Coordinates of the grid and associated information

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Coordinates of the grid and associated information#

The size of the grid (number of latitudes, longitudes and vertical levels) is chosen when compiling LMDz-SACS, so that is it embedded in the executable.

The input files are then read based on the size of the grid: there is no check on the actual values of the coordinates. Caution is then required to ensure that different grids with the same number of latitudes/longitudes/vertical levels are not used for various files, particularly for the mass fluxes in the same simulation.

vcoord.nc#

The actual longitudes and latitudes are read in vcoord.nc by subroutine dynstate1 (in dyn3d/dynstate0.F90).

The format of vcoord.nc is as follows, with NLON the number of cells in longitude, NLAT the number of cells in latitude, NLEV the number of vertical layers e.g. for a grid defined as 96x95x39 in compile_dispersion, NLON = 96, NLAT = 95, NLEV=39.

netcdf vcoord {
dimensions:
	index = 100 ;
	rlonu = NLON+1 ;
	rlatu = NLAT+1 ;
	rlonv = NLON+1 ;
	rlatv = NLAT ;
	sigs = NLEV ;
	sig = NLEV+1 ;
	temps = UNLIMITED ; // (1 currently)
variables:
	double controle(index) ;
		controle:title = "Parametres de controle" ;
	double rlonu(rlonu) ;
		rlonu:title = "Longitudes des points U" ;
	double rlatu(rlatu) ;
		rlatu:title = "Latitudes des points U" ;
	double rlonv(rlonv) ;
		rlonv:title = "Longitudes des points V" ;
	double rlatv(rlatv) ;
		rlatv:title = "Latitudes des points V" ;
	double ap(sig) ;
		ap:title = "Coefficient A pour hybride" ;
	double bp(sig) ;
		bp:title = "Coefficient B pour hybride" ;
	double cu(rlatu, rlonu) ;
		cu:title = "Coefficient de passage pour U" ;
	double cv(rlatv, rlonv) ;
		cv:title = "Coefficient de passage pour V" ;
	double aire(rlatu, rlonv) ;
		aire:title = "Aires de chaque maille" ;

// global attributes:
		:title = "Fichier demarrage dynamique" ;
		:NCO = "4.3.1" ;
		:nco_openmp_thread_number = 1 ;
}
The size of index (100) is the maximum size of the controle variable which contains various parameters relative to the grid or otherwise and used to initialize variables and/or check against other readings:

  • NLON

  • NLAT

  • NLEV

  • day_ini = ??? a un rapport avec irec lu dans la chimie = le numero du jour dans l’année? Mais pourquoi 400 alors??? XXX

  • year_ini: a initial year - not used in the off-line code

  • rad: the radius of the planet in meters, as an integer i.e. 6400000 for the Earth TO CHECK

  • omeg: the angular velocity of the planet i.e. 7.272205e-05 rad/s for the Earth

  • g: the gravitational acceleration on the planet’s surface i.e 9.8 m/s2 for the Earth

  • cpp: the heat capacity of the atmosphere as an ideal gas i.e. 1004.70885 J/K/kg for air for the Earth

  • kappa: XXXX i.e. 0.285716 for air for the Earth

  • daysec: the number of seconds in a solar day i.e. 86400 for the Earth

  • dtvr: the time step on the on-line model in s.

  • etot0: XX?XX not used in the off-line code

  • ptot0: XX?XX not used in the off-line code

  • ztot0: XX?XX not used in the off-line code

  • stot0: XX?XX not used in the off-line code

  • ang0: XX?XX not used in the off-line code

  • pa: XX?XX not used in the off-line code

  • preff: the standard atmosphere’s pressure at the surface i.e. 101325 Pa on the Earth

  • clon: rate of the zoom of the grid along the longitude. 0 for a regular grid (see routine dyn3d/inigeom.F90)

  • clat: rate of the zoom of the grid along the latitude. 0 for a regular grid (see routine dyn3d/inigeom.F90)

  • grossismx: XX? to do with the zoom?XX. 1 for a regular grid.

  • grossismy:XX? to do with the zoom?XX. 1 for a regular grid.

  • an indicator 0 for a regular grid, 1 for a grid with a zoom

  • dzoomx: extension of the zoom in longitude - only required if zoomed grid

  • dzoomy: extension of the zoom in latitude - only required if zoomed grid

  • an indicator for ysinus XX?XX - only required if regular grid

  • taux: the steepness of the transition for the zoom in longitude - only required if zoomed grid

  • tauy: the steepness of the transition for the zoom in longitude - only required if zoomed grid

Other variables can be found in vcoord.nc if the file is also to serve for initial conditions.

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