AOD_TH

Level

Definition

≤0.3

I

V is above 10 km, pollution-free weather, low particulate matter concentration

0.3 - 0.8

II

V is at 5 - 10 km, which is a slightly polluted day with slightly poor air quality

0.8 - 1.5

III

V is 2.5 - 5 km, indicating moderate pollution and poor air quality

>1.5

IV

V less than 2.5 km, for heavy pollution weather, poor air quality