Real-time satellite imagery detects these particulates — tiny bits of matter suspended in the atmosphere as aerosols that are part of what makes up smog. When the smog is so heavy, these clouds of air pollution can be easily seen from Space. This has two reasons. First, smog is optically thicker in the visual range and thus reduces the contrast of objects below it, or fades them away completely. Second, unlike typical clouds, smog is not white and can have brown tones.
Industrial pollution, including the burning of coal for energy and heating, releases tiny particles to the atmosphere. Factors such as unfavorable wind and weather patterns, the surrounding mountain’s orthography, and the cold atmosphere suppress a layer of air and cause these particles to accumulate into thick, heavy smog.
The photo on the left is Shanghai with heavy smog, while the one on the right was snapped three days later after wind and rain cleared the air.