Retrieval of thermal infrared cooling rates from eos instruments
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Retrieval of thermal infrared cooling rates from EOS instruments. Daniel Feldman Thursday IR meeting January 13, 2005. Outline. Introduction Methodology Clear vs. Scattering Instrumentation questions Representative scenarios. Introduction.

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Retrieval of thermal infrared cooling rates from eos instruments

Retrieval of thermal infrared cooling rates from EOS instruments

Daniel Feldman

Thursday IR meeting

January 13, 2005


Outline
Outline instruments

  • Introduction

  • Methodology

  • Clear vs. Scattering

  • Instrumentation questions

  • Representative scenarios


Introduction
Introduction instruments

  • State vector components are frequently retrieved to derive standard products

  • We intend to explore in detail infrared cooling rate retrievals in clear and scattering atmospheres using EOS instruments:

    • AIRS

    • TES

    • MODIS/MISR


Motivation
Motivation instruments

  • Closure of infrared radiation balance for input to regional-scale models

  • Evaluate the direct forcing of mineral dust in the infrared via direct measurement.

  • Ultimately improve parameterizations of treatment of radiation in regional-scale models.


Previous work
Previous work: instruments

  • Cooling rate retrieval:

    • Liou and Xue (1988)

    • Liou (2002)

  • AIRS dust:

    • X. Huang (JGR 2004)

    • Thomas (AGU)

    • Pierangelo (ACP 2004)


Liou and xue 1988 2002
Liou and Xue (1988 & 2002) instruments

  • Analytic expression derives spectral and band radiance as a Fredholm integral of cooling rate profile and kernel transmittance function.

  • Assumptions:

    • Utilize either Goody random model or correlated-k

    • Transmittance function assumes constant form over spectral and band regions

    • Planck function for band equals Planck function for spectral channel.

  • Limitations:

    • Clear-sky calculations only, transmission function takes simple form


  • Project Flow Chart instruments


    Methodology
    Methodology instruments

    • Heating/cooling rate profile retrieval methods show distinct differences compared to standard retrievals

      • Standard retrieval performs an inversion of the forward model mapping state vector to radiances.

      • Given full radiance field, heating rate calculation is trivial

      • Challenge of heating/cooling rate retrieval involves determining spectral and channel information to perform forward model heating/cooling rate calculation.


    Clear sky roadmap
    Clear-sky Roadmap instruments

    • Utilize LBRTM with RADSUM

    • For faster calculations, use Modtran 5

    • Develop framework for cooling rate retrieval

      • Test cooling rate retrieval algorithm for H2O (800-960) using AIRS scan pattern

    • Perform retrieval test by first deriving a state vector and then deriving the cooling rate.



    Presence of mineral dust
    Presence of Mineral Dust instruments

    • Included Volz description of dust indices of refraction and tri-model log-normal distribution of aerosols per Seinfeld and Pandis (AOD ~ 1)



    Cooling rate retrieval with scattering in source function
    Cooling rate retrieval with scattering in source function instruments

    • Doubling-adding module on top of LBLRTM called CHARTS

    • User-supplied spectral functions for Modtran 5

    • Derivation by Liou and Xue no longer valid because source function is not Planck function.

      • What are valid assumptions that can be made about source function?


    Current foci of ir mineral dust research
    Current foci of IR mineral dust research instruments

    • Composition

      • Sokolik et al.

    • Phase function/sphericity

    • Spatial/height distribution

      • Pierangelo et al.

      • Mahowald

    • Particle Size Distribution

      • MODIS/MISR products

    • AERONET validation

      • Thomas


    Cooling rate retrieval road map
    Cooling Rate Retrieval Road Map instruments

    • Use Modtran 5 to develop a cooling rate retrieval program similar to that described by Liou.

      • Need validation with AIRS spectra

      • Use of DISORT option

      • Problems with sertran parameters

    • Test out program sensitivity to dust layer using range of dust fields provided by Mahowald.


    Numerical methods for cooling rate retrieval
    Numerical methods for cooling rate retrieval instruments

    • Create cooling rate jacobians with respect to standard state vector

    • Look at variation in band radiance with respect to view angle

    • Explore band radiance variations with respect to state components

    • Effect of uncertainty in measurements and state components (chain rule)

    I = radiance

    x = state vector

    T = heating/cooling (h/c) rate

    z = height coordinate

    k = state vector component index

    j = channel index

    n = matrix index for h/c rate designation


    Questions for future
    Questions for future: instruments

    • AIRS vs. TES

      • TES has coverage over bright surfaces

      • AIRS radiances are better validated

    • Surface emissivity

      • MODIS 5km land emissivity map?

    • Role of AERONET for validation


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