NOx during ozone depletion events in the arctic troposphere at Ny-Ålesund, Svalbard

Measurements of NO_x, ozone, non-methane hydrocarbons (NMHC), and other atmospheric constituents were made at the Zeppelin-mountain atmospheric monitoring station near Ny-Ålesund, Svalbard, during the spring of 1994. On a few occasions, we observed tropospheric ozone depletion events with minimum ozone mixing ratios of 3.9 ppbv that lasted for up to 2 days. This paper presents the first measurements of NO_x during ozone depletion events. The objective of this work is to explore the role of NO_x during those periods. During depletion periods, mixing ratios of NO_x, total NMHC, and acetylene dropped to minima of < 4.5 pptv, 3.6 ppbCv, and 123 pptv, respectively. These mixing ratios were significantly lower than the means for our campaign, which were 23.6 pptv, 14.3 ppbCv, and 478 pptv, respectively. Because NO₂ would quickly scavenge the BrO radical, the low observed NO_x mixing ratios are consistent with proposed mechanisms involving catalytic destruction of ozone by the Br radical. A mechanism involving NO_x to recycle halogen radicals seems unlikely in light of the current study.