What grade is "Seeing the weather from the clouds"?

The text of the first volume of the seventh grade

Seeing the weather from the clouds is a popular science exposition of the 22 nd lesson of the first volume of the seventh grade Chinese in People's Education Press. The author is Zhu Yongxi and the reader is Zijun.

The author introduces the relationship between clouds and weather in logical order from two aspects with vivid language: the relationship between different forms of clouds and weather; The relationship between different glorious clouds and the weather. Structurally, the whole paper adopts the relationship of total-subtotal.

Thin clouds in the sky are often a symbol of good weather; And those low and thick clouds are often signs of rain and snow, and we can judge the weather according to various signs. Although it is not very accurate, the proverb has been passed down for generations.

Cloud formation: Cloud is a visible polymer suspended in the atmosphere, which is composed of a large number of tiny water droplets, ice crystals and dust. Because the atmospheric pressure decreases with the increase of height, the air will expand and cool down when it rises, and the saturated water pressure will also decrease. When the water vapor in the air reaches saturation, it condenses into a large number of tiny water droplets floating in the air, forming clouds.