Long-duration shipboard performance of a humidity-conditioned optical particulate matter monitor along inter-polar transit routes: Antarctic inter-unit agreement and Arctic redeployment

Abstract. Optical particulate matter (PM) measurements aboard ships are vulnerable to relative-humidity (RH)-dependent particle growth, sampling disturbances, and platform exhaust. We evaluated the long-duration field performance of the Tiny Aerosol Monitor with Tiny Aerosol Conditioner (TAM/TAC) using two co-deployed instruments during an Antarctic voyage and the subsequent Arctic redeployment of the same physical instrument (unit 70). The Antarctic loggers recorded every scheduled 10 min time step from 25 October 2022 to 3 May 2023 (27,342 records per unit), and unit 70 recorded every scheduled time step during the Arctic deployment from 21 June to 11 October 2023 (16,124 records). A prespecified quality-control rule excluded 50 Antarctic unit-70 records with nonzero instrument status codes, leaving 27,292 valid Antarctic pairs; unit 71 and the Arctic unit-70 dataset contained no flagged records. Across PM₁.₀, PM₂.₅, PM₄.₀, and PM₁₀, Antarctic inter-unit correlations were 0.995–0.997, equal-variance Deming slopes were 0.992–1.033, and relative mean biases were −1.1 % to +2.1 %. Paired relative precision was 9.0–9.8 % for PM₂.₅–PM₁₀ and 16.3 % for PM₁.₀, for which the route-wide mean was only about 1.53 µg m⁻³. In the polar subsets, TAC reduced mean ambient RH from 54.0 % to 32.2 % in the Antarctic and from 73.7 % to 34.5 % in the Arctic; internal RH was at or below 40 % for 99.99 % and 100 % of valid records, respectively. These results provide evidence of timebase continuity, inter-unit comparability, and repeatable humidity control across two extreme marine deployments. They do not establish absolute accuracy, inlet efficiency, or freedom from ship-exhaust contamination, which require a collocated reference instrument and ship-relative wind or exhaust-tracer measurements.