Atmospheric measurement of chemical species using spectroscopic technique

Physical and chemical key parameters of the Earth´s environment such as temperature, UV radiation field, oxidative capacity, acidity and etc., are determined by the amount of trace gases and aerosols in the atmosphere. It is thus of crucial importance to measure the accurate concentrations of the trace chemical component of the atmosphere for the purpose of predicting global warming, stratospheric ozone depletion, tropospheric ozone increase, and acid deposition. The concentrations of trace gases range from over 300 ppm of carbon dioxide to less than 0.1 ppt of OH radical. Several spectroscopic techniques are used to determine concentrations of these trace chemical species in the troposphere. Among these method the most sensitive is the laser induced fluorescence method which is now applied to measure OH radicals in the troposphere as well as in the stratosphere. UV absorption method is used to measure O₃ in local mode by a commercial instrument. It is also used in LIDAR mode to measure the vertical profile of ozone in both the troposphere and stratosphere. OH measurement by LIF and O₃ measurement by local UV absorption method and by UV-LIDAR method are discussed in some detail. Several examples of field measurement of OH and O₃ are also presented