clap > Continuous Light Absorption PhotometerInstrument Type(s) > Baseline • External • Guest

The continuous light absorption photometer (CLAP) operates on the same principle as the particle soot absorption photometer (PSAP), i.e., continuously measuring transmission through a filter substrate as sample air is drawn through it. The absorbing aerosol particles are collected in the filter.

The CLAP is part of the aerosol observing system (AOS).


  • Fixed
  • AMF1
  • AMF2
  • AMF3

Active Locations

Facility Name Start Date
Barrow, Alaska, new building (NAD83) at NOAA facility 2020-10-22


Moffett C, M Mehra, T Barrett, M Gunsch, K Pratt, and R Sheesley. 2022. "Contemporary sources dominate carbonaceous aerosol on the North Slope of Alaska." Science of The Total Environment, 831, 154641, 10.1016/j.scitotenv.2022.154641.

Andrews E. 2022. Continuous Light Absorption Photometer (CLAP) Instrument Handbook. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-TR-280. 10.2172/1872557.


Ohata S, T Mori, Y Kondo, S Sharma, A Hyvärinen, E Andrews, P Tunved, E Asmi, J Backman, H Servomaa, D Veber, K Eleftheriadis, S Vratolis, R Krejci, P Zieger, M Koike, Y Kanaya, A Yoshida, N Moteki, Y Zhao, Y Tobo, J Matsushita, and N Oshima. 2021. "Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic." Atmospheric Measurement Techniques, 14(10), 10.5194/amt-14-6723-2021.


Li H, G McMeeking, and A May. 2020. "Development of a new correction algorithm applicable to any filter-based absorption photometer." Atmospheric Measurement Techniques, 13(5), 10.5194/amt-13-2865-2020.


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.

View All Related Publications