Land surface model ¶

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 of the skin surface 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 radiation model to provide radiative fluxes at the surface.

Energy balance solver ¶

The energy balance of the Earth's surface reads \begin{equation}

C_0 \dfrac{dT_0}{dt} = R_\mathrm{n} - H - LE - G

\label{eq:energybalance}

\end{equation} where #!Latex $C_0$, $T_0$ are the heat capacity and radiative temperature of the surface skin layer, respectively. $R_\mathrm{n}$, $H$, $LE$, and $G$ are the net radiation, sensible heat flux, latent heat flux, and ground (soil) heat flux at the surface, respectively. $H$ is calculated as \begin{equation}

H = - \rho\ c_\mathrm{p}\ \dfrac{1}{r_\mathrm{a}} ( \theta_1 - \theta_0 )

\end{equation} where $\rho$ is the density of the air, $c_\mathrm{p} = \unit[1005]{J\ kg^{{-1} K}{-1}}$ is the specific heat at constant pressure, $r_\mathrm{a}$ is the aerodynamic resistance, and $\theta_0$ and $\theta_1$ are the potential temperature at the surface and at the first grid level above the surface, respectively. $r_\mathrm{a}$ 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.

Soil model ¶

Usage ¶

References ¶