Abstract
Methane plays an important role in the radiative balance of the Earth climate: about 20% of the manmade global warming is related to methane emissions. To contribute to the study of CH4 trends, we have developed a compact lightweight spectrometer (2.5 kg) by combining an antimonide laser diode at 3.24 µm with an 8 m optical multipass path cell open to the atmosphere. This laser sensor is to be operated from weather balloons to provide with regular in situ methane soundings from ground level up to ~ 25 km. In this paper, the laser sensor is described as well as the processing of the absorption spectra and the calibration of the instrument. The concentration data obtained from recent stratospheric balloon flights are reported and discussed.
Highlights
Methane is the second most important greenhouse gas released by human activities [1]
Methane accounts for roughly 20% of the manmade global warming that is observed nowadays [2, 3]
It seems its role in climate change could be strongly growing [4,5,6,7]
Summary
Methane is the second most important greenhouse gas released by human activities [1]. Recent generation of laser diodes, like the antimonide ones, offer an emission wavelength close to 3.3 micron, a spectral region where the strong υ3 fundamental vibrational band of C H4 lays. It makes it possible to develop highly compact laser diode spectrometers by reducing the required absorption path length. Amulse is a French acronym for “Atmospheric Measurements by Ultra-Light SpEctrometer” With this project, the strategy consists of delivering numerous regular in situ vertical concentration profiles of C H4 from ground to ~ 20 km, using weather balloons to be launched by nonspecialists within the framework of atmospheric observational networks. We report atmospheric data achieved during recent balloon flights
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