Update README.md (#119)

README.md

@@ -44,19 +44,20 @@ For more information, see the [documentation for `Pkg.jl`](https://pkgdocs.julia
 
 ## Why? What's the difference between ClimaOcean and [Oceananigans](https://github.com/CliMA/Oceananigans.jl)?
 
-`ClimaOcean` is for realistic global and regional ocean-only, and ocean + sea-ice models.
-[Oceananigans](https://github.com/CliMA/Oceananigans.jl) is a lower-level package for simulation the dynamics of ocean-flavored fluids that can be used for _both_ realistic and idealized problems.
-While "idealized" problems come in all shapes and sizes, "realistic" problems are more narrowly defined, and require
+`ClimaOcean` is for _realistic_ ocean-only and ocean + sea-ice simulations, in a region of the ocean ("regional") or covering the whole Earth.
+[Oceananigans](https://github.com/CliMA/Oceananigans.jl) is a lower-level package for simulating the dynamics of ocean-flavored fluids that can be used for _both_ idealized problems and, given enough effort, realistic problems as well.
+While "idealized" problems come in multifarious shapes and sizes, "realistic" problems tend to be more narrowly defined, and require
 
-* Simulating the evolution of momentum, ocean temperature (or heat), salinity, and sometimes ocean biogeochemistry.
+* Simulating the evolution of specific tracers: ocean temperature (or heat), salinity, and sometimes ocean biogeochemistry.
 * Computing fluxes of heat, water vapor, momentum, and trace gases between the ocean and atmosphere (where the atmospheric state is either prescribed or "coupled" and itself evolving) -- and also between sea ice and the atmosphere, when a sea ice component is included.
-* Initializing the ocean model with realistic bathymetry and to some known ocean state at the beginning of the simulation.
+* Initializing the ocean model with realistic initial conditions derived from observations of the ocean, and realistic bathymetry.
 
-`ClimaOcean` uses `Oceananigans` and `ClimaSeaIce` to build `OceanSeaIceModel` capable of performing all of these tasks, and more.
-Note also that, at least at the moment, `ClimaOcean`'s ocean functionality is focused on hydrostatic modeling with `Oceananigans`' `HydrostaticFreeSurfaceModel`.
+`ClimaOcean` leverages `Oceananigans` and `ClimaSeaIce` to build `OceanSeaIceModel`s capable of meeting these requirements to simulate the dynamics of specific regions of the Earth's ocean.
+So if you're using `ClimaOcean`, it's a very good idea to become proficient in [`Oceananigans`](https://github.com/CliMA/Oceananigans.jl) as well.
+Note also that, at least at the moment, `ClimaOcean` is focused on hydrostatic modeling with `Oceananigans`' `HydrostaticFreeSurfaceModel`.
 
 In summary, if you're interested in realistic, hydrostatic regional or global simulations you may find `ClimaOcean` useful.
-Otherwise, stick with [Oceananigans](https://github.com/CliMA/Oceananigans.jl).
+Otherwise, you can stick with [Oceananigans](https://github.com/CliMA/Oceananigans.jl).