Changes between Version 8 and Version 9 of doc/tec/nudging

Timestamp:

Apr 24, 2014 8:21:53 PM (11 years ago)

Author:

boeske

Comment:

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doc/tec/nudging

@@ -1 +1 @@
 === Nudging ===
 
-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 order to simulate less idealized flow situations [wiki:doc/tec/lsf  large scale forcing] can be used in PALM.
+Horizontal large scale advection of scalars, large scale subsidence and large scale pressure gradients are then considered and additional tendencies are added to the progonostic equations.
 
-One possibility to account for tendencies in the LES model resulting from larger scales 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). It can be used to simulate less idealized flow situations and to adjust the simulation to an observed state when cyclic boundary conditions are used. In case that continuous measurement data over a longer time period (weeks to month to years) is available (for example from a meteorological super-site or intensive measurement campaigns), these periods can also be simulated with LES. The LES results could for example be used for the comparison with larger-scale models to test parameterizations. The simulation of longer time periods permits to calculate statistics and to identify situations in which the differences to the larger scale model are significant (Neggers et al., 2012).\\
+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). It can be used to adjust the simulation to an observed state when cyclic boundary conditions are used. In case that continuous measurement data over a longer time period (weeks to month to years) is available (for example from a meteorological super-site or intensive measurement campaigns), these periods can also be simulated with LES. The LES results could for example be used for the comparison with larger-scale models to test parameterizations. The simulation of longer time periods permits to calculate statistics and to identify situations in which the differences to the larger scale model are significant (Neggers et al., 2012).\\
 
 Instead of taking nudging data from measurements it is also possible to use data from a larger scale model to drive PALM. Further information about nudging can for example be found in Yamada and Koike, 2011; Schlünzen et al., 2011 or Neggers et al., 2012.\\