Free tropospheric and boundary‐layer airborne measurements of ozone over the latitude range of 58°S to 70°N

Abstract

Reported here are O 3 data recorded during the 1977 and 1978 Gametag field experiments. Nearly two thirds of these data were recorded in the free troposphere over the altitude range of 5–6.5 km. The remaining one third were collected in the atmospheric boundary layer, typically 0.3–1 km above the surface terrain. The latitude range covered by these measurements was 58°S to 70°N and involved flight operations over northern Canada, Alaska, the southeastern/central Pacific (northern hemisphere), and the central/western Pacific in the southern hemisphere. This data base is unique in that all ozone measurements were recorded on the same set of three ozone analyzers, on a single aircraft platform, and over a short time span. Key observations include (1) systematically higher average free tropospheric O 3 levels in the northern versus southern hemisphere with the global minimum in ozone occurring at tropical latitudes; (2) extensive O 3 layering within the free troposphere over large geographical areas of the northern hemisphere and, to a much lesser extent, remote areas of the southern hemisphere; (3) boundary‐layer O 3 concentration levels which were consistently lower than free tropospheric O 3 levels in remote areas of the northern hemisphere but only slightly lower than those levels observed in the southern hemisphere; and (4) the finding in April/May 1978 of a latitudinal zone, 13°S to 2°N, virtually devoid of boundary layer O 3 . A comparison of these data with those of other investigators, together with a discussion of the relevancy of these observations to our present understanding of the tropospheric O 3 budget, is presented.