High Latitude Springtime Photochemistry
Part I: NOx, PAN and Ozone Relationships
Harald J. Beine,1,3 Daniel A. Jaffe,1* John A. Herring,1,4 Jennifer A. Kelley,1 Terje Krognes,2 Frode Stordal2
1. Geophysical Institute and Department of Chemistry, University of Alaska, 903 N. Koyukuk Dr., Fairbanks, Alaska 99775-7320, U.S.A.
2. Norwegian Institute for Air Research (NILU), Instituttveien 18, N-2007 Kjeller, Norway.
3. Now at 2.
4. Now at American Geophysical Union, 2000 Florida Ave, NW, Washington, DC 20009, U.S.A.
* Corresponding author.
Accepted for publication in the Journal of Atmospheric Chemistry
Abstract. Spring time measurements of NOx, ozone, PAN, J(NO2), and other compounds were made near Ny-Ålesund, Svalbard (78°54'N, 11°53'E), in 1994 and Poker Flat, Alaska (65°08'N, 147°29'W), in 1995. At Svalbard median mixing ratios for PAN and NOx of 237 and 23.7 pptv, respectively, were observed. The median mixing ratios at Poker Flat for PAN and NOx were 79.5 and 85.9 pptv, respectively. These data are used to estimate thermal PAN decomposition using several different approaches. At Svalbard PAN decomposition was very small, while at Poker Flat up to 30 pptv/h PAN decomposed. At both sites the NOx/PAN ratio increased with temperature between -10 and 20°C implying that PAN decomposition is an important NOx source. In-situ ozone production was calculated from the measured NO, NO2, O3, J(NO2), and temperature data, using the steady state assumption Median ozone production was 605 pptv/h at Poker Flat, and one order of magnitude smaller at Svalbard during the daytime. Only at Poker Flat could a direct influence on the diurnal ozone cycle be observed from in-situ production. These results imply that PAN decomposition is a major source of NOx in the high latitude troposphere, and that this contributes to the observed spring maximum in surface ozone.