Abstract
Aircraft measurements of key reactive nitrogen species (NO, NO2, HNO3, PAN, PPN, NO3‐, NOy), C1 to C6 hydrocarbons, acetone, O3, chemical tracers (C2Cl4 CO), and important meteorological parameters were performed over eastern Canada during July to August 1990 at altitudes between 0 and 6 km as part of an Arctic Boundary Layer Expedition (ABLE3B). In the free troposphere, PAN was found to be the single most abundant reactive nitrogen species constituting a major fraction of NOy and was significantly more abundant than NOx and HNO3. PAN and O3 were well correlated both in their fine and gross structures. Compared to data previously collected in the Arctic/subarctic atmosphere over Alaska (ABLE3A), the lower troposphere (0–4 km) over eastern Canada was found to contain larger reactive nitrogen and anthropogenic tracer concentrations. At higher altitudes (4–6 km) the atmospheric composition was in many ways similar to what was seen over Alaska and supports the view that a large‐scale reservoir of PAN (and NOy) is present in the upper troposphere over the entire Arctic/subarctic region. The reactive nitrogen budget based on missions conducted from the North Bay site (missions 2–10) showed a small shortfall, whereas the budget for data collected from the Goose Bay operation (missions 11–19) showed essential balance. It is calculated that 15–20 ppt of the observed NOx may find its source from the available PAN reservoir. Meteorological considerations as well as relationships between reactive nitrogen and tracer species suggest that the atmosphere over eastern Canada during summer is greatly influenced by forest fires and transported industrial pollution.
Highlights
Powered by the California Digital Library University of CaliforniaJOURNAL OF GEOPHYSICAL RESEARCH, VOL. 99, NO. D1, PAGES 1821-1835, JANUARY 20, 1994
Expedition3A (ABLE3A) provided measurementsof a large number of reactive nitrogen species, ozone, hydrocarbons, Northern high latitudes are of great interest to atmospheric anthropogenic tracers and important meteorological scientists because of the high predicted sensitivity of this parametersover Alaska and Greenlandduringthe summer(July region to climatic change and the paucity of available data. to August) of 1988 [Harriss et al, 1992]
3b and 3c the combinedaffect of forestfires and pollutionis of PAN for the North Bay (NB) and Goose Bay (GB) missionswere larger than those seenin the enhancedmixing ratiosof HNO3 and0 3 below 1- for the Alaska missions.At the free troposphericaltitudesof km altitude observed during mission 9
Summary
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 99, NO. D1, PAGES 1821-1835, JANUARY 20, 1994. Aircrafmt easuremeonfktseyreactivneitrogesnpecie(Ns O,NO2,HNO3,PAN,PPNN, O3-,NOy),C1 to C6 hydrocarbons,acetone, 0 3, chemical tracers (C2C14, CO), and important meteorological parameterswere performedover easternCanadaduringJuly to August 1990 at altitudesbetween 0 and 6 km as part of an Arctic BoundaryLayer Expedition(ABLE3B). In the free troposphere,PAN was found tobethesinglemosat bundarnetactivneitrogesnpeciecsonstitutinagmajorfractionof NOy andwas significantlymoreabundanthanNOx andHNO3. PAN andO3 werewell correlatedbothin theirfine and grossstructures.Comparedto data previouslycollectedin the Arctic/subarcticatmosphereover Alaska (ABLE3A), the lower troposphere(0-4 km) over easternCanadawas found to contain larger reactive nitrogen and anthropogenictracer concentrations.At higher altitudes (4-6 km) the atmospheric compositionwas in many ways similar to what was seenover Alaska and supportsthe view that a large-scarleeservooirf PAN(andNOy) is presenitn the uppertropospheoreverthe entire. Arctic/subarcticegion.The reactivenitrogenbudgetbasedon missionsconductedfrom the North Bay site (missions2-10) showeda smallshortfall,whereasthe budgetfor datacollectedfrom the GooseBay operation(missions11-19) showedessentialbalance.It is calculatedthat 15-20 ppt of the observed NDx may find its sourcefrom the availablePAN reservoir.Meteorologicalconsiderationsas well as relationshipsbetweenreactive nitrogenand tracer speciessuggestthat the atmosphereover eastern Canadaduringsummeris greatlyinfluencedby forestfires and transportedindustrialpollution
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