A preliminary report on the numerical simulation of the three‐dimensional structure and variability of atmospheric N2O

Abstract

A numerical simulation of atmospheric N₂O using the GFDL 3‐D tracer model with a small uniform surface source (15 Mton yr⁻¹) and stratospheric destruction (150 yr lifetime) has been run to a state near transport and chemical statistical equilibrium. The resulting N₂O tropospheric distribution is relatively uniform with a slight excess in the Southern Hemisphere. In the model stratosphere there is a sharp poleward decrease in N₂O mixing ratio away from high values in the tropics with pronounced winter minimums at 50°S and 60°N. Even with the small uniform surface source, relative standard deviations of N₂O in the surface layer range from 0.1% to 0.8%, well within the range of recent measurements. Additional experiments suggest that motions acting upon N₂O accumulation in the source region boundary layer and upon the mixing ratio gradient between the troposphere and lower stratosphere are the major sources of tropospheric N₂O variability.