Changes between Version 2 and Version 3 of palm

Timestamp:

Dec 7, 2017 8:29:04 AM (7 years ago)

Author:

maronga

Comment:

--

palm

@@ -3 +3 @@
 
 In the LES mode, the filtering process yields four subgrid-scale (SGS) covariance terms. These SGS terms are parametrized using a 1.5-order closure after Deardorff (1980). PALM uses the modified version of Moeng and Wyngaard (1988) and Saiki et al. (2000). The closure is based on the assumption that the energy transport by SGS eddies is proportional to the local gradients of the mean quantities.
+
+The following sections outline the most important specifics of PALM. For a more detailed description, see [wiki:doc PALM documentation] and related publications (Raasch and Schröter, 2001; Maronga et al., 2015).
 
 == Discretization in time and space ==
@@ -16 +18 @@
 Following Monin-Obukhov similarity theory (MOST) a constant flux layer can be assumed as boundary condition between the surface and the first grid level where scalars and horizontal velocities are defined. In PALM we assume that MOST can be also applied locally and we therefore calculate local fluxes, velocities, and scaling parameters. This scheme involves calculation of the Obukhov length ''L'', which can be either done based on variables of the previous time step ("circular"), via a Newton iteration method, or via a look-up table for the stability parameter ''z/L''.
 
+== External forcing and nesting ==
+Usually, PALM is used to simulate the flow in the boundary layer which is a certain part of the atmosphere. Processes occurring on larger scales than those in the boundary layer including large scale advection of scalars, large scale pressure gradients or large scale subsidence have also to be considered in the model, especially when focusing on realistic situations observed during measurement campaigns. In limited domain models with non-cyclic boundary conditions the large scale state enters through the boundary conditions at the lateral walls, and is usually taken from larger-scale models. An additional possibility to account for tendencies in the LES model resulting from larger scales than those in the boundary layer is the usage of nudging. Nudging is a (Newtonian) relaxation technique which adjusts the large-eddy simulation to a given, larger scale flow situation (Anthes, 1974; Stauffer and Bao, 1993). Alternatively, a nesting system is available which allows for self-nesting of PALM, i.e. running a parent domain run at coarse grid resolution and large model domain with a nested child model domain run at finer resolution and smaller domain.
+
+== Ocean option and coupling to atmosphere ==
+PALM allows for studying the ocean mixed layer (OML) by using an ocean option where the sea surface is defined at the top of the model, so that negative values of ''z'' indicate the depth.
+
+A coupled mode for the atmospheric and oceanic versions of PALM has been developed in order to allow for studying the interaction between turbulent processes in the ABL and OML. The coupling is realized by the online exchange of information at the sea surface (boundary conditions) between two PALM runs (one atmosphere and one ocean). The atmospheric model uses a constant flux layer and transfers the kinematic surface fluxes of heat and moisture as well as the momentum fluxes to the oceanic model. Flux conservation between the ocean and the atmosphere requires an adjustment of the fluxes for the density of water.
+
+== Embedded models ==
+PALM comes with an increasing number of embedded models:
+  * Cloud microphysics
+  * Lagrangian particle model (LPM)
+  * Lagrangian cloud model (LCM)
+  * Canopy model
+  * 1D model for precursor runs
+  * Land surface model
+  * Radiation models
+  * Wind turbine model 
+
+For more details, see [wiki:doc PALM documentation].