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J. Delamere , E. Mlawer, V. Payne, S. Clough ( AER, Inc.)

J. Delamere , E. Mlawer, V. Payne, S. Clough ( AER, Inc.) D. Turner ( U. Wisconsin ), P. Green ( Imperial College ) E. Westwater ( U. Colorado ), N. Cimini ( U. L’Aquila ).

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J. Delamere , E. Mlawer, V. Payne, S. Clough ( AER, Inc.)

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  1. J. Delamere, E. Mlawer, V. Payne, S. Clough (AER, Inc.) D. Turner (U. Wisconsin), P. Green (Imperial College) E. Westwater (U. Colorado), N. Cimini (U. L’Aquila) Investigation of Far-Infrared Radiative Processes Using Measurements from the ARM North Slope of Alaska Climate Research Facility Improved Understanding of Far-Infrared Radiative Processes in the Earth's Atmosphere J. Delamere, E. Mlawer, V. Payne (AER, Inc.) S. Clough (Clough Associates) D. Turner (U. Wisconsin) R. Gamache (U. Mass. Lowell)

  2. Cooling Rate Calculation MLS Atmosphere • Maximum cooling occurs in the far-IR (10 to 650 cm-1,  > 15 m) Why the Far-IR? Clough & Iacono (1995) • Up to 40% of the OLR occurs in far-IR So important but significantly understudied…..

  3. Post-SHEBA Effect of Change Far-IR Mid-IR Total The SHEBA Experience • Collocated far-IR radiance measurements (AERI) and atmospheric profiling instruments deployed in the Arctic in 1997 • 4 cases from October used to adjust foreign water vapor continuum model (Tobin et al., JGR, 1999)

  4. Post-SHEBA Far-IR Residuals

  5. ARM North Slope of Alaska Facility • Daily radiosonde launches • Continuous operation of AERI • Continuous operation of 2 microwave radiometers: 23.8 & 31.4 GHz (since 1998) and 183 GHz (since 2006)

  6. Validate and refine, where necessary, the water vapor continuum model and the water vapor line parameters • Evaluate modeled optical properties of ice clouds • Incorporate improvements into GCM-appropriate radiative transfer models (e.g. RRTM). Radiative Heating in Underexplored Bands Campaign (RHUBC) • Collect high-resolution, downwelling radiance measurements in the IR in low precipitable water vapor (PWV) conditions. • Collect collocated measurements of the atmospheric state, including radiosondes and 183 GHz radiance measurements from which accurate water vapor fields can be obtained. • Using the atmospheric state measurements, calculate the downwelling surface radiance with a line-by-line radiative transfer model (LBLRTM) • Compare the measurements to the model calculations.

  7. RHUBC - Phase 1 RHUBC-I: North Slope of Alaska Feb-March 2007 Principal Investigators: David Turner and Eli Mlawer

  8. RHUBC - Phase 1 RHUBC-I: North Slope of Alaska Feb-March 2007 Principal Investigators: David Turner and Eli Mlawer

  9. PWV retrievals Key RHUBC Instruments • Key Far-Infrared Radiance Instruments • AERI-ER (25 - 3.3 µm) • TAFTS (125 - 15 µm) • Key Water Vapor Instruments • Vaisala RS-92 radiosondes • GVR (183.31 GHz) • GSR (183.31 GHz) • MP-183 (183.31 GHz)

  10. Reduced std. dev. of spectral infrared residuals using “scaled-sonde” approach Creating the Atmospheric Profile Radiosonde Profile (T,WV) Surface Met Data + Climatology

  11. 183 GHz Study Air-broadened Half-Widths of the 22 GHz and 183 GHz Water Vapor Lines (Accepted IEEE TGRS, 2008) V. Payne, J. Delamere, S. Clough, K. Cady-Pereira, J. Moncet, E. Mlawer (AER, Inc.) R. Gamache (University of Massachusetts - Lowell)

  12. 183 GHz Spectroscopic Parameters • Line intensity • Known to within 0.5% • Clough et al., 1973 • Width • HITRAN 2000+ value ~5% different from most recent HITRAN update • ~3% PWV error at 0.2 cm PWV • Temperature dependence of width • HITRAN 2000+: 0.64 (unrealistic) • HITRAN 2004+: 0.77

  13. Objective: Determine best value of 183 GHz width using ground-based radiometric measurements G-band Vapor Radiometer (GVR): Manufacturer: ProSensing (ARM SBIR) Operating continuously at the NSA 4 double sideband channels 183.31 +/- 1, 3, 7, 14 GHz Measurements averaged for 35 minutes around radiosonde launch Model: MonoRTM HITRAN line parameters (with some exceptions) CKD Continuum Model Date range used: January to October 2007 Includes RHUBC campaign “Clear-sky” conditions (no liquid cloud) Determination of 183 GHz Width

  14. Sensitivities to PWV and half width changes are distinct Crucial for half width retrieval “Pivot point”: +/-2 GHz 183+/-3 channel is least sensitive to the width can be used to get good first guess at PWV scaling for sondes Width retrieval uses channels on either side of pivot point Crucial for information on width Frequency [GHz] Retrieval of 183 GHz Half Width

  15. Improved and continuous estimates of atmospheric water vapor for dry conditions MonoRTM v3.3 http://rtweb.aer.com Retrieval of 183 GHz Width: Results • GVR-based width retrieval:0.0992 cm-1/atm( 2.5 %) • CRB calculations (Gamache): 0.0997 cm-1/atm ( 3 %) • See poster by Payne et al.

  16. Response of Tb to PWV 120 K Retrieval of PWV from GVR • Response of ±1, ±3 GHz channels: • Non-linear • ±14 GHz channel: • anomalous residuals at higher PWV • PWV retrieval: Use ±7 GHz channel • Use cases in linear region • Threshold of 120 K • Reduce set from 100 to 39cases

  17. Results of NSA PWV retrievals

  18. Extended Range Atmospheric Emitted Radiance Interferometer: Operating continuously at the NSA Range 3.3 - 25 µm with 0.5 cm-1 resolution Calibrated with two internal reference blackbodies traceable to NIST standards Accuracy better than 1% ambient radiance Corrections are applied to data (~ 1 RU) AERI-ER at NSA

  19. Removed cloud (liquid or ice) cases Case Selection for Far-IR Study • Removed cases with interference from nearby radar in AERI measurements (26 cases remain)

  20. Removed cloud (liquid or ice) cases Case Selection for Far-IR Study • Removed cases with interference from nearby radar in AERI measurements (26 cases remain)

  21. CO2 N2O Radiative Transfer Model • LBLRTM v11.1 • WV Continuum • MT_CKD_1.2 • Improved CO2 • Line-coupling (Niro et al., 2005) • Modified CO2 Continuum • Line intensities • HITRAN 2004 with Updates • Widths • HITRAN 2004 with Updates

  22. Sensitivity of Far-IR

  23. Preliminary Foreign Continuum Adjustment

  24. Initial Half-Width Adjustments • Update HITRAN 2004 line parameters • - New CRB calculations for air-broadened half-width, temperature dependence of the width, and line shift

  25. Summary of Far-IR Study (to date) • Suite of 22 optimal cases established • PWV values from radiosondes scaled to agree with 183 GHz retrievals • Initial adjustment to MT_CKD continuum released (MT_CKD_2.1) • Improved spectral residuals result from use of newly calculated CRB line widths relative to HITRAN 2004+ widths • Final analysis pending receipt of consistent set of CRB widths/pressure shifts • Improved water vapor continuum fit forthcoming (Clough)

  26. RHUBC-II Cerro Chajnantor, Chile Aug-Oct 2009

  27. RHUBC-II (Expected PWV)

  28. RHUBC-II (The Near-IR)

  29. Additional Slides

  30. Atmospheric State Profiles • PWV range: 0.07 to 2.2 cm • Vaisala RS-92 sondes + 40 m Meteorological Tower data • Sonde RH values “bottom out” at 10-12 km • Leads to unrealistic H2O values in stratosphere • Stratospheric values set to climatological values 100 cases

  31. MonoRTM v3.3 http://rtweb.aer.com Retrieval of 22 GHz width • MWRP at Southern Great Plains • See poster by Payne et al. • MWRP-based width retrieval: 0.0900 cm-1/atm( 1.6 %) • CRB calculations: 0.0913 cm-1/atm( 3.0 %)

  32. HITRAN Width Information

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