Comparing Satellite Observations to Emissions

In this tutorial, we will see how to combine satellite observation data instead of surface data, along with ancillary data (footprints, emissions, boundary conditions), into a ModelScenario. This allows us to compute modelled outputs and compare them with satellite-based atmospheric measurements.

This tutorial builds on the tutorials Adding observation data and Adding ancillary spatial data.

Note

Plots created within this tutorial may not show up in static or online documentation outputs.

Using the tutorial object store

As in the previous tutorials, we will use the tutorial object store to avoid cluttering your personal object store.

from openghg.tutorial import use_tutorial_store

use_tutorial_store()

Omit this step if you’re analysing data in your local object store.

1. Loading data sources into the object store

We begin by adding satellite observation, footprint, flux, and (optionally) boundary conditions data to the object store.

We’ll use helper functions from openghg.tutorial to populate example data:

from openghg.tutorial import (
populate_column_data,
populate_satellite_footprint,
populate_flux_data_satellite,
populate_bc_southamerica
)

populate_column_data()
populate_satellite_footprint()
populate_flux_data_satellite()
populate_bc_southamerica()

2. Creating a model scenario

We can now create a ModelScenario linking satellite observations with ancillary inputs.

from openghg.analyse import ModelScenario

scenario = ModelScenario(satellite="gosat",
               species="ch4",
               platform="satellite",
               max_level=3,
               domain="southamerica",
               obs_region="brazil"
               source="all")

Using these keywords, this will search the object store and attempt to collect and attach observation(satellite), footprint(satellite), flux and boundary conditions data. This collected data will be attached to your created ModelScenario. For the observations this will be stored as the ModelScenario.obs attribute. This will be an ObsColumnData object which contains metadata and data for your observations.

scenario.obs

To access the undelying xarray Dataset containing the observation data use

..code:: ipython3

ds = scenario.obs.data

The ModelScenario.footprint attribute contains the linked FootprintData (again, use .data to extract xarray Dataset):

scenario.footprint

And the ModelScenario.fluxes attribute can be used to access the FluxData. Note that for ModelScenario.fluxes this can contain multiple flux sources and so this is stored as a dictionary linked to the source name:

scenario.fluxes

Finally, this will also search and attempt to add boundary conditions. The ModelScenario.bc attribute can be used to access the BoundaryConditionsData if present.

scenario.bc

scenario.bc.data.attrs

An interactive plot for the linked observation data can be plotted using the ModelScenario.plot_timeseries() method:

scenario.plot_timeseries()

You can also set up your own searches and add this data directly. One benefit of this interface is to reduce searching the database if the same data needs to be used for multiple different scenarios.

from openghg.retrieve import get_obs_column, get_footprint, get_flux, get_bc

satellite = "gosat"
domain = "southamerica"
obs_region = "brazil"
species="ch4"

obs_column_data = get_obs_column(
    species="ch4",
    max_level=3,
    satellite=satellite,
    start_date="2016-01-01 14:59:12.500000+00:00",
    end_date="2016-01-01 18:10:16.500000+00:00",
    obs_region="brazil",
)

fp_column_data = get_footprint(
        satellite=satellite,
        domain=domain,
        obs_region=obs_region,
        start_date="2016-01-01 14:59:12.500000+00:00",
        end_date="2016-01-01 19:10:16.500000+00:00",
        model="name",
    )

flux_data = get_flux(species="ch4", source="all", domain="southamerica")

bc_results = get_bc(species=species,
                    domain=domain,
                    bc_input="CAMS",
                    )

scenario_direct = ModelScenario(obs_column=obs_column_data, footprint=fp_column_data, flux=flux_data, bc=bc_results, platform="satellite", max_level=3)

Note

You can create your own input objects directly and add these in the same way. This allows you to bypass the object store for experimental examples. At the moment these inputs need to be ObsData, ObsColumnData, FootprintData, FluxData or BoundaryConditionsData objects, which can be created using classes from openghg.dataobjects. Simpler inputs will be made available.

3. Comparing data sources

Once your ModelScenario has been created you can then start to use the linked data to compare outputs. For example we may want to calculate modelled observations at our site based on our linked footprint and emissions data:

modelled_observations = scenario.calc_modelled_obs()

This could then be plotted directly using the xarray plotting methods:

modelled_observations.plot()  # Can plot using xarray plotting methods

The modelled baseline, based on the linked boundary conditions, can also be calculated in a similar way:

modelled_baseline = scenario.calc_modelled_baseline()
modelled_baseline.plot()  # Can plot using xarray plotting methods

To compare these modelled observations to the observations themselves, the ModelScenario.plot_comparison() method can be used. This will stack the modelled observations and the modelled baseline by default to allow comparison:

scenario.plot_comparison()

The ModelScenario.footprints_data_merge() method can also be used to created a combined output, with all aligned data stored directly within an xarray.Dataset:

combined_dataset = scenario.footprints_data_merge()
combined_dataset

When the same calculation is being performed for multiple methods, the last calculation is cached to allow the outputs to be produced more efficiently. This can be disabled for large datasets by using cache=False.

For a ModelScenario object, different analyses can be performed on this linked data. For example if a daily average for the modelled observations was required, we could calculate this by setting our resample_to input to "1D" (matching available pandas time aliases):

modelled_observations_daily = scenario.calc_modelled_obs(resample_to="1D")
modelled_observations_daily.plot()

Explicit resampling of the data can be also be skipped by using a resample_to input of None. This will align the footprints to the observations by forward filling the footprint values. Note: using platform="flask" will turn on this option as well.

modelled_observations_align = scenario.calc_modelled_obs(resample_to=None)
modelled_observations_align.plot()

To allow comparisons with multiple flux sources, more than one flux source can be linked to your ModelScenario. This can be either be done upon creation or can be added using the add_flux() method. When calculating modelled observations, these flux sources will be aligned in time and stacked to create a total output:

scenario.add_flux(species="ch4", domain=domain, source="anthro")

scenario.plot_comparison()

Output for individual sources can also be created by specifying the sources as an input:

# Included recalculate option to ensure this is updated from cached data.
modelled_obs_anthro = scenario.calc_modelled_obs(sources="anthro", recalculate=True)
modelled_obs_anthro.plot()

Plotting functions to be added for 2D / 3D data

4. Cleanup

If you’re finished with the data in this tutorial you can cleanup the tutorial object store using the clear_tutorial_store function.

from openghg.tutorial import clear_tutorial_store

clear_tutorial_store()