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!

Geog lesson on the 5th of Feb

All systems depend on regulatory forces and systems which might have

1. Positive feedback ---Consequence is enhanced. This feedback will drive the system further away from its original setpoint. It will encourage change and cause an unstable eqilibrium. Eg. enhanced greenhouse effect à world becomes hotter.

2. Negative feedback ---Will tend to re-establish equilibrium because it discourages change. It lets the system remain stable. Eg. Increase in carbon dioxide à reduce carbon emissions à carbon dioxide level will return to original level.

PLANETARY HEAT

Global shortwave radiation cascade absorbed by:
1. OZONE ( stratosphere) DIFFUSED INSOLATION
2. CLOUDS AND AEROSOLS ( troposphere)
3. Earth’s surface DIRECT INSOLATION

Global longwave radiation cascade emitted by:

1. EARTH’S SURFACE – directly to space
- Absorbed by greenhouse gases*
2. ATMOSPHERE – directly to space*
- Absorbed by earth’s surface
Heat comes from ~ surface emissions
~latent heat transfer
~sensible heat transfer
~absorption of shortwave radiation from atmosphere
Gases and clouds

*majority of the heat radiated

Key words:
Global shortwave radiation cascade : Rays from the sun entering earth
Global longwave radiation cascade: Rays that are reflected/ leaving the earth
Diffused insolation: Heat that is absorbed is scattered
Direct insolation: Suface that absorbs heat directly
Albedo: Amount of heat reflected back

Reflections:
The best way to remember the way in which planetary heat is balanced is to keep in mind that the incoming solar insolation and outgoing radiation must be equal in quantity. The planetary heat balance is a very important system to the Earth. In reference to Global warming today, there is enhanced greenhouse effect because of the increase in amount of carbon dioxide in the air which will trap more longwave radiation. Thus causing an increase in temperature on Earth. Yupps. So that is how the planetary heat balance can be used to explain why our climate is changing.

By: Valerie Yeo