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SOSVRT: A Polarized Radiative Transfer Model and its Application

SOSVRT: A Polarized Radiative Transfer Model and its Application. Minzheng Duan dmz@mail.iap.ac.cn Institute of Atmospheric Physics, CAS, Beijing. Brief introduction of Institute of Atmospheric Physics, Chinese Academy of Science. LASG (numerical modeling of Climate)

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SOSVRT: A Polarized Radiative Transfer Model and its Application

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  1. SOSVRT: A Polarized Radiative Transfer Model and its Application MinzhengDuan dmz@mail.iap.ac.cn Institute of Atmospheric Physics, CAS, Beijing

  2. Brief introduction ofInstitute of Atmospheric Physics, Chinese Academy of Science

  3. LASG (numerical modeling of Climate) LAPC (BNL physics and chemistry) RCE-TEA (Regional climate of East-Asia) LACS (Cloud and Severe Strom) CMSR(Monsoon) NZC (Co-center) LAGEO (Remote Sens. & Middle Atmos.)

  4. Key Laboratory of Middle Atmosphere and Global Environment Observation Atmospheric Dynamics for the middle Atmosphere Radiation Transfer and remote sensing Atmospheric Electricity Atmospheric and Environmental Observation Techniques MWR MMR Wind Profile Radar

  5. Outline • Background • SOSVRT • Techniques to speed up SOS • Impact of vertical info. • Summary

  6. Why Polarization • Nature of Atmosphere scattering: • Polarization ~Properties of particles in Atmosphere • Errors due to neglecting polarization • More polarized instrument (POLDER, PARASOL, CIMEL, APS, DPC……)

  7. Instrument Design If the input light is polarized, errors due to the instrumentation could be corrected after measurement through radiative transfer simulations

  8. Radiative Transfer Equation Absorption

  9. Radiative Transfer Equation

  10. Numerical Algorithms • MC: (Kattawar & Plass, 1968; Roberti & Kummerow, 1999; Wu & Lu, 989) • Adding-doubling method (De Haan et al., 1987; Evans & Stephens, 1991; Hansen, 1971) • Inverse of matrix method(Schulz et al., 1999; Siewert, 2000) • Successive order of Scattering ( Duan, 2004; 6s; Pstar) • SCIATRAN (2009?)

  11. Why Successive order of Scattering • Provides clear physical insights • Easy treating for vertical inhomo. • Parameterization in climate models and inverse methods

  12. ? Successive order of Scattering • Shortcoming: • Slow convergence with a high single scattering albedo & optically thick media

  13. How many orders needed ?

  14. For the polarization It is supposed before that just a few orders are needed ？ Sergey V Korkin, Alexei I Lyapustin and Alexander L Marshak, On the accuracy of double scattering approximation for atmospheric polarization computations, JQSRT 113(2):172-181 (2012)

  15. Rayleigh scattering Small aerosols

  16. Large Aerosol Water cloud

  17. ice cloud(Phase function from Yang.)

  18. Techniques used in SOSVRT • Analytical Fourier Decomposition of Phase Matrix • mutual inverse operators • symmetric relationships • Truncation of scattering orders • Post-processing procedure

  19. Techniques to speeding up Analytical Fourier Decomposition

  20. Techniques to speeding up Mutual inverse operators By using above equation , matrix multiplication will be replaced by multiplication of matrix diagonal, the number of multiplications reduces by 75%

  21. Techniques to speeding up Symmetric relationships reduces by 1/2 reduces by 3/4

  22. Post-processing procedure

  23. Tests and comparisons • randomly-oriented oblate spheroids with • a/b=1.999987 • x=3 • m=1.53-0.006i • w=0.973527 • t=1 • Model 2 of Fuick et al, JQSRT,47, 1992

  24. Tests and comparisons

  25. Impact of vertical stratification • the whole atmosphere is artificially stratified as a pack of many homogeneous sub-layers with different optical propertiies.

  26. Impact on radiance

  27. 0 25 50 75 0 25 50 75

  28. Impact on Fluxes

  29. How many layers need?

  30. Impacts on O2-A & CO2 SWIR bands Gas Absorption in O2-A & CO2 SWIR bands

  31. Normalized Refectance at TOA theta=5 Theta=35 Theta=65

  32. Summary • The SOS method is often thought to be inefficient for optically thick media • An efficient RTM has been developed, and several techniques are used to speed up the SOS method, post-processing is introduced to improve the accuracy. • Could be used for clear sky(aerosol), and optically thin atmosphere(cirrus) • Take Care of the errors due to stratification • Free of charge

  33. 谢谢

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