Climatology of nitric oxide in the upper stratosphere, mesosphere, and thermosphere: 1979 through 1986

Spectral scan data from the solar backscattered ultraviolet (SBUV) instrument on Nimbus 7 for the wavelength range 200–400 nm have been analyzed to determine the strengths of several of the nitric oxide (NO) gamma band fluorescence features as a function of time and of latitude. The integrated column amount of nitric oxide above an altitude of approximately 45–50 km is inferred from analysis of the strengths of the (10), (01), and (02) nitric oxide gamma bands. Analysis shows that there are about 5 – 6 × 10 14 molecules cm −2 of nitric oxide cumulative above 48 km over a wide range of latitudes, increasing sharply near the winter terminator by about a factor of 3 to 12 – 15 × 10 14 molecules cm −2 . Between 1979 and 1986, column NO near the equator decreased by about a factor of 2, from 6.4 × 10 14 molecules cm −2 to 3.3 × 10 14 molecules cm −2 . The time dependence of the decrease correlates well with solar activity, following the decline in solar activity from solar maximum in 1979 to solar minimum in 1985–1986. At middle and high latitudes, NO appears to have reached a maximum in 1982–1983, a few years after the solar cycle maximum, and has decreased since, but the magnitude of the trend is smaller.