Surface types

Surface types are required by the scene objects (EarthScene) to carry information about what type of surface model the radiative transfer calculations should use. As laid out in the EarthScene type, one surface is mapped to exactly one spectral window - there is currently no support for "sharing" a surface between different spectral windows. If users want to fix the retrieved surface properties between two separate retrieval windows, they must manually impose correlations through the prior covariance matrix.

The NoSurface type can be used for up-looking instrument retrievals (e.g. sun-tracking spectrometers).

The BeerLambertRTMethod currently supports only the NoSurface and LambertianPolynomialSurface surface types. The MonochromaticRTMethod using the XRTM solver requires a different set of surface properties as they are set-up to be potentially polarized BRDFs with strong angular dependence, and they can be recognized by the "Kernel" suffix in the surface type name. For example, LambertianPolynomialKernel represents a (spectrally varying) Lambertian surface in the XRTM context, and [RPVPolynomialKernel] is a (spectrally varying) surface characterized by the Rahman-Pinty-Verstraete[RPV1993] kernel.

RetrievalToolbox.LambertianPolynomialKernel — Type

  • swin::AbstractSpectralWindow

  • order::Int64

  • coefficients::Vector

Type that implements the Lambertian BRDF kernel for which the BRDF amplitude can be a spectrally varying polynomial of arbitrary order.

RetrievalToolbox.LambertianPolynomialSurface — Type

  • swin::AbstractSpectralWindow

  • order::Int64

  • coefficients::Vector

Type to hold a Lambertian surface for which the amplitude can be a spectrally varying polynomial of arbitary order order.

RetrievalToolbox.RPVPolynomialKernel — Type

  • swin::AbstractSpectralWindow

  • order::Int64

  • coefficients::Vector

  • hotspot::Any

  • asymmetry::Any

  • anisotropy::Any

Type that implements the Rahman-Pinty-Verstraete BRDF kernel for which the BRDF amplitude can be a spectrally varying polynomial of arbitrary order. The other three parameters, hotspot asymmetry and anisotropy, are kept fixed throughout the spectral window which this surface is attached to.