Virtual measurement input file

The virtual measurement input file comprises all information required to setup virtual sites within the model domain. Therefore, different global attributes as well as variables are mandatory. Please note, each attribute and variable name is in the format name<id>, where id is an integer number running from 1 to number of stations. The following global attributes must be present in the virtual setup file.

Global attributes	Type	Explanation / Remarks
number_of_stations	NC_INT	Number of considered sites.
origin_x<id>	NC_FLOAT	Origin x-coordinate of the measurement site in UTM.
origin_y<id>	NC_FLOAT	Origin y-coordinate of the measurement site in UTM.
site<id>	NC_CHAR	Name of the site. The name of the site will be used to name the final NetcDF files.
featureType<id>	NC_CHAR	Type of the measurement. Allowed strings are: timeSeries, timeSeriesProfile, and trajectory.
soil_sample<id>	NC_BYTE	Bit value indicating that at the current site also soil quantities should be sampled ( = 1 ). If no soil quantities are sampled this value should be 0.

In the following, the required dimensions/variables will be listed. Please note, NetCDF dimensions of the coordinate variables E_UTM, N_UTM, z, and station_h depend on the type of the measurement. For timeseries, the observation is a stationary one with a fixed number of locations. The number of fixed coordinates (e.g. several sensors at a mast, i.e. for each site there can be several stations) is stored in the dimension station<id>. For timeSeriesProfile or trajectory, however, the coordinate variables depend on the dimensions tray<id> and ntime<id>, being the number of trajectories and the maximum number of timesteps measured for a trajectory, according to the [UC]2 data standard.

Variables	Type	Explanation / Remarks
E_UTM<id> (station<id>) or (tray<id>,ntime<id>)	NC_FLOAT	UTM easting coordinate of the measurement location(s).
N_UTM<id> (station<id>) or (tray<id>,ntime<id>)	NC_FLOAT	UTM northing coordinate of the measurement location(s).
z<id> (station<id>) or (tray<id>,ntime<id>)	NC_FLOAT	Sensor height above sea level. The relative measurement height calculates from z-station_h.
station_h<id> (station<id>) or (tray<id>,ntime<id>)	NC_FLOAT	Surface altitude with respect to sea level.
measured_variables<id>(num_vars<id>,10)	NC_CHAR	List of character strings (length = 10) with variable names.

Creating input setup files

An example setup file for virtual measurements can be found here​. This file was created with the script palm_cvd​ which comes with revision -r4400. To execute the script just run palm_cvd .cvd.config_<your file suffix>. palm_cvd​ can be steered with a configuration file. In case 'real-world' campaigns shall be emulated, palm_cvd​ reads the relevant coordinate information of the observational data, the sampled quantities as well as further metatdata, and merges these into a setup file, so that PALM can internally setup the corresponding sampling locations on the numeric grid. Therefore, palm_cvd​ assumes that the 'real-world' data follows the (UC)2 data standard. With this approach, trajectory measurements (e.g. airborne- or other mobile measurements), stationary tower measurements, or vertical soundings can be emulated in PALM.
Further, independent of any campaign data, it is possible to prescribe additional sites with palm_cvd​, where the respective UTM coordinates and the sampled quantities need to be specified in the config file. At the moment only stationary coordinates can be specified in the config file. However, it is planned to extend palm_cvd and its config file to be able to specify also trajectory measurements or more advanced sampling approaches such as Lidar scans.