# [Greenline] 1D turbulence

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## Problem
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Extract the 1D turbulence of ICON (Fortran) into a Fortran standalone granule. The granule should ideally match.

Use ICON-NWP as base, there was a big refactor.

## Appetite
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## Solution
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The 1D turbulence granule should live in its own repository that contains all relevant source code for the module.
We propose to open the repository at the C2SM github space to start with.

The setup of the repository should be aligned with the [microphysics Fortran granule](https://gitlab.dkrz.de/icon-libraries/muphys).

Also the same testing infrastructure/libraries might be used.

The granule should be built with CMake.

It might use libraries from [icon-libraries](https://gitlab.dkrz.de/icon-libraries).

The interface should make it easy to be used from other languages as we want to add python bindings and use it from icon4py. The granule may keep local fields and variables as internal state if necessary, but should otherwise be stateless. See notes on [granule interface](https://pad.gwdg.de/laDDDeV7TQCpxoSKoyOt5g) from ICON-C

All model fields should be passed at runtime as simple types: arrays of scalars or scalars

The entrypoint in is in `src/atm_phy_schemes/turb_diffusion.f90`.

## Rabbit holes
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## No-gos
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## Progress
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- [x] Task 1 ([PR#xxxx](https://github.com/GridTools/gt4py/pulls))
- [x] Subtask A
- [x] Subtask X
- [ ] Task 2
- [x] Subtask H
- [ ] Subtask J
- [ ] Discovered Task 3
- [ ] Subtask L
- [ ] Subtask S
- [ ] Task 4