Cloudiness refers to the number of clouds covering the horizon of the sky. The location of the estimated cloud cover must be able to see the whole sky. When the sky is partially blocked by obstacles such as mountains and houses, the cloud cover should be estimated from the uncovered part of the sky. If a part of the sky is covered by precipitation, this part of the sky should be regarded as covered by clouds that produce precipitation.

Cloud amount observation includes total cloud amount and low cloud amount. Total cloud cover refers to the total amount of the sky covered by all clouds during observation, and low cloud cover refers to the fraction of the sky covered by clouds of low cloud family, all of which are recorded as integers.

Estimate the position of cloud cover and see the whole sky as much as possible. When a part of the sky is blocked by obstacles (such as mountains and houses), the cloud cover should be estimated from the unblocked sky. If a part of the sky is covered by precipitation, this part of the sky should be covered by clouds that produce precipitation.

The recording method of low cloud cover is the same as that of total cloud cover:

When there is no low cloud or a small amount of cloud in the whole day, but the amount is less than 0.5%, the low cloud amount is recorded as 0; When the sky is half covered by low clouds, the low cloud amount is recorded as 5; The whole sky is covered by low clouds, and the low cloud amount is recorded as 10, but if there is a cloud gap to see blue sky or high-altitude clouds, the low cloud amount is recorded as10-; For example, when the sky is full and there is a gap between the two, you can see the high-rise clouds from the gap, but you can't see the blue sky. At this time, the total cloud cover is 10, and the low cloud cover is10-; Another example is that the sky is covered, and there is a small gap between them to see the blue sky. At this time, the total cloud cover is recorded as 10-, and the low cloud cover is also recorded as 10-.