Monday, 1 October 2007

How latitude and altitude affect temperature...

***IMPORTANT! THIS IS IN THE EXAM!***

How does latitude affect temperature?

We all know by now that the Earth can be broadly divided into 3 climate types: tropical, temperate and polar. We also know by now that the further we travel from the Equator, the colder it gets. Hence, at the high latitudes, close to 90° North and South, temperatures are much lower than at the Equator.

Why is this so? Why is the temperature in Singapore so different from that in Greenland?

There are various reasons for this. The most important one has to do with what is known as the angle of solar incidence. Angle of solar incidence refers to the angle at which the Sun's rays strike the Earth's surface.

In the above diagram, N.P. represents the North Pole. 'Insolation' refers to the amount of incoming solar radiation, but that is beyond the scope of the syllabus. The dotted line represents the limit of the atmosphere.

At the Equator, the incoming solar radiation strikes the Earth at a right angle. Hence the heat from the Sun is concentrated and more intense, and is spread over a small area. Also, at this latitude, the Sun's rays travel a short distance through the atmosphere. Because of the shorter distance travelled, Less heat is lost to the atmosphere, and therefore more of the Sun's rays reach the Earth's surface.

On the other hand, at high latitudes, the incoming solar radiation strikes the Earth at an acute angle. The Sun's rays also have to pass through a longer distance in the atmosphere before reaching the Earth's surface. Hence more heat is lost to the atmosphere. Even though the rays which strike the polar regions carry the same amount of heat as the rays which strike the tropical regions, this heat is diffused and dispersed over a large area.

Let's use a flashlight as an analogy:



A represents the Sun's rays hitting the Earth at the Equator. The heat is focused and concentrated over a small area and is more intense.

B represents the Sun's rays hitting the Earth at the North Pole. The heat is diffused and dispersed over a larger area.

I hope you remember that in primary school, you learned that it is hottest at midday, when the Sun is directly overhead, whereas it is cooler in the morning and evenings, when the Sun is lower in the sky. This is the same general principle by which latitude affects temperature.

In summary:

• At different latitudes, the Sun's rays strike the Earth at different angles
• At the Equator, the Sun's rays strike the Earth at a right angle, hence the heat is more intense and concentrated over a small area. Less heat is lost to the atmosphere as the rays travel a shorter distance through the atmosphere.
• At the poles, the Sun's rays strike the Earth at an acute angle, dispersing and diffusing the heat over a larger area. More heat is lost to the atmosphere as the rays travel a longer distance through the atmosphere.

One final note: While it is hot and wet in the tropical regions, it is cold in the polar regions, so cold that most of the precipitation is frozen, and falls as snow.

How does altitude affect temperature?

Most of you would be aware that it tends to be very cold at high altitudes, such as on mountaintops, or up in the sky. Logically, one would expect that the higher the altitude, the higher the temperature, because mountaintops are closer to the Sun than objects at sea level. This is incorrect.

In actual fact, the atmosphere is NOT warmed by direct contact with the Sun's rays. What really happens is that the Earth's surface absorbs most of the heat. Then, as the Earth's surface warms up, the heat diffuses into the lower layers of the atmosphere, warming it, which in turn transfers some of the heat to the upper layers of the atmosphere.


Of course, this means that the layers of atmosphere closest to the Earth's surface receive the most heat from the Earth's surface.

What happens at high altitudes, such as on mountains, or in the upper layers of the atmosphere, is that at such great height, far from the Earth's surface, there is very little heat reaching this altitude. Most of the heat is being trapped within the lower layers of the atmosphere close to the Earth's surface.

Try and visualise a thermos flask with several layers of cloth wrapped around it. The thermos flask represents the Earth, warmed by heat from the Sun. The layers of cloth represent the layers of the atmosphere, with the layers of cloth closest to the thermos flask representing the layers of atmosphere closest to the Earth's surface. The layers of cloth on the outside would be much cooler, because most of the heat from the thermos flask is trapped in the inner layers of cloth.

In summary:

• The atmosphere is progressively warmed by the heat radiating from the Earth's surface
• The lower layers of the atmosphere closest to the Earth's surface are warmed first, and then subsequently transfer heat to the upper layers. As the heat is transferred upwards, some heat is continuously being lost.
• At high altitudes, there is very little heat left to be transferred at this height.

7 comments:

linxin-pei said...

Yes,I'm highly honoured to be the first person on this blog (or at least I like COMMENTED) And I would like to ask when will "work in progress" be completed? Though I greatly appreciate the fact that you have put up such an extensive and comprehensive reference for us, however,the TIME (Yes,time equals gold) is running out. Please accept my deepest gratitude if you have viewed the insignificant little comment. Oh and BTW, some hints and tips on the highly revered (And tested) Geographical topic of Rocks and Landforms would make an immense impact upon our now less-than- satisfactory performance. Our laziness, unfortunatly prevails thus printing would be an considerably easier option to the widely used technique of manual note-taking. Once again, thanks for, ahem, paying attention to my ranting.

My Life said...

ohh. hahahahhahahahahas. hi mr kwan. guess who am i ? lols. nice effort. can see u are trying to help us (:

lovelygirl said...

OMG... that's one whole chunk. I waited for it yesterday like hours.. but it didn't come. Only till today. Aww.. Mr Kwan you helped us alot... Thanks for your efforts, we will do our best in the exams =)) And can you do away with the verification code? It's kind of a hassle.

Blade,or maybe Darren will do ><" said...

O.o so many
thks for puting dis up
i read it twice le
1. was i went n see wat the blog was about den watch video it was nice but nid to bluff ><"
2.JUST THE DAY BE4 THE EXAM!
i relli go n read it coz i dun wan to fail T_T lolz
just a comment next time ur blog dun hav so many links
i spend lots of time to read it as many many many.....links
k i go slp le nid enuff slp ltr cannot concentrete>dun noe how to spell><"
thks i noe alot ppl will lyk it^^
also at all u sites.....

Blade,or maybe Darren will do ><" said...

how do u do the number thingy
example> singapore is at 1'degree'N
103'degree'E>>>>>i dun get it!!!
can u giv a quick reply PLZZ ....if u r on9 n reading dis><"

Blade,or maybe Darren will do ><" said...

ooo nvm le i ask my 'professional bro' Lolz its ok now the text book so chim but i gt it all figured it out
pro rig><"....i noe ^^

Aatmik said...

great stuff
i checked out everything else but you had the only clear answer for why a higher place is colder.

thankyou
Pico Sellers