Learning Atmospheric Chemistry - Helpful hints from Harvard. Also has some pointers for general academia.
Atmospheric Chemistry online textbook (from Harvard): http://acmg.seas.harvard.edu/people/faculty/djj/book/
2016 Report on The future of atmospheric chemistry research (free pdf download)
Measurements for air quality - UCAR training modules
Different types of mathematical models for the atmosphere - NOAA lecture
NASA Applied Remote Sensing Training (ARSET): https://appliedsciences.nasa.gov/sites/default/files/2021-03/Online_Resource_Guide.pdf