net_radiation package

Created on Apr 6 2015 @author: Hector Nieto (hnieto@ias.csic.es).

Modified on Jan 27 2016 @author: Hector Nieto (hnieto@ias.csic.es).

DESCRIPTION

This package contains functions for estimating the net shortwave and longwave radiation for soil and canopy layers. Additional packages needed are.

PACKAGE CONTENTS

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:
  • S_dn (float) – Incoming shortwave radiation (W m-2).
  • sza (float) – Solar Zenith Angle (degrees).
  • Wv (float, optional) – Total column precipitable water vapour (g cm-2), default 1 g cm-2.
  • press (float, optional) – atmospheric pressure (mb), default at sea level (1013mb).
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.
pyTSEB.net_radiation.calc_emiss_atm(ea, t_a_k)[source]

Atmospheric emissivity

Estimates the effective atmospheric emissivity for clear sky.

Parameters:
  • ea (float) – atmospheric vapour pressure (mb).
  • t_a_k (float) – air temperature (Kelvin).
Returns:

emiss_air – effective atmospheric emissivity.
Return type:

float

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.
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:
  • ea (float) – atmospheric vapour pressure (mb).
  • t_a_k (float) – air temperature (K).
  • p (float) – air pressure (mb)
  • z_T (float) – air temperature measurement height (m), default 2 m.
  • h_C (float) – canopy height (m), default 2 m,
Returns:

L_dn – Longwave atmospheric irradiance (W m-2) above the canopy
Return type:

float
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:
  • theta (float) – incidence zenith angle.
  • x_lad (float, optional) – Chi parameter for the ellipsoidal Leaf Angle Distribution function, use x_lad=1 for a spherical LAD.
  • radians (bool, optional) – Should be True if theta is in radians. Default is False.
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.
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.
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.
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:
  • sza (float) – Solar Zenith Angle (degrees)
  • press (Optional[float]) – atmospheric pressure (mb)
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.
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.
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.