aos: Aerosol Observing System

The aerosol observing system (AOS) is the primary platform for in situ aerosol measurements at Earth’s surface. Each AOS has a different complement of instruments, which are selected to ensure the best measurements at each deployment site.

The AOS measures aerosol optical properties to better understand how particles interact with solar radiation and influence the Earth’s radiation balance. These measurements are useful for calculating parameters used in radiative forcing calculations, such as the aerosol single scattering albedo, asymmetry parameter, mass scattering efficiency, and hygroscopic growth. Measurements made with the AOS form a long-term record at the ARM fixed sites. Shorter measurement records are available from mobile deployments in a wide variety of geographical regions.  These measurements are valuable for:

  • identifying long-term changes in aerosol properties
  • identifying atmospheric processes controlling aerosol life cycle and their influence on clouds
  • providing experimental data for developing and testing atmospheric climate models.


  • Fixed
  • AMF1
  • AMF2
  • AMF3


acsm: Aerosol Chemical Speciation Monitor

aeth: Aethalometer

aosmet: Meteorological Measurements associated with the Aerosol Observing System

aps: Aerodynamic Particle Sizer

caps-pmex: Cavity Attenuated Phase Shift Extinction Monitor

ccn: Cloud Condensation Nuclei Particle Counter

clap: Continuous Light Absorption Photometer

co-analyzer: Carbon Monoxide Analyzer

cpc: Condensation Particle Counter

ghg: Greenhouse Gas Monitor

htdma: Humidified Tandem Differential Mobility Analyzer

nephelometer: Nephelometer

nox: Nitrogen Oxides Monitor

ozone: Ozone Monitor

pass: Photoacoustic Soot Spectrometer

pils: Particle Into Liquid Sampler

psap: Particle Soot Absorption Photometer

ptr-ms: Proton Transfer Reaction Mass Spectrometer

smps: Scanning mobility particle sizer

so2: Sulfur Dioxide Monitor

sp2: Single Particle Soot Photometer

tap: Tricolor Absorption Photometer

tracegas: Trace gas concentrations

uhsas: Ultra-High Sensitivity Aerosol Spectrometer

Active Instrument Locations

Facility Name Instrument Start Date
External Data (satellites and others) 1998-01-01
Oliktok Point, Alaska; AMF3 2016-06-21
Lamont, OK (Extended and Co-located with C1) 2016-10-24
Graciosa Island, Azores, Portugal 2013-08-15


Shen Y, A Virkkula, A Ding, K Luoma, H Keskinen, P Aalto, X Chi, X Qi, W Nie, X Huang, T Petäjä, M Kulmala, and V Kerminen. 2019. "Estimating cloud condensation nuclei number concentrations using aerosol optical properties: role of particle number size distribution and parameterization." Atmospheric Chemistry and Physics, 19(24), 10.5194/acp-19-15483-2019.

Uin J, A Aiken, M Dubey, C Kuang, M Pekour, C Salwen, A Sedlacek, G Senum, S Smith, J Wang, T Watson, and S Springston. 2019. "Atmospheric Radiation Measurement (ARM) Aerosol Observing Systems (AOS) for Surface-Based In-Situ Atmospheric Aerosol and Trace Gas Measurements." Journal of Atmospheric and Oceanic Technology, 36(12), 10.1175/JTECH-D-19-0077.1.
Research Highlight

Li J, H Chen, Z Li, P Wang, X Fan, W He, and J Zhang. 2019. "Analysis of Low-level Temperature Inversions and Their Effects on Aerosols in the Lower Atmosphere." Advances in Atmospheric Sciences, 36(11), 10.1007/s00376-019-9018-9.

Glicker H, M Lawler, J Ortega, S de Sá, S Martin, P Artaxo, O Vega Bustillos, R de Souza, J Tota, A Carlton, and J Smith. 2019. "Chemical composition of ultrafine aerosol particles in central Amazonia during the wet season." Atmospheric Chemistry and Physics, 19(20), 10.5194/acp-19-13053-2019.

Aiken AC, F Gallo, J Uin, SR Springston, J Wang, G Zheng, C Kuang, A McComiskey, R Wood, C Flynn, A Theisen, E Azevedo, P Ortega, and H Powers. 2019. Eastern North Atlantic (ENA) Aerosol Supplementary Site (S1) Data Analysis Report. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-TR-229.

Liu J and Z Li. 2019. "Aerosol properties and their influences on low warm clouds during the Two-Column Aerosol Project." Atmospheric Chemistry and Physics, 19(14), 10.5194/acp-19-9515-2019.

Jensen M, E Bruning, D Collins, A Fridlind, P Kollias, C Kuang, D Rosenfeld, A Ryzhkov, A Varble, SD Brooks, S Collis, E Defer, J Fan, J Flynn, S Giangrande, R Griffin, J Hu, R Jackson, M Kumjian, T Logan, T Matsui, G McFarquhar, C Nowotarski, J Quaas, M Oue, R Sheesley, J Snyder, P Stier, S Usenko, S van den Heever, M van Lier Walqui, Y Wang, Y Xu, and G Zhang. 2019. Tracking Aerosol Convection Interactions ExpeRiment (TRACER) Science Plan. Ed. by Robert Stafford, DOE/SC-ARM-19-017.

McFarquhar G, R Marchand, C Bretherton, S Alexander, A Protat, S Siems, R Wood, and P DeMott. 2019. Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) Field Campaign Report. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-19-008.

Zheng X, B Xi, X Dong, T Logan, Y Wang, and P Wu. 2019. "Investigation of Aerosol-Cloud Interactions under Different Absorptive Aerosol Regimes using ARM SGP Ground-Based Measurements." Atmospheric Chemistry and Physics Discussions, , 10.5194/acp-2019-478.

Schiro K and J Neelin. 2019. "Deep Convective Organization, Moisture Vertical Structure and Convective Transition using Deep-Inflow Mixing." Journal of the Atmospheric Sciences, 76(4), 10.1175/JAS-D-18-0122.1.

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