Seasonal formation of nitrous oxide laminae in the mid and low latitude stratosphere

The seasonal and global distributions of laminae in nitrous oxide (N2O), a long-lived tropospheric source gas, are examined in a multi-year, three-dim ensional model simulation. The frequency of laminae occurrences is describe d as a function of geographical location and season. Enhanced laminae occur rence is found in the midlatitude surf zones of both hemispheres, but there are zonal asymmetries, especially in the northern hemisphere. In boreal wi nter and spring, laminae intruding from mid-latitudes into the deep tropics are found across the Pacific Ocean, on the southern flank of the Aleutian High. A "quiet zone", free of laminae, lies on the summer side of the equat or, and separates the winter from the summer stratosphere. It coincides in latitude with the location of the N2O low-latitude maximum. High laminae oc currences are again found in the extratropics of the summer hemisphere.