Stratospheric attenuation in the near ultraviolet

Abstract

Comparison between measurements of atmospheric attenuation at 3800 Å, made during a rocket flight at 30° S in April 1964, and values computed for a dust-free atmosphere demonstrated the existence of extra attenuation which exceeded that due to Rayleigh air scattering at levels below 30 km. By using a model with a simple exponential decay of extra attenuation coefficient with height, the best fit to the observations was obtained with a scale height of 3.25 km and an attenuation coefficient at 28.9 km of 1.06 x 10 -3 km -1 . The approximate height range over which the model was valid was from 20 to 40 km. Additional measurements from the Ariel II satellite indicated the persistence of this attenuation from April to August 1964 between 30° S and 20° N with significantly less attenuation at 45° S. The attenuation was produced by the eruption at Bali in March 1963, and the scale height of the attenuation was consistent with an annual mean value for the vertical eddy diffusivity in the height range 20 to 35 km at 30° S of between 2000 and 6000 cm 2 /s.