Abstract
The results of methane profiling in the lower troposphere by Raman lidar from Lille University observatory platform (France), are presented. The use of powerful DPSS tripled Nd:YAG laser allowed profiling of methane background mixing ratio of 2 ppm in the night time up to 4000 m with 100 m height and 1 hour temporal resolution. Enhancement of CH4 mixing ratio inside the boundary layer comparing to the free troposphere values was observed.
Highlights
IntroductionMethane is currently the second (after carbon dioxide) most important greenhouse gas of anthropogenic origin
Methane is currently the second most important greenhouse gas of anthropogenic origin
For narrowband 354.7 nm laser radiation the vibrational Raman line of methane is at 395.7 nm, while the oxygen Raman overtone (3089 cm-1) is at 398.4 nm, which can be rejected by the interference filter
Summary
Methane is currently the second (after carbon dioxide) most important greenhouse gas of anthropogenic origin. [1,2] and references therein) and on a permolecule basis, methane is about 30 times more effective a greenhouse gas than carbon dioxide. The wideband radiation of excimer lasers requires the use of wideband interference filters in Raman channel, which, in turn, increases the sky background noise and possible contribution of aerosol fluorescence. Significant progress in the development of the interference filters, detectors and laser sources during the last two decades provides, the opportunity to develop the CH4 Raman lidar based on a relatively compact tripled Nd:YAG laser. For narrowband 354.7 nm laser radiation the vibrational Raman line of methane is at 395.7 nm, while the oxygen Raman overtone (3089 cm-1) is at 398.4 nm, which can be rejected by the interference filter
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