Why are there clouds in the sky? It's white, sometimes it's gray.

Cloud is the foundation of precipitation and the middle link of the earth's water cycle. The occurrence and development of cloud is always accompanied by energy exchange. The shapes of clouds are ever-changing, and specific clouds often appear in specific weather, so clouds have certain indicative significance for weather changes. (1) Formation conditions and classification of clouds in the atmosphere. The important conditions for condensation are the existence of condensation nuclei and the supersaturation of air. For the formation of clouds, its supersaturation is mainly caused by adiabatic cooling caused by vertical rise of air. The form and scale of ascending motion are different, and the state, height and thickness of the formed cloud are also different. There are four main ways to improve the atmosphere: 1. Thermal convection refers to the convective upward movement caused by uneven surface heating and unstable atmospheric stratification. Clouds formed by convection are mostly cumulus clouds. 2. Dynamic uplift refers to the large-scale upward movement of warm and humid airflow under the action of front and convergent airflow. The clouds formed by this movement are mainly layered clouds. 3. Atmospheric fluctuation refers to the fluctuation caused when the atmosphere flows through the uneven ground or below the inversion layer. Clouds produced by atmospheric fluctuations mainly belong to fluctuation clouds. 4. Topographic uplift refers to the upward movement caused by the forced uplift of the atmosphere when it is blocked by topography. Clouds formed by this movement include cumulus clouds, wavy clouds and layered clouds, which are usually called topographic clouds.