Abstract:
In the dust free atmosphere supersaturation of several hundred percent is required to initiate cloud condensation The supersaturation ratios required to initiate nucleation in
the dust free atmosphere has theoretically been shown to be of the order of 4. In the atmosphere sizable amount of water-insoluble and water-soluble particles (aerosols) are pre-sent. • These particles, act as the condensing nuclei which are activated at supersaturation as low as 0:.17. in the troposphere. Ions, as clusters, or trapped by submicron aerosol particles can also form condensation nuclei.
The sizes of the condensing nuclei and aerosol particles present in the atmosphere are comparable to the wavelength of visible radiation. According to the Mie theory of scattering, the scattering,properties of particles are the function of their size parameter, refractive index and the angle of scattering.
The thesis deals with the experimental study of water vapour condensation in an artificially simulated cloud in a cool-ing chamber. The experimental measurements are based on Mie theory of scattering. The scattered light from the condensing droplets illuminated by a 5 mw He-Ne laser beam is detected at scattering angles of 45° and 135° simultaneously. The experimentally observed ratio of intensities of scattered light is matched with theoretically calculated value for an assumed size distribution of scatterers. This method also enables one to determine the number density of the particles. The whole work is aimed to study the effect of ions on water vapour condensation and divided into five ,chapters.
