IS2104: Atmosphere and Hydrosphere

Reflections

Lesson 11 February 24, 2010

Filed under: Uncategorized — 09ip01 @ 9:29 pm

Today, we learnt that in most cities of today, energy goes in, waste comes out, and the waste does not get converted back to energy. This results in an open cycle, much like the system of a car; fuel goes in, exhaust comes out, no recycling; a one way system.

We also watched a video, in which we were shown a city plan, in which the grass and plants in the location where it is to be built were planned to be lifted to the rooftops of the buildings, forming an extremely large garden. Also, there were waste recyclers to break down the waste of the city and use it to generate more energy. Not only that, the location’s natural aspects were carefully noted, and the city’s design was tailored to ensure that all apartments will get some sunlight, and the wind spread evenly in the entire city. This way, energy goes in, waste gets recycled in to energy, and so on and so forth. Now, it is more like a closed cycle. E.g. water cycle

I feel that the lesson today is that cycles are important. Without them, everything will go out of balance, such as how the modern industry and cities are threatening to shatter the delicate equilibrium of the environment. Another point would be that we should not rely on the natural cycles to keep bringing things back to an equilibrium. Some natural cycles take much longer to replenish depleted resources than the rate at which they are consumed: e.g. fossil fuels.

Some, such as the architects of this intriguing city plan, have already begun attempts to right the failing balance. Will it be in time, though, I wonder?

-Weijie

 

Lesson 10 February 23, 2010

Filed under: Uncategorized — 09ip01 @ 4:48 pm

Today’s lesson we learnt about the revolution and rotation of the sun, and also why there are seasons as well as day and night.

A revolution is also called a year. The Earth takes 365.25 day to revolve around the sun.  Revolution is the reason of seasons.

Earth’s rotation is the rotation of the solid Earth around its own axis. The Earth rotates towards the east. As viewed from the North Star Polaris, the Earth turns counter-clockwise.One rotation is a day. It’s the reason for day and night.

During the year, the seasons change depending on the amount of sunlight reaching the Earth as it revolves around the Sun.

The seasons are caused as the Earth, tilted on its axis, travels in a loop around the Sun each year. Summer happens in the hemisphere that tilted towards the Sun, and winter happens in the hemisphere that tilted away from the Sun. When the Earth travels around the Sun, the hemisphere that is tilted towards or away from the Sun changes.

This graph shows the revolution of the earth and the reason of seasons:


The hemisphere that is tilted towards the Sun is warmer because sunlight travels more directly to the Earth’s surface so less gets scattered in the atmosphere. That means that when it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere. The hemisphere tilted towards the Sun has longer days and shorter nights. That’s why days are longer during the summer than during the winter.

In general, the further away from the equator, the cooler summer and winter temperatures become. At the equator there is always summer because each day the Sun strikes at about the same right angle. Every day of the year the equator receives about 12 hours of sunlight. The poles remain cool because they are never tilted in a direct path of sunlight. Much light is scattered by the atmosphere before reaching the Earth surface at the poles. During midwinter, when a pole is tilted away from the Sun, there is no daylight at all. The sun never rises! However, during the summer, a pole receives sunlight all the time and there is no night!

Summer happens in the hemisphere tilted towards the Sun, and winter happens in the hemisphere tilted away from the Sun.


–Pang Yuwei

 

Lesson #9 (22/2)

Filed under: Uncategorized — 09ip01 @ 12:34 am

Composition of air in the Earth’s atmosphere -> carbon cycle -> planetary heat balance -> precipitation -> weather and climate

When we talk about weather and climate, these few words come to our mind:

– Cold

– Hot

– Sunny

– Cloudy

– Humid

– Rain

– Thunderstorm

– Hail

– Snow

The difference between climate and weather is that weather is the state of atmosphere now, but climate is the average weather at a certain area over about 30 years.

To give words that are the most important when you think about weather,

Warm – regarding planetary heat balance

Temperature

Wet – determined by location, and precipitation

Water

Humidity – does it involve precipitation and ground water?

Wind

All those words are involved with the weather and climate and other parts which we have learnt about (e.g. planetary heat balance, precipitation, etc), which are conditions that affect life.

Then we take a look at the map, why is the centre near the equator drier than the north and south?

– The earth is an obloid sphere.

When radiation reaches the centre (near the equator), it is hotter as the radiation is stronger. This is direct insolation.

At the ice caps (which is further from the sun as compared to the equator area), it is colder as radiation spreads out and thus the heat is not so strong. This is diffused insolation.

So the heat from the sun is strongest at the equator.

– Rachel

(P.S. someone teach me how to upload pictures!)

 

Lesson #8 February 9, 2010

Filed under: Uncategorized — 09ip01 @ 10:59 pm

Today, we learnt about the formation of rain, how rain is formed. Basically, there are three types of rain formation, namely

– Orographic (relief) rain

– Frontal rain

– Convectional rain

So firstly, how does rain come from the clouds? Clouds are actually made up of mass of water droplets. These water droplets are very small, so small that they can remain in the air. So, these water droplets would coalesce (blend/come together) together to form larger water droplets and once these larger water droplets are large enough, they would then be heavy enough to precipitate down as rain. Basically, mass of water droplets would make up cloud droplets and many of these cloud droplets would make up your cloud!

Then why do clouds look dark when it is going to rain? When it is going to rain, there would be many of these cloud droplets. So, as it is too dense, it will block and scatter the light from the sun, thus it will appear dark!  Water droplets actually will bounce off each other.  Therefore, a dust particle is needed to stick the water droplets together, preventing them from bouncing off.

What is adiabatic cooling? Adiabatic cooling is basically the cooling of air when it rises. We know that warm air rises and when it rises, it becomes cooler and this drop in temperature is due to the decrease in atmospheric pressure at higher altitudes. Thus, if the pressure of the rising air decreases, it will expand. Therefore, when it expands, it will lose heat to the surrounding and cool down and thus the water vapour would condense into water droplets. Similarily, adiabatic heating would refer to when the air is being forced to descend, it would be compressed and thus its temperature would rise. However, in order for condensation, the air must contain moisture, if not there won’t be water vapour! IMPORTANT!

So now lets move on to the different types of rain.

Orographic rain is basically when warm maritime air is forced upwards due to a mountain range, it will undergo adiabatic cooling and thus the water vapour would condense into water droplets and form clouds. And when these clouds get too heavy to be suspended, heavy rain falls. However, rain would only take place around the top of the mountain range as when air descends on the other side of the mountain range, it will undergo adiabatic heating, compressed and warmed and thus will produce little rain as condensation would cease, creating a rain shadow.

Frontal rain is basically when two air masses of different temperature, density and humidity meet such as the meeting of a tropical maritime air and a polar air mass. A zone called a front separates them. At the warm front, the lighter warm air would rise over the cold air which remains close to the ground. The warm air would then undergo adiabatic cooling and thus rain would fall. The rain would fall steadily ranging from a few hours to several days.

Convectional rain basically occurs when the continuous heating of the ocean from the sun would cause the moist air above to heat up. The warm air would undergo adiabatic cooling and thus rain will fall as well. The cycle is like convection as its name suggests. However, this only occurs commonly in warmed or heated areas such as equatorial/tropical regions and normally happens in the afternoon, evening period. The rain would be intense however short-lasting.

Okay, im done. I know its alot and sorry for putting up so late at night. But anyway, good luck to everyone for the test tmr. Happy mugging!

Bryan

 

Lesson#7 (3/2/10) February 3, 2010

Filed under: Uncategorized — 09ip01 @ 11:20 pm

Today, we learnt about the formation of clouds and a recipe on how to make clouds from Mr Heah. Based on the diagram above, we can see that clouds are formed from the condensation of the water vapour/moisture. The reason behind this is because the atmosphere is cold and has a low pressure, hence the water vapour will condense and become clouds.

So here’s the recipe for making your very own cloud:

Ingredients:

– 1 plastic bottle that is a bit wet inside

– 1 box of matches

Instructions:

  1. Squeeze the bottle repeatedly
  2. Light the match and then extinguish it. Get some of the smoke into the bottle.
  3. Squeeze the bottle repeatedly again.
  4. Let go of the bottle, and remove the bottle cap. And tada! You’ll be able to see some fog/clouds escaping from the bottle slowly.

Actually, I think this mini cloud making process is similar to the cloud making process in the atmosphere. The squeezing of the bottle is probably to cause low pressure in it, just like the atmosphere. And the interior of the bottle is cool too (due to the low pressure PV=nRT) just like the atmosphere. So this kind of makes an ideal environment for condensation to occur. But what about the smoke? Surely there must be a reason for adding it right? Sometimes when I take the bus to school and the air-con is at full blast, I’ll see some condensation on the window. Water vapour from the surrounding air condenses on the cool surface of the window. My guess is, besides having a cool environment; having a “surface” is probably required for water vapour to condense on. So the smoke acts as a “surface” for the water vapour to condense on and so you will see your cloud being formed.

-Esther

 

lesson #5 February 1, 2010

Filed under: Uncategorized — 09ip01 @ 11:17 pm

oh my goodness, wordpress is hard to use, that aside, previously, we learnt about the atmosphere and the gases present in it that will help to maintain a delicate balance where life balances on. This week, we learn more about carbon dioxide and how it regulates the temperature on our Earth. We finished up on the carbon cycle and we learnt about how, when one factor changes in the carbon cycle, it would indirectly affect the other factors as well. Next, we were allocated 40 minutes to draw out a diagram that would help illustrate the planetary heat balance.

the notes do not really make much sense to me, because i do not understand how 100 units of heat available at the top of the atmosphere could lead to 117 units of heat being present on the surface of earth. i hope you all had more success than i did. im sorry this is so rushed out, but i’ll publish this as it is first and come back to edit it later on.

denise