1 gaseous_correction

gaseous_correction

1.1 Classes

Name	Description
Gas_correction_CKDMIP	CKDMIP-based gaseous correction using transmission model coefficients.
Gas_correction_O3	Ozone absorption correction module
Gaseous_correction	Gaseous correction module

1.1.1 Gas_correction_CKDMIP

gaseous_correction.Gas_correction_CKDMIP(
    srf,
    thres_correction=0.5,
    list_gases=None,
)

CKDMIP-based gaseous correction using transmission model coefficients.

Computes band-averaged transmission coefficients by integrating over the sensor spectral response function (SRF). Supports correction for multiple absorbing gases (O3, H2O, CH4, CO2, N2, N2O, etc.) using a parametric model T = Teq ** (x ** n) where x is the normalized column amount.

1.1.1.1 Parameters

Name	Type	Description	Default
srf	xr.Dataset	The sensor spectral response function. Must contain all bands present in the input dataset.	required
thres_correction	float	Minimum transmission threshold. Transmission values below this threshold are replaced with NaN to avoid extreme reflectance corrections. Default is 0.5.	0.5
list_gases	list of str	Gases to include in the correction. Default is all available gases in the transmission model: ['CH4', 'CO2', 'H2O', 'N2', 'N2O', 'O2', 'O3'].	None

1.1.1.2 Methods

Name	Description
process_block	Apply CKDMIP gaseous correction to a single block.

1.1.1.2.1 process_block

gaseous_correction.Gas_correction_CKDMIP.process_block(block)

Apply CKDMIP gaseous correction to a single block.

Computes the combined transmission from all gases (O3, H2O, etc.) using log-space accumulation for numerical stability: prod(Teq^(xn)) = exp(sum(x^n * log(Teq))) then divides the reflectance by the total gas transmission.

1.1.2 Gas_correction_O3

gaseous_correction.Gas_correction_O3(
    ds,
    srf,
    dir_common,
    K_OZ=None,
    spectral_dim='bands',
)

Ozone absorption correction module

1.1.2.1 Methods

Name	Description
run	Apply O3 transmission

1.1.2.1.1 run

gaseous_correction.Gas_correction_O3.run(bands, Rtoa_gc, ok, air_mass, ozone)

Apply O3 transmission

ozone : total column in Dobson Unit (DU)

1.1.3 Gaseous_correction

gaseous_correction.Gaseous_correction(
    ds,
    srf=None,
    input_var='rho_toa',
    ouput_var='rho_gc',
    spectral_dim='bands',
    K_NO2=None,
    K_OZ=None,
    no2_correction='legacy',
    gas_correction='o3_legacy',
    list_gases=None,
    dtype='float32',
    **kwargs,
)

Gaseous correction module

1.1.3.1 Parameters

Name	Type	Description	Default
ds	xr.Dataset	The dataset to which the gaseous correction is applied. The bands of ds shall be contained in srf.	required
srf	xr.Dataset	The sensor spectral response function (SRF).	None
input_var	str	Name of the input variable in ds (Top of atmosphere reflectance)	'rho_toa'
ouput_var	str	Name of the output variable in ds	'rho_gc'
spectral_dim	str	Name of the spectral dimension in input_var and output_var	'bands'
no2_correction	str	Method for NO2 correction. Options: “legacy” (default, uses climatology-based NO2 correction) or any other value to skip.	'legacy'
gas_correction	str	Method for gas correction. Options: “o3_legacy” (default, legacy O3 correction), “ckdmip” (CKDMIP transmission coefficients).	'o3_legacy'
K_NO2	Dict | None	Explicit NO2 absorption coefficients per band. If None, coefficients are calculated from the SRF or central wavelengths.	None
K_OZ	Dict | None	Explicit ozone absorption coefficients per band. If None, coefficients are calculated from the SRF or central wavelengths.	None
list_gases	list of str	Subset of gases to include in the CKDMIP correction (used when gas_correction='ckdmip'). Valid gas names are ['CH4', 'CO2', 'H2O', 'N2', 'N2O', 'O2', 'O3']. If None (default), all gases available in the transmission model are used.	None

1.1.3.2 Example

Apply gaseous correction to l1

Gaseous_correction(l1).apply()