Tuesday, March 31, 2009
WATER BALANCE
When △S = 0, what will happen?
-The soil cannot absorb water any more
- This kind of soil cannot attract more water.
- Using the wrong kind of soil.
All in all, there is no soil storage.
That’s all for today’s lesson. Although it is very short, it is quite important for us to have a better understanding on water cycle.
Wednesday, March 25, 2009
25 March 2009 Geog Blog Post
We talked about the drainage basin and how it helped...um...drain water and stuff like that. We also talked about how to locate and find the start and end of the drainage basin. How different types of soil have different types of storage capacity, known as infiltration capacity. Which is the amount of water the soil can hold before overflowing. Now for water, the most important thing about water and the most unique is the fact that it is bonded by hydrogen bonds. Water has a very very VERY wide temperature range, this means that remains in liquid form over a wide range of temperatures.brendan
Tuesday, March 24, 2009
Introduction to Hydrosphere
Hey all.Today we had lesson on Hydrosphere at the beautiful garden.
If all of you recalled, we already touched on hydrosphere last time - the basic water cycle. Water evaporates from water bodies, rises, expands and cools (adibetic cooling). Then the cloud gets heavy and water droplets fall from the sky as raindrops.
Water is ESSENTIAL for life. Some micro-organism can survive without atmosphere but NOT water. During seasons change, life forms are also affected due to the water available. For example, during winter and autumn , plants start to wilt due to the scarcity of water. During spring and summer, life flourish. Not just seasons, the place also affects the amount of water available. For example, at the tropical countries where it is wet and warm, forests are very densed. At deserts, there are very little plants due to the scarcity of water.
To understand the drainage system- imagine yourself as a cute little water droplet. What will happen to you?
- Fall onto the soil, seep into the soil and join the ground water (infiltration). Infiltration capacity is defined as the amount of water the soil can hold.
- Flow laterally downslope (throughflow)
- Flow laterally horizontally (baseflow)
- Get intercepted by trees and leaves (interception). Tree by itself acts like an inverted drainage system.
Changing the ground from soil to concrete can change the entire system of drainage. This changes the amount of groundwater available and the amount of water available in soil thus affecting the availability of water for plants and affecting the whole bio system.
Now, isn't that interesting and amazing? Thank you!
JH.
Summary Of Atmosphere
Hello Everyone! This will be the Summary of the first half of our Physical Geography Module, IS2104. We have learnt a lot about The Atmosphere of our Earth throughout the entire Term 1.Well, the Atmosphere's structure can be split into 4 sections - Troposphere, Stratosphere, Meosphere and Thermosphere. The Troposhere distributes heat energy throughout the Earth, while the Stratosphere contains the Ozone Layer. The Atmosphere is composed of 21% Oxygen, 78% Nitrogen and 1% Other Gases. Carbon dioxide (<>. The Greenhouse Effect traps heat from the sun in the atmosphere and also helps reflect infared radiation.
Progressing on, we learnt about the Planetary Heat Balance, which is a system that helps to keep Earth in thermodynamic equilibrium. 100 Units of heat energy from the sun enters the Earth. 19 units of insolation are absorbed in the atmosphere(17 by Clouds And Aerosols; 2 By Ozone), 23 units are scattered and subsequenly absorbed by the Earth's surface as diffused insolation, 28 units are absorbed by the surface as direct insolation, and hence the total number of units of heat energy absorbed by both the Earth's surface and atmosphere is 70 units. However, much of this shortwave solar radiation is also lost back to space. 4 units return via surface reflection, 20 units via cloud reflection, and 6 units via back scattering of sunlight, bringing the total loss of shortwave radiation to 30 units.
Longwave radiation also leaves the Earth. 7 units via sensible heat and 23 units via latent heat transfer. Earth's surface also emmits 117 units of longwave radiation, of which 6 are directly lost to space, and 111 units are trapped by greenhouse gases. (NOTE: This is Where Humans are changing the Atmosphere's composition and subsequently causing Global Warming) The Earth's atmosphere emmits 160 units of longwave energy, which comprise 111 units of surface emissions of longwave radiation, 23 units from latent heat transfer, 7 units from sensible heat transfer, and 19 units from the absorption of shortwave radiation by atmospheric gases and clouds. 64 units of atmospheric emissions is lost directly to space, while 96 units travel to the Earth where it is absorbed and transferred into heat energy.
Moving on, we studied rain - types and formation. Adiabatic cooling occurs when air rises, expands and cools. Relief Rain is formed when adiabatic cooling occurs near relief. Air is forced to go over the elevation, it cools, expands, rises and thus results in rain forming on the windward side of the elevtation. Frontal Rain occurs when a warm air mass and cold air mass collide. Warm air comes from the equatorial regions, while cold air comes from the polar regions. When the two air masses collide, warm air is forced to rise, Adiabatic cooling occurs, thus clouds form and rain results. Such rain is found at temperate regions, where cold air and warm air meet. Convectional Rain occurs when warm air rises. The Earth's surface heats up, as it absorbs heat energy from the sun, and the surface of the Earth transfers heat to the air via conduction. When the warm air rises, adiabatic cooling takes place and clouds from, causing convectional rain. Such rain is found at tropical regions, beause it is sufficently warm, and it occurs usually in the afternoon and evening.
Climate basically refers to how warm and wet a particular location is, over a period of time. The former is measured in terms of temperature, and the latter in terms of precipitation. We can use Climographs to describe climate patterns of different locations. The Earth's climate is not uniform throughout, and varies all around. Essentially, the Earth's tilt and shape result in the distribution of Earth's climate. Climates are distributed among lattitudes. It is warm at the equator, and gets cooler as you progress along the lattitudes, towards the poles. At the equator, the sun's radiation is spread over a small area and is hence very intense, resulting in equatorial regions being very warm. Moving away from the equator, the sun's radiation is spread over increasingly large areas and is thus less and less intense, resulting in temperatures turning lower and lower.
The seasons of the Earth are caused by the changing orientation of the hemisphere with regard to the sun, when the Earth revolves around the sun. The Earth is tilted at an angle of 23.5 Degrees, and during 6 months of the year, one hemisphere receives more sunlight than the other. During Solstices, the particular hemisphere receiving more sunlight will officially begin summer, while the other hemisphere will begin winter. During Equinoxes, both hemispheres will have equal amount of sunlight. Equinoxes indicate the time whereby one hemisphere will begin receving more sunlight, and the other, less.
Finally, Mr Heah also taught us about the Global Air Circulation. The Earth can be split into the Polar Cell, Ferrel Cell and Hadley Cell. Warm air from the equator rises and eventually sinks at the polar regions. This would be the Hadley Cell. At the Polar region, air also rises, and this would be the Polar Cell. A third cell exists in between both, and is known as the Ferrel Cell. Almost no air rises from the Ferrel Cell, and there is thus very little precipitation there. Since this is so, there are few clouds above the Ferrel Cell, resulting in unstable and unregulated temepratures that vary drastically with the time of the day A.K.A DESERTS. A final point to note would be that due to Earth rotating from east to west, the pathway of air will swing westwards.
Thank You and I hope this has been beneficial.
Andrew
Friday, March 6, 2009
Last Night's Rain
Monday, March 2, 2009
Geography lesson, 2nd March 2009
Today, we have started a new topic in atmosphere which is the Global Air Circulation. Basically, we have learnt how air circulate around Earth. And thus we know why desserts are not formed around the equater.Today's lesson Mr Heah introduced us a way to make our own simple model of air circulation. Firstly, we need to remove all possible variables to be able to see how only one factor affects the other. So, we romoved all the factors but HEAT from the sun. Because of the uneven distributed heat energy from the sun, for the equator part heat energy is distributed the most intensely part, thus it is the hottest. But for the poles, because energy is distributed to a largest surface area, it is the most diffused around there. And because atmosphere is liquid, convection current will be set up. Therefore, hot air will rise from equator and sink down at the poles. This model is called single cell model which has been blamed for too simplistic.
Then, Mr Heah introduced us another model called three cell model. Basically, in this model, air rise from the equator, and cold air will still sink at the poles. But, along the way that air is travelling, they will sink as well. This convection cell is called Hadley Cell. And around some where near the poles, there will be air rise as well. This cell is then called Polar cell. Then, in between those two cells, there is one more convection current cell, Ferrel cell.
And based on this diagram, we can see why desserts are always formed around from somewhere above equator. As you all can see from the diagram, for the Ferrel cell, the air rises from the terminal which is nearer to the pole and sinks at somewhere above equator. And for Hadley Cell, the air also sinks at the point that air sinks for Ferrel Cell. Thus, there is almost no air rises from that place. Furthermore, because rain is formed when hot air rises(water evaporate) and water vapor condenses then to form clouds and rainfalls. However, for that area, air won't rise, thus there would be very little percipitation here. Thus, desserts are always formed here. Whereas, although, equator recieve the most intensive heat from the sun, but because there are a lot of water evaporate as well, hence, this place recieve quite amount of precipitation every year. Also, we have talked about the cause of charatistics of dessert using air circulation to exphenlain. Because there will only be clouds formed if there is water evaporate from the grand, there will be no or little clouds in the sky. And the clouds can help reflect or keep the heat from the sun, so they can help regulate heat and temperature of a place. Therefore, in dessert, during day time, the temperature is very high whereas at night the temperature is very low.
After finding this three cell model to discribe the air circulation, we added in another affecting factor, the rotation of earth itself. Then, there is another more complicated model.
Because earth will rotate from east to west, the pathway for air flow will swing to the west a bit due to inertia.
From this lesson, the most important thing that I have learnt is how to solve a complicated question. It is just like how to generate the model for air circulation. First of all, we need to break down all the affecting factors and then concentrated on one factor. Then, after that, we should continue to add in other parts to make the model(answer) complete. Also, one more thing to notice is that when we are solving other confusing problems, we should take the easier one to do first and keep adding other harder parts to perfect your answer.
Wen Yu