A. _Upper clouds_, average altitude 9000 metres.[2]
a. 1. Cirrus.
b. 2. Cirro-stratus.
B. _Intermediate clouds_, between 3000 m. and 7000 m.
a. 3. Cirro-cumulus.
4. Alto-cumulus.
b. 5. Alto-stratus.
Encyclopaedia Britannica, 11th Edition, "Clervaux" to "Cockade" Volume 6, Slice 5 · 第 25 / 41 题