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

Composition and Structure of the atmosphere.

Atmosphere, in general, is a layer of gases that may surround a material with sufficient mass, supported by gravity. Earth’s atmosphere is up to 10,000km. However, there is no definite boundary between atmosphere and the outer space. Now, talk about the construction of space, although there is no definite boundary between layer and layer, based on the concentration of gases… Earth’s atmosphere is divided into 5 main layers:

- Troposphere: Up to 15km, which has the highest concentration of gases and also this is where we live.

- Mesosphere: up to 95/120km, this is where most meteors burn up when it goes to the atmosphere.

- Stratosphere: up to 50/60km, contains ozone layer.

- Thermosphere: up to 600km,extremely low pressure, temperature increase with height.

- Exosphere: up to 10,000km, contains many free-moving particles.

Compositions of the earth’s atmosphere:

• nitrogen (N₂: 78%),
  
• oxygen (O₂: 21%),
  
• other gases ( carbon dioxide CO₂: 0.036%, water vapour, methane, helium, krypton, argon, neon, hydrogen, nitrous oxide, iodine, carbon monoxide, ammoniac).
  

The question now is why is it so important to know what is the construction and composition of the Earth’s atmosphere? It’s not very difficult to remember these but to keep it being balance is not such a easy work. This is important because Earth’s atmosphere is such a fantastic combination, it gives us lives. Constant in line is change and every little thing that change in the atmosphere can affect the destiny of all human being. For example: Carbon dioxide (CO₂) 0.036%, needed for plants to perform photosynthesis in order to make carbon hydrates and sugar. CO₂ also keeps heat from escaping from the earth so that we won’t freeze to death. However, along with modernization and industrialization , the amount of CO₂ is increasing day by day. This means that heat is trapped in the atmosphere much more than before and results in global warming.

Another thing about the atmosphere is also important to learn about is the ozone layer. Ozone (O₃) is very unstable. It helps screen out UV-C ray (280-100nm), which is very harmful to human and UV-B which can cause cancer. The UV ray hits ozone to split it up to oxygen molecules and atom to form a oxygen-ozone cycle. The chemical equations:

- O₃ → O₂ + O

- O+ O₃→2O₂

- 3O₂ → 2O₃

However, the ozone layer depletes rapidly recently. One of the reasons is CFC gas (chlorofluorocarbons) from the refrigerators. It goes in between the oxygen-ozone cycle and this over effect make ozone decrease.

- CFCl₃ → CFCl₂ + Cl (UV rays)

- Cl + O₃ → ClO + O₂

- ClO + O₃ → Cl + 2 O₂

Another question in the lesson that needs to answer is temperature in the thermosphere can reach beyond 1200 degree Celsius but we can still freeze to death is because of the extremely low pressure and there are too little gas molecules in thermosphere. As 99.99997% mass of the atmosphere is below 100km, the temperature can be high but the chance for the molecules to reach human skin is very small. That’s the reason why we can still freeze there.

In short, through the lesson, I have had an overview of the atmosphere. As a matter of fact, I also learn the pros and cons of the change in atmosphere that can affect our live. I also learn to understand some invisible cycles that’s continuously happening to maintain conditions for life. Finally, it’s fun to know chemical equations of the ozone and ozone depletion.

Done by: Dao Thuy An (03)

The blog is made!
:D

-aditi.