NEDAS.datasets.amsr2.rtm_amsr_fcts module

AMSR Ocean Algorithm; Frank J. Wentz, Thomas Meissner; Remote Sensing Systems; Version 2; November 2; 2000.

Tb=f(V,W,L,Ts,Ti,c_ice)

  • V: columnar water vapor [mm]

  • W: windspeed over water [m/s]

  • L: columnar cloud liquid water [mm]

  • Ts: sea surface temperature [K]

  • Ti_ansrx: ice effective temperature [K]

  • c_ice: ice concentration [0-1]

  • e_icex: ice emissivity

NEDAS.datasets.amsr2.rtm_amsr_fcts.calc_epsilon(Ts, channel, freq=None)[source]

Calculates the dielectric constant ε of sea water (epsilon)

Parameters:

  • Ts (float, numpy array) – Surface temperature

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

epsilon – Dielectric constant of sea water

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.calc_ocean_emissivity(W, Ts, theta, channel)[source]

Calculates emissivity of sea surface

Parameters:

  • W (float, numpy array) – Windspeed over water

  • Ts (float, numpy array) – Surface temperature

  • theta (float) – Incidence angle

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

emissivity – Sea surface emissivity

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.calc_emissivity(V, L, Ts, Tb, theta, channel)[source]

Calculates effective surface emissivity

Parameters:

  • V (float, numpy array) – Columnar water vapor

  • L (float, numpy array) – Columnar cloud liquid water

  • Ts (float, numpy array) – Surface temperature

  • Tb (float or numpy array) – Observed brightness temperature

  • theta (float) – Incidence angle

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

emissivity – Effective surface emissivity

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.calc_transmittance(V, L, Ts, TD, theta, channel)[source]

Calculates athmosphere transmittance

Parameters:

  • V (float, numpy array) – Columnar water vapor

  • L (float, numpy array) – Columnar cloud liquid water

  • Ts (float, numpy array) – Surface temperature

  • TD (float, numpy array) – Effective downwelling temperature

  • theta (float) – Incidence angle

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

tau – Athmosphere transmittance

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.calc_down_up_welling(V, L, Ts, theta, channel)[source]

Calculates atmosphere up and downwelling temperatures

Parameters:

  • V (float, numpy array) – Columnar water vapor

  • L (float, numpy array) – Columnar cloud liquid water

  • Ts (float, numpy array) – Surface temperature

  • theta (float) – Incidence angle

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

TD, TBD, TU, TBU, tau – TD : Effective downwelling temperature TBD : Downwelling brightness temperature TU : Effective upwelling temperature TBU : Upwelling brightness temperature tau : Athmosphere transmittance

Return type:

floats or numpy arrays

NEDAS.datasets.amsr2.rtm_amsr_fcts.calc_omega(W, tau, channel, freq=None)[source]

Calculates correction factor for sea surface reflectance

Parameters:

  • W (float, numpy array) – Windspeed over water

  • tau (float or numpy array) – Athmosphere transmittance

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

omega – Correction factor for sea surface reflectance

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.observed_tb(V, W, L, Ts, ice_conc, theta, channel)[source]

Calculates brightness temperature as seen by the sensor over sea. No correction for wind direction.

Parameters:

  • V (float, numpy array) – Columnar water vapor

  • W (float, numpy array) – Windspeed over water

  • L (float, numpy array) – Columnar cloud liquid water

  • Ts (float, numpy array) – Surface temperature

  • ice_conc (float, numpy array) – Sea ice concentration

  • theta (float) – Incidence angle

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

Tb – Observed brightness temperature

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.simulated_tb_v01(V, W, L, Ts, ice_conc, theta, channel)[source]

Simulates brightness temperature from constant ice and water emissivity values. No correction for wind direction.

Parameters:

  • V (float, numpy array) – Columnar water vapor

  • W (float, numpy array) – Windspeed over water

  • L (float, numpy array) – Columnar cloud liquid water

  • Ts (float, numpy array) – Surface temperature

  • ice_conc (float, numpy array) – Sea ice concentration

  • theta (float) – Incidence angle

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

Tb – Simulated brightness temperature

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.simulated_tb_v02(V, W, L, Ts, ice_conc, theta, channel)[source]

Simulates brightness temperature from constant ice and computed water emissivity values. No correction for wind direction.

Parameters:

  • V (float, numpy array) – Columnar water vapor

  • W (float, numpy array) – Windspeed over water

  • L (float, numpy array) – Columnar cloud liquid water

  • Ts (float, numpy array) – Surface temperature

  • ice_conc (float, numpy array) – Sea ice concentration

  • theta (float) – Incidence angle

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

Returns:

Tb – Simulated brightness temperature

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.calc_emissivity_plan(x, y, channel, dict_coeffs)[source]

Computes emissivity (z) as a plan: z = a1*x + a2*y + c Coefficients a1, a2, c have been computed from TPD files with SIC = 1

Parameters:

  • x (float, numpy array) – input variables of plane with x, y = T2M, DAL

  • y (float, numpy array) – input variables of plane with x, y = T2M, DAL

  • a1 (float) – coefficients of equation of plane

  • a2 (float) – coefficients of equation of plane

  • c (float) – value of intercept

Returns:

z – Simulated emissivity

Return type:

float or numpy array

NEDAS.datasets.amsr2.rtm_amsr_fcts.simulated_tb_v03(V, W, L, Ts, ice_conc, theta, channel, ow_bias=0, opt_em=0, dal=None, dict_coeffs={}, file_atlas=None, file_ml=None)[source]

Simulates brightness temperature from computed ice and water emissivity values. No correction for wind direction.

Parameters:

  • V (float, numpy array) – Columnar water vapor

  • W (float, numpy array) – Windspeed over water

  • L (float, numpy array) – Columnar cloud liquid water

  • Ts (float, numpy array) – Surface temperature

  • ice_conc (float, numpy array) – Sea ice concentration

  • theta (float) – Incidence angle

  • channel ({'6v', '6h', '10v', '10h', '19v', '19h', '22v', '22h', '37v', '37h', '50v', '50h', '52v', '52h', '90v', '90h'})

  • ow_bias (float, scalar) – open water bias (K) for Tbs

  • opt_em (float, scalar) – 0:’fix’, 1:’dal’, 2:’atlas’

  • dal (float, numpy array) – Distance Along the Line (K)

  • dict_coeffs (dictionnary, dict_coeffs[channel]['a1'], dict_coeffs[channel]['a2'], dict_coeffs[channel]['c']) – Coefficients for computation of ice emissivity from DAL and Ts

Returns:

Tb – Simulated brightness temperature

Return type:

float, numpy array