Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

Routine AAF CLOWD Optical Radiative Observations (RACORO)

22 January 2009 - 30 June 2009

Lead Scientist: Andrew Vogelmann

Observatory: AAF, SGP

The ARM Aerial Facility (AAF) supported the Routine AAF Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) field campaign, led by principal investigator Andrew Vogelmann. During this long-term campaign, the AAF conducted routine flights at the ACRF Southern Great Plains site to sample low-altitude liquid-water clouds in the boundary layer. The purpose was to obtain representative statistics of cloud microphysical properties needed to validate retrieval algorithms and support process studies and model simulations of boundary layer clouds and, in particular, CLOWD-type clouds. See the RACORO Data Guide for a summary of contacts, aircraft instrumentation, instrument status per flight, and flight patterns used.

Steering Committee: Andrew Vogelmann, Greg McFarquhar, John Ogren, Dave Turner, Jennifer Comstock, Graham Feingold, and Chuck Long

Additional Information

Science Questions

The spread of climate sensitivity estimates among general circulation models arises primarily from inter-model differences in the representations of aerosol and cloud processes (IPCC, 2007); in particular, low-level, boundary-layer clouds constitute the largest uncertainty in climate models. This is due to large discrepancies in the radiative responses simulated by models in regions dominated by low-level cloud cover and to the large areas of the globe covered by these regions. Thin, low-level cloud properties are very sensitive to changes in aerosol loading, and the aerosol effect on cloud albedo remains the dominant uncertainty in radiative forcing (IPCC, 2007).

  1. Investigate Aerosol-Cloud Interactions. Along with measurement of cloud properties, RACORO will observe aerosol properties associated with cloud variability, such as aerosol amount, aerosol size distribution, and the number of cloud condensation nuclei. These data enable scientists to address the vexing problem of deciphering how aerosols affect cloud properties. This attribution is confounded by the meteorological variability that requires RACORO-type long-term statistics to resolve.
  2. Improve Cloud Simulations in Climate Models. Meteorological state will be measured by aircraft and surface instrumentation. These observations will provide critical information on properties such as moisture availability and updraft intensity at cloud base, which will facilitate improving our understanding of how meteorological factors influence cloud dynamics, cloud properties, and aerosol-cloud interactions. The collection of statistics and their seasonal variations will provide the constraints needed to evaluate and improve climate model simulations of these clouds.
  3. Validate ACRF Remotely-Sensed Cloud Properties. The suite of radiometers at the ACRF site and on satellites provide observations that can be used to remotely retrieve cloud liquid-water amount and cloud drop size. These retrievals are essential for obtaining the type of long-term observations needed for cloud and climate studies. However, recent ACRF research has shown that large differences exist between different state-of-the-art techniques. RACORO observations will be used to help validate these retrievals and investigate the radiative impact of these clouds on the Earth's energy budget.


Brookhaven National Laboratory– In April, a team of scientists led by BNL will test a linear array of scanning microwave radiometers to retrieve profiles of cloud water content at the SGP site. Data obtained during RACORO overflights may be used to validate this novel array approach for ground-based cloud property retrievals.

National Aeronautics and Space Administration– In June, scientists from NASA will join the RACORO campaign with an instrumented King Air B200 research aircraft. It will fly above the Twin Otter to obtain complementary measurements of aerosol and cloud microphysical properties. Measurements from both aircraft and the ground will also be used to validate a new sensor for upcoming missions by the Glory satellite.


Jennifer Comstock
Graham Feingold
Chuck Long
Greg McFarquhar
John Ogren
David Turner


Lu C, Y Liu, S Yum, J Chen, L Zhu, S Gao, Y Yin, X Jia, and Y Wang. 2020. "Reconciling Contrasting Relationships between Relative Dispersion and Volume‐Mean Radius of Cloud Droplet Size Distributions." Journal of Geophysical Research: Atmospheres, 125(9), e2019JD031868, 10.1029/2019JD031868.

Gao S, C Lu, Y Liu, F Mei, J Wang, L Zhu, and S Yan. 2020. "Contrasting Scale Dependence of Entrainment‐Mixing Mechanisms in Stratocumulus Clouds." Geophysical Research Letters, 47(9), e2020GL086970, 10.1029/2020GL086970.

Goss HB, KS Dorsey, CB Ireland, MR Wasem, RA Stafford, and R Jundt. 2020. 2019 Atmospheric Radiation Measurement (ARM) Annual Report. Ed. by Kathryn Dorsey, ARM user facility. DOE/SC-ARM-19-032.


Liu Y. 2019. "Introduction to the Special Section on Fast Physics in Climate Models: Parameterization, Evaluation, and Observation." Journal of Geophysical Research: Atmospheres, 124(15), 10.1029/2019JD030422.


Lu C, C Sun, Y Liu, G Zhang, Y Lin, W Gao, S Niu, Y Yin, Y Qiu, and L Jin. 2018. "Observational Relationship between Entrainment Rate and Environmental Relative Humidity and Implications for Convection Parameterization." Geophysical Research Letters, 45(24), 10.1029/2018GL080264.

Lu C, Y Liu, B Zhu, S Yum, S Krueger, Y Qiu, S Niu, and S Luo. 2018. "On Which Microphysical Time Scales to Use in Studies of Entrainment-Mixing Mechanisms in Clouds." Journal of Geophysical Research: Atmospheres, 123(7), 10.1002/2017JD027985.
Research Highlight


Romps D and A Vogelmann. 2017. "Methods for Estimating 2D Cloud Size Distributions from 1D Observations." Journal of the Atmospheric Sciences, 74(10), 10.1175/JAS-D-17-0105.1.

Yeom J, S Yum, Y Liu, and C Lu. 2017. "A study on the entrainment and mixing process in the continental stratocumulus clouds measured during the RACORO campaign." Atmospheric Research, 194, 10.1016/j.atmosres.2017.04.028.

Cecchini M, L Machado, M Andreae, S Martin, R Albrecht, P Artaxo, H Barbosa, S Borrmann, D Fütterer, T Jurkat, C Mahnke, A Minikin, S Molleker, M Pöhlker, U Pöschl, D Rosenfeld, C Voigt, B Wenzierl, and M Wendisch. 2017. "Sensitivities of Amazonian clouds to aerosols and updraft speed." Atmospheric Chemistry and Physics, 17(16), 10.5194/acp-2017-89.


Oue M, P Kollias, KW North, A Tatarevic, S Endo, AM Vogelmann, and WI Gustafson Jr.. 2016. "Estimation of cloud fraction profile in shallow convection using a scanning cloud radar." Geophysical Research Letters, 43(20), 10.1002/2016gl070776.
Research Highlight

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Campaign Data Sets

IOP Participant Data Source Name Final Data
Elisabeth Andrews Adjusted Cloud Condensation Nuclei Concentrations Order Data
Elisabeth Andrews Aersol Optical Properties- Derived Order Data
Jennifer Comstock Merged Data Order Data
Owen Cooper GOES Visible Imagery Order Data
Glenn Diskin Diode Laser Hygrometer Order Data
Hermann Gerber Cloud Integrating Nephelometer Order Data
Haflidi Jonsson CIRPAS Basic Parameters Order Data
Haflidi Jonsson CIRPAS Cabin Order Data
Haflidi Jonsson Cloud and Aerosol Spectrometer (CAS) Order Data
Haflidi Jonsson Cloud, Aerosol and Precipitation Spectrometer Order Data
Haflidi Jonsson Forward Scattering Spectrometer Probe Order Data
Haflidi Jonsson Passive Cavity Aerosol Spectrometer Order Data
Paul Lawson Merged CAS and 2D-S Particle Size Distributions Order Data
Chuck Long Tilt Corrected Radiation Files Order Data
Chuck Long Tilt Corrected Radiation and MFR Calibrated Files Order Data
Greg McFarquhar Best Estimate Microphysical Cloud Properties Order Data
Greg McFarquhar Two-Dimensional Cloud Imaging Probe Order Data
Roy Woods Dual Column Cloud Condensation Nuclei Counter Order Data
Shaocheng Xie Cloud Modeling Best Estimate- Cloud and Radiation Order Data
Shaocheng Xie Constrained Variational Objective Analysis Data Order Data

SGP Data Sources

Name Full Name Browse Data
ABRFC Arkansas-Red Basin River Forecast Center Browse Data
AERI Atmospheric Emitted Radiance Interferometer Browse Data
AERINF AERI Noise Filtered Browse Data
AERIPROF AERI Profiles of Water Vapor and Temperature Browse Data
AEROSOLBE Aerosol Best Estimate Browse Data
AIP Aerosol Intensive Properties Browse Data
AOD Aerosol Optical Depth, derived from atmospheric extinction of solar irradiance Browse Data
AOS Aerosol Observing System Browse Data
AOSCCNAVG Aerosol Observing System (AOS): cloud condensation nuclei data, averaged Browse Data
ARMBE ARM Best Estimate Data Products Browse Data
ARMBE2DGRID 2D Gridded Surface Data Set Browse Data
ARMBESTNS Station-based Surface Products Browse Data
ARSCL Active Remote Sensing of CLouds Browse Data
AVHRR Advanced Very High Resolution Radiometer Browse Data
BAEBBR Best-Estimate Fluxes From EBBR Measurements and Bulk Aerodynamics Calculations Browse Data
BEFLUX Best-Estimate Radiative Flux Browse Data
BRS Broadband Radiometer Station Browse Data
CCN Cloud Condensation Nuclei Particle Counter Browse Data
CCNPROF Cloud Condensation Nuclei Profile Browse Data
CEIL Ceilometer Browse Data
CLDTYPE Cloud Type Classification Browse Data
CO Carbon Monoxide Mixing Ratio System Browse Data
CO2FLX Carbon Dioxide Flux Measurement Systems Browse Data
CSPHOT Cimel Sunphotometer Browse Data
DISDROMETER Impact Disdrometer Browse Data
EBBR Energy Balance Bowen Ratio Station Browse Data
ECOR Eddy Correlation Flux Measurement System Browse Data
FLASK Flask Samplers for Carbon Cycle Gases and Isotopes Browse Data
GOES Geostationary Operational Environmental Satellites Browse Data
GOES-UTH Upper Tropospheric Relative Humidity from GOES Satellite Data Browse Data
IAP In-situ Aerosol Profiles (Cessna Aerosol Flights) Browse Data
INTERPSONDE Interpolated Sonde Browse Data
IRT Infrared Thermometer Browse Data
KSUMESO Kansas State University Mesonet Browse Data
LASSO LES ARM Symbiotic Simulation and Observation (LASSO) Browse Data
LSSONDE Microwave Radiometer-Scaled Sonde Profiles Browse Data
MERGESONDE Merged Sounding Browse Data
MET Surface Meteorological Instrumentation Browse Data
MFR Multifilter Radiometer Browse Data
MFRSR Multifilter Rotating Shadowband Radiometer Browse Data
MFRSRCLDOD Cloud Optical Properties from MFRSR Using Min Algorithm Browse Data
MICROBASE Continuous Baseline Microphysical Retrieval Browse Data
MMCR Millimeter Wavelength Cloud Radar Browse Data
MMCRMODE MMCR mode moments, derived by ARSCL process Browse Data
MOLTS Model Output Location Time Series Browse Data
MPL Micropulse Lidar Browse Data
MPLAVG MPL: data averaged to fixed 30 second interval, e.g. for polarized data Browse Data
MPLCMASK Cloud mask from Micropulse Lidar Browse Data
MWR Microwave Radiometer Browse Data
MWRHF Microwave Radiometer - High Frequency Browse Data
MWRRET MWR Retrievals Browse Data
NCEPGFS National Centers for Environment Prediction Global Forecast System Browse Data
NDROP Droplet number concentration Browse Data
NFOV Narrow Field of View Zenith Radiometer Browse Data
NIMFR Normal Incidence Multifilter Radiometer Browse Data
NOAACRN NOAA Climate Reference Network Browse Data
NWSUPA National Weather Service Upper Air Measurements Browse Data
OKM Oklahoma Mesonet Browse Data
OKMSOIL Oklahoma Mesonet Soil Moisture Browse Data
ORG Optical Rain Gauge Browse Data
PASS Photoacoustic Soot Spectrometer Browse Data
PBLHT Planetary Boundary Layer Height Browse Data
PGS Precision Carbon Dioxide Mixing Ratio System Browse Data
QCECOR Quality Controlled Eddy Correlation Flux Measurement Browse Data
QCRAD Data Quality Assessment for ARM Radiation Data Browse Data
RADFLUXANAL Radiative Flux Analysis Browse Data
RAIN Rain Gauge Browse Data
RL Raman Lidar Browse Data
RLPROF Raman LIDAR Vertical Profiles Browse Data
RUC Rapid Update Cycle Model Data Browse Data
RWP Radar Wind Profiler Browse Data
SFCCLDGRID Surface Cloud Grid Browse Data
SHALLOWCUMULUS Fair-Weather Shallow Cumulus Identification Browse Data
SIRS Solar and Infrared Radiation Station Browse Data
SODAR Mini Sound Detection and Ranging Browse Data
SONDE Balloon-Borne Sounding System Browse Data
SONDEADJUST Sonde Adjust Browse Data
SONDEGRID Gridded Sonde VAP Product Browse Data
SUOMIGPS SuomiNet Global Positioning System Browse Data
SURFSPECALB Surface Spectral Albedo Browse Data
SURTHREF Surface Temperature and Humidity Reference System for Sondes Browse Data
SWATS Soil Water and Temperature System Browse Data
SWFLUXANAL Shortwave Flux Analysis Browse Data
SWS Shortwave Spectroradiometer Browse Data
TDMA Tandem Differential Mobility Analyzer Browse Data
TDMADAP Aerosol Properties derived from TDMA Measurements Browse Data
THWAPS Temperature, Humidity, Wind and Pressure Sensors Browse Data
TSI Total Sky Imager Browse Data
TWR Facility-specific multi-level Meteorological Instrumentation Browse Data
TWRMR Tower Water-Vapor Mixing Ratio Browse Data
USDARAD US Department of Agriculture (USDA) Radiation Monitoring Data Browse Data
VARANAL3D Three-dimensional Constrained Variational Analysis Browse Data
VDIS Video Disdrometer Browse Data
VISST Minnis Cloud Products Using Visst Algorithm Browse Data
WACR W-Band (95 GHz) ARM Cloud Radar Browse Data
WPDN Wind Profiler Demo Network Browse Data
WPDNGPS Wind Profiler Demonstration Network GPS Browse Data