Vertical and Horizontal Fluxes of Ozone at the Tropopause from the First Year of GASP Data

Abstract

Ozone measurements taken from commercial airliners (GASP data) are used to estimate the vertical and horizontal fluxes of ozone near the tropopause. The annual average flux of O₃ into the troposphere at 30–50°N is 7.8 × 10¹⁰ molecules cm⁻² s⁻¹, which is nearly the same as indirect estimates based on surface O₃ data, thus supporting the hypothesis that the amount of ozone in the troposphere is essentially controlled by injection from the stratosphere. The present GASP estimates of the total flux of O₃ into the troposphere verify the model results of Cunnold et al. (1975), although the distribution of flux between mean motions and diffusion is different and thus suggests that models with coarse horizontal resolution must continue to parameterize much vertical transport by diffusion coefficients. A significant variation in the east-west spatial autocorrelation function of O₃ near the tropopause is found to be about 1900 km. Monthly estimates of the horizontal transient eddy flux of ozone are generally smaller than seasonal or yearly results based on ozonesonde data. This is perhaps because the present estimates are made over monthly periods to reduce the influence of correlation between the annual variations in ozone and meridional wind. The available data support the hypothesis that transient eddy fluxes of O₃ have large longitudinal variations.