Formation of Rain!!!

Today, we discuss about the formation of rain and the distinct kinds of rain.
How the rain is formed?
In the simplest way, the water droplets form from warm air. The warm air will rise and as the warm air rises into the sky. The air cools and expends when it rise and keeps rising till its temperature is as the same as the temperature of surrounding air. The air is cool enough then the water vapor in the air begins to form the water droplets. When enough of water droplets collect together, the clouds are formed. However, not all clouds become rain because the cool air can hold less water vapor compared with the warm cloud. When the clouds have enough water droplets, and the clouds are heavy enough, the drops fall as the gravity. That is rain.

There are a lot of causes of the rain such as mountains, low-pressure areas, cold &warm fronts. On this lesson, Miss Lin introduced the rain formed in mountains—the orographic rainfall.

The orographic rainfall contains two kinds which are forced uplift and free uplift.

Forced uplift（a stable condition）The stable air is forced by maybe the wind to rise over a relief barrier. Because the stable air remain cooler that the surrounding, it trends to fall backward all the time. The uplift is reduced and the growth of raindrops is poor. Hence the rainfall is light drizzle. The forced uplift produces hill fog.
Free Uplift referred the unstable conditions. The air is triggered to rise without stop. The top of clouds may reach high in the atmosphere where a temperature far below freezing has. Collision and icing will occurs to increase the quantity of droplets. The free uplift causes a very large amount of rainfall.
The Feeder-seeder mechanism
Some clouds will fall through the low-level clouds. The high-level clouds are called seeder and the low-level clouds are called feeder clouds.

OK. That is all for today! O(∩_∩)O~
Done by Chen Zhuhe!