Converts from scaled radiance to radianceΒΆ

Performs a conversion of a scaled radiance to a spectral radiance.

Transform: SatRadianceFromScaledRadiance

- filter: Variable Transforms
  Transform: SatRadianceFromScaledRadiance
  transform from:
    name: ObsValue/scaledRadiance
    channels: *all_channels
  number of scale factors: 10
  scale factor variable: MetaData/channelScaleFactor
  scale factor start: MetaData/startChannel
  scale factor end: MetaData/endChannel

Parameters

  • transform from is a required parameter and is of type ufo::Variable. This type requires a name and usually a list of channels. The name will typically be ObsValue/scaledRadiance.

Radiance scaling is done using scale factors for a range of channels. The following variables are required to specify the scale factors and which channels they should be applied to.

  • number of scale factors is a required parameter and specifies how many scale factors need to be read in.

  • scale factor variable is a required parameter and of type ufo::Variable. This specifies the name of the array containing the \(channelScaleFactor\) values to be used with the equation in the method section below.

  • scale factor start is a required parameter and of type ufo::Variable. This specifies the name of the array containing the smallest channel number with which to use a given \(channelScaleFactor\).

  • scale factor end is a required parameter and of type ufo::Variable. This specifies the name of the array containing the largest channel number with which to use a given \(channelScaleFactor\).

  • get scaling factors from multiple arrays is a boolean with a default value of false. By default (false) the arrays associated with scale factor variable, scale factor start and scale factor end values will each be read from single arrays. The array associated with scale factor variable is of size number of scale factors. If set to true the radiance scale factors are expected to be in separate arrays of size number of locations e.g.

    • number of scale factors: 3 then

    • MetaData/channelScaleFactor1, MetaData/channelScaleFactor2, MetaData/channelScaleFactor3

    • MetaData/startChannel1, MetaData/startChannel2, MetaData/startChannel3

    • MetaData/endChannel1, MetaData/endChannel2, MetaData/endChannel3

Example with additional options

This example shows all the options being used with the scaling factors being read in from single arrays. e.g. MetaData/channelScaleFactor(2).

- filter: Variable Transforms
  Transform: SatRadianceFromScaledRadiance
  transform from:
    name: ObsValue/scaledRadiance
    channels: *all_channels
  number of scale factors: 2
  scale factor variable: MetaData/channelScaleFactor
  scale factor start: MetaData/startChannel
  scale factor end: MetaData/endChannel

If the first two entries in MetaData/channelScaleFactor are 7 and 9, in MetaData/startChannel are 1 and 50 and in MetaData/endChannel are 49 and 100. For channels 1 to 49 a scale factor of 7 will be used and for channels 50 to 100 a scale factor of 9 will be used.

This examples shows all the options being used with the scaling factors being read in from separate arrays. Each array is of size, number of locations e.g. MetaData/channelScaleFactor1, MetaData/channelScaleFactor2, MetaData/channelScaleFactor3. In this case the values associated with location one will be read in. This is because the scale factors are independent of location.

- filter: Variable Transforms
  Transform: SatRadianceFromScaledRadiance
  transform from:
    name: ObsValue/scaledRadiance
    channels: *all_channels
  number of scale factors: 3
  scale factor variable: MetaData/channelScaleFactor
  scale factor start: MetaData/startChannel
  scale factor end: MetaData/endChannel
  get scaling factors from multiple arrays: true

Method

The following calculation is performed by this variable transform:

\[L(\nu) = L_{scal}(\nu)10^{-channelScaleFactor}\]
where:

  • \(L(\nu)\) is the spectral radiance at a given wavenumber.

  • \(L_{scal}(\nu)\) is the scaled radiance at a given wavenumber.

  • \(channelScaleFactor\) is the exponent.