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

Measurements of NOx, 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 NOx during ozone depletion events. The objective of this work is to explore the role of NOx during those periods. During depletion periods, mixing ratios of NOx, 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 NOx mixing ratios are consistent with proposed mechanisms involving catalytic destruction of ozone by the Br radical. A mechanism involving NOx to recycle halogen radicals seems unlikely in light of the current study.