Ml2pl interpolates atmospheric data at model levels to pressure levels. Input and output are in NetCDF format.
Ml2pl was first written to process history files of
LMDZ (files named hist....nc
). It
also works with atmospheric data from other sources. It is used in
Climaf.
If you want to use this program on the computers jean-zay at Idris, or irene at TGCC, or spirit at IPSL, the program is already installed at the following paths.
On jean-zay:
/gpfswork/rech/lmd/rdzt899/bin/ml2pl.sh
On irene:
/ccc/work/cont003/gencmip6/guezl/bin/ml2pl.sh
On spirit:
/data/guez/bin/ml2pl.sh
-
The NetCDF-C library (version ≥ 4.6).
-
The NetCDF-Fortran library (version ≥ 4.5).
-
The Fortran compiler that was used to compile your installed NetCDF-Fortran library.
-
NCO.
-
Git (Git is used by CMake to fetch a dependency).
-
Git-annex (optional, to download the NetCDF test files).
Under Ubuntu ≥ 20.04 or Linux Mint ≥ 20, you can install all these dependencies with the following command:
sudo apt install libnetcdff-dev gfortran cmake nco git git-annex
-
Get Ml2pl from Github.
-
Create a build subdirectory in the Ml2pl directory you have just downloaded:
cd Ml2pl mkdir build cd build
-
Decide in which directory you want to install Ml2pl after compilation and type the command below with your choice after
-DCMAKE_INSTALL_PREFIX=
(enter an absolute path). The installation process will install a shell script,ml2pl.sh
, in$CMAKE_INSTALL_PREFIX/bin
. It is convenient for$CMAKE_INSTALL_PREFIX/bin
to be in yourPATH
environment variable. For example:cmake .. -DFETCH=ON -DCMAKE_INSTALL_PREFIX=~/.local
Note that this requires a network connection.
-
Type:
make install
You do not need to keep the downloaded directory Ml2pl (nor the build
directory) after installation. Note that the installation process also
installs a Fortran executable file, ml2pl
, in
$CMAKE_INSTALL_PREFIX/libexec
. Do not remove this file.
Most users should not need these advanded instructions.
-
You can choose any name and any location for the build directory. You have to refer to the source directory when you run cmake from the build directory:
mkdir /wherever/any/name cd /wherever/any/name cmake /where/I/downloaded/Ml2pl -DFETCH=ON -DCMAKE_INSTALL_PREFIX=~/.local
-
The option
-DFETCH=ON
instructs CMake to download, compile and install the libraries Jumble, NetCDF95 andNumer_Rec_95
. If you have already installed these libraries, you can omit the FETCH option. -
On some machines, you may have to choose a run-time environment for
ml2pl.sh
. For example, if you have several compilers and you have selected one at build time with environment modules, you probably need to select it also at run time.ml2pl.sh
tries to source a file namedml2pl_runtime_env.sh
in the libexec subdirectory ofCMAKE_INSTALL_PREFIX
. So create this file there if you need it. There is a template forml2pl_runtime_env.sh
. -
After cloning the repository, the NetCDF entries in the
Tests
subdirectory are broken links. This saves network bandwidth and disk space. If you want to use the NetCDF files for tests, install git-annex (see Dependencies) and type:git annex get .
This will download the NetCDF files to the right location inside the the
.git
subdirectory, such that the symlinks inTests
are fixed.
-
If your installation of NetCDF or NetCDF-Fortran is in a non-standard location, and CMake does not find it, then re-run cmake setting the variable
CMAKE_PREFIX_PATH
to the directory of installation of NetCDF or NetCDF-Fortran. CMake will then search${CMAKE_PREFIX_PATH}/lib
,${CMAKE_PREFIX_PATH}/include
, etc. For example:cmake . -DCMAKE_PREFIX_PATH:PATH=/path/to/my/favorite/installation
-
If you have several Fortran or C compilers on your machine, it is possible that CMake does not choose the ones you want. Note that when you run cmake, it prints lines telling which compilers it is going to use. For example :
-- The Fortran compiler identification is GNU 11.3.0 -- The C compiler identification is GNU 11.3.0
So if you want other compilers, remove everything in the build directory and run cmake again setting the variables FC and CC to the compilers you want. For example:
rm -r * # in the build directory! FC=ifort CC=icc cmake .. -DCMAKE_INSTALL_PREFIX=~/.local
Running the command with argument -h
will produce a help message:
$ ml2pl.sh -h
usage: ml2pl.sh [OPTION]... input-file output-file [pressure-file]
Interpolates NetCDF variables from model levels to pressure
levels.
Options:
-h : this help message
-p variable : name of 4-dimensional variable in the input file
or the pressure file containing the
pressure field at model levels
-v variable[,variable...]: names of variables you want to interpolate,
or extrapolate if target pressure level is below
surface
-w variable[,variable...]: names of variables you want to interpolate,
or set to 0 if target pressure level is below
surface
-m variable[,variable...]: names of variables you want to interpolate,
or set to missing if target pressure level is
below surface
The interpolation is linear in logarithm of pressure. The input variables depend on longitude, latitude, vertical level and time. There is no constraint on dimension names nor dimensions lengths.
At given longitude, latitude and time, if a target pressure level is
lower than the lower bound of the input pressure field, then variables
are extrapolated to this target pressure level. If a target pressure
level is higher than the higher bound of the input pressure field,
then each variable may be extrapolated or set to 0 or set to missing
at this target pressure level. This is controlled by options -v
,
-w
and -m
.
All computations are done with single-precision real numbers.
input-file, output-file and pressure-file are NetCDF files.
You must list the variables you want to interpolate, each variable
listed after either -v
, -w
or -m
. There must be at least one variable
listed, following either -v
, -w
or -m
. In the same command, you
can have several options -v
, -w
or -m
with associated variables.
The pressure field at model levels can be specified in input-file or
pressure-file either through hybrid coefficients and surface pressure
or directly from 4-dimensional pressure. In both cases, pressure must
decrease when the index of model level increases. This is checked
quickly in the program. If option -p
is not used then the program
will look for NetCDF variables ap
, b
(hybrid coefficients) and
ps
(surface pressure) in the input file or the pressure file. If the
program does not find NetCDF variable ap
then it looks for NetCDF
variables a
and p0
and computes ap = a * p0
.
Let us call ap
and b
must be ap
and b
is ap
and b
: (ap(l) ap(l 1)) / 2
and (b(l) b(l 1)) / 2
.
The target pressure levels should be in a text file called
press_levels.txt
in the current directory at run-time. The first
line of the file is skipped, assuming it is a title line. Target
pressure levels should be in the same unit as input pressure at model
levels, as given by the 4-dimensional pressure or hybrid coefficients
and surface pressure. Target pressure levels can be in any order, one
value per line. There should be at least one target pressure
level. There is no other constraint on these values nor on the number
of values.
There is an example for file press_levels.txt
.
The program loops on time index and does not use four-dimensional, space plus time, variables. So the amount of main memory used depends on spatial resolution of the fields but not on the number of dates.
If
(B is for bytes).
Footnotes
-
On Mac OS, after downloading the application from the CMake web site, run it, then click on "How to Install For Command Line Use" in the Tools menu. ↩