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Characteristics of aerosol extinction in lower stratospheric altitudes over a tropical station are studied using the ruby lidar data at Trivandrum (8°55′N, 77°E) for the period 1986–1987. The integrated stratospheric aerosol extinction as well as the aerosol extinction at fixed altitudes in this region showed a significant negative correlation with tropopause temperature. This is attributed to tropospheric convective activity. Though the direct correlation between ambient temperature and aerosol extinction is insignificant at these altitudes, the partial correlation eliminating the influence of tropopause temperature becomes increasingly significant at altitudes far from the tropopause. This indicates the increasing influence of stratospheric microphysical processes at higher altitudes, that is, near the altitude of stratospheric aerosol peak.

The relationship between backscattering beta(a), and extinction alpha(a) coefficients of aerosols at a ruby laser wavelength of 694.3 nm is studied using Mie scattering theory. A simple relationship of the form beta(a) = C(a)alpha(ka)(a) is assumed, and the dependence of k(a) and C(a) on different aerosol characteristics such as size distribution and refractive index is studied. The validity of a similar relationship is examined for a turbid atmosphere (troposphere and lower stratosphere) containing both aerosols and air molecules.

Aerosol extinction profiles obtained from lidar data at Trivandrum (8.6 deg N, 77 deg E) are compared with corresponding Stratospheric Aerosol and Gas Experiment II extinction profiles. The agreement between the two is found to be satisfactory. The extinction profiles obtained by both the experiments showed a prominent peak at 23-24 km altitude in the stratosphere. The study revealed large variability in upper tropospheric extinction with location (latitude).

Regular radiosonde measurements conducted by the India Meteorological Department at eleven stations spread over a latitude range of 8.5°–28.6°N for a period of nine years are used for the, study of the tropical tropopause characteristics, altitude (H), temperature (T) and pressure (P). The results are examined in the light of the hypothesis of Reid and Gage. It has been shown that large-scale cloud cover affects the tropopause parameters for annual and semiannual periods, while for longer periods (biennial) the cloud cover effect is not significant.

A method of obtaining the physical characteristics of aerosols has been developed using bistatic continuous wave lidar observations on atmospheric scattering. The results obtained using this method are also presented.