Measurements of water vapour, surface ozone and ethylene using differential absorption lidar

The measurement of various minor constituents in the atmosphere is of great significance to understand physics, Chemistry and dynamics of the atmosphere. Ozone in the troposphere is one of the most important trace species as it is a greenhouse gas trapping the longwave radiation in 9.6 mum band affecting the energy budget of the earth-atmosphere system. It is also a pollutant produced as a result of anthropogenic activities such as fossil fuel burning and has potential to affect human health and vegetation if it is allowed to attain high concentrations. Water vapour also plays a significant role in climate studies and the chemistry of the atmosphere. Ethylene is an urban pollutant and its concentration as low as 10 ppb is toxic to plants. A differential absorption lidar system using a tunable CO2 laser has been designed and developed at National Physical Laboratory, New Delhi, to monitor various minor constituents in the atmosphere. Some times ethylene concentration was found to be more than 20 ppb while that of surface ozone was more than 140 ppb which is a health hazard. In this paper salient features of experimental set up and results obtained will be presented in detail.