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For ERA5 data the point interval on the native Gaussian grid is about 0.3 28 degrees. You can download ERA5 data using Python and specify a custom grid and resolution in your script. You should set the horizontal resolution to no higher slightly lower than 0.3x0.3 28 degrees (about 30km), for example to 0.25 degrees, approximating the irregular grid spacing on the native Gaussian grid.
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