CoCiP++ is a work-in-progress C++20 implementation of the Contrail Cirrus Prediction tool (CoCiP).

It is designed to be used both as a standalone program and as a library.

• C++ compiler supporting C++20
• CMake
• Git

The following are included as Git submodules and are compiled with the project:

• yaml-cpp

Clone the GitHub repo with

git clone https://github.com/jcbart/CoCiPPlusPlus.git

and, in the top-level directory, run the following command to gather the Git submodules:

git submodule update --init --recursive

Use the following commands to configure the project in a directory named build:

mkdir build
cd build
cmake ..

The project can be compiled in any directory by instead running cmake /path/to/CoCiPPlusPlus.

Configuration options that can be used in the cmake command are listed below:

• -DCMAKE_BUILD_TYPE=Debug: Compile with debug flags and no optimisation (default is -DCMAKE_BUILD_TYPE=Release).
• -DCOCIP_BUILD_EXECUTABLE=OFF: Do not build an executable; only a static library will be built (default is -DCOCIP_BUILD_EXECUTABLE=ON).

Finally, run

cmake --build .

to compile and build.

Successful compilation will create a static library named libcocip.a and, unless turned off, an executable named CoCiP.

If they do not already exist, CMake will copy the default input files CoCiP-config.yaml and CoCiP-params.yaml to the build directory.

Runtime configuration options can be specified in CoCiP-config.yaml. Parameters can be specified in CoCiP-params.yaml. These files must be in the current working directory. Alternatively, a path to a YAML file containing configuration options can be specified in the command line.

Run the program with the command ./CoCiP /optional/path/to/config.

Outputs are (currently) written to cocip.out.

The static library can be used to include CoCiP++ in another project.

Include the headers in include/CoCiP++.

Declare a CoCiP object.

Assign a shared pointer to a Params object to CoCiP::params and a unique pointer to a derived IMet object (e.g. ArrayMet) to CoCiP::met respectively.

Assign flight inputs and initial time and location to the CoCiP object, as well as initial meterological values to the CoCiP::met object if required.

Call CoCiP::formation.

If CoCiP::sac is true, call CoCiP::simulate_wake_vortex_downwash, then CoCiP::initial_properties.

If CoCiP::persistent is true, call CoCiP::process_downwash_flight passing the segment heading angle.

In a loop, advect the plume location, update the meterological variables, time, and location, then call CoCiP::evolve passing the segment length ratio, the segment heading angle, and the time step duration. End the loop is CoCiP::persistent is not true.

CoCiP++ is location agnostic. It does not advect the plume internally; this behaviour must be driven externally. The time and location are used solely to estimate solar direct radiation.

The plume will sediment and and alter CoCiP::altitude, so ensure that advection does not overwrite this alteration.

CoCiP++ is based on the pycontrails implementation of CoCiP. It is up to date with pycontrails v0.60.3.

Currently, CoCiP++ is missing the following features:

• Extended K15 model
• Humidity scaling
• Contrail contrail overlap

This project has been developed by Jack Bartlett.

The original CoCiP model was developed by Ulrich Schumann and detailed in Schumann (2012).

Acknowledgement for the transliterated code is directed to pycontrails.