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. The observations are stationary ones 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 record dimension station<id>.. Please note, for featureType = trajectory the variables station_h and z are not required but the variable height.

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

Creating input setup files

palm_cvd has two options. First, the custom-mode, where you can manually setup a variable number of measurements points (in UTM coordinates) and specify the respective output variables yourself. However, so far only point- or tower measurements are possible, complex trajectories cannot be described this way. In the second mode, palm_cvd already reads existing NetCDF files from observation campaigns and extract the required information. However, this requires that the input NetCDF files are already formatted according to the [UC]2 data standard. It can be found here.

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 (custom-mode). 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.

palm_cvd reads a config file (a default config file is available in /trunk/SCRIPTS/.cvd.config.default). The measurement input file requires a number of global attributes which you can specify accordingly. If you cannot give any reasonable information here, just leave it empty.

[global]

author = name, mail-adress
contact_person = 
acronym = 
comment = 
data_content = 
dependencies = 
keywords = 
source = 
campaign = iop 1
location = B
site = Ernst Reuter Platz
institution = Leibniz Universität Hannover, Institute of Meterology and Climatology # for (UC)2 conform in/output please follow guidelines in table A3
palm_version = 6.0
references =

In case there exist already NetCDF files with the required metadata, you need to specify the path to the data in the input-section:

[input]

data_path = < path to your observational input data >

If you do not have such files, just leave it empty.

The output path and name of your setup file need to be specified here:

[output]

output_path     = < your output path >
output_filename = vm_driver

In case you want to specify measurement locations manually, you need to adjust the following section in .cvd.config.xxx:

[custom_positions]

# Give the number of custom sampling coordinates
number_positions = 4

# Give site coordinates: E_UTM (m), N_UTM (m), z (m).
# Please give z in meters above ground.
#
#             [ E_UTM,    N_UTM,      z (agl) ]

coordinates1: [ 387670.0, 5819090.0,  4.0     ]
coordinates2: [ 387676.0, 5819139.0,  1.0     ]
coordinates3: [ 387630.0, 5819065.0,  41.0    ]
coordinates4: [ 387270.0, 5819191.0,  8.5     ]

# Give the variables that shall be sampled. Note, there is a 
# number of default variables that will be always sampled, which is:
# u, v, w, theta and hus (mixing ratio).
# On top of these, you can individually prescribe further variables
# for each site. In order to prescribe further variables, please
# follow the naming convention defined in the [UC]2 data standard.

vars_to_be_measured1: [ "u", "v", "w", "theta", "rlus", "rsus" ]
vars_to_be_measured2: [ "rnds", "wdir" ]
vars_to_be_measured3: [ "us" ]
vars_to_be_measured4: [ "utheta", "vtheta", "wtheta", "wspeed" ]

A list of variables that are currently supported and their naming convention can be found here.