Abstract
Abstract. To investigate the origin of springtime aerosols in the Arctic region we performed ground-based and airborne 355 nm Raman lidar observations in the north of Norway (Hammerfest). Two lidars were embedded (i) on an ultralight aircraft for vertical (nadir) or horizontal line-of-sight measurements and (ii) in an air-conditioned van on the ground for vertical (zenith) measurements. This field experiment was designed as part of the Pollution in the ARCtic System (PARCS) project of the French Arctic Initiative and took place from 13 to 26 May 2016. The consistency among lidar measurements is verified by comparing nadir, horizontal line of sight, and ground-based Raman lidar profiles. Dispersion of the order of 0.01 km−1 is obtained among lidar-derived aerosol extinction coefficients at 355 nm. The aerosol load measured in the first 3 km of the troposphere remains low throughout the campaign, with aerosol optical thickness (AOT) of 0.1 at 355 nm (∼0.05 at 550 nm). The main contributors to the evolution of the aerosol load at low altitude prove to be one of the flares of the nearby Melkøya gas processing facility, the oceanic source, and the transport of aerosols from industrial sites in Russia. Moreover, ground-based lidar measurements allowed us to identify three cases of long-range aerosol transport (between 3 and 8 km above the mean sea level). Using back trajectories computed with the Lagrangian model FLEXPART-WRF, these aerosol plumes are shown to be the result of the strong forest fires that occurred in the area of Fort McMurray, in Canada. They can at most double the AOT value over the Arctic area, with an anomaly of 0.1 on the AOT at 355 nm.
Highlights
The pristine Arctic environment is very sensitive and can be disturbed by anthropogenic activities, with irreparable consequences
The Pollution in the ARCtic System (PARCS) experiment took place during large-scale weather conditions disturbed by the strong El Niño of 2015–2016 (Hu and Fedorov, 2017), which led to temperatures in the Arctic planetary boundary layer (PBL) 3 to 4 ◦C above the 10-year normal climatic conditions
The aerosol extinction coefficient (AEC) retrieved for flights 10 and 11 are given in Fig. 9 with the mean vertical profiles between the ground level and the ceiling flight altitude in both cases; aerosol optical thickness (AOT) are low with a small variability of the order of 0.05 ± 0.01
Summary
The pristine Arctic environment is very sensitive and can be disturbed by anthropogenic activities, with irreparable consequences. The PARCS experiment took place during large-scale weather conditions disturbed by the strong El Niño of 2015–2016 (Hu and Fedorov, 2017), which led to temperatures in the Arctic planetary boundary layer (PBL) 3 to 4 ◦C above the 10-year normal climatic conditions Associated with such exceptional atmospheric conditions, transport in the high troposphere favoured the presence of air masses from North America. During the ACCESS airborne campaign in summer 2012 (Roiger et al, 2015), extensive boreal forest fires resulted in significant aerosol transport to the Arctic (Raut et al, 2017) These plumes originating from Siberian wildfires are very common during late spring and summer, and they may be mixed with aerosols coming from highly polluting industrial sources such as oil and gas rigs or petroleum refineries.
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