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.