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

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