| 3 | | Usually, the LES model 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. This method isn't possible with cyclic horizontal boundary conditions (because there are no real lateral boundaries). In case of cyclic boundary conditions PALM uses a method developed by Neggers et al. (2012), which is switched on by parameter [../../app/inipar#large_scale_forcing large_scale_forcing]. '''This method does not work with non-cyclic horizontal boundary conditions! ''' Furthermore, it requires to use a flat topography. In case of cyclic boundary conditions, this forcing is prescribed homogeneously in the horizontal directions and thus depends on height and time only. The relation between larger scales (LS) pressure |
| | 3 | Usually, the LES model 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. This method isn't possible with cyclic horizontal boundary conditions (because there are no real lateral boundaries). In case of cyclic boundary conditions PALM uses a method developed by Neggers et al. (2012), which is switched on by parameter [../../app/initialization_parameters#large_scale_forcing large_scale_forcing]. '''This method does not work with non-cyclic horizontal boundary conditions! ''' Furthermore, it requires to use a flat topography. In case of cyclic boundary conditions, this forcing is prescribed homogeneously in the horizontal directions and thus depends on height and time only. The relation between larger scales (LS) pressure |
