NARR data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web
site at https://psl.noaa.gov/

The original "air.201806.nc" datafile was downloaded from 
https://psl.noaa.gov/data/gridded/data.narr.pressure.html

Specific download link (~650 MB):
ftp://ftp.cdc.noaa.gov/Datasets/NARR/pressure/air.201806.nc [Last accessed on 
2020-06-17]


The following files are a direct slice of this data:
- export_dist.txt
- export_heights.txt
- export_press_atmosphere.txt
- export_temp_atmosphere.txt


This data file was not included here, because it has a very niche use for the
AstroAtmosphere package and is a large file. The tradeoff seems to me to not very
favourable, and therefore it is omitted.