A UT/LS ozone climatology of the nineteen seventies deduced from the GASP aircraft measurement program

摘要

We present ozone measurements of the Global Atmospheric Sampling Program(GASP) performed from four commercial and one research aircraft in the late1970s. The GASP quality assurance and control program was reviewed,and an ozone climatology of the upper troposphere and lower stratosphere (UT/LS)of the years 1975–1979 was built. The data set wasestimated to have an overall uncertainty of 9% or 3 ppb whichever isgreater for the first two years and 4% or 3 ppb for the remaining years,i.e. after implementation of silicone rubber membranes in the pumps. Twocases of nearly coincident flights of two GASP airliners along the sameflight route, and the comparison with independent observations from theliterature, including ozonesondes and aircraft campaigns, indicate that theozone measurements are of high quality. The UT/LS climatology of the GASPdata set is in general agreement with that derived from MOZAIC in the 1990sin regions covered by both programmes. GASP provides unique large-scaleclimatological information on UT/LS ozone above the northern hemispherePacific region, which is not covered by MOZAIC. There, the GASP climatologyconfirms several characteristic features derived from individual researchaircraft campaigns and from ozone soundings. In particular, summertime ozonein the UT over the midlatitude eastern Pacific Ocean was significantly lowerin the 1970s than over the American continent. The generally lower ozoneconcentrations in the tropics near the dateline as compared to farther eastare indicative of convective uplifting of ozone poor air from the marineboundary layer.