Fixing African easterly wave density plots in TC analysis

[chengzhuzhang]

Description

Karthik (@karthik-balaguru) noted the odd Y shapes in easterly wave density plots in recent TC analysis results (issue 1). And @paullric also noticed that the ERA5 results are also off, which always have a base value of ~5 (issue 2).

• Closes #<ISSUE_NUMBER_HERE>

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

If applicable:

• New and existing unit tests pass with my changes (locally and CI/CD build)
• I have added tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)

[chengzhuzhang]

Not sure the root cause of issue 2, but I think plotting libraries changes caused the second issue over versions. By reading in files without subsetting the region, it fixed the issue. (Now, the region is bounded only when plotting)

Issue 1 remains, I will keep investigating.

[chengzhuzhang]

Comparing with apply tempest-extremes (TE) on native ne120pg2 vs data regrided to 720x1440. The Y shapes only appear with native grid data. Below are the AEW density plots.

The AEW density plots uses three TE functions:
VariableProcessor to calculate relative vorticity
DetectNodes and StitchNodes to detect and stitch candidates
Finally HistogramNodes to generate histogram for the detection.
Detailed steps can be found here

@paullric I'm not sure if TE is applied properly in this case, any advice for further trouble shooting is appreciated!

[chengzhuzhang]

Also to add that:
TC count increases if the storms are tracked on the regridded output. ~73 (regridded data on 720x1440) vs ~67 (native ne120) for one year of data.