What are the 4 general air mass classifications?

Related questions

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5. What is considered high and low barometric pressure?
6. What is a comfortable barometric pressure?
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Tags

1. #masses
2. #arctic
3. #latitude
4. #moderately
5. #categories
6. #tropical
7. #polar
8. #areas
9. #region
10. #there
11. #equatorial