The direct and scattered solar flux within the stratosphere

Abstract

Solar ultraviolet flux data were obtained within the atmosphere by using Fastie‐Ebert double monochromators carried on a balloon‐borne gondola and a rocket payload. Both the direct and scattered components of the solar ultraviolet flux at wavelengths from 190 to 320 nm were measured at the balloon float altitude of 40 km. The nearly identical spectrometer carried on the rocket flight measured the direct solar flux from 60 to 38 km during a parachute descent. The ozone column content above 40 km and the temperature profile and ozone density below 40 km are deduced from the scattered and direct solar flux components. It is shown that the Nimbus 7 solar flux data is consistent with the present data and with the ozone absorption cross sections of Inn and Tanaka (1959). The same is not true with the solar flux data of Broadfoot (1972), where a systematic error is clearly evident. The calculated and measured values of the scattered solar flux are found to agree quite closely. The scattered flux at 40 km is shown to be 20% of the direct flux at wavelengths longer than 300 nm and about 10% within the Schumann‐Runge band region of O2. This implies increased rates of photolysis for the production of O(1D), O(3P), and other minor species throughout most of the stratosphere and mesosphere. The 10% scattering within the O2 Schumann‐Runge band region leads to a 2% increase in O3 density at 40 km.