Christian Frankenberg on behalf of all contributors

Transcription

1 Satellite remote sensing of methane Christian Frankenberg on behalf of all contributors

2 Input from Ariane Razavi 2, Tobias Kerzenmacher 1, Bart Dils 1, Cathy Clerbaux 2,3, Pierre- François Coheur 2, Martine De Mazière 1, D. Hurtmans 2, Nicolas Kumps 1, Ann Carine Vandaele 1, Thomas Blumenstock 4, Philippe Demoulin 5, Pierre Duchatelet 5, Frank Hase 2, Nicolas Jones 6, Emmanuel Mahieu 5, Justus Notholt 7, Katinka Petersen 7, Theo Ridder 7, Mathias Schneider 2, Cindy Senten 1, Gauthier Vanhaelewyn 1, Corinne Vigouroux 1, Ulrich Platt 8, Markus Woyde 8, Ilse Aben 9 1 Belgian Institute for Space Aeronomy 2 Université Libre de Bruxelles, 3 LATMOS-IPSL, Paris, 4 IMK-ASF, Forschungszentrum Karlsruhe and Universität Karlsruhe, 5 University of Liège, 6 University of Wollongong, 7 University of Bremen 8 IUP Heidelberg 9 SRON Utrecht

3 Outline Brief introduction on SWIR and TIR retrievals Evolution of SCIAMACHY retrievals First IASI results

4 Blackbody curves, solar vs.. earth radiation SCIAMACHY IASI

5 Blackbody curves, solar vs.. earth radiation

6 Advantages SWIR ++ high sensitivity for the boundary layer TIR ++ height information

7 The short-wave part: SCIAMACHY results

8 SCIAMACHY 88 channel grating spectrometer Moderate spectral resolution (0.24nm at 2.3µm) UV-Near infrared spectral coverage (unique) 120x30km ground pixel size for 2.3µm Global coverage within 6 days

9 SCIAMACHY onboard ENVISAT in space since March 2002 Satellite remote sensing task - HYMN final workshop, Brussels, October HYMN2009 final meeting

10 CO 2 as cloud filter and air-mass proxy

11 First results, 2005 Frankenberg et al, Science, 2005 Satellite remote sensing task - HYMN final workshop, Brussels, October HYMN2009 final meeting

12 The nagging problem?? Frankenberg et al., JGR 2005

13 Multi-spectra fit, results for the Q-Branch Analysis of 4 methane spectra with N 2 pressure from hPa, 0.011cm -1 Frankenberg et al, ACP, 2008

14 Implications on SCIAMACHY retrievals Seasonal bias of about 1% Frankenberg et al, ACP, 2008

15 Atmospheric water vapor Implication on SCIA CH 4 retrievals Optimised treatment of water absorptions (Jenouvrier et al. 2007) Frankenberg et al, GRL 2008 Satellite remote sensing task - HYMN final workshop, Brussels, October 2009 HYMN final meeting

16 Atmospheric water vapor Implication on SCIA CH4 retrievals Frankenberg et al, Science, 2005 About 20-40ppb difference Frankenberg et al, GRL 2008 Satellite remote sensing task - HYMN final workshop, Brussels, October HYMN2009 final meeting

17 Revised tropical emissions NOAA only + old SCIA + new SCIA Satellite remote sensing task - HYMN final workshop, Brussels, October 2009 HYMN final meeting

18 Animation over Asia, 2005, rice emissions

19 Long term analysis, why interesting? Rigby, M., et al. (2008), Renewed growth of atmospheric methane, GRL. (using AGAGE, not NOAA!) Dlugokencky et al. (2009), Observational constraints on recent increases in the atmospheric CH4 burden, GRL, in press: 1) Artic T is high 2) Tropical precip is high 23Tg emission anomaly in 2007!!

20 Most sensitive region, the Q-branch of the 2ν2 3 band Frankenberg et al, ACP, 2008

21 Degrading detector pixels, Random Telegraph Noise

22 But luckily one important pixel still works

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28 Time-series over the Sahara Satellite remote sensing task - HYMN final workshop, Brussels, October HYMN2009 final meeting

29 Interpretation of SCIAMACHY methane (especially when you compare to ground-based or TIR sounders )

30 Column averaged vs.. surface mixing ratio

31 Column averaged vs.. surface mixing ratio

32 The long-wave part: IASI results

33 IASI instrument Nadir looking FTS 12 km pixel x nadir + scanning = +/ Spectral coverage = cm-1 Spectral resolution = 0.5 cm-1 Radiometric noise ~ K 120 spectra along the swath (2400 km) Each 50 km along the trace 2 global coverages per day (up to spectra/day) Priorities: Numerical weather predictions (temperature and humidity profiles each kilometer in the troposphere) Tropospheric chemistry and climate (integrated concentrations or vertical profiles for a series of target trace gases) Satellite remote sensing task - HYMN final workshop, Brussels, October HYMN2009 final meeting

34 IASI instrument LATMOS ULB ν 4 band ν 3 band 2 possible regions for CH 4 retrievals Measurements and products : Climate: T, CO 2, H 2 O, CH 4 Stratospheric Ozone: O 3, HNO 3 Tropospheric Chemistry: O 3, CO, HNO 3 + others Operational applications : Pollution, fires, volcanoes, storms

35 CH 4 retrieval and validation 2 retrieval algorithms using a LBL forward model and inversion based on OEM or Tikhonov regularisation are currently used for the inversion of the CH4 data product: Atmosphit at LATMOS/ULB global product ASIMUT at BIRA-IASB retrievals targeted above HYMN validation sites The ground-based FTIR CH 4 data have been harmonised within the HYMN project Ny Ålesund Kiruna Bremen Jungfraujoch Colocation criteria for comparison: - same day - within a 100 km radius around the ground based stations (60km for Kiruna, for St Denis IASI pixels only over ocean) Reunion Island Izaña Wollongong

36 Methane retrieval regions Transmittance Normalized radiance IASI spectrum ν 4 band IASI spectrum ν 3 band H 2 O N 2 O 0.2 HDO N 2 O Interval: 0.0 CH 4 CH Wavenumber [cm -1 ] Wavenumber [cm -1 ] cm cm -1 Retrieved parameters: Tsurf, CH 4, H 2 O and N 2 O Tsurf, solar reflectance η, CH 4, HDO and N 2 O

37 CH 4 retrieved with Atmosphit in ν 4 absorption band Global distribution : 4-10 October 2008 Methane averaged column vmr (normalized with the N 2 O) Only nadir spectra smoothed on a 4 x 4 grid Filters: cloud coverage <15%, emissivity >0.96, residual RMS < W/(m 2 sr m 1 ), OEM errors <1.5% New distributions are currently being processed to observe seasonal variations

38 CH 4 retrieved with Atmosphit in ν 3 absorption band 340 Brightness temperature [K] Day Night Thermal + reflected solar radiation (depends on the measurement hour, the type of surface, the angle between the sun and the satellite) wavenumber [cm -1 ] Simultaneous fit of the two spectral regions: improved sensitivity near the Earth s surface better de-correlation of two partial columns More tests will be conducted on a larger scale to determine the full possibility of the methane ν 3 band

39 CH 4 retrieved with ASIMUT in ν 4 absorption band The retrievals of CH4 profiles are done in a two stage process: first the surface temperature, H2O profile in seven layers and the O3 column in the following 2 windows, cm -1 mainly CO2, H2O and O3, noise = W/cm 2 /Sr/cm cm -1 with mainly H2O, noise = W/cm 2 /Sr/cm - 1 The results from the first stage are used to retrieve CH4 profile in 13 layers and the N2O column in the following 3 windows: cm -1 mainly H2O and N2O, noise = W/cm 2 /Sr/cm cm -1 mainly CH4 and H2O, noise = W/cm 2 /Sr/cm cm -1 mainly CH4 N2O and H2O, noise = W/cm 2 /Sr/cm -1 monthly MODIS surface emissivities on a 0.05 degree latitude/longitude grid (MYD11C1) are used for the retrievals.

40 CH 4 retrieved with ASIMUT in ν 4 absorption band

41 CH 4 retrieval with ASIMUT and validation Example at St Denis, La Réunion Groundbased DOF 2.5 to 2.4 Saint-Denis, Reunion (5 August 2007) Daily means (top) and percent differences (bottom) of methane VCD. Saint-Denis, Réunion June to September 2007 IASI DOF 2 to 1.7 Troposphere only

42 Conclusions I New methane spectroscopic parameters in the NIR available Atmospheric water vapor detected to be a crucial error source Seasonal bias over Australia resolved Tropical enhancements not as high as previous inversions suggested Inversions still point at underestimated tropical sources but are more consistent with the ground-based network

43 CONCLUSIONS II Two retrieval schemes for inverting CH 4 averaged column VMR (Atmosphit( Atmosphit) ) and profiles (ASIMUT) are being investigated. At present, the inversions exploit the ν 4 band of CH 4 ; About 2 DOF are achieved. In the near- future, the ν 3 band will be included in the inversions to increase the information content. First validation results of IASI CH 4 profiles from ASIMUT above HYMN FTIR stations show reasonable agreements. Based on 3 example cases of the structure function for the CH 4 retrievals at St Denis, Kiruna, and Wollongong, the precision of the ASIMUT retrievals is in the range 0.06 to 0.1 E19 mol/cm 2 or <2 to 3%. This is within the 5% required precision for meaningful CH 4 data. Future work: Refine retrievals and validation exercises, both for ASIMUT and Atmosphit