Institut für Umweltphysik (IUP) Institut für Fernerkundung (IFE)

1. CarbonSat L1L2 Study Final Presentation, 3-Jul-2013 Universität Bremen, FB1 Physik und Elektrotechnik Institut für Umweltphysik (IUP) Institut für Fernerkundung (IFE) • Consolidation of • SNR, spectral resolution & coverage: • Retrieval Simulations XCO2 and XCH4 with focus on Clouds & Aerosols • ESA Study CarbonSat Earth Explorer 8 Candidate Mission • “Level-2 and Level-1B Requirements Consolidation Study“ • ESA Contract No4000105676/12/NL/AF M. Buchwitz, H. Bovensmann, M. Reuter, J. Heymann, O. Schneising Institute of Environmental Physics (IUP) / Institute of Remote Sensing (IFE), University of Bremen (UB), Bremen, Germany 1

2. Purposeofpresentation • Atprojectstartithadbeendecidedtoinvestigatewith high priorityifcertainrequirementscanbemodifiedtoobtain a lesschallenginginstrument • PriorityNo 1: • Lessdemandingspectralresolution ? • Ifyes, whichotherrequirementsneedtobemodifiedforcompensationtoavoidperformanceloss ? 2

3. Goal Shouldn‘titbepossibletomakeitbetter ? Initial concept 3

4. Approach 4

5. Approach - II • Currentwisdom @ projectstart: Veryhigh spectralresolutionismandatoryespeciallytohaveenoughinformationto deal withaerosolsandcirrusclouds (OCO, GOSAT, …) • However: Information contentofspectra also depends on SNR, spectralcoverage, etc. • Based on simulatedretrievalsusing different instrumentconfigurationsthisaspecthasbeeninvestigatedby IUP • -> This presentation • The IUP resultshavebeenindependentlyverified/studiedusing • independentsimulations -> seeUoLpresentation • andanalysisof real GOSAT data -> seeSRON presentation 5

6. Simulation framework Estimation of random &systematic errors of CarbonSatXCO2 & XCH4 retrievals: Retrieved – true = systematic error XCO2 and XCH4 True XCO2 & XCH4 (Model) Atmosphere CO2(z), CH4(z), p(z), T(z), ... Retrieved XCO2 & XCH4 +/- random error Albedo, SZA, aerosols, clouds, ... a priori information: CO2, CH4, ... Observing System = Instrument + Retrieval Algo RTM BESD/C Various scenarios (aerosols, clouds, ...) Instrument Model Radiance Radiance @ instrument resolution & sampling, SNR, ... Specification (MRD) Instrument errors NOV-7090-SL-2551 6

7. Simulation framework - II • Radiative Transfer Model (RTM): • SCIATRAN (Rozanov et al., 2005, 2006) • Instrument Model: • Simple CarbonSat instrument model considering spectral range, spectral resolution, spectral sampling, signal-to-noise (SNR) performance • Retrievalalgorithm: • Bremen optimal EStimation DOAS, BESD/C (Bovensmann et al., 2010, Buchwitz et al., 2013) • Furtherdevelopedwithinthisproject 7

8. Studiedinstrumentconfigurations NIR, SW1 SW2 * # # Improvedcirrusdetection * Lesserrors due toVeget. Chloro. Fluores. (Frankenberg et al., 2012) 8

9. Studiedinstrumentconfigurations: Instrument I07 • Instrument I07: Relaxed spectral resolution + extended spectral coverage + optimized SNR: • NIR: The extension of the spectral range to also cover 749–759 nm • permits to consider more clear Fraunhofer lines: • Less errors due to VCF (Vegetation Chlorophyll Fluorescence) • In line with strong recommendation of Frankenberg et al., 2012, for future GHG satellites • SWIR-2: The extension of the spectral range to also cover ~1930 nm • permits to use “saturated” water bands: • Improved cirrus detection (see also SRON presentation using GOSAT) • In addition: Increased SNRin the NIR and SWIR -2 bands. Possible due to the lower spectral resolution in these bands compared to the “initial” instruments (I01, I02). 9

10. Geophysical Scenarios Here: Solar Zenith Angle (SZA) 50°, vegetation albedo (“VEG50 scenario”). 10

11. Systematic & randomerrors: XCO2 • Instrument 7 (I07, blue, extended spectral region) gives the lowest bias (best accuracy) for nearly all 15 scenarios • XCO2 precision shows less scenario dependence but a pronounced instrument dependence. • I07 clearly gives the best performance also for the XCO2 precision. I07 (*#) (*) SWIR-2 only I07 (#) Desertaersol & AOD x 1.5 (*) VCF x2 11

12. Systematic & randomerrors: XCH4 • Note: Instrument 6 has no CH4 channel (no SWIR-1) • Differences quite small • Nevertheless, I07 gives best results I07 I07 12

13. Other parameters: Vegetation Chlorophyll Fluorescence (VCF) VCF as GHG retrievalby-product • Some dependence of the systematic error on the cloud scenario (8 and 9). • Less sensitivity to e.g. clouds can be obtained using a dedicated VCF algorithm based on clear Fraunhofer lines (bottom) • So far only a very simple initial VCF retrieval scheme has been implemented, therefore, some bias remains (e.g., scenarios 3, 4 and 13). • Best results for I07 Dedicated VCF retrieval 13

14. Other paras: Cirrus Optical Depth (COD) andaltitude (CTH) • I07gives best results • More results please see TN-3d and following presentations … 14

15. Recommendationsbased on IUP-UB analysis • Spectral resolution can be relaxed as follows: • NIR: 0.045 nm -> 0.1 nm • SWIR-2: 0.13 -> 0.5 nm • However, this requires for compensation the following changes: • NIR: • Spectral range: 756-773 nm -> 747-773 nm • SNRref@Lref (T): 110@3x1012 -> 150@3x1012phot/s/nm/cm2/sr • SNRref (G): 2 x new SNRref (T) • SWIR-2: • Spectral range: 2043-2095 nm -> 1905-2095 nm • SNRref@Lref (T): 50@3x1011 -> 90@3x1011phot/s/nm/cm2/sr • SNRref (G): 2 x new SNRref (T) • These recommendations have been considered for MRD updates ! 15

16. In summary: Before … Earth Explorer 8 (EE8) Candidate Mission 16

17. … and after Earth Explorer 8 (EE8) Candidate Mission 17

18. Preliminaryconclusions CS v2 The onlyremainingquestionis … 18

19. The end ? Story tobecontinued: Don‘t miss thefollowingpresentations Isthisalreadythe ? 19