aos > Aerosol Observing SystemInstrument Type(s) > Baseline • External • Guest

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

acsmcdce: ACSM, corrected for composition-dependent collection efficiency

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

tao: Tropical Atmosphere Ocean from Buoys

tap: Tricolor Absorption Photometer

tracegas: Trace gas concentrations

uhsas: Ultra-High Sensitivity Aerosol Spectrometer

Active Instrument Locations

Facility Name Instrument Start Date
Lamont, OK (Extended and Co-located with C1) 2016-10-24
Houston, TX; AMF1 (main site for TRACER) 2021-04-14
Graciosa Island, Azores, Portugal 2013-08-15
Oliktok Point, Alaska; AMF3 2016-06-21


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Knopf DA, P DeMott, J Creamean, T Hill, N Riemer, N Hiranuma, A Laskin, R Sullivan, A Fridlind, X Liu, and M West. 2020. Aerosol-Ice Formation Closure Pilot Study (AEROICSTUDY) Field Campaign Report. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-20-017.

Springston SR, D Chand, BD Ermold, JE Shilling, and CJ Flynn. 2020. Ozone Monitor (OZONE) Instrument Handbook. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-TR-179.

Gallo F, J Uin, S Springston, J Wang, G Zheng, C Kuang, R Wood, E Azevedo, A McComiskey, F Mei, A Theisen, J Kyrouac, and A Aiken. 2020. "Identifying a regional aerosol baseline in the eastern North Atlantic using collocated measurements and a mathematical algorithm to mask high-submicron-number-concentration aerosol events." Atmospheric Chemistry and Physics, 20(12), 10.5194/acp-20-7553-2020.
Research Highlight

Mouchel-Vallon C, J Lee-Taylor, A Hodzic, P Artaxo, B Aumont, M Camredon, D Gurarie, J Jimenez, D Lenschow, S Martin, J Nascimento, J Orlando, B Palm, J Shilling, M Shrivastava, and S Madronich. 2020. "Exploration of oxidative chemistry and secondary organic aerosol formation in the Amazon during the wet season: explicit modeling of the Manaus urban plume with GECKO-A." Atmospheric Chemistry and Physics, 20(10), 10.5194/acp-20-5995-2020.

Iguchi T, S Rutledge, W Tao, T Matsui, B Dolan, S Lang, and J Barnum. 2020. "Impacts of aerosol and environmental conditions on maritime and continental deep convective systems using a bin microphysical model." Journal of Geophysical Research: Atmospheres, 125(12), e2019JD030952, 10.1029/2019JD030952.

Wang Y, S Xie, S Tang, and W Lin. 2020. "Evaluation of an Improved Convective Triggering Function: Observational Evidence and SCM Tests." Journal of Geophysical Research: Atmospheres, 125(11), e2019JD031651, 10.1029/2019JD031651.
Research Highlight

Zheng X, B Xi, X Dong, T Logan, Y Wang, and P Wu. 2020. "Investigation of aerosol-cloud interactions under different absorptive aerosol regimes using Atmospheric Radiation Measurement (ARM) southern Great Plains (SGP) ground-based measurements." Atmospheric Chemistry and Physics, 20(6), 10.5194/acp-20-3483-2020.

Lubin D, D Zhang, I Silber, R Scott, P Kalogeras, A Battaglia, D Bromwich, M Cadeddu, E Eloranta, A Fridlind, A Frossard, K Hines, S Kneifel, W Leaitch, W Lin, J Nicolas, H Powers, P Quinn, P Rowe, L Russell, S Sharma, J Verlinde, and A Vogelmann. 2020. "AWARE: The Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment." Bulletin of the American Meteorological Society, 101(7), 10.1175/BAMS-D-18-0278.1.


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.

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