Tilt and Shape (23 Feb)

MAK (IE TING AMANDA) SAYS HELLO. :D

So I’m here to post on today’s lesson. Basically, the lesson was spent answering, or trying to figure out the answers for two questions.

1. Explain the distribution of Earth’s climate.

2. Why are there seasons?

Miss Lin split us into groups of threes and fours to discuss. Like, some of us were supposed to work on the first question while the rest had to do the second. Some of us were told to present our answers on the board but we weren’t that clear, so Miss Lin ended up explaining instead.

We referred to the colourful world map given to us a few lessons ago to answer the first question. It can be seen from the map that at the Polar Regions, the climate is much colder than at the Equator. Reason being, the radiation from the Sun is being spread over a larger area when shone at the Earth’s surface at the poles than at the equator. The diagram below should give you a better picture.

So, as you can see, supposedly six rays hit upon Earth - three at the North pole and three at the equator. The intensity of sunlight does not decrease due to the distance but the rays are like, spread out at the pole. So the concentration there is lesser as compared to the equator. Therefore, it is hotter at the equator! Yeah, it's something along these lines.

We learnt that this uneven heating is known as differential insolation. Insolation refers to the amount of solar radiation energy received on an area in a given time.

Okay, then Miss Lin drew another diagram to aid our understanding on the distribution of the Earth’s climate.

I only drew the Northern Hemisphere because it looks neater. :D
(I hope the diagram's correct..)

Okay fine, I'm a little lazy too but yeah. As long as you understand how the convection currents at the Northern Hemisphere work, you will understand how the Southern works too. The principle is the same, just flip the Northern Hemisphere over, using the equator (where the words "Low Pressure" are at) as the line of symmetry, and you will get your Southern Hemisphere.

I think it's damn cool to have different names to the convection currents at different parts. Besides that, I made a brief explanation on what happens at the Polar Cell. If it's too small, maybe you can look at it here.

High Pressure --> Air cannot rise --> No clouds formed --> No precipitate --> No water --> Desert --> At the High Pressure Belt.

As the air at the North pole is cold, its density is really high and therefore the air has high pressure. So, the air can't possibly rise and form clouds. Without clouds, you can't get rain yeah? And no rain means no water. If there is no water over a long period of time, the land will be dry and tata, you get your desert at the High Pressure Belt!

I guess this answers today's commonly asked question: How come there are deserts at the Tropic of Cancer/Capricorn and not at the equator?!

Also, we learnt that there are seasons because the Earth receives different amounts of sunlight at different times. Thus, during the first half of the year, the Northern Hemisphere which is tilted towards the Sun will be warmer as it receives a greater amount of insolation, while the Southern Hemisphere receives lesser insolation. The Northern Hemisphere will experience summer while the Southern Hemisphere experiences winter. Basically, during the later half of the year, the Northern Hemisphere experiences winter and the Southern Hemisphere, summer. This cycle goes on and on. And so, we have the four seasons. The equatorial countries do not experience the four seasons as the equator is where the subsolar point is. The subsolar point is the point on Earth where the Sun’s rays meet the surface at a right angle, with no change in the amount of solar radiation received throughout the year.

I’d say this lesson is pretty interesting. I mean, we get to understand how deserts become deserts. So if you actually have those fantasies of a giant blowing away all the water and drying up a piece of land to make it a desert, you should now realise that the giant does not exist. So the reason why the Earth’s climate is like this is all due to the convection currents in our atmosphere. The rising of hot air and the sinking of cold air cause the difference in air pressure which in turn causes the convection currents.

It is also amazing to find out how much a degree change in latitude or longitude can affect the amount of sunlight received. In our daily lives, I doubt a degree change actually means anything to anyone; it seems so insignificant. But wow, things are indeed different out in space.

So yeah, that’s about all for today! I hope this isn’t too screwed. :D