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Validation of Forward Model with Interferometric Measurements for Passive Remote Sensing

Validation of Forward Model with Interferometric Measurements for Passive Remote Sensing. Mark Shephard, Tony Clough, Jennifer Delamere, Karen Cady-Pereira, and Eli Mlawer Atmospheric and Environmental Research (AER), Inc. Atmospheric Temperature Profiles.

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Validation of Forward Model with Interferometric Measurements for Passive Remote Sensing

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  1. Validation of Forward Model with Interferometric Measurements for Passive Remote Sensing Mark Shephard, Tony Clough, Jennifer Delamere, Karen Cady-Pereira, and Eli Mlawer Atmospheric and Environmental Research (AER), Inc.

  2. Atmospheric Temperature Profiles • Temperature field must be correct for atmospheric species retrievals • Error in the Forward Model including Spectroscopy is a significant contributor to the retrieval error • Improved SNR of present and future high resolution passive sensors • ACE, AIRS, IASI, MIPAS, TES,….. • Reported errors in water vapor validations, attributed to water vapor forward model error, are actually due to errors in the temperature field

  3. High resolution Interferometer Sounder (HIS) CAMEX • HIS : CAMEX (Sept. 29, 1993) • HIS Band1 (600-1074 cm-1) spectral resolution of 0.32 cm-1 : CO2 v2 • HIS Band2 (1075-1830 cm-1) spectral resolution of 0.73 cm-1:H2O • upwelling radiation from an aircraft at 20. km off the Virginia coast • well studied case (i.e. IASI model validation intercomparison) • Atmospheric Specification • Radiosonde profile for Temp. and H2O • CO2 climatological value: 354 ppmv • Forward Model • Spectroscopic Parameters: HITRAN • LBLRTM: Line Shape and Line Coupling • Continuum: MT_CKD Spectral resolution : 1/(2 x max optical path)

  4. HIS CAMEX Temperature Retrieval CO2 v2 region (680-800 cm-1): HIS Band1 • generally used for temperature retrievals

  5. HIS CAMEX Retrievals: H2O Spectral Region H2O vapor region (1250-1550 cm-1) : HIS Band2 • Simultaneouswater vaporand temperature retrieval Methane 

  6. HIS CAMEX Remarks • HIS CAMEX Retrievals • The most significant reduction in the Band 2 residuals is obtained by the simultaneous retrieval of water vapor and temperature • Retrieved temperature from CO2 v2 (Band1) is NOT consistent with retrieved temperature from H2O (Band2) • Forward Model for CO2 and H2O is inconsistent and/or • HIS Band1 and Band2 radiance measurements are inconsistent (not likely) • TES presently performs a simultaneous temp., water vapor, and ozone • TES 1B2 (920-1160 cm-1)spectral region:H2O and O3

  7. AIRS : Chesapeake Bay Case Study : Sept. 13, 2002 6:43 Z • AIRS (Atmospheric Infrared Sounder) • grading spectrometer: 2378 channels 650 - 2675 cm-1 • Resolution: resolving power of 1200 • 0.5 cm-1 @ 600 cm-1; 2.0 cm-1 @ 2400 cm-1 • upwelling radiation from space • Atmospheric Specification • Temperature: radiosonde < 100mb, AIRS retv > 100 mb • H2O: radiosonde < 100mb, extrapolated sonde value > 100 mb • O3: US Std. scaled to TOMS total column • CO2 : Climatological value 370 ppmv • Other profiles: US Std. Atmosphere

  8. AIRS : Chesapeake Bay Case Study : Sept. 13, 2002 6:43 Z CO2 (n2)O3 (308 DU) CH4 H2O (1.62 prec. cm)N2OCO2 (n3) Stratosphere Troposphere • AIRS 1200 Resolving Power • LBLRTM HITRAN 2000 - LBLRTM (Gaussian) HITRAN 2000 Obs. - Calc.

  9. AIRS Temperature Retrievals CO2 (n2) O3 CH4 H2O N2OCO2 (n3)

  10. AIRS Temperature Retrieval Averaging Kernals CO2 v3 (2150 - 2350 cm-1) CO2 v2 (660 - 800 cm-1) • Averaging kernals • CO2 v2 and CO2 v3similar • sensitive over the whole profile

  11. Summary • Temperature field must be correct for atmospheric species retrievals • Forward Model (LBLRTM and Spectroscopic Line Parameters) • CO2 v2inconsistent with N2O/CO2 v3 (n2 is ~4% too large) • CO2n2inconsistent with H2O • CO2 v3 appears to be consistent with other species H2O / CH4 • Ultimate Objective: • Consistency: within species between species • Consistency with different spectral regions/different instruments • thermal-interferometer, thermal-grating, thermal-MWR, IR-Occultation,… • TES • Currently: H2O and O3 spectral regions for temperature retrieval • Objective: add CO2 v2 spectral region to the temperature retrievals • significantly more degrees of freedom • Near Term: ad hoc corrections to the forward model • Longer Term: Collaboration with Mary Ann Smith Group (NASA): lab. measurements

  12. Backup Slides

  13. AIRS : Residuals vs Brightness Temperature n2 band n3 band Stratosphere Troposphere Stratosphere:  Temperature Calc. Troposphere:  Temperature Calc. Troposphere:  Temperature Calc.

  14. CO2 Line Shape Chi function: The spectral function by which the Lorentz line shape (impact) must be multiplied to obtain the “true” line shape. Sub-Lorentzian chi function accounts for the duration of collision effects. • Continuum: Includes following contributions • 25 cm-1 beyond line center • within -/+ 25 cm-1 at 25 cm-1 value

  15. Radiance(mW / m^2 sr cm-1) N2O Q Branch CO2 Q Branch Wavenumber (cm-1) AERI_ER Validation in the Polar Window ARM NSA Retrieved Column Water Vapor HITRAN 2000/2004 mt_ckd_1.1

  16. AERI Downwelling at the Surface ARM SGP Moist Toth _1%

  17. Temperature and H2O Correlation Coefficients (subset)Simultaneous Retrieval … 18 19 20 21 22 23 24 TEMP TEMP TEMP TEMP TEMP TEMP TEMP … P(mb) 273 325 423 546 702 850 1017 4 WATER 249 0.11 0.18 -0.03 -0.05 -0.04 0.00 -0.01 5 WATER 300 0.06 0.23 0.11 -0.10 -0.03 -0.01 -0.02 6 WATER 374 -0.04 0.11 0.38 -0.02 -0.05 0.01 -0.05 7 WATER 479 -0.06 -0.05 -0.01 0.45 0.11 -0.01 -0.07 8 WATER 620 -0.02 0.01 -0.20 0.21 0.20 0.05 -0.04 9 WATER 794 0.01 -0.01 -0.01 -0.01 -0.23 0.50 0.25 10 WATER 899 0.00 0.00 -0.02 0.01 -0.17 0.29 0.53

  18. Observations • HIS : CAMEX (Sept. 29, 1993) • spectral resolution of 0.32 cm-1 • upwelling radiation from an aircraft at 20. km over water • well studied case (i.e. IASI model validation intercomparison) • AIRS : Chesapeake Bay (Sept. 13, 2002) and Gulf of Mexico (Nov. 21, 2002) • grading spectrometer with a resolving power of 1200 • upwelling radiation from space • SHIS : AFWEX (Dec. 10, 2000) • spectral resolution of 0.48 cm-1 • upwelling radiation from an aircraft at 10.7 km over land • below the tropopause, reducing ozone interference and avoiding temperature folding • AERI : ARM North Slope Alaska (March 11, 2001) • spectral resolution of 0.48 cm-1 • downwelling radiation from the surface • low water vapor (0.17 prec. cm) * Spectral resolution is computed as : 1/(2*max optical path)

  19. AERIDownwelling at the Surface Arctic SHIS AFWEXUpwelling at 10 km Dry

  20. Acronyms • AERI: Atmospheric Emitted Radiance Interferometer • AFWEX: ARM/FIRE Water vapor Experiment • Dec. 10, 2000: sonde launch 02:28 GMT: 10 km: over land in Wisc. • AIRS: Atmospheric Infrared Sounder • Grading spectrometer: 2378 channels : 650-2675 cm-1 : I/DI = 1200 resolving power • ARM: Atmospheric Radiation Measurement Program • CAMEX: Convection and Moisture Experiment • Sept. 29, 1993: sonde launch 03:51 GMT: 20 km: over water • IASI: Infrared Atmospheric Sounder Interferometer • ISSWG: IASI Sounder Science Working Group • LBLRTM: Line-by-Line Radiative Transfer Model • NSA: North Slope of Alaska, USA, ARM site • SHIS: Scanning High resolution Interferometer Sounder • SGP: Southern Great Plains, USA, ARM site • north-central Oklahoma and south-central Kansas • TES: Tropospheric Emission Spectrometer • Infrared spectral range from 650-3050 cm-1 • Nadir (0.1cm-1) and limb viewing(0.025 cm-1) with 16 detectors (~2.3 km)

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