Tony Clough, Mark Shephard and Jennifer Delamere Atmospheric & Environmental Research, Inc. Colleagues University of Wisconsin International Radiation Symposium Busan, Korea August 2004 Spectroscopic Issues Associated with Atmospheric Remote Sensing
Mar 17, 2016
Tony Clough, Mark Shephard and Jennifer Delamere Atmospheric & Environmental Research, Inc.
ColleaguesUniversity of Wisconsin
International Radiation SymposiumBusan, KoreaAugust 2004
Spectroscopic Issues Associated with Atmospheric Remote Sensing
Evaluation of CCM3 with HIRS Radiances
Iacono et al., JGR 2003Cloud Cleared: Bates
Channel 4: Temperature Field
Channel 12: Water Vapor Field
Remote Sensing of OzoneOzone Sonde Issues (Spatial, Temporal, Accuracy)
• extremely valuable
Ozone Spectroscopy• Flaud - French Group: 0%
• Maryanne Smith - Langley: +3%
• UV: -5%
• Microwave: Pure Rotation Lines
Remote Sensing of Water Vapor at the ARM SitesSonde Issues (Spatial, Temporal, Accuracy (Bias))
Column: Microwave
• Atmospheric Measurement (mwr scaled sondes)
• Transition Frequencies
• Strengths (Stark Effect: 0.5%)
• Widths (Temperature Dependence)
• Shape: Voigt
• Continuum
Tropospheric Profile: Raman Lidar• Night/Day
• Cloud Clearing
Spectral Brightness Temperature and MWR Frequencies
MWRP / MonoRTM Residuals (5 frequencies) HalfWidth: MONORTM Value PWV: Retrieved from 23.835 GHz BT_MWRP
a + b * BT_MWRP
MWR - Modeled (PWV scaled to match 23.8 GHZ MWR)
Atmospheric Validation of Forward Model
1. Measurement• Instrument Function - Photometry
• AERI - HIS AIRS sfc air space
2. Characterization of the Atmospheric Path including Surface• Sonde
- Temperature
- Water Vapor
3. Forward Model• Line Parameters
• LBLRTM (line shape)
• Continuum
Atmospheric Spectroscopy from Space: long paths, cold temperatures
(AIR
Sob
s-A
IRS
calc
)-
(SH
ISob
s-S
HIS
calc
) (K
)
“AIRS SHIS Comparison 2” (21 November 2002) Excluding channels strongly affected by atmosphere above ER2
Revercomb et al.
Remote Sensing of Temperature in the Infrared• Carbon Dioxide
• Transition Frequencies (Pressure Shift)
• Strengths
• Widths (Temperature Dependence)
• Shape:
• Voigt
• Chi Function (function and temperature dependence)
• Galatry …. (transition from Doppler to Voigt)
• Line Coupling (Perturbation Approach/Exact Diagonalization)• Q Branches• P and R Branches
• Continuum
Chi function: The spectral function by which the Lorentz line shape (impact) must be multiplied to obtain the “true” line shape.
0.0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20 25
Chi
Fun
ctio
n
Wavenumbers from Line Center (cm-1)
Clough et al., 1978Cousin (a) N2 296K
Cousin (c) N2 238KChi_LBLRTM_v_8
LBLRTM Chi Function for CarbonDioxide
impact
Continuum: Includes following contributions • 25 cm-1 beyond line center • within -/+ 25 cm-1 at 25 cm-1 value
1E-32
1E-31
1E-30
1E-29
1E-28
1E-27
1E-26
1E-25
1E-24
0 200 400 600 800 1000 1200 1400
SP
SD
F [
1/(c
m-1
m
olec
/cm
^2)]
Wavenumber (cm-1)
impactClough et al., 1978LBLRTM_v_8
CO2 Continuum(Symmetrized Power Spectral Density Function: SPSDF)
*
AERI Downwelling at the Surface ArcticSHIS AFWEX Upwelling at 8 km Dry
• AIRS 1200 resolving power• LBLRTM HITRAN 2000• LBLRTM (Gaussian)
CO2 (2) O3 CH4 H2O (1.63 prec. cm pwv) CO2 (3)
HITRAN 2000
AIRS Validation with Sonde/Climatological Profile
Troposphere
Stratosphere
H2O
Residuals vs Brightness Temperature
2 band 3 band
Stratosphere
Troposphere
ClimatologySonde
Temperature Retrieval using the 3 CO2 Band
AIRS Validation with Retrieved Temperature Profile
• AIRS 1200 resolving power• LBLRTM HITRAN 2000• LBLRTM (Gaussian)
CO2 (2) O3 CH4 H2O (1.63 prec. cm pwv) CO2 (3)
H2O
AIRS Validation with Retrieved Temperature Profile (3)
• AIRS 1200 resolving
power• LBLRTM HITRAN
2000• LBLRTM
(Gaussian)
CO2 (2) O3 CH4 H2O (1.63 prec. cm pwv) CO2 (3)
H2O
• AIRS 1200 resolving
power• LBLRTM HITRAN
2000• LBLRTM (Gaussian)
CO2 (2) O3 CH4 H2O (1.63 prec. cm pwv) CO2 (3)
HITRAN 2000
AIRS Validation with Sonde/Climatological Profile
Temperature Retrieval for CAMEXBand1: CO2Band 2: Water Vapor (simultaneous)
1000
100
50
-6 -4 -2 0 2 4 6Temperature Change (K)
B1-Sonde
B2-Sonde
1000
100
50
-6 -4 -2 0 2 4 6Temperature Change (K)
B2-B1
2
Remote Sensing of Water Vapor in the Infrared
• Atmospheric Measurement (mwr scaled sondes)
• Transition Frequencies (Pressure Shifts)
• Strengths
• Widths (Temperature Dependence)
• Shape: Voigt
• ContinuumDefinition: Continuum is that absorption with slow spectral dependence which,
when added to the line by line absorption, provides agreement with
measurement.
Scaling: Dependence on pressure, temperature and mixing ratio must be ‘robust’
mt_ckd: Contributions from two sources:
• Allowed line contribution
• Collision-Induced contribution
-10-505
10
400.000 420.000 440.000 460.000 480.000 500.000 520.000 540.000 560.000 580.000 600.000
-10-505
10
400 420 440 460 480 500 520 540 560 580 600
0
20
40
60
80
100
400 420 440 460 480 500 520 540 560 580 600
Wavenumber ( cm-1)
AERI - LBL_HITRAN_2000 pwv: 0.204 cm
AERI - LBL_HITRAN_2004 pwv: 0.204 cm
260 K
166 KAERILBL_HITRAN_2004
Widths Transferred
Rad
ianc
e (m
W /
m^2
sr c
m-1
)
Wavenumber (cm-1)
AERI_ER Validation in the Polar Window ARM NSA
Retrieved Column Water Vapor HITRAN 2000/2004 mt_ckd_1.1
N2O Q BranchCO2 Q Branch
_1%
Toth
AERI Downwelling at the Surface ARM SGP Moist
CAMEX HIS Upwelling at 20 km Ocean - low pwv
Temp: R (2) CO2 Water Vapor: Retrieved
Temp: R (2) CO2 Water Vapor: Sonde
Temp: Retrieved Water Vapor: Retrieved
HIS CO Region: Upwelling at 20 km Ocean low pwv
__ __ __ __ __
H2O CO2 Q
SummaryWater Vapor
• Effectively no ground truth• Reasonable consistency across the band• NO evidence (yet) for
- line shape other than Voigt- higher spectral content for the continuum
Significant improvement in line parameters since IRS 2004 (MIPAS-EOS) BUTSpectroscopy is the current limitation on the accuracy of retrievals from space!
Carbon Dioxide• 2 and 3 are not consistent (2 strengths are effectively ~4% .gt. 3)• Water vapor temperature retrieval consistent with 3• Issues
chi factorContinuumLine coupling: Q and P & R
http://rtweb.aer.com