Development of DIAL for molecules related to earth warming

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Range-resolved differential absorption lidar (DIAL) has already been in the practical use for the detection of naturally abundant atmospheric ozone and water vapor. It has also been used in the measurements of some highly abundant species of pollutant molecules. Recent progress in high-power tunable IR sources makes the range-resolved detection of other important species possible. We have developed a high-power Ram an laser which is continuously tunable up to 3.2 mum and pumped by a Ti : sapphire laser. Using the HITRAN data base, we surveyed useful absorption lines 'for range-resolved DIAL measurement in the wavelength rage from one to five micrometers, and found that CO_2, CO, N_2O, CH_4 in the troposphere were detectable. A detailed simulation of the DIAL measurement of these species was made for many absorption lines, taking into account the interference from other species.We performed DIAL measurement of CO_2 which has a Ti : sapphire laser. The Ti : sapphire laser has an output energy of 30 mJ with a bandwidth of 20 pm.We have succeeded in observing horizontal distributions of CO_2 in the atmosphere within the detection ranges from 300 m to 700 m with rage resolution of 100m and with time resolution of 10 minutes.