Zhao Pei
HELLO! HELLO! :)
So it is finally my turn to blog! Minh and Yida are absent both today. They are roommates of each other. I can not image what they were doing in their room while we were having Geo lessons...
Haha. Sorry for being so random. Today we talked a lot about the SEASONS and the DESERT. I think Minh had talked a lot about the seasons in his previous blog. So I shall focus on desert today:)
We are in the DESERT now! If you look at the world map carefully, you will notice that most deserts do not distribute among the equator. Places at the equator receive more sunlight and radiation than other places in the world. But why deserts are not found in equator?
Before we answer that question, we shall focus on the following two questions: "how does the air move around the earth? " and "how does gas transfer the heat? "
You can draw a diagram to show how the air move around the earth. And this is our answer :D
HOWEVER, all of us forget that the world we live in is 3D! But never mind, the teacher said we grabbed the concept already! :)
We shall take notice that warm air does not transfer forever, it will sink/rise once it gets cool/warm.
So here is correct version:
It is the same with this diagram below:
And we shall not forget that the earth will rotate from the west to the east. Therefore:
(I think I drew too many diagrams today and I hope they are useful.)
Last Question: Why desert are not found in the equator?
-What define deserts? What made deserts? (Dry! Lack of water→desert!!! Desert depends on amount of precipitation, not heat. )
Because ,the air is cooled down and therefore the air sinks at the hemispheres. (Which means there is no adiabetic cooling and air there will never rise.) Therefore there is very little precipitation around those areas. That is why you can see clear blue sky in the desert in the day time. Because there is no cloud covering, the temperature of desert is very high in the day time(40̊ C-50̊ C) and id very low at night (around-10̊ C).
So, that is about it, I hope:)
Comments:
Just to add on, I believe that the global air circulation is also one of the reasons why we
experience a tropical climate at the equator. For the presence of precipitation, there has to be adiabatic cooling. If we observe the 3-cell model, we notice that the Hadley cell, fuelled by heat from the sun, gives rise to rising air from the equator. Consequently, precipitation is greatest around the equator and gives us our tropical climate.
Similarly, as precipitation is the least where air descends, deserts also occur at the poles where the cool air sinks. As there is no precipitation, this polar deserts experience little snow, yet due to their location on the Earth, they still experience the cold climate unique to the poles. Its kinda cool actually :)
Victoria
posted by 08ip01 at
10:26 PM
5 Comments:
Farrel cell is actually indirectly driven by Polar and Hadley cells. For explanation, take note that the direction of air flow in between those two cells perfectly adhere, hence an induced air cell can form there.
Actually a better question can be: Why are deserts commonly found along the tropics?
Ans: According to the tricellular model, air sinks at the two tropics, hence there's no air rising up and no adiabatic cooling. As a result, cloud cannot be formed and there's no rain as well.
I am quite certain that most of us now knoww taht deserts are not only caused by the tricellular model but also because of the type of percipitation called relief or orographic rain. In such cases, the moist winds which carry water vapour for percipitation is is obstructed by the presence of mountain. It is because of this that there will be rain on thw leeward slope of the mountain but not on the downward slope on the other side, causing deserts to form there. Boy aren't we lucky that there arent any mountains in Singapore :D
It is also interesting to note that winds that have traveled a long distance will lose a great deal of their moisture, hence the deserts are extremely dry. The most moist air comes from the sea, and when it gets inland, it becomes drier. Continental deserts, such as the Gobi deserts, are formed due to their position inland, on arid land. Their temperatures fluctuate a lot too, hovering between -40degrees celsius in the night and 40degrees celsius in the day.
Regarding the tri-cellular model, does the tilt of the earth affect this? Remember that warm air rises at the equator (probably cause it heats up faster due to getting more intense radiation, if i remember correctly), so does that mean that during summer, due to the tilt of the earth, the tropic of cancer will heat up faster, thus experiencing adiabetic cooling?
And if this happen, shouldnt deserts have a 'rainy' season or something?
Post a Comment
Subscribe to Post Comments [Atom]
<< Home