Effect of a major warming upon stratospheric NO2

In late February 1979 a stratospheric warming occurred during which the winter polar vortex near 10 mbar split into two smaller vortices situated on opposite sides of the north pole. Measurements of stratospheric NO2 over North America showed a very low NO2 abundance (4×1014 cm−2) near the center of one of the new vortices at ∼50°N, suggesting that polar air had been carried to this location and had maintained its high‐latitude partitioning of odd nitrogen for up to a week at lower latitude. The ‘missing’ odd nitrogen near the center of the dsiplaced vortex must have been stored as a photolytically stable species, presumably HNO3. Colorado remained near the outer edge of the new vortex and had higher NO2 (∼4×1015 cm−2) than normal. The displaced vortex thus carried with it a radial gradient in stratospheric NO2 even larger than that known to be associated with the normal undisplaced winter polar vortex.