In Situ Northern Mid-Latitude Observations of ClO, O 3 , and BrO in the Wintertime Lower Stratosphere

• Published in: Science
• Main Authors: Brune, W. H., Toohey, D. W., Anderson, J. G., Starr, W. L., Vedder, J. F., Danielsen, E. F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Association for the Advancement of Science (AAAS) 1988
• Subjects: Arctic; Great Slave Lake
• Online Access: http://dx.doi.org/10.1126/science.242.4878.558; https://www.science.org/doi/pdf/10.1126/science.242.4878.558

In order to test photochemical theories linking chlorofluorocarbon derivatives to ozone (O 3 ) depletion at high latitudes in the springtime, several related atmospheric species, including O 3 , chlorine monoxide (ClO), and bromine monoxide (BrO) were measured in the lower stratosphere with instruments mounted on the NASA ER-2 aircraft on 13 February 1988. The flight path from Moffett Field, California (37°N, 121°W), to Great Slave Lake, Canada (61°N, 115°W), extended to the center of the polar jet associated with but outside of the Arctic vortex, in which the abundance of O 3 was twice its mid-latitude value, whereas BrO levels were 5 parts per trillion by volume (pptv) between 18 and 21 kilometers, and 2.4 pptv below that altitude. The ClO mixing ratio was as much as 65 pptv at 60°N latitude at an altitude of 20 kilometers, and was enhanced over mid-latitude values by a factor of 3 to 5 at altitudes above 18 kilometers and by as much as a factor of 40 at altitudes below 17 kilometers. Levels of ClO and O 3 were highly correlated on all measured distance scales, and both showed an abrupt change in character at 54°N latitude. The enhancement of ClO abundance north of 54°N was most likely caused by low nitrogen dioxide levels in the flight path.