Instrumental techniques for remote sensing of the atmosphere in the infrared

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2016 Mahesh Kumar Sha Group: Infrared Observation & Lab Experiments Royal Belgian Institute for Space

1 Instrumental techniques for remote sensing of the atmosphere in the infrared Maido Observatory Summer School (MOSS) Reunion Island 28 Nov. 03 Dec Mahesh Kumar Sha Group: Infrared Observation & Lab Experiments Royal Belgian Institute for Space Aeronomy (BIRA-IASB) Ringlaan 3, 1180 Brussels, Belgium Tel. +32-(2) MOSS, Reunion Island 28 Nov. 03 Dec. 2016

2 Lecture content 1. Scientific background 2. Measurement techniques 3. Basic principles of a Fourier transform spectrometer 4. GHG measurement networks: Description and applications Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

3 Scientific context Global warming a major concern for survival on Earth IPCC report: Climate Change 2013 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

4 Scientific context IPCC report: Climate Change 2013 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

Scientific context Understanding of the exchange of Greenhouse Gases (GHGs)

CO2 and CH4) at the surface Global estimates of GHG surface fluxes are

5 Scientific context Understanding of the exchange of Greenhouse Gases (GHGs) and thereby identifying and quantifying the sources and sinks of GHGs (e.g. CO2 and CH4) at the surface Global estimates of GHG surface fluxes are presently based on combining ground based- and satellite measurements emissions partitioning Fig. source: Basu et. al. ACP 2013 (updated figure) Global Carbon Budget 2016 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

Scientific context Perturbation of the global carbon cycle caused by anthropogenic activities, averaged globally for the decade 2006 2015 (GtCO2/yr) 91% 44% 9% 31% 1987 1998 2015 26% High

6 Scientific context Perturbation of the global carbon cycle caused by anthropogenic activities, averaged globally for the decade (GtCO2/yr) 91% 44% 9% 31% % High growth of atmos. CO2 concentration in 1987, 1998 and 2015 reflects a strong El Niño, weakening the land sink Global Carbon Project 2016 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

7 GHG measurement networks Ground-based in-situ measurement network (surface air sampling, tower ~500 m) Derived fluxes are accurate but are affected by surface exchange and vertical transport highly variable but poorly simulated in global models Limited / no column measurements which limits its use for satellite validation In-situ aircraft (0 20 km) / aircore (0 35 km ) measurements Derived fluxes are accurate, measurements are possible at several altitude, but very sparse Ground-based mid-ir remote sensing measurement network (NDACC-IRWG) Column measurements of GHGs in the mid-ir using FTS instruments, over 20 measurement sites world wide spanning from the Arctic to the Antarctic locations Carbon cycle science and validation of satellite instruments Needs infrastructure, expertise for instrument handling; expensive and not easy to move instrumentation Ground-based near-ir remote sensing measurement network (TCCON) Column measurements of GHGs in the near-ir using FTS (Bruker IFS 125HR) instruments, over 22 measurement sites world wide spanning from the Arctic to 45 S High precision and inter-calibration accuracy, carbon cycle science and satellite validation Needs infrastructure, expertise for instrument handling, expensive and not easy to move instrumentation Ground-based near-ir remote sensing measurement network (COCCON, ) Column measurements of GHGs in the near-ir using portable, low cost FTS High precision and inter-calibration accuracy, carbon cycle science and satellite validation Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

8 Basic principles of an Fourier Transform Spectrometer (FTS) A FTS performs a physical Fourier transformation of a signal A monochromatic light source is recorded as a cosine formed intensity distribution as a function of path length which is then recorded by a detector in the form of an electric signal The variation of the path length defines the measured frequency Constructive interference: x = nλ Destructive interference: x = (n+1/2)λ Schematic diagram of a Michelson interferometer with linear slide and cube corners Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

9 Basic principles of an FTS Spectrum and its corresponding interferogram FTS FT F( ) f ( x) e 2 i x dx FTS FT Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

Interferogram transformed via FFT into spectrum (L1) Spectrum is used to retrieve information

10 Solar absorption measurements using FTIR spectrometry Sun as the source Sun tracker + FTIR spectrometer Meteorological sensors Meteo station Recorded signal is interferogram (L0) Interferogram transformed via FFT into spectrum (L1) Spectrum is used to retrieve information of the gases using a retrieval algorithm (L2) Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

Ile de La R eunion NDACC-IRWG and TCCON site University of La Réunion at St. Denis (87 m), Lat: 20.

485 E NDACC measurements with Bruker IFS 125M campaign basis since 2004 and on a continuous basis since

2011: TCCON (InGaAs and Si) & NDACC (InSb) Observatoire du Maïdo (2155 m) Lat: 21.079 S, Lon: 55.

11 Ile de La R eunion NDACC-IRWG and TCCON site University of La Réunion at St. Denis (87 m), Lat: S, Lon: E NDACC measurements with Bruker IFS 125M campaign basis since 2004 and on a continuous basis since 2009 Bruker IFS 125HR, CaF2 Beamsplitter & optics, Home-built tracker & electronics Since September 2011: TCCON (InGaAs and Si) & NDACC (InSb) Observatoire du Maïdo (2155 m) Lat: S, Lon: E Bruker IFS 125HR, KBr Beamsplitter & optics, Home-built tracker & electronics Since March 2013: NDACC (InSb and HgCdTe) & TCCON (InGaAs) Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

12 GHG measurement networks NDACC-IRWG Network for the Detection of Atmospheric Composition Change Infrared Working Group (NDACC-IRWG): A network of ground-based Fourier Transform Spectrometers recording direct solar spectra in the mid-infrared. Recorded absorption spectra are used to retrieve concentrations of a number of gaseous atmospheric components, including: O3, HNO3, HCl, HF, N2O, CH4, CO, HCN, C2H6 and ClONO2 as mandatory. Retrieval of other constituents, including NO, NO2, OCS, C2H2, HCOOH, H2CO, CFCs, HCFCs. Applications: Derive vertical column amounts of trace gases. Primarily developed to study the stratospheric distribution of trace gases from high altitude sites away from urban centers to avoid surface generated pollution. Recently with the broadening of focus to measure tropospheric gas distribution, sites at lower latitudes and closer to urban centers are acceptable. Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

13 NDACC objectives Started in 1992 with the following goals Long-term time series for detecting and understanding changes and trends in atmospheric composition and parameters Establish scientific links and feedbacks between climate change and atmospheric composition Satellite calibration, validation and gap filling Collaborative support to scientific field campaigns and other chemistry and climate observing networks Model validation Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

14 NDACC-IRWG requirements Spectral range of cm-1 (minimum); ~ µm Maximum OPD >= 250 cm Continuous spectral coverage (except for the 6-7µm region) in a small number (< 8) of spectral bands Make measurements with each filter on a timely interval on an ongoing basis Routine monitoring of instrument line shape (ILS) using HBr cell spectra Good alignment necessary with precise information of the modulation efficiency and phase error High signal-to-noise ratio of the spectra is necessary to detect weak absorption lines Retrieval software available within the network: SFIT and PROFFIT At Réunion Island measurements performed with Bruker IFS 125M, Bruker IFS 125HR with KBr beamsplitter and liquid nitrogen cooled InSb detector and MCT detector. The spectrometer is equipped with dual beam acquisition mechanism. Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

15 Time series of few species of NDACC-IRWG data at Maïdo Time series of a few selected gases Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

16 GHG measurement network TCCON Total Carbon Column Observing Network (TCCON): A network of ground-based Fourier Transform Spectrometers recording direct solar spectra in the near-infrared. Recorded spectra are used to retrieved accurate and precise column-averaged abundances of atmospheric constituents CO2, CH4, CO, N2O, H2O, HDO, HF, O2. Applications: In synergy with other surface measurements, it will improve estimates of surface fluxes of GHGs => improved prediction of their future concentration => better prediction of climate. Data used for carbon flux studies and validation of satellite measurements. Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

17 TCCON requirements Minimum spectral range of cm-1; µm Maximum OPD >= 45 cm, sun tracker with pointing accuracy of 1 mrad (~0.05 ) Surface pressure measurement accuracy better than 0.3 mbar Surface temperature measurement accuracy better than 1 K Routine monitoring of instrument line shape (ILS) using HCl cell spectra Modulation efficiency shall vary by less than 5% over the 0 to 45 cm OPD Bruker IFS 125HR with CaF2 beamsplitter and room-temperature DC-enabled InGaAs detectors, and with DC-enabled Si detectors for the O2 A band if the spectrometer is equipped with dual beam acquisition. Source: Bruker IFS125HR_manualBruke Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

18 TCCON measurements Atmospheric measurement Zoom of an ifg FT Optical path difference [cm] Wavenumber [cm -1 ] HCl cell measurement Zoom of an ifg FT Optical path difference [cm] Wavenumber [cm -1 ] Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

19 TCCON output Common analysis software GGG uses network wide to do the analysis of the data Retrieval results are total column amounts of the gases VC gas in molecules cm -2 VC gas = f gas z n z dz, f Z gas z = mole fraction of the gas, n z = total s number density, Z s = surface altitude VC gas tend to be strongly influenced by surface pressure (topography) Calculate column-averaged dry-air mole fractions (DMFs, X gas ) X gas = VC gas VC O ; where is the DMF of O 2 Advantage direct comparison of measurements during different seasons, between sites and with in-situ measurements, elimination of systematic error common to gas and O 2 cancel out, Dry-air mole fractions of the gas is then corrected for the air-mass dependence correction and a bias correction which ties the data to the currently-accepted WMO scale through calibration factors calculated using in-situ profiles measurements obtained from aircraft or balloons Data from each site is available at Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

20 Timeseries of TCCON data at St. Denis station High accuracy / precision requirement by TCCON Error in XCO2 < 0.25% (~1 ppm) until SZA ~82 Error in XCH4 < 0.5% (~5 ppb) until SZA ~85 Error in XCO < 4% and decreases with SZA XN2O ~1% (~3 ppm) and reasonably independent of SZA Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

21 Timeseries of TCCON data at St. Denis station Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

22 TCCON CO2 and CH4 global data St. Denis TCCON site Wennberg et al. presentation at the annual TCCON meeting, Jeju 2016 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

TCCON application towards satellite (OCO-2) validation Wunch et al. AMTD 2016; doi:10.

23 TCCON application towards satellite (OCO-2) validation Wunch et al. AMTD 2016; doi: /amt , 2016 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

24 TCCON application towards satellite (OCO-2) validation Wunch et al. AMTD 2016; doi: /amt , 2016 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

TCCON application towards model validation Copernicus Atmospheric Monitoring Service (CAMS) Time series of XCO at the Réunion Island TCCON compared to o-suite (red), control run (blue) and high

25 TCCON application towards model validation Copernicus Atmospheric Monitoring Service (CAMS) Time series of XCO at the Réunion Island TCCON compared to o-suite (red), control run (blue) and high resolution NRT FC model (yellow) of CAMS Figure courtesy: Bavo Langerock; Validation report of the CAMS near-real time global atmospheric composition service CAMS84_2015SC1_D _ Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

Langerock; Validation report CAMS84_2015

26 TCCON application towards model validation CAMS validation of CO2 and CH4 using TCCON data XCO2 Figure courtesy: Bavo Langerock; Validation report CAMS84_2015SC1_D _ XCH4 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

27 TCCON and NDACC-IRWG FTIR networks summary Column measurements of GHGs in the near-ir GHGs CO2, CH4, CO, N2O, HF, H2O, HDO, O2 Detector InGaAs and Si Profile scaling retrieval Standardized instruments (Bruker IFS 125HR), measurement setup, data analysis (GGG) Over 20 measurement sites world wide Investigate the flux of carbon exchange between the atmosphere, land and ocean, satellite validation Carbon cycle science and urban GHG emissions Satellite and model validation Column measurements of trace gases in the mid-ir 20 species among which 10 are mandatory: O3, CO, HCl, HF, CH4, N2O, C2H6, HCN, ClONO2, HNO3 Detector InSb and HgCdTe Profile retrieval Less uniform instrumentation and setup, data analysis (SFIT 4, PROFFIT) Over 25 measurement sites world wide Understanding physical and chemical state of the stratosphere and troposphere and assessing the impact of atmospheric changes on climate Ozone chemistry, troposphere chemistry and pollution, VOC's & CFC-substitutes study,... Satellite and model validation Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

This venture was tackled in cooperation with Bruker Optik GmbH.

28 GHG measurement networks COCCON Collaborative Carbon Column Observing Network: COCCON Karlsruhe Institute of Technology (KIT) started in 2011 the development of a novel compact NIR-FTIR spectrometer for carbon cycle research. This venture was tackled in cooperation with Bruker Optik GmbH. The EM27 spectrometer was decided upon as a starting point. Prototype EM27 Measurement container with Bruker IFS 125HR Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

29 GHG measurement networks COCCON Results achieved with the prototype were exciting M. Gisi, F. Hase, S. Dohe, T. Blumenstock, A. Simon, A. Keens: XCO2 measurements with a tabletop FTS AMT, 2012 The spectrometer is now offered as a standard item from Bruker ( EM27/SUN ). The serial production instrument is an upgrade, e.g. it uses a new acquisition electronics, offers wider spectral coverage and a redesigned tracker. Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

30 Necessity of a new measurement network Ground-based remote sensing measurements with a portable spectrometer Column measurements of GHGs in the near-ir using FTS (Bruker EM27/SUN) RockSolid pendulum interferometer used stable ILS over longer time Instruments are light weight, simple handling and portable making it suitable for mobile network measurement sites world wide, will give significant contribution towards carbon cycle science and satellite validation A factor of 5 to 6 times cheaper than the IFS 125HR Bruker spectrometer High precision and inter-calibration accuracy Network map of TCCON and NDACC-IRWG stations Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

tracker Sun tracking using optical feedback by the camtracker software EM27/SUN spectrometers measuring side-by-side Longterm stability of the EM27SUN

31 COCCON Instrument overview EM27/SUN spectrometer from Bruker RockSolidTM pendulum interferometer MOPD: 0.9 cm; Resolution: 0.5 cm-1, double sided InGaAs (Indium Gallium Arsenide) detector used Spectral range: cm-1 Dimensions: 47 x 63 x 35 cm Mass: ~ 25 kg including tracker Sun tracking using optical feedback by the camtracker software EM27/SUN spectrometers measuring side-by-side Longterm stability of the EM27SUN XCO2 < 0.1% Side-by-side intercomparison Calibration factors before / after campaign stable within 0.025% Fig. Source: Bruker Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

32 Retrieval strategy EM27/SUN PROFFIT (prf-em27) software used for retrieval of gas profiles PT profiles with intraday variability used HITRAN09 database with home made line list for water vapor; HITRAN08 database used for interfering species WACCM Ver. 6 climatology used as apriori Scaling retrieval performed Retrieval possible even with partial cloudy scenes Red: IFG dc threashold and modulation fluctuation Black: All data Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

33 Spectral windows used by PROFFIT Examples of spectral fit Spectral range used for retrieval of gases: O 2 : cm -1 H 2 O: cm -1 CO 2 : cm -1 CH 4 : cm -1 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

34 EM27/SUN intercalibration 6 spectrometers measured side-by-side at the rooftop of IMK in Karlsruhe Spectrometer scaling factor Spectrometer O2 XCO2 XCH Source: M. Frey Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

COCCON application Spectra measured by an EM27/SUN InGaAs detector 5000

35 COCCON application Spectra measured by an EM27/SUN InGaAs detector cm-1 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

36 Retrieval results: CO2 source from industrial region Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

37 Retrieval results: CO2 source from industrial region Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

38 COCCON application Few examples of the potential of the portable spectrometers Upstream-downstream observations of a target area CO 2 CH 4 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

39 COCCON application Estimating the CO2 source strength of an area (typically a megacity) Deployment in Berlin first of its kind Participants: T. Blumenstock, M. Frey, J. Groß, F. Hase, M. K. Sha, M. Kiel, G. Mengistu-Tsidu Support: R. Kohlhepp (DWD), K. Schäfer (IMK-IFU) Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

40 COCCON application XCO2 time series during the Berlin campaign F. Hase et al., Detecting greenhouse gas emissions of Berlin part 2..., AMT 2015 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

41 COCCON application Simplified source strength of Berlin (Total source strength: 730 kg CO2/sec) F. Hase et al., Detecting greenhouse gas emissions of Berlin part 2..., AMT 2015 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

42 COCCON application Comparison with simplified model F. Hase et al., Detecting greenhouse gas emissions of Berlin part 2..., AMT 2015 Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

Butz, F. Klappenbach, J. Kostinek, M. Berthleff) doi:10.

43 COCCON application Mobile platform measurements from a vehicle or ship Polarstern cruise (Mar/Apr 2014) (Remote-C group at KIT: A. Butz, F. Klappenbach, J. Kostinek, M. Berthleff) doi: /amt Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

44 COCCON application Polarstern cruise (Mar/Apr 2014) Klappenbach el al., Accurate mobile remote sensing of XCO2 and XCH4 doi: /amt Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

COCCON application Extended ground based network for satellite validation SCIAMACHY, GOSAT, OCO-2 and future satellite missions TCCON measurements at KIT + 3 EM27SUN spectrometer measurements

45 COCCON application Extended ground based network for satellite validation SCIAMACHY, GOSAT, OCO-2 and future satellite missions TCCON measurements at KIT + 3 EM27SUN spectrometer measurements Note: XCO2 gradient along OCO-II track of about 1 ppmv / 10 km analysis TCCON spectra: S. Dohe analysis COCCON spectra: M. Kumar Sha Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

46 COCCON summary COCCON aim: Increase the density of ground-based XCO2 and XCH4 observations for the quantification of sources and sinks of atmospheric carbon and for satellite validation Dedicated observation of O2, H2O, CO2, CH4 and CO (newly added) in the spectral range of 4000 and 9000 cm-1 COCCON approach: Create a periphery of EM27/SUN spectrometers around the TCCON FTIR core. Exploit mobility of the EM27/SUN spectrometers in performing calibration vs TCCON reference. Temporary arrangement into configurations to meet certain scientific demands (satellite validation, ground albedo / modelling, encircle source region) COCCON start: Initiated by KIT; Instrument recalibration and service to be done in Karlsruhe (availability of TCCON spectrometer and Bruker support). Operation of spectrometers in cooperation with local groups. Campaign based measurements possibilities in collaboration with research groups. COCCON analysis: Retrieval tools for pre-processing of spectra and subsequent analysis with PROFFIT. Provide guideline for instrument characterization. COCCON data: Network wide data archiving facility in collaboration with NDACC/TCCON. Standardized data format to allow sensible use together with data from TCCON. Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

47 Thank you for your attention Let s go to Maïdo Mahesh Kumar Sha, MOSS, Reunion Island 28 Nov. 03 Dec

Relevance of the Total Carbon Column Observing Network (TCCON) for satellite calibration and validation

Relevance of the Total Carbon Column Observing Network (TCCON) for satellite calibration and validation Untersuchungen des Kohlenstoffkreislaufs T. Warneke 1, J. Notholt 1, T. Blumenstock 2, H. Boesch