net_radiation package¶
Created on Apr 6 2015 @author: Hector Nieto (hector.nieto@ica.csic.es)
DESCRIPTION¶
This package contains functions for estimating the net shortwave and longwave radiation for soil and canopy layers. Additional packages needed are.
- meteo_utils package for the estimation of meteorological variables.
PACKAGE CONTENTS¶
calc_difuse_ratio()
estimation of fraction of difuse shortwave radiation.calc_emiss_atm()
Atmospheric emissivity.calc_K_be_Campbell()
Beam extinction coefficient.calc_L_n_Kustas()
Net longwave radiation for soil and canopy layers.calc_Sn_Campbell()
Net shortwave radiation.calc_tau_below_Campbell()
Radiation transmission through a canopy.
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pyTSEB.net_radiation.
calc_difuse_ratio
(S_dn, sza, press=1013.25, SOLAR_CONSTANT=1320)[source]¶ Fraction of difuse shortwave radiation.
Partitions the incoming solar radiation into PAR and non-PR and diffuse and direct beam component of the solar spectrum.
Parameters: Returns: - difvis (float) – diffuse fraction in the visible region.
- difnir (float) – diffuse fraction in the NIR region.
- fvis (float) – fration of total visible radiation.
- fnir (float) – fraction of total NIR radiation.
References
[Weiss1985] Weiss and Norman (1985) Partitioning solar radiation into direct and diffuse, visible and near-infrared components, Agricultural and Forest Meteorology, Volume 34, Issue 2, Pages 205-213, http://dx.doi.org/10.1016/0168-1923(85)90020-6.
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pyTSEB.net_radiation.
calc_emiss_atm
(ea, t_a_k)[source]¶ Atmospheric emissivity
Estimates the effective atmospheric emissivity for clear sky.
Parameters: Returns: emiss_air – effective atmospheric emissivity.
Return type: References
[Brutsaert1975] Brutsaert, W. (1975) On a derivable formula for long-wave radiation from clear skies, Water Resour. Res., 11(5), 742-744, htpp://dx.doi.org/10.1029/WR011i005p00742.
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pyTSEB.net_radiation.
calc_longwave_irradiance
(ea, t_a_k, p=1013.25, z_T=2.0, h_C=2.0)[source]¶ Longwave irradiance
Estimates longwave atmospheric irradiance from clear sky. By default there is no lapse rate correction unless air temperature measurement height is considerably different than canopy height, (e.g. when using NWP gridded meteo data at blending height)
Parameters: Returns: L_dn – Longwave atmospheric irradiance (W m-2) above the canopy
Return type:
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pyTSEB.net_radiation.
calc_K_be_Campbell
(theta, x_lad=1, radians=False)[source]¶ Beam extinction coefficient
Calculates the beam extinction coefficient based on [Campbell1998] ellipsoidal leaf inclination distribution function.
Parameters: Returns: - K_be (float) – beam extinction coefficient.
- x_lad (float, optional) – x parameter for the ellipsoidal Leaf Angle Distribution function, use x_lad=1 for a spherical LAD.
References
[Campbell1998] Campbell, G. S. & Norman, J. M. (1998), An introduction to environmental biophysics. Springer, New York https://archive.org/details/AnIntroductionToEnvironmentalBiophysics.
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pyTSEB.net_radiation.
calc_L_n_Kustas
(T_C, T_S, L_dn, lai, emisVeg, emisGrd, x_LAD=1)[source]¶ Net longwave radiation for soil and canopy layers
Estimates the net longwave radiation for soil and canopy layers unisg based on equation 2a from [Kustas1999] and incorporated the effect of the Leaf Angle Distribution based on [Campbell1998]
Parameters: - T_C (float) – Canopy temperature (K).
- T_S (float) – Soil temperature (K).
- L_dn (float) – Downwelling atmospheric longwave radiation (w m-2).
- lai (float) – Effective Leaf (Plant) Area Index.
- emisVeg (float) – Broadband emissivity of vegetation cover.
- emisGrd (float) – Broadband emissivity of soil.
- x_lad (float, optional) – x parameter for the ellipsoidal Leaf Angle Distribution function, use x_lad=1 for a spherical LAD.
Returns: - L_nC (float) – Net longwave radiation of canopy (W m-2).
- L_nS (float) – Net longwave radiation of soil (W m-2).
References
[Kustas1999] Kustas and Norman (1999) Evaluation of soil and vegetation heat flux predictions using a simple two-source model with radiometric temperatures for partial canopy cover, Agricultural and Forest Meteorology, Volume 94, Issue 1, Pages 13-29, http://dx.doi.org/10.1016/S0168-1923(99)00005-2.
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pyTSEB.net_radiation.
calc_L_n_Campbell
(T_C, T_S, L_dn, lai, emisVeg, emisGrd, x_LAD=1)[source]¶ Net longwave radiation for soil and canopy layers
Estimates the net longwave radiation for soil and canopy layers unisg based on equation 2a from [Kustas1999] and incorporated the effect of the Leaf Angle Distribution based on [Campbell1998]
Parameters: - T_C (float) – Canopy temperature (K).
- T_S (float) – Soil temperature (K).
- L_dn (float) – Downwelling atmospheric longwave radiation (w m-2).
- lai (float) – Effective Leaf (Plant) Area Index.
- emisVeg (float) – Broadband emissivity of vegetation cover.
- emisGrd (float) – Broadband emissivity of soil.
- x_LAD (float, optional) – x parameter for the ellipsoidal Leaf Angle Distribution function, use x_LAD=1 for a spherical LAD.
Returns: - L_nC (float) – Net longwave radiation of canopy (W m-2).
- L_nS (float) – Net longwave radiation of soil (W m-2).
References
[Kustas1999] Kustas and Norman (1999) Evaluation of soil and vegetation heat flux predictions using a simple two-source model with radiometric temperatures for partial canopy cover, Agricultural and Forest Meteorology, Volume 94, Issue 1, Pages 13-29, http://dx.doi.org/10.1016/S0168-1923(99)00005-2.
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pyTSEB.net_radiation.
calc_potential_irradiance_weiss
(sza, press=1013.25, SOLAR_CONSTANT=1320, fnir_ini=0.5455)[source]¶ Estimates the potential visible and NIR irradiance at the surface
Parameters: Returns: - Rdirvis (float) – Potential direct visible irradiance at the surface (W m-2)
- Rdifvis (float) – Potential diffuse visible irradiance at the surface (W m-2)
- Rdirnir (float) – Potential direct NIR irradiance at the surface (W m-2)
- Rdifnir (float) – Potential diffuse NIR irradiance at the surface (W m-2)
- based on Weiss & Normat 1985, following same strategy in Cupid’s RADIN4 subroutine.
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pyTSEB.net_radiation.
calc_spectra_Cambpell
(lai, sza, rho_leaf, tau_leaf, rho_soil, x_lad=1, lai_eff=None)[source]¶ Canopy spectra
Estimate canopy spectral using the [Campbell1998] Radiative Transfer Model
Parameters: - lai (float) – Effective Leaf (Plant) Area Index.
- sza (float) – Sun Zenith Angle (degrees).
- rho_leaf (float, or array_like) – Leaf bihemispherical reflectance
- tau_leaf (float, or array_like) – Leaf bihemispherical transmittance
- rho_soil (float) – Soil bihemispherical reflectance
- x_lad (float, optional) – x parameter for the ellipsoildal Leaf Angle Distribution function of Campbell 1988 [default=1, spherical LIDF].
- lai_eff (float or None, optional) – if set, its value is the directional effective LAI to be used in the beam radiation, if set to None we assume homogeneous canopies.
Returns: - albb (float or array_like) – Beam (black sky) canopy albedo
- albd (float or array_like) – Diffuse (white sky) canopy albedo
- taubt (float or array_like) – Beam (black sky) canopy transmittance
- taudt (float or array_like) – Beam (white sky) canopy transmittance
References
[Campbell1998] Campbell, G. S. & Norman, J. M. (1998), An introduction to environmental biophysics. Springer, New York https://archive.org/details/AnIntroductionToEnvironmentalBiophysics.
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pyTSEB.net_radiation.
calc_Sn_Campbell
(lai, sza, S_dn_dir, S_dn_dif, fvis, fnir, rho_leaf_vis, tau_leaf_vis, rho_leaf_nir, tau_leaf_nir, rsoilv, rsoiln, x_LAD=1, LAI_eff=None)[source]¶ Net shortwave radiation
Estimate net shorwave radiation for soil and canopy below a canopy using the [Campbell1998] Radiative Transfer Model, and implemented in [Kustas1999]
Parameters: - lai (float) – Effecive Leaf (Plant) Area Index.
- sza (float) – Sun Zenith Angle (degrees).
- S_dn_dir (float) – Broadband incoming beam shortwave radiation (W m-2).
- S_dn_dif (float) – Broadband incoming diffuse shortwave radiation (W m-2).
- fvis (float) – fration of total visible radiation.
- fnir (float) – fraction of total NIR radiation.
- rho_leaf_vis (float) – Broadband leaf bihemispherical reflectance in the visible region (400-700nm).
- tau_leaf_vis (float) – Broadband leaf bihemispherical transmittance in the visible region (400-700nm).
- rho_leaf_nir (float) – Broadband leaf bihemispherical reflectance in the NIR region (700-2500nm).
- tau_leaf_nir (float) – Broadband leaf bihemispherical transmittance in the NIR region (700-2500nm).
- rsoilv (float) – Broadband soil bihemispherical reflectance in the visible region (400-700nm).
- rsoiln (float) – Broadband soil bihemispherical reflectance in the NIR region (700-2500nm).
- x_lad (float, optional) – x parameter for the ellipsoildal Leaf Angle Distribution function of Campbell 1988 [default=1, spherical LIDF].
- LAI_eff (float or None, optional) – if set, its value is the directional effective LAI to be used in the beam radiation, if set to None we assume homogeneous canopies.
Returns: - Sn_C (float) – Canopy net shortwave radiation (W m-2).
- Sn_S (float) – Soil net shortwave radiation (W m-2).
References
[Campbell1998] Campbell, G. S. & Norman, J. M. (1998), An introduction to environmental biophysics. Springer, New York https://archive.org/details/AnIntroductionToEnvironmentalBiophysics. [Kustas1999] Kustas and Norman (1999) Evaluation of soil and vegetation heat flux predictions using a simple two-source model with radiometric temperatures for partial canopy cover, Agricultural and Forest Meteorology, Volume 94, Issue 1, Pages 13-29, http://dx.doi.org/10.1016/S0168-1923(99)00005-2.