An estimate of the flux of stratospheric reactive nitrogen and ozone into the troposphere

The globally averaged net downward annual fluxes of reactive nitrogen (NO y ) and O 3 from the stratosphere are estimated using observed correlations of N 2 O with NO y and O 3 . The linearity of the observed correlations in the lower stratosphere allows the downward fluxes of NO y and O 3 to be related to the upward flux of N 2 O. The upward flux N 2 O can be calculated from a mass balance and stratospheric photochemistry. In this way, the complicated photochemistry and transport of NO y and O 3 can be bounded by a much simpler calculation involving N 2 O. The estimated NO y net flux of 0.45 Tg (N) yr −1 (range 0.23–0.73) is slightly less than previous estimates, but within the range of uncertainty. Precipitation of NO y from the Antarctic winter stratosphere may be a significant fraction of the annual global flux out of the lower stratosphere. The global budget for stratospheric NO y shows that an N 2 O lifetime greater than 160 years is inconsistent with extensive mass flow through the Antarctic winter vortex. The estimated O 3 flux of 3.5×10 10 molecules cm −2 s −1 (range 1.5–6.8) agrees well with previous estimates using completely independent techniques.