Merge pull request #4076 from CliMA/jefftyoder-docs-terminology

Update installation instructions with terminology section

Author: jefftyoder

docs/make.jl

@@ -24,7 +24,7 @@ makedocs(;
     ),
     pages = [
         "Home" => "index.md",
-        "Installation instructions" => "installation_instructions.md",
+        "Getting Started" => "getting_started.md",
         "Contributor Guide" => "contributor_guide.md",
         "Equations" => "equations.md",
         "Microphysics" => "microphysics.md",

docs/src/getting_started.md

@@ -0,0 +1,55 @@
+## Installing Julia
+
+ClimaAtmos is provided as a Julia package, so it requires having Julia installed. Information about Julia packages is available on the [Julia website](https://julialang.org).
+
+First, download and install Julia by following the instructions at [https://julialang.org/downloads/](https://julialang.org/downloads/). Then, you can launch a Julia REPL by running `$ julia --project`
+
+## Installing ClimaAtmos.jl
+
+ClimaAtmos.jl is a [registered Julia package](https://julialang.org/packages/). To install
+
+```julia
+julia> using Pkg
+
+julia> Pkg.add("ClimaAtmos")
+```
+
+Alternatively, you can clone the `ClimaAtmos`
+[repository](https://github.com/CliMA/ClimaAtmos.jl) with:
+
+```
+$ git clone https://github.com/CliMA/ClimaAtmos.jl.git
+```
+This is useful if you want to keep up with bleeding-edge changes between major releases.
+
+Now change into the `ClimaAtmos.jl` directory with 
+
+```
+$ cd ClimaAtmos.jl
+```
+
+To use ClimaAtmos, you need to instantiate all dependencies with:
+
+```
+$ julia --project
+julia> ]
+(ClimaAtmos) pkg> instantiate
+```
+
+## Some common terminology in ClimaAtmos
+The following terms are frequently used within the source code and between collaborators. Feel free to open a GitHub issue if you come across any other key terms that we've missed here.
+- `Yₜ`: The tendency state vector, where `Yₜ.sfc` components are modified.
+- `Y`: The current state vector.
+- `p`: Cache containing parameters, precomputed fields (radiation fluxes, surface
+       conditions, precipitation fluxes), atmospheric model configurations, and
+       slab model properties.
+- `t`: Current simulation time.
+
+The state `Y` is not assigned by default. If you want to explore the state variable, you can follow the steps below. Note that all but the last step below are executed by the [driver](https://github.com/CliMA/ClimaAtmos.jl/blob/main/.buildkite/ci_driver.jl).
+
+```Julia
+import ClimaAtmos as CA
+config = CA.AtmosConfig([your_path_to_config_file])
+simulation = CA.get_simulation(config)
+Y = simulation.integrator.u
+```