Atmospheric NO3. II - Observations in polar regions

Stratospheric NO3 is expected to depend strongly upon two major factors: solar illumination and temperature. This paper presents observations in the polar regions that confirm the influence of both of these on the NO3 column abundance. Measurements of the absorption of incoming lunar radiation near 662 nm as the sun rises exhibit large changes that apparently reflect the rapid photolysis of NO3. The increase in upper stratospheric temperature that occurs in early spring in polar regions should also affect the seasonal changes in stratospheric NO3 abundances. Observations of stratospheric NO3 at 76.5 deg N in early February are contrasted with those obtained at 77.8 deg S in late August and September. Large seasonal differences in stratospheric temperatures between these two locations and times are shown to be in excellent agreement with the observed NO3 column amounts, providing further support for current understanding of the factors controlling the stratospheric NO3 abundance and its variability. These findings provide further evidence against a stratospheric 'scavenger' for NO3, even in polar latitudes, where the scavenging effect was believed to be most pronounced.