SpaceVaringInputs and TimeVaryingInputs

Most models require external inputs to work. Examples of inputs are an analytic function that prescribes the sea-surface temperature in time, or a file that describes the types of plants on the surface of the globe. The SpaceVaringInputs and TimeVaryingInputs modules provide a unified infrastructure to handle all these cases.

TimeVaryingInputs

This extension is loaded when loading ClimaCore is loaded. In addition to this, if NetCDF files are used, NCDatasets has to be loaded too. Finally, a Regridder is needed (which might require importing additional packages).

A TimeVaryingInput is an object that knows how to fill a ClimaCore Field at a given simulation time t. TimeVaryingInputs can be constructed in a variety of ways, from using analytic functions, to NetCDF data. They expose one interface, evaluate!(dest_field, tv, time), which can be used by model developers to update their Fields.

This example shows that TimeVaryingInput can take different types of inputs and be used with a single interface (evaluate!). In all of this, TimeVaryingInputs internally handle all the complexity related to reading files (using FileReaders), dealing with parallelism and GPUs, regridding onto the computational domains (using Regridders and DataHandling), and so on.

TimeVaryingInputs support:

  • analytic functions of time;
  • pairs of 1D arrays (for PointSpaces);
  • 2/3D NetCDF files;
  • linear interpolation in time (default) and nearest neighbors.

Example

Let target_space be the computational domain (a ClimaCore Space) and cesm_albedo.nc a NetCDF file containing albedo data as a function of time in a variable named alb.

import ClimaUtilities: TimeVaryingInputs
import ClimaCore
import NCDatasets
import ClimaCoreTempestRemap
# Loading ClimaCore, NCDatasets, ClimaCoreTempestRemap loads the extensions we need

function evolve_model(albedo_tv, albedo_field)
    new_t = t + dt
    # First, we update the albedo to the new time
    evaluate!(albedo_field, albedo_tv, new_t)
    # Now we can do all the operations we want we albedo_filed
    # rhs = ...
end

# Let us prepare an empty Field that will contain the albedo
albedo_field = zero(target_space)

# If the albedo is an analytic function of time
albedo_tv_an = TimeVaryingInput((t) -> 0.5)

# If the albedo comes from data

# reference_date is the calendar date at the beginning of our simulation
reference_date = Dates.DateTime(2000, 1, 1)
albedo_tv = TimeVaryingInputs.TimeVaryingInput("cesem_albedo.nc", "alb", target_space;
                                               reference_date)
# When using data from files, the data is automatically interpolated to the correct
# time

# In either cases, we can always call evolve_model(albedo_tv, albedo_field), so
# model developers do not have to worry about anything :)

SpaceVaryingInputs

This extension is loaded when loading ClimaCore is loaded. In addition to this, if NetCDF files are used, NCDatasets has to be loaded too. Finally, a Regridder is needed (which might require importing additional packages).

SpaceVaryingInputs uses the same building blocks as TimeVaryingInput (chiefly the DataHandling module) to construct a Field from different sources.

TimeVaryingInputs support:

  • analytic functions of coordinates;
  • pairs of 1D arrays (for columns);
  • 2/3D NetCDF files.

In some ways, a SpaceVaryingInput can be thought as an alternative constructor for a ClimaCore Field.

Example

Let target_space be a ClimaCore Space where we want the Field to be defined on and cesm_albedo.nc a NetCDF file containing albedo data as a time in a variable named alb.

julia import ClimaUtilities: SpaceVaryingInputs import ClimaCore import NCDatasets import ClimaCoreTempestRemap

Loading ClimaCore, NCDatasets, ClimaCoreTempestRemap loads the extensions we need

Albedo as an analytic function of lat and lon

albedolatlonfun = (coord) -> 0.5 * coord.long * coord.lat

albedo = SpaceVaryingInputs.SpaceVaryingInput(albedolatlonfun)

albedofromfile = SpaceVaryingInputs.SpaceVaryingInput("cesmalbedo.nc", "alb", targetspace)


## API

@docs ClimaUtilities.SpaceVaryingInputs.SpaceVaryingInput ClimaUtilities.TimeVaryingInputs.AbstractInterpolationMethod ClimaUtilities.TimeVaryingInputs.NearestNeighbor ClimaUtilities.TimeVaryingInputs.LinearInterpolation ClimaUtilities.TimeVaryingInputs.evaulate! Base.in Base.close ```