle Counter Browse Data
CEIL Ceilometer Browse Data
CEILPBLHT Boundary-layer height data with CEIL Browse Data
CO-ANALYZER Carbon Monoxide Analyzer Browse Data
CPC Condensation Particle Counter Browse Data
HTDMA Humidified Tandem Differential Mobility Analyzer Browse Data
INTERPSONDE Interpolated Sonde Browse Data
IRT Infrared Thermometer Browse Data
MARINEMET Marine Surface Meteorological Instrumentation Browse Data
MARINEPRECIP Marine Precipitation Instrumentation Browse Data
MPL Micropulse Lidar Browse Data
MPLCMASK Cloud mask from Micropulse Lidar Browse Data
MPLPOLFSSHIPCOR MPL Corrected for Ship Motion Browse Data
MWACR Marine W-Band (95 GHz) ARM Cloud Radar Browse Data
MWACRARSCL Marine W-band ARM Cloud Radar, Active Remote Sensing of Clouds Browse Data
MWACRSHIPCOR MWACR Ship Motion Correction Browse Data
MWR Microwave Radiometer Browse Data
MWR3C Microwave Radiometer, 3 Channel Browse Data
MWRRET MWR Retrievals Browse Data
NAV Navigational Location and Attitude Browse Data
NAVBE Navigational Location and Attitude Best Estimate Browse Data
NEPHELOMETER Nephelometer Browse Data
OZONE Ozone Monitor Browse Data
PBLHT Planetary Boundary Layer Height Browse Data
PRP Portable Radiation Package Browse Data
PSAP Particle Soot Absorption Photometer Browse Data
RWP Radar Wind Profiler Browse Data
SONDE Balloon-Borne Sounding System Browse Data
SONDEGRID Gridded Sonde VAP Product Browse Data
S-TABLE Stabilized Platform Browse Data
TSI Total Sky Imager Browse Data
UHSAS Ultra-High Sensitivity Aerosol Spectrometer Browse Data
VISST Minnis Cloud Products Using Visst Algorithm Browse Data
WACRARSCL W-band Cloud Radar Active Remote Sensing of Cloud Browse Data