ngauxcart −− create an auxiliary file with dropsonde or satellite wind data for ngradcart
ngauxcart [-n] [-l] [-s svx:svy:reftime] [--satel sigmult:fname] -- jday0 lon0 dx nx lat0 dy ny alt0 dz nz
Ngauxcart reads a Candis file on the standard input consisting of sounding data. Satellite wind data may also be input via a separate file specified on the command line.
Sounding data must be in the form of one sounding per variable slice. Each slice should have the variables "pres" (pressure in hPa), "u_wind" and "v_wind" (wind components in m/s), and the scalar field "jday" which gives the day and time as the number of days, including a fractional part, since the beginning of the year. The pressure and wind component fields should be one-dimensional and depend on the same index field. The pressure itself may be this index field. Levels for which data do not exist should be indicated by the bad data value. The time ordering of the files and the order in pressure (dropsonde or upsonde) do not matter. Conversion of pressure to height is done assuming a standard atmosphere with temperature 300 K at the surface and a temperature decrease with height of 5.5 K/km. The surface pressure is assumed to be 1020 hPa.
Satellite wind data typically should have been converted to Candis using pycSatWinds.py. They must be in the format of one data point per slice, with each data point containing at least the following scalar fields: yday,lon,lat,pres,u_wind,v_wind, where yday,lon,lat, and pres are the year day(including fractional part), longitude(degrees_east), latitude(degrees_north), and pressure level(hPa) of the measurement. U_wind,v_wind are quality controlled components of the wind vector in m/s. pressure is treated in the same way as the sounding case.
The output Candis file is a 3-D grid with three variable fields, "vax", "vay", and "sigma", containing mostly bad data. However, at locations with valid sounding information, the average horizontal wind from soundings is stored in vax and vay. In these locations sigma = 1. (Sigma is used to indicate the weight given to sounding data relative to radar data.) If no sounding information is available at a grid point, but a valid average satellite wind is available there, then it is stored in vax and vay. Sigma is assigned to take the value specified in the command line. This file is used as input to Ngradcart.
The nine mandatory arguments define the grid:
Lon0, lat0, and alt0 define the lower southwest corner of the grid in degrees (longitude and latitude) and kilometers (altitude).
Dx, dy, and dz define the grid interval in kilometers unless the -l flag is invoked, in which case it is degrees (longitude and latitude) and kilometers (altitude).
nx, ny, and nz define the number of grid points in the x, y, and z directions.
Optional arguments are as follows:
--satel sigmult:fname option specify the value of sigma that will be associated with average of that satellite wind and the file name containing the satellite data.
-n specifies that sounding data is not expected on the standard input.
-l produces a lon-lat grid.
-s transforms the positions of systems into the moving reference frame of the system of interest. Note that the -s and -l options work as in Ngradcart.
NGRADCART(1) and the more detailed documentation in this directory.
This program was written by David Raymond. Handling of satellite data was added by Carlos Lopez Carrillo.