| | 41 | If surface heating/cooling or a surface waterflux is applied, a horizontal temperature (humidity) gradient inside the boundary layer will develop, because the temperature/humidity profiles at the inflow are constant. The resulting horizontal differences in buoyancy can trigger an undesired circulation inside the entire domain and instabilities at the inflow boundary (see pt_damping_factor). These effects can be avoided by setting [../../initialization_parameters#recycling_method_for_thermodynamic_quantities recycling_method_for_thermodynamic_quantities] = 'absolute_value'. In this case, the absolute instantaneous values of theta (and q if humidity = .TRUE.) are recycled, so that the potential temperature (humidity) values at the inflow boundary and the recycling plane are identical. With this method there is no horizontal temperature (humidity) gradient and thus the circulation and the instabilities at the inflow boundary will not occur. The mean inflow profile of the potential temperature (humidity) will now change in time (growing boundary layer), in contrast to the inflow profile of all other quantities (e.g. u,v,w) that are constant. In order to avoid this mismatch, the boundary layer height should be kept constant by applying a [../../initialization_parameters#large_scale_subsidence large_scale_subsidence] to scalar quantities. Note that [../../initialization_parameters#pt_damping_factor pt_damping_factor] has no effect if recycling_method_for_thermodynamic_quantities = 'absolute_value'. |
