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The package i3d
The program i3d.f90 can be used for interpolation of the CLaMS output (usually stored on irregular grid in init*.nc) on an arbitrary different irregular grid (e.g. experimental data). In particular, it can be applied for interpolation on a spatially highly resolved regular grid that, on the one side, does not destroy the fine structures in the spatial distributions calculated with CLaMS and, on the other side, makes easier the handling of the CLaMS output (e.g. plotting).
How to get the source code
The source code of this package is under control of the CVS (Concurrent Version System) utility. To get the source code the environment variable CVSROOT must be set to /usr/local/icg/icg1/archive. The command
cvs co -P i3d
creates a directory i3d in the current working directory and copies the current version of the i3d package to this directory.
The directory i3d includes the following subdirectories:
doc: latex file for documentation
mod: module files
obj: object files
source: source code
templates: templates for configuration file
Compiling
The program can be compiled on different platforms with the makefile stored in the directory i3d:
gmake i3d
The program will be compiled for the used platform and an executable i3d will be created.
Configuration file
The options for the execution of i3d are set in the configuration file i3d.inp:
1) y ! north_hemisphere (y/n)
2) 30., 90. ! lat_min, lat_max
3) 3 ! 0=nearest, 1=weighted, 2=both, 3=weighted_new
4) 2 ! number of tags
CH4
O3
5) n ! use one init-file
6) /private/CNx_ECN_3d_24_1.5 ! input directory (init-files)
CNx ! prefix of init-files (3 character)
7) data/mipas_isen_noonpos_030103_030131.nc ! input file (aircraft/satellite data)
8) outdir ! output directory
9) testout ! output prefix
10) y ! write warnings (y/n) 1) y ! north_hemisphere (y/n)
2) 30., 90. ! lat_min, lat_max
3) 3 ! 0=nearest, 1=weighted, 2=both, 3=weighted_new
4) 2 ! number of tags
CH4
O3
5) y ! use one init-file
6) test1/init_BN0_02100112.nc ! init-file
7) test1/pos_A_0_01100112.nc ! input file (aircraft/satellite data)
8) test1 ! output directory
9) testout ! output prefix
10) n ! write warnings (y/n)Remarks:
- Start triangle for the walking triangle algorithm: y/n -- north/south hemisphere (does not work. Now, the $n/2$ ($n-$number of all triangles) is chosen as a start triangle).
- Latitude range of the (external) grid where interpolations have to be determined.
Number of species to add to input file (line 7) and their names. If Variable TRACER should be added to input file, it should be specified at the end of the list.
If the number of species is "0", all species from CLaMS file (line 6) listed on Variable SPECIES and Variable TRACER are added to input file.- use one CLaMS file for all dates in input file (y/n)
CLaMS input files:
line5='y': Name of CLaMS file
line5='n': directory with CLaMS output and prefix of these files- Output directory
Name of the NetCDF output file
- Write warnings if triangle is not found
The walking triangle algorithm
The walking triangle algorithm is described in [1]. It describes how in 2D (and 3D) a Delaunay triangle can be found that contains a given point X. The walking triangle uses the following criterion to find such a triangle:
X is inside of a triangle ABC if the given point X and the triangle point that does not define the considered triangle side are on the same side of the considered triangle side for each of the 3 possible sides of the triangle.
E.g. for the side AB, the following relation has to be valid:
with
. This means that X and C are onthe same side of AB if both scalar products have the same sign.
The walking triangle algorithm checks if X is inside of the the start triangle by applying criterion for each triangle side. If for one triangle side this criterion is not valid, one has to walk to the corresponding neighboring triangle. In this way one walks in this triangle world directly to the triangle containing X.
References
[1] M. Sambridge, J. Braun, and H. McQueen. Geophysical parameterization and interpolation of irregular data using natural neighbors. Geophys. J. Int., 122:837--857, 1995.