Current knowledge about black carbon (BC) emission estimates, state-of-the-art measurement methods, near-surface BC concentrations ([BC]), and mixing ratios in snow is consolidated for the Arctic. Since no direct method exists to measure [BC], results from modern indirect methods differ among devices. Pan-Arctic wide [BC] and changes are hard to access; monitoring often ends once national ambient air quality standards are met. Few remote sites have long records. Past measurements showed distinct differences among the various Arctic climate regions. Past and own observations in communities permit qualitative discussion of the diurnal course, response to weather, season, or different emission situations like weekdays and weekends at a given site and/or among sites. Comparison of data from collocated aethalometer indicated more similar accuracy than found in mid-and low-latitudes despite of much lower ambient temperatures and [BC]. Snow samples give an incomplete glimpse at the removal and input into ecosystems.

A tribal-owned network of aerosol monitors and meteorological stations was installed at Ts'aahudaaneekk'onh Denh (Beaver), Gwichyaa Zheh (Fort Yukon), Jałgiitsik (Chalkyitsik), and Danzhit Khànląįį (Circle) in the Yukon Flats, Alaska. Surface inversions occurred under calm wind conditions due to radiative cooling. In May, local emissions governed air quality with worst conditions related to road and river dust. As the warm season progressed, worst air quality was due to transport of pollutants from upwind wildfires. During situations without smoke or when smoke existed at layers above the surface inversion, concentrations of particulate matter of less than 2.5 micrometer in diameter or less (PM 2.5) were explainable by the local emissions; 24-h means remained below 25 μg•m −3. Absorption of solar radiation in the smoke layer and upward scattering enhanced stability and fostered the persistence of the surface inversions. During smoke episodes without the presence of a surface inversion, daily mean concentrations exceeded 35 μg•m −3 often for several consecutive days, at all sites. Then concentrations temporally reached levels considered unhealthy.

The characteristics and climatology of funnel clouds in Alaska were examined using operational radiosondes, surface meteorological observations, and reanalysis data. Funnel clouds occurred under weak synoptic forcing between May and September between 11 am and 6 pm Alaska Daylight Time with a maximum occurrence in July. They occurred under Convective Available Potential Energy >500 J•kg −1 and strong low-level wind shear. Characteristic atmospheric profiles during funnel cloud events served to develop a retrieval algorithm based on similarity testing. Out of more than 129,000 soundings between 1971 and 2014, 2724, 442, and 744 profiles were similar to the profiles of observed funnel cloud events in the Interior, Alaska West Coast, and Anchorage regions. While the number of reported funnel clouds has increased since 2000, the frequency of synoptic situations favorable for such events has decreased.

The impacts of low and high-frequency variability from teleconnections between large scale atmospheric processes and local weather as well as emissions changes on concentrations of particulate matter of 2.5 µm or less in diameter ([PM 2.5 ]) were examined for the Fairbanks Metropolitan Area (FMA). October to March and May to August mean [PM 2.5 ] were 1.8 and 3.1 µg•m −3 higher for positive than negative annual mean Pacific Decadal Oscillation. Annual mean [PM 2.5 ] were 3.8 µg•m −3 lower for positive than negative Southern Oscillation Index. On 1999-2018 average, [PM 2.5 ] decreased 2.9 µg•m −3 •decade −1. On average over October to March, decadal and inter-annual variability caused higher or similar differences in mean observed [PM 2.5 ] and its species than emission-control measures. The 2006 implementation of Tier 2 for new vehicles decreased observed sulfate concentrations the strongest (~4.95 µg•m −3 •decade −1) of all occurred emissions changes. On average, observed [PM 2.5 ] showed elevated values at all sites when wind blew from directions of hot springs. The same was found for the sulfate, ammonium and non-metal components of PM 2.5. Observations showed that these geothermal waters contain sulfate, ammonia, boric acid and non-metals. Hot springs of such composition are known to emit hydrogen sulfide and ammonia that can serve as precursors for ammonium and sulfate aerosols.

Near-surface PM 2.5 and meteorological observations were performed in three rural communities in the high latitude Yukon Flats valley at various times during the cold season (October to April). These data were synthesized with data from other meteorological sites, NCEP reanalysis and MAIAC retrieved aerosol optical depths data to analyze the role of mesoscale processes and radiation on air quality. Under weak large-scale forcing mountain-valley circulations develop that are driven by the differences in insolation. During the long dark nights, radiative cooling occurs in the near-surface layer of the mountain slopes of the Brooks, Ogilvie and White Mountains Ranges and at the bottom of the valley. Here surface-based inversions (SBI)-known as roof-top inversions-forms, while the cold air drains from the slopes. A frontal wedge forms when the cold air slides over the relatively colder air in the valley. Drainage of cold air from the Brooks Range governed the circulation and cold air pooling in the valley. Concentrations during times with and without SBI differed significantly (at 95% confidence) at two sites indicating that local emissions were the major contributor. At the site, which is closest to the mountains, concentrations marginally changed in the presence of inversions. At all sites, 24-h mean PM 2.5 remained below the National Ambient Air Quality Standard.