The Four-Wavelength Photoacoustic Aerosol Absorption Spectrometer PAAS-4λ

• Main Authors: Schnaiter, Franz Martin, Linke, Claudia, Asmi, Eija, Servomaa, Henri, Hyvärinen, Antti-Pekka, Ohata, Sho, Kondo, Yutaka, Järvinen, Emma
• Format: Text
• Language: English
• Published: 2023
• Subjects: Arctic
• Online Access: https://doi.org/10.5194/amt-2022-332; https://amt.copernicus.org/preprints/amt-2022-332/

In this paper the Photoacoustic Aerosol Absorption Spectrometer PAAS-4λ is introduced. PAAS-4λ was specifically developed for long-term monitoring tasks in (unattended) air quality stations. It uses four wavelengths coupled to a single acoustic resonator in a compact and robust set-up. The instrument has been thoroughly characterized and carefully calibrated in the laboratory using NO 2 /air mixtures and Nigrosin aerosol. It has an ultimate 1 σ detection limit below 0.1Mm -1 at a measurement precision and accuracy of 3 % and 10 %, respectively. In order to demonstrate the PAAS-4λ suitability for long-term monitoring tasks, the instrument is currently validated at the air quality monitoring station Pallas in Finland, about 140 km north of the Arctic circle. Eleven months of PAAS-4λ data from this deployment are presented and discussed in terms of instrument performance. Intercomparisons with the filter-based photometers COSMOS, MAAP, and AE33 demonstrate the capabilities and value of PAAS-4λ, also for the validation of the widely used filter-based instruments.