Differences in Ozone and Particulate Matter Between Ground Level and 20 m Aloft are Frequent During Wintertime Surface-Based Temperature Inversions in Fairbanks, Alaska

Meeta Cesler‐maloney (1) , William R. Simpson (1) , Tate Miles (1) , Jingqiu Mao (1) , Kathy S. Law (2) , Tjarda J. Roberts (3)

1 Department of Chemistry and Biochemistry [Fairbanks]
2 TROPO - LATMOS
3 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

During winter in Fairbanks, Alaska, fine particulate matter (PM2.5) accumulates to large concentrations at breathing level, yet little is known about atmospheric composition aloft. To investigate vertical differences of pollutants, we measured PM2.5 and ozone (O3) at 3 m and 20 m above ground level (AGL) in Fairbanks during winter (November 2019 - March 2020). We measured temperature and PM2.5 at 3 m, 6 m, 9 m and 11 m AGL on a tower to quantify surface-based temperature inversions (SBI) and near surface PM2.5 gradients. We defined SBIs as data with an 11 m minus 3 m temperature difference greater than 0.5°C. We observed the largest differences in PM2.5 and O3 when SBIs were present. During SBIs, PM2.5 accumulated to large concentrations at 3 m but to a lesser extent at 20 m, demonstrating reduced vertical mixing. During SBIs, the median PM2.5 concentration was 4.8 microgram m-3 lower at 20 m than at 3 m. When PM2.5 concentrations were large at 3 m, O3 was often completely chemically removed (titrated) but was still present at 20 m. During SBIs, the O3 mixing ratio was more than 2 nmol mol-1 larger at 20 m than at 3 m in 48% of the data. Results show that during SBIs, pollution in Fairbanks is mixed to altitudes below 20 m AGL and that the oxidation regime of the atmosphere changes from 3 m to 20 m AGL, as large differences in O3 mixing ratios were measured during SBIs.

Keywords: ozone; PM2.5; Alaska pollution; Atmospheric Composition; Pollutants; Fairbanks

Domains: Atmospheric and Oceanic Physics [physics.ao-ph]; Environmental Sciences

Meeta Cesler‐maloney, William R. Simpson, Tate Miles, Jingqiu Mao, Kathy S. Law, et al.. Differences in Ozone and Particulate Matter Between Ground Level and 20 m Aloft are Frequent During Wintertime Surface-Based Temperature Inversions in Fairbanks, Alaska. Journal of Geophysical Research: Atmospheres, 2022, 127 (10), pp.e2021JD036215. ⟨10.1029/2021JD036215⟩. ⟨insu-03664305⟩