An airborne infrared laser spectrometer for in-situ trace gas measurements: application to tropical convection case studies

摘要: Abstract. A three-channel laser absorption spectrometer called SPIRIT (SPectrometre InfraRouge In situ Toute altitude) has been developed for airborne measurements of trace gases in the troposphere and lower stratosphere. More than three different species can be measured simultaneously with high time resolution (each 1.6 s) using individual CW-DFB-QCLs (Continuous Wave Distributed FeedBack Quantum Cascade Lasers) coupled to a single Robert multipass optical cell. The lasers are operated time-multiplexed mode. Absorption mid-infrared radiations occur cell (2.8 L effective path lengths 134 151 m) at reduced pressure, detection achieved HgCdTe detector cooled by Stirling cycle. performances instrument described, particular precisions 1, 1 3 %, volume mixing ratio (vmr) sensitivities 0.4, 6 2.4 ppbv determined s CO, CH4 N2O, respectively (at 1σ confidence level). Estimated accuracies without calibration about %. Dynamic measuring ranges four decades established. first deployment was realized aboard Falcon-20 research aircraft DLR (Deutsches Zentrum fur Luft- und Raumfahrt) within frame SHIVA (Stratospheric Ozone: Halogen Impacts Varying Atmosphere) European project November-December 2011 over Malaysia. convective outflows from two large systems near Borneo Island (6.0° N–115.5° E 5.5° N–118.5° E) were sampled above 11 km altitude on 19 November 9 December, respectively. Correlated enhancements CO vmr detected when crossed outflow anvil both systems. These interpreted as fingerprint transport boundary layer up through system then horizontal advection outflow. Using these observations, fraction air contained fresh calculated range between 22 31 showing variability taking place during transport.