Why sky blue? Why does it rain and why does it snow?

When the weather is clear, there will be many tiny dust, water droplets, ice crystals and other substances in the air. When sunlight passes through the air, long-wavelength red light, orange light and yellow light can penetrate the atmosphere and directly hit the ground, while short-wavelength colors such as blue, purple and indigo are easily blocked by particles suspended in the air, thus scattering light in all directions and making the sky appear blue. In fact, the scattered blue light is only a small part, and most of the blue light and purple light that have not encountered particles still hit the earth directly, so the white light that hits the earth is still red, orange, yellow, green, blue, indigo and purple. Have you noticed that the sky will become bluer after the heavy rain? The clearer the weather, the bluer the sky. This is because there are a lot of dust particles, water droplets and ice crystals in the air in such weather. Why does it rain? When rivers, lakes and oceans are exposed to sunlight, water becomes steam. Water vapor rises into small water droplets and finally becomes clouds. The water droplets or ice crystals that make up the cloud are supported by the airflow below, and the rising airflow continuously transports the water vapor below to the cloud. Small water droplets and small ice crystals in the cloud collide with each other in motion, and the volume will increase. The water droplets in the lower layer of the cloud gradually get bigger. After the volume of ice crystals in the upper layer of the cloud increases, they will fall between the water droplets in the lower part of the cloud, and the water droplets will become bigger and bigger. When these water droplets are too big for the updraft to contain them, it will rain. Supplement: The temperature is quite low in winter, and the ground temperature is below zero, so the temperature of the upper clouds is even lower. Water vapor in the cloud can be directly condensed into small ice crystals and small snowflakes. When these snowflakes increase to a certain extent, the airflow will not hold, and it will fall from the clouds to the ground. This is snow. Water is the foundation of all kinds of life on the earth, and its changes and movements have created our world today. On the earth, water is constantly circulating. The water in the ocean and on the ground is heated and evaporated into the sky. The water vapor moves to other places with the wind. When they encounter cold air, they form precipitation and return to the earth's surface. There are two kinds of precipitation: one is liquid precipitation, which is rain; The other is solid precipitation, which is snow or hail. The precipitation that falls on the earth's surface in the form of solid in the atmosphere is called atmospheric solid precipitation. Snow is one of the most extensive, universal and main forms of atmospheric solid precipitation. There are many kinds of atmospheric solid precipitation, including beautiful snowflakes, hail that can cause great harm, and snow graupel and ice particles that we don't often see. Due to the difference of meteorological conditions and growth environment in the sky, all kinds of atmospheric solid precipitation are caused. The names of these atmospheric solid precipitation vary from place to place, from person to person, varied and extremely inconsistent. For convenience, the International Ice and Snow Committee under the International Hydrological Association held a special international conference in 1949 on the basis of soliciting the opinions of experts from various countries, at which the proposal of "Concise Classification of Atmospheric Solid Precipitation" was adopted. This concise classification divides atmospheric solid precipitation into ten types: snowflake, star snowflake, columnar snowflake, needle snowflake, multi-branch snowflake, axial snowflake, irregular snowflake, graupel, ice particle and hail. The first seven kinds are collectively called snow. Why can't the last three be called snow? It turns out that there are two processes for gaseous water vapor to become solid water. One is that water vapor first becomes water, and then water condenses into ice crystals. Another is that water vapor directly becomes ice crystals without water. This process is called water condensation. Therefore, snow is solid precipitation formed by condensation of water vapor in the sky. Ten forms of atmospheric solid precipitation: snowflake, star snowflake, columnar snowflake, needle snowflake, multi-branch snowflake, axial snowflake, irregular snowflake, graupel, ice particle and hail.