Me- Haha, hello everybody!!
Class- Haha, hello hello!!
Okay, let’s talk about our Geo lesson on Mon :)
Firstly, we shall remember “GEOG”:
❤G- Good Attitude
❤E- Engagement
❤O- Ownership
❤G- Growth
This is very important for our Geo lessons❤
Now, let's talk about the following question:
“Why aren’t deserts found at equator???”
We all know deserts are very warm but…
Does it mean that deserts are located at the warmest region of the earth which is known as “equator”?
The answer is NO.
A desert is a landscape or region that receives very little precipitation. Deserts can be defined as areas that receive an average annual precipitation of less than 250 mm (10 in), or as areas in which more water is lost than falls as precipitation.
Thus, the real answer to the question is related closely with Global Air Circulation!! Now, let’s talk about the global air circulation, yeah!!
Firstly, we assume the earth is at rest. As what we have learnt before, air flows from the cold parts to the warm parts because cold air is heavier than worm air. Therefore, it should flow from the poles to the equator. However, because of the influences of convection and convergence, when the air reaches the equator, it will be lifted vertically and then flows horizontally. Finally, the air will flow back to the poles from the equator. The upper air at the poles then will sink as it is cooler. By doing so, air circulation is completed!!vvvvv
However, as the earth is rotating from the west to the east all the time, the first model is not completely correct. The rotation will develop the one-cell circulation to three. The three cells are known as: the Polar cell, the Ferrel cell and the Hadley cell.Both of the Polar cell and the Hadley cell are driven by heat while the Ferrel cell is driven by the other two!! From the model above we can see that the air is sinking at the shaded region. As what we have learnt before, air will keep rising when it is warm. It will finally form clouds and make RAIN!! However, there is no adiabatic cooling of the air of the shaded region and it sinks so that there will not be clouds thus there is not RAIN!! Therefore there is very little precipitation there. Thus, deserts are formed there!!!
So, this is why deserts are found at those areas instead of at the equator!!!
Haha, done, yeah!!!
:D
Done by Liu Tong :P
Hi Liu Tong! Thanks for your post! :) The diagrams are really very neat and pretty! :)
ReplyDeleteAnd thank you for putting up my expectations on the blog so people are always reminded of them! No excuses anymore!
BUT...Do take a look at PhysicalGeography.net and check through your diagrams carefully! Will go through it in class. But I know you did do some extra work yourself, and appreciate it! :)
- Ms Tang =)
heyy, An is here, about the formation of desert, we all know that desert ca also be formed by showdow rain, which is the effect of orographic rain. As warm air is forced to move up, rain is commonly found on the top of the mountain. As a result, in the leeward side of the mountain, wind has less moisture and therefore less rain.
ReplyDeleteIn addition, winds that travel long distance also lose moisture and it is also one of the cause of the formation of desert. ( For example Gobi and the interior part of Sahara. :D
oh yeah, in my opinion our 3 cells model is very nice but then the location of desert is a bit wrong I think. Because deserts are formed between the Hadley and Farrel cell, and I thought it should be at about 30 degree in both north and south? Haha, sorry, I'm a bit too detail ald.
ReplyDelete:D
WOW! I'm really amazed at your post. Previously, I always thought that deserts are only at the equator and didn't think about such thing as the movement of air. But I think there is something you missed out, there are also deserts found at the polar region, yup. :) due to the air movement too.
ReplyDeleteLuke