Scattering and Polarimatric Components in Community Radiative Transfer Model

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Scattering and Polarimatric Components in
Community Radiative Transfer Model
Quanhua (Mark) Liu
F. Weng, Y. Han, P. van Delst, R. Treadon, J.
Derber at JCSDA
The 4rd JCSDA Science Workshop, May 31- June 1,
2006, Camp Springs, MD
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Important Components in CRTM

• Versatile transmittance models (OPTRAN, OSS)
• Cloud scattering and absorption
• Advanced surface emissivity models (NESDIS,
  FASTEM)
• Various solvers for radiative transfer equations
• Infrared and Microwave Sensors
• Module platform to incorporate new research and
  education components

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Radiative Transfer Model
Radiative transfer solver is one of the key
components of CRTM. Delta 4 stream vector
radiative transfer model (UCLA) Direct ordinate
tangent linear radiative transfer (DOTLRT)

- NOAA/ETL Successive
Order of Iteration (SOI) Uni. Wisc. Advanced
Doubling-Adding Method (ADA) NOAA/STAR Many
other models, such as CIRA/CU SHDOMPPDA,
two-stream model (Schmetz), Eddington
approximation (Kummerow), and a linearized
discrete ordinate radiative transfer model
(Spurr et al.).
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ADA Method
Layer transmission and reflection
Layer source function
Vertical integration
the surface reflection matrix, loop k from n ? 1
TOA radiance
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Remark
Numerically exactly Analytical expressions
replace the most complicated terms source
functions. F90/F95 matrix and vector manipulation
makes coding simple, also simple for
tangent-linear and adjoint coding, good for code
maintenance Add a viewing angle in the streams
for satellite radiance Fast, about 60 times
faster than the original double-adding method
Easy extension, for example Double the size of
vector and matrix dimension and other minor
change for the atmospheric residual polarization
(completed) Add a sun angle in the streams and
add a loop over azimuthal-component for
visible/UV radiance simulation (working)
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Comparison, 23.8 GHz
A rain cloud having an effective radius of 200
microns and 0.5 mm water content was put at 850
hPa. One layer ice cloud having the same
effective particle size and 0.1 mm ice water path
is located at 300 hPa
Zenith angle ADA VDISORT DA 0 272.9645
272.9656 272.9655 10 272.9358
272.9369 272.9369 20 272.8342
272.8354 272.8354 30 272.6054
272.6065 272.6064 40 272.0529
272.0542 272.0541 50 271.1577
271.1594 271.1593 65 269.0612
269.0637 269.0635
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Comparison, 10.8 micron
An ice cloud having an effective particle size of
20 microns and 0.1 mm ice water path was located
at 300 hPa and a liquid water cloud at 850 hPa
having an effective particle size of 10 microns
and 0.5 mm are chosen.
Zenith angle ADA VDISORT DA 0
240.7513 240.7514 240.7514 10
240.5512 240.5513 240.5512 20
239.9758 239.9757 239.9757 30
239.1067 239.1065 239.1065 40
238.0799 238.0798 238.0798 50
237.0585 237.0585 237.0585 65
235.6128 235.6129 235.6129
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Phase Function Model
Rayleigh function molecular scattering
(1871) Henyey-Greenstein approximate scattering
(1941) for particles having finite size, no
polarization. HG-Rayleigh scattering matrix
(1)
The normalization factor C and the asymmetry
factor G used in HG part in HG-Rayleigh can
analytically derived from
(2)
-----?
---? Gf(g)
(3)
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Test HG-Rayleigh Scattering Matrix in CRTM
g0.027 r90 micron
Many thanks to Prof. Lious group to provide
phase coefficients using finite-difference time
domain method.
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Test HG-Rayleigh Scattering Matrix in CRTM
g0.27 r276 micron
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WINDSAT Polarimetric Measurements
Stokes components (IR/MW) Intensity
surface/atmosphere and space emission Polarization
surface emission /reflection, atmospheric
scattering The third and the fourth Components
discontinuity /roughness of surfaces, 3D effect,
non-spherical scatterers
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New Measurements and Challenge
Clouds, ice edge, sea ice, clearly delineates
water/land and water/ice boundaries. Geographic
data NOT used!!!
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3D Radiative Transfer Simulation, emissivity1
U component contributed from 3D effect only for
spherical scatterers.
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Simulation and Measurement
Simulations for Bonnie
Windsat observation for Isabel
The third Stokes parameter from Windsat
observations of 3rd Stokes parameter clearly
reveals the vortex structure of surface wind.
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Radiances in Studying Hurricane (Warm Core from
SSMIS Observations at 54.4 GHz)
The SSMIS measures radiances in 24 channels
covering a wide range of frequencies (19 183
GHz) conical scan geometry at an earth incidence
angle of 53 degrees maintains uniform spatial
resolution, across the entire swath of 1700 km.
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AMSU-A Radiances at 54.4 GHz, CRTM needed to
remove the Limb Effect
Due to the limb effect, warm core is no longer
observable. CRTM is needed for quantitatively
analysis.
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Limb Correction
Applying the limb adjustment developed by Dr.
Goldberg et al. (2001), AMSU-A 54.4 GHz can show
the warm core of Katrina.
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Discussion

• ADA mathematically elegant and coding is simple.
  It is fast (60 times faster than original
  double-adding)
• Can be easily extend including visible/UV (use
  sun zenith as an additional stream and one loop
  over azimuth components)
• New HG-Rayleigh is a good approximation for cloud
  scattering in MW and aerosol scattering in IR.
• Polarimetric ocean model available, but lack of
  the polarimetric snow/ice models.