The package pos

The package pos helps to create an ensemble of n APs. Especially, their initial special positions (described in isentropic coordinates spanned by longitude, latitude and the potential temperature) and their initial times (in Julian seconds) can be created. The geometric properties (positions, Voronoi areas,...) and the dynamical properties (PV, EQLAT, TEMP, PRESS,....) of the APs are derived from the meteorological input files using the pos***-family of the programs.

In the subdirectory source the most important programs from the pos-family are

• pos_example.f90: An easy example how to create the initial positions of APs

• pos_area.f90: 2d or 3d initial positions of APs with equal isentropic areas (+ PV_INIT)

• pos_3d.f90: Different 2d or 3d initial configurations

• pos_dyn.f90: This program completes the geometric positions of the APs with their dynamical properties, i.e.~PV, EQLAT, TEMP, PRESS,...

• pos_voronoi.f90: Voronoi areas are calculated and added to the pos/init-file

• pos_chem.f90: modifies chemical fields (O3, HCL etc) in init-files on lower and upper bound

Each pos_* program creates an output file in NetCDF data format. It is named:

• pos_xxx_yymmddhh.nc

  xxx : prefix, 1-3 characters
  yymmddhh : year, month, day, hour
  e. g.: pos_ABC_99022812.nc
  

In this file the starting positions of the trajectories (longitudes, latitudes and theta) are stored on the variables LAT, LON and THETA. The corresponding starting times are saved on the variable TIME_INIT. Furthermore, the variables PV_INIT, EQLAT, TEMP, PRESS, TND (density) and VORONOI_AREA can be created.