Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

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

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


Almeida G. 2023. "The Role Played by the Bulk Hygroscopicity on the Prediction of the Cloud Condensation Nuclei Concentration Inside the Urban Aerosol Plume in Manaus, Brazil: From Measurements to Modeled Results." Atmospheric Environment, 295, 10.1016/j.atmosenv.2022.119517.

O’Donnell S, A Akherati, Y He, A Hodshire, J Shilling, C Kuang, J Fast, F Mei, Siegfried Schobesberger7, J Thornton, J Smith, S Jathar, and J Pierce. 2023. "Look Up: Probing the Vertical Profile of New Particle Formation and Growth in the Planetary Boundary Layer with Models and Observations." Journal of Geophysical Research: Atmospheres, 128(3), e2022JD037525, 10.1029/2022JD037525.


Waman D, S Patade, A Jadav, A Deshmukh, A Gupta, V Phillips, A Bansemer, and P DeMott. 2022. "Dependencies of Four Mechanisms of Secondary Ice Production on Cloud-Top Temperature in a Continental Convective Storm." Journal of the Atmospheric Sciences, 79(12), 10.1175/JAS-D-21-0278.1.

Browne EC, B Dobson, H Stark, M Canagaratna, and D Worsnop. 2022. Characterizing New Particle Formation and Growth Field Campaign Report. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-22-007. 10.2172/1903618.

Angot H, B Blomquist, D Howard, S Archer, L Bariteau, I Beck, M Boyer, M Crotwell, D Helmig, J Hueber, H Jacobi, T Jokinen, M Kulmala, X Lan, T Laurila, M Madronich, D Neff, T Petäjä, K Posman, L Quéléver, M Shupe, I Vimont, and J Schmale. 2022. "Year-round trace gas measurements in the central Arctic during the MOSAiC expedition." Scientific Data, 9(1), 10.1038/s41597-022-01769-6.

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