Trace gases (CO2, CH4, N2O) surface concentration diagnostic

[jlenh]

Description

This new diagnostic aims to evaluate surface concentrations of trace gases by comparing model outputs with surface flask measurements made available by NOAA's GML for CO2, CH4, and N2O. A recipe is added for each supported trace gas and relies on the corresponding NOAA GML dataset entry #3847 .

The diagnostic relies on two scripts stored in esmvaltool/diag_scripts/surface_trace_gases/:

• diagnostic_surface_trace_gases.py : Plots the different surface trace gas evaluations.
• utils_surface_trace_gases.py: Utility functions used for the surface trace gas evaluation routines. Some of this code relies on the diagnostic developed for AOD evaluation see Add support for aerosol optical depth climatology metrics to the AutoAssess replacement #3048 . This code helps for the co-location process between model data and station locations. The rest are utils functions for the purpose of this new diagnostic.

The diagnostic contains four different plotting routines which produce a total of five plots. In the case of zonal plots, the latitude ranges considered are 60N - 90N, 30N - 60N, 30S - 30N, 90S - 30S, and are plotted in a row each. The surface concentrations are extracted at the stations' locations for all the analysis of the zonal quantities.
For each model entry in the recipe, the following plots will be produced:

• Seasonal maps of the trace gas surface concentration overlaid with station data points. A complimentary scatter plot compares the surface concentration at the station locations with the model data extracted at these same locations for each season.
• Zonal plots of surface concentration time series and seasonal cycle. The left column plot includes a monthly surface concentration time series. The center-left column plot includes a yearly surface concentration scatter plot. The center-right column plot includes multi-annual monthly anomaly. The right column plot includes a yearly min/max months time series. The plot is inspired from Figure 8 of Folberth et al. (2018).
• Zonal plots of surface concentration amplitude, growth, and corresponding sensitivity between the two quantities. The left column plot includes a yearly concentration amplitude time series. The center column plot includes a yearly concentration growth time series. The right column plot includes a yearly sensitivity of amplitude/growth time series.
  And all model entries will be integrated in the following plot:
• Taylor diagram of trace gas surface concentration for the observations and the different models from the recipe.

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• Closes Trace gases (CO2, CH4, N2O) surface concentration diagnostic #4012

Requires:

• Downloader & cmorizer for NOAA GML surface flask trace gases  #3847
• Add CMORized NOAA GML surface flask concentration measurement of N2O #4059
• Add preprocessor to extract surface values from 3D atmospheric variables ESMValCore#2641
• Add entry for n2os variable ESMValCore#2724

Before you get started

• ☝ Create an issue to discuss what you are going to do

Checklist

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New or updated recipe/diagnostic

• 🧪 Recipe runs successfully
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[jlenh]

(finally) ready for review!

Anybody available from @ESMValGroup/tech-reviewers and @ESMValGroup/science-reviewers ?

• Tests are failing because the new preprocessor extract_surface_from_atm (Add preprocessor to extract surface values from 3D atmospheric variables ESMValCore#2641) does not seem to be in the ESMValCore version used for the tests.
• Happily taking some suggestions or advice to make the colocation a bit faster (tried some parallelization but did not really improve performance)