M. Koike et al., Impact of aircraft emissions on reactive nitrogen over the North Atlantic Flight Corridor region, J GEO RES-A, 105(D3), 2000, pp. 3665-3677
The impact of aircraft emissions on reactive nitrogen in the upper troposph
ere (UT) and lowermost stratosphere (LS) was estimated using the NOy-O-3 co
rrelation obtained during the Subsonic Assessment (SASS) Ozone and Nitrogen
Oxide Experiment (SONEX) carried out over the U.S. continent and North Atl
antic Flight Corridor (NAFC) region in October and November 1997. To evalua
te the large-scale impact, we made a reference NOy-O-3 relationship in air
masses, upon which aircraft emissions were considered to have little impact
. For this purpose, the integrated input of NO, from aircraft into an air m
ass along a 10-day back trajectory (Delta NOy) was calculated based on the
Abatement of Nuisance Caused by Air Traffic/European Commission (ANCAT/EC2)
emission inventory. The excess NOy (dNO(y)) was calculated from the observ
ed NO, and the reference NOy-O-3 relationship. As a result, a weak positive
correlation was found between the dNO(y) and Delta NOy and dNO(y) and NOx/
NOy values, while no positive correlation between the dNO(y) and CO values
was found suggesting that dNO(y) values can be used as a measure of the NOx
input from aircraft emissions. The excess NOy values calculated from anoth
er NOy-O-3 reference relationship made using in situ condensation nuclei da
ta also agreed with these dNO(y) values, within the uncertainties. At the N
AFC region (45 degrees N-60 degrees N) the median value of dNO(y) in the tr
oposphere increased with altitude above 9 km and reached 70 parts per trill
ion by volume (pptv) (20% of NOy) at 11 km. The excess NOx was estimated to
be about half of the dNO(y) values, corresponding to 30% of the observed N
Ox level. Higher dNO(y), values were generally found in air masses where O-
3 = 75-125 ppbv, suggesting a more pronounced effect around the tropopause.
The median value of dNO(y) in the stratosphere at the NAFC region at 8.5-1
1.5 km was about 120 pptv. The higher dNO(y) values in the LS were probably
due to the accumulated effect of aircraft emissions, given the long reside
nce time of affected air in the LS. Similar dNO(y) values were also obtaine
d in air masses sampled over the U.S. continent.