The vertical distribution of aerosol concentration and size distribution function over the tropics and their role in radiation transfer

Abstract

By measuring the atmospheric attenuation of the direct solar radiation and the angular distribution of the scattered radiation at different altitudes, the altitude profile of the aerosol concentration and size distribution function can be obtained. This principle has been employed to study the vertical distribution of aerosols over the tropical site, Thumba (8.5°N, 76.9°E), using rocket-borne photometers upto an altitude of 22km in February 1980. Later, a suntracking multichannel photometer was developed and flown on a balloon platform from Hyderabad (17.5°N, 78.6°E) on April 18, 1984 and aerosol measurements were made upto an altitude of 32km. Comparison of the two sets of data shows that the aerosols measured over Thumba are influenced by the near equatorial eruption of Sierra Negra volcano which occurred three months earlier. Mie scattering coefficients are computed for different wavelengths for the aerosol concentrations and size distribution functions measured over Thumba and Hyderabad and the spectral variations are compared.