Convert radiance to brightness temperature¶
The observed values in the level 1 satellite data products are sometimes in spectral radiance values. This variable transform allows for the values to be converted into brightness temperatures using an input spectral radiance and a choice of frequency, wavenumber or wavelength.
Transform: SatBrightnessTempFromRad
- filter: Variable Transforms
Transform: SatBrightnessTempFromRad
transform from:
name: ObsValue/radiance
channels: 1-22
spectral variable:
name: MetaData/sensorCentralWavenumber
channels: 1-22
radiance units: wavenumber
Parameters
transform from
is a required parameter and is of typeufo::Variable
. This type requires a name and usually a list of channels.spectral variable
is a required parameter and is of typeufo::Variable
. This type requires a name and usually a list of channels.radiance units
is a required parameter and takes a string variable which must besensorCentralWavenumber
,sensorCentralWavelength
orsensorCentralFrequency
. In ufo, wavenumbers are in , wavelengths are in and frequencies are in Hz.minimum value
is an optional parameter and specifies the minimum tolerable output value. Any values below this are filled with the missing value indicator.maximum value
is an optional parameter and specifies the maximum tolerable output value. Any values above this are filled with the missing value indicator.planck1
is a parameter which species the value of of the first planck constant, in the formula below. The default value is 1.191042972e-16. This option is only included to allow backwards compatibility and is not recommended to use.planck2
is a parameter which species the value of of the second planck constant, in the formula below. The default value is 1.4387769e-2. This option is only included to allow backwards compatibility and is not recommended to use.
Examples with additional options
The below yaml extract shows how all the filter options can be used:
- filter: Variable Transforms
Transform: SatBrightnessTempFromRad
transform from:
name: ObsValue/radiance
channels: 1-22
spectral variable:
name: MetaData/sensorCentralFrequency
channels: 1-22
radiance units: frequency
minimum value: 150.0
maximum value: 350.0
planck1: 1.191042953e-16
planck2: 1.4387774e-2
Method
The brightness temperature at a given wavenumber (
- where:
is a pre-computed constant ( ) is a pre-computed constant ( ) is the wavenumber in is the radiance.
As shown in the parameters above, there is also the option to provide values for