Spectroscopic study of CH 4 at 3.24 µm for atmospheric applications. Development of the PicoSDLA-CH 4 sensor and the TRO-Pico balloon campaign

Transcription

1 Spectroscopic study of CH 4 at 3.24 µm for atmospheric applications. Development of the PicoSDLA-CH 4 sensor and the TRO-Pico balloon campaign M. GHYSELS 1, J. COUSIN 1, L. GOMEZ 1,N. AMAROUCHE 3, E. D. RIVIERE 1, H. TRAN 4, G. DURRY 1,2 1 Groupe de Spectrométrie Moléculaire et Atmosphérique, GSMA, UMR CNRS 7331 UFR Sciences Exactes et Naturelles, BP 1039, REIMS Cedex 2, France 2 IPSL, Laboratoire Atmosphères, Milieux, Observations Spatiales, UMR CNRS 8190, Guyancourt, France 3 Division technique de l'institut National des Sciences de l'univers, 1, place Aristide Briand, 92195, Meudon Cedex, France 4 Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA, UMR CNRS 7583), Université Paris XII, Avenue du Général de Gaulle, Batiment 350, Créteil Cedex, France M. Ghysels et al, ASA/HITRAN

2 Why measuring methane? Methane is a tracer : convection, isentropic transport. Application: TRO Pico campaign in Brazil Methane is a greenhouse gas (it s contribution may increase in the future) Methane is a source of water vapor in the stratosphere by oxidation process. Indirect impact on the ozone layer. Validation of space mission dedicated to methane is needed (ex: LIDAR Merlin) M. Ghysels et al, ASA/HITRAN

3 Why the PicoSDLA- CH4 compact sensor? PicoSDLA-CH 4 onboard TWIN (PI A. Engels, University of Frankfurt) to increase flight opportunities by releasing launch constraints : to be flown under weather balloons. to be flown as piggy back onboard larger gondola. M. Ghysels et al, ASA/HITRAN

4 SDLA Weight : 80 kg L = 56 at 1.65 µm PicoSDLA-CH 4 Weight : 15kg L = 3.6 m at 3.24 µm SDLA L = 56 m at 1.65 µm (2000) In situ measurements Direct absorption spectroscopy Collaboration with DT-INSU (Meudon) PicoSDLA-CH 4 : Precision <5% Measurement time <1s Weight < 15kg M. Ghysels et al, ASA/HITRAN

5 M. Ghysels et al, ASA/HITRAN

6 Optical cell Gold coating retroreflector DFG Laser head Detector Germanium filter M. Ghysels et al, ASA/HITRAN

7 CDFG Laser module Laser head Optical fiber Novawave Technologies (Dr. J. JOST), Inc. (USA) 20 cm x 12 cm x 2.5 cm 980g Signal diode Pump diode DFG laser source 1.5 µm 1 µm PPLN crystal 3.24 µm DFG laser source R(6) transition ν 3 band of CH 4 (3086 cm -1, 3.24 µm, MIR) Strong fundamental band Reduction of optical path lenght : 56m 3.6 m M. Ghysels et al, ASA/HITRAN

8 Balloon campaigns M. Ghysels et al, ASA/HITRAN

9 Kiruna 2011 In the frame of ENRICHED project : 1 test flight as piggy back onboard TWIN experiment PicoSDLA-CH 4 onboard TWIN (PI A. Engels, University of Frankfurt) 9

10 ms 20 km Atmospheric spectra P = hpa T = C (1.49 ± 0.01)ppmv Precision : 5% at 20km (elementary spectra) 12 km M. Ghysels et al, ASA/HITRAN

11 TRO-Pico, Brazil 1 scientific flight, 14th march 2012 Data process underway Flight under small balloon during convection PicoSDLA-CH 4 TRO-Pico, march 2012 M. Ghysels et al, ASA/HITRAN

12 Spectroscopic study M. Ghysels et al, ASA/HITRAN

13 Why spectroscopy? Objectif : To Process balloon datas During flight : temperature range from 293 to 203 K Experiment : from 293 to 213K (limitation for cooling) M. Ghysels et al, ASA/HITRAN

14 Temperature dependence of line coefficients Determination of γ air, β air, ζ air and temperature dependence Study on R(6) manifold, ν 3 band of CH 4 Collaboration with Ha Tran (LISA, Créteil) and Laura Gomez (INTA, Espagne) Home-made laser source M. Ghysels et al, ASA/HITRAN

15 M. Ghysels et al, ASA/HITRAN ) ), ( 1 ), ( Im ), ( 1 ), ( (Re 1 ln 2 ) ( = Φ z y s x w z z y s x w z y s x w z z y s x w x m D π ς π γ π Hard-LM profile Line-mixing [Pine, 1996] Rautian Hard-LM Rautian Line-mixing at low pressures 30 hpa Ambient temperature R(6) in air Experimental spectrum

16 Position (cm 1 ) γ air (T ref ) (1/atm) This work n γ γ air (295K) (1/atm) Pine ± ± ± ± ± ± ± ± ± ± ± ± Rel. Dif (%) Results Position (cm 1 ) β air (T ref ) (1/atm) This work n β β air (295K) (1/atm) Pine ± ± ± ± ± ± ± ± ± ± ± ± Rel. Dif (%) Position (cm 1 ) ζ air (T ref ) (1/atm) This work n ζ ζ air (295K) (1/atm) Pine Rel. Dif (%) ± ± ± ± ± ± ± ± ± ± XX XX 0 XX 16

17 Kiruna (Sweden) 2011, Altitude 19.6 km 1 Transmission x 10-3 Wavenumber (cm -1 ) Application on in-situ measurements With HITRAN values : ρ CH4 = 1.49 ppmv With new parameters : ρ CH4 = 1.41 ppmv Differences of 5% M. Ghysels et al, ASA/HITRAN

18 Predominant line-mixing at high pressures Conclusions Residuals of the same order of magnitude for LM and Hard-LM at high pressures Line-mixing also at low pressures Comparison at ambient temperature with Pine values [Pine, 1996] : good agreement Perspectives Process balloon spectra including new parameters (ongoing) M. Ghysels et al, ASA/HITRAN

19 Equipe PicoSDLA: Scientific supervisor: Georges Durry (GSMA) GSMA, Université de Reims : Mélanie Ghysels, Julien Cousin, Laura Gomez-Martin Division technique de l'insu (Paris, CNRS) : Nadir Amarouche, Fabien Frérot, Jean-Christophe Samaké, Christophe Berthod, Louis Rey-Grange M. Ghysels et al, ASA/HITRAN