Minh - 23th Feb - Distribution of Climate.

Basically during today lesson, we had to try to answer the question: "Explain the distribution of the Earth's Climate".


As usual, we broke the question into smaller parts and asked questions about every single one first, rather than diving in an ocean of info without knowing what exactly that we need. I realised that even simple questions matter much. We all thought about how the climates are distributed without questioning what "Climate" and "distribution" themselves mean. Questioning and answering those simple things really help us simplify the problem. "Climate" actually refers to how wet and warm the place is, therefore factors affecting the distribution of Climate must be those that affect the temperature and the wetness of the place. Cool! The problem has been narrowed down!



Next, the class was divided into two sides as you all knew. I fell to the season variation side. Our objective is to study why there are seasons on Earth ( I'm feeling that our side is actually answering the temperature half of the question ). And now, using all the progress that my group has made today, I would explain for you why there are seasons on Earth.




Firstly, seasons refer to different periods of the year when the temperature of each period is generally different from each other. 4 seasons Spring, Summer, Autumn and Winter nicely fit in a cycle of one year. Summer refers to the period when the temperature is highest throughout the year, and Winter refers to the period when the temperature is lowest. Spring and Autumn are rather intermediate period between Summer and Winter so the temperature at those time is in between that of Winter and Summer. Another thing to take note is that Spring comes after Winter and before Summer; Autumn comes after Summer and before Winter. Sounds simple, right?



So basically we differentiate seasons based on the temperature. And, as we all know, the temperature of a place generally propotionates to the amount of Sunlight received by that place. Therefore, the Sun has to be somewhat responsible for the distribution of heat on Earth throughout the year.




However, after studying the causes of season variation on Earth, I figured out that the REVOLUTION of the earth around the Sun and the TILT of the earth actually play important roles in causing season variation. And now I will explain to you with a simplified version of the picture that you can find in the notes itself.

First I shall explain a little bit about the picture.

The fish-ball like thing is actually our Earth in different position around the sun, and you should know that the Earth takes 1 year to travel 1 round in its orbit around the Sun. Therefore, the position of the Earth at a point of time is the same as its position one year later. And you also know that the Earth TILTs at an angle of 23.5 degrees with respect to plane that contains its orbit around the Sun. The yellow colour represents the part of the Earth that receives sunlight and blue represents the part of the Earth which does not. The equator represented by the red line divides the Earth into two halves, called North and South HEMISPHEREs.

Okay, now we have enough info to explain season variation. Let's put them together. As you can see, when the Earth is in the right-most position, which corresponds to 21-22 December, you can see that the South Hemisphere (S) generally receive more light than the North Hemisphere (N). And considering the Earth's "free body diagram" in this position, there are much more interesting things that you can see.


In the "free body diagram", the two tiny violet dots represent the two points on Earth which are symmetrical about the equator. As the Earth rotates, the two dots move along the two green lines with the same speed. On the diagram, you all can see that the dot in the South Hemisphere spends more time (More than 12 hrs a day) in the yellow region which is daytime while the dot in the North Hemisphere spends more time (More than 12 hrs a day) in the blue region which is night time, therefore the temperature the South hemisphere is generally higher than that of the North hemisphere and reaches its peak. Therefore, It's summer in the South Hemisphere and Winter in the North Hemisphere.


As the Earth revolves around the Sun for one more quarter of a year, to the second position on 21-22 March, the difference between daylength and nightlength becomes smaller and smaller and finally equal to each other. The temperature is generally the same in the two hemispheres. Because the daylength in the South Hemisphere is generally shorter than previously, therefore the temperature drops with comparison to the 21-22 December point and becomes mild. Similarly, the North hemisphere generally becomes warmer. Hence, on 21-22 March, It's Spring in North hemisphere and Autumn in the South hemisphere.



From here, you can figure out the rest, right?



The 23.5 degrees tilt of the Earth is very important for season variation. If this tilt does not exist, there would not be any difference between daylength and nightlength throughout the year at any point on Earth, hence no seasons.



However, there are much more interesting things than the season variation alone. By shifting the green line along the direction perpendicular to the equator, we get another result that the places near the two poles would have greater difference between the duration of daytime and night time during Winter or Summer and people living around the equator do not have to worry so much about the variation of daylength and nightlength because they have 12hrs of daytime and 12hrs of night time throughout the year. This helps us explain why the temperature of places near the equator varies very slightly as they receive a consistent amount of sunlight throughout a year.



And for the places which is at 66.5 degrees or beyond, there is an interesting phenomenon that a 24 hours or longer daytime/ night time can occur. And at the two extremes, the people who live near the two poles have possibly experienced a period of 6 months with, or without the Sun. You can try to explain this fact using what I've told you previously in this entry. Haha. Doing Physical Geog is fun, right?!?



Basically that's what I've got so far. We've gone through what seasons are, the key factors that causes season variation and the mechanism behind season variation.

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After diving into the pages full of words, I realised that the best way to learn something is to try to visualize it!!! So actually I focus on the picture first and even redraw them all so that I can imagine what is happening. And it was actually very effective because it took me only 15 minutes to digest the content in 8-10 pages of the handout. And after you've understood the thing, try to rehearse everything by your own words. By doing so, you would construct a system where everything has its own place and its own roles, hence reduce the amount of work that your memory has to carry out. Moreover, after you put everything in a complete system, actually you would realise that there are many unnecessary things that you can ignore. One more time, you can minimize the amount of info that our limited memory has to store. Personally I think that's the most effective way to study for me.

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Yawn!!!

I Think I SHOULD and MUST go to bed now.

Tmr Training 6.35 a.m, horrible.

Save me, God.

And all the best, Chandel (kidding only why so serious?).