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Changes between Version 14 and Version 15 of doc/tec/lsm

Timestamp:: Apr 5, 2016 7:43:22 AM (9 years ago)
Author:: maronga
Comment:: --

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doc/tec/lsm

-                      v14
+                      v15
 == Overview ==
 Since r1551 a full land surface model (LSM) is available in PALM. It consists of a four layer soil model, predicting soil temperature and moisture content, and a solver for the energy balance, predicting the temperature of the skin layer. Moreover, a liquid water reservoir accounts for the presence of liquid water on plants and soil due to precipitation. The implementation is based on the ECMWF-IFS land surface parametrization (H-TESSEL) and its adaptation in the DALES model (Heus et al. 2010).
 Note that the use of the LSM requires using a [wiki:doc/tec/radiation radiation model] to provide radiative fluxes at the surface.
+Since r1551 a full land surface model (LSM) is available in PALM. It consists of a four layer soil model, predicting soil temperature and moisture content, and a solver for the energy balance, predicting the temperature of the skin layer. Moreover, a liquid water reservoir accounts for the presence of liquid water on plants and soil due to precipitation. The implementation is based on the ECMWF-IFS land surface parametrization (H-TESSEL) and its adaptation in the DALES model ([#heus Heus et al. 2010]).
+Note that the use of the LSM requires using some kind of [wiki:doc/tec/radiation radiation model] to provide radiative fluxes at the surface.
 == Energy balance solver ==
 …
 \end{equation*}
 }}}
 where ''ρ'' is the density of the air, ''c'',,p,, = 1005 J kg^-1^ K^-1^$ is the specific heat at constant pressure, ''r'',,a,, is the aerodynamic resistance, and ''θ'',,0,, and ''θ'',,1,, are the potential temperature at the surface and at the first grid level above the surface, respectively. ''r'',,a,, is calculated via Monin-Obukhov similarity theory, based on roughness lengths for heat and momentum and the assumption of a constant flux layer between the surface and the first grid level:
+where ''ρ'' is the density of the air, ''c'',,p,, = 1005 J kg^-1^ K^-1^ is the specific heat at constant pressure, ''r'',,a,, is the aerodynamic resistance, and ''θ'',,0,, and ''θ'',,1,, are the potential temperature at the surface and at the first grid level above the surface, respectively. ''r'',,a,, is calculated via Monin-Obukhov similarity theory, based on roughness lengths for heat and momentum and the assumption of a constant flux layer between the surface and the first grid level:
 {{{
 #!Latex
 …
 \end{equation*}
 }}}
 where ''u'',,*,, and ''θ'',,*,, are the friction velocity and the characteristic temperature scale according to Monin-Obukhov similarity scaling.
+where ''u'',,*,, and ''θ'',,*,, are the friction velocity and the characteristic temperature scale according to Monin-Obukhov similarity scaling (these are calculated in [source:trunk/SOURCE/surface_layer_fluxes.f90 surface_layer_fluxes.f90]).
 === Parameterization of ''G'' ===
 ''G'' is parametrized as (Duynkerke 1999)
+''G'' is parametrized as (see [#dynkerke Duynkerke 1999])
 {{{
 #!Latex
 …
 $m_\mathrm{soil,1}$: Soil moisture of the uppermost layer)
 }}}
+The total evapotranspiration is then calculated as
+{{{
+#!Latex
+\begin{equation*}
+LE = c_\mathrm{veg} (1 - c_\mathrm{liq})\ LE_\mathrm{veg} + c_\mathrm{liq}\ c_\mathrm{veg}\ LE_\mathrm{liq} + (1 - c_\mathrm{veg}) \ LE_\mathrm{soil}
+\end{equation*}
+}}}
+where ''c'',,veg,,, and ''c'',,liq,, is the surface fraction covered with vegetation and liquid water, respectively.
 === Prognostic equation for the liquid water reservoir ===
 …
 \end{equation*}
 }}}
+The total evapotranspiration is then calculated as
+{{{
+#!Latex
+\begin{equation*}
+LE = c_\mathrm{veg} (1 - c_\mathrm{liq})\ LE_\mathrm{veg} + c_\mathrm{liq}\ c_\mathrm{veg}\ LE_\mathrm{liq} + (1 - c_\mathrm{veg}) \ LE_\mathrm{soil}
+\end{equation*}
+}}}
+where ''c'',,veg,,, and ''c'',,liq,, is the surface fraction covered with vegetation and liquid water, respectively.
+For positive values of ''LE'',,liq,,, liquid water is evaporating from the surface, while negative values indicate precipitation (rain, dew).
 == Soil model ==
 The soil model consists of prognostic equations for the soil temperature and the volumetric soil moisture which are solved for multiple layers. The soil model only takes into account vertical transport within the soil and no ice phase is considered. By default, the soil model consists of four layers, in which the vertical heat and water transport is modelled using the Fourier law of diffusion and Richards' equation, respectively. Also, root fractions can be assigned to each soil layer to to account for the explicit water withdrawal of plants used for transpiration from the respective soil layer.
+The soil model consists of prognostic equations for the soil temperature and the volumetric soil moisture which are solved for multiple layers. The soil model only takes into account vertical transport within the soil and no ice phase is considered. By default, the soil model consists of four layers, in which the vertical heat and water transport is modelled using the Fourier law of diffusion and Richards' equation, respectively. Also, root fractions can be assigned to each soil layer to account for the explicit water withdrawal of plants used for transpiration from the respective soil layer.
 === Soil heat transport ===
 …
 }}}
 The hydraulic diffusion coefficient is calculated after Clapp and Hornberger (1978) as
+The hydraulic diffusion coefficient is calculated after [#clapp Clapp and Hornberger (1978)] as
 {{{
 #!Latex
 …
 }}}
 The hydraulic conductivity is calculated either after Van Genuchten (1980) (as in H-TESSEL):
+The hydraulic conductivity is calculated either after [#vangenuchten Van Genuchten (1980)] (as in H-TESSEL):
 {{{
 #!Latex
 …
 \end{equation}
 }}}
 or after Clapp anf Hornberger (1978):
+or after [#clapp Clapp and Hornberger (1978)]:
 {{{
 #!Latex
 …
 }}}
 For more details, see also Viterbo et al. (1995) and [#balsamo Balsamo et al. (2009)].
+For more details, see also [#viterbo Viterbo et al. (1995)] and [#balsamo Balsamo et al. (2009)].
 == Technical details ==
 …
 $T_\mathrm{soil}$: temperature of the uppermost soil layer
 }}}
+Time stepping is the same as in the atmospheric part of the model (default: 3rd-order Runge-Kutta). Note that for ''C'',,sk,, = 0, the prognostic equation for ''T'',,0,p,, reduces to a diagnostic equation:
+Time stepping is the same as in the atmospheric part of the model (default: 3rd-order Runge-Kutta).
+Note that for ''C'',,sk,, = 0, the prognostic equation for ''T'',,0,p,, reduces to a diagnostic equation:
 {{{
 #!Latex
 …
 == References ==
 * [=#balsamo]Balsamo G, Vitebo P, Beljaars A, van den Hurk B, Hirschi M, Betts AK, Scipal K. 2009. A revised hydrology for the ECMWF model: Verification from field site to terrestrial water storage and impact in the integrated forecast system. J. Hydrometeorol. 10: 623–643.
+* [=vangenuchten]
+* [=clapp]
+* [=#clapp]Clapp, RB and Hornberger GM. 1978. Empirical Equations for Some Soil Hydraulic Properties. Water Res. Res., 14: 601-604.
+* [=#duynkerke]Duynkerke PG. 1999. Turbulence, radiation and fog in Dutch stable boundary layers. Boundary-Layer Meteorol. 90: 447–477, doi:10.1023/A:1026441904734.
+* [=#heus]Heus T, Van Heerwaarden CC, Jonker HJJ, Siebesma AP, Axelsen S, Dries K, Geoffroy O, Moene AF, Pino D, De Roode SR, Vil`a-Guerau de Arellano J. 2010. Formulation of the dutch atmospheric large-eddy simulation (dales) and overview of its applications. Geosci. Model Dev. 3: 415–444.
 * [=#jarvis]Jarvis PG. 1976. The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field. Philos. Trans. Roy. Soc. London 273B: 593–610.
+* [=#heus]Heus T, Van Heerwaarden CC, Jonker HJJ, Siebesma AP, Axelsen S, Dries K, Geoffroy O, Moene AF, Pino D, De Roode SR, Vil`a-Guerau de Arellano J. 2010. Formulation of the dutch atmospheric large-eddy simulation (dales) and overview of its applications. Geosci. Model Dev. 3: 415–444.
+* [=#duynkerke]Duynkerke PG. 1999. Turbulence, radiation and fog in Dutch stable boundary layers. Boundary-Layer Meteorol. 90: 447–477, doi:10.1023/A:1026441904734.
+* [=#vangenuchten]van Genuchten M. 1980. A closed form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Amer. J. 44: 892–898.
 * [=#viterbo]Viterbo P, Beljaars ACM. 1995. An Improved Land Surface Parameterization Scheme in the ECMWF Model and Its Validation. J. Climate 8: 2716–2748.