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Saturday, January 29, 2011

Hey peeps! Sry I can’t post as much as Sylvia either.. X)
Heat budget system
The heat budget system is important to earth as it helps to keep us warm, and thus makes earth habitable. Therefore, we cannot live on mars or any other planets because this system (including other cycles) is absent, and hence the planets cannot maintain a suitable temperature.
The heat budget system must be balanced.  If not, the earth will either heat up or cool down too much. If it is balanced, there would be a constant temperature.

Shortwave reaches the earth as (1-4microm) ultraviolet light, infrared and light radiation entering the earth’s system. This gets reflected back into space by clouds, air particles and land surfaces. Long wave radiation (longer than about 4 microm) is heat, which becomes either trapped in the atmosphere or lost to space.

30% of the sun’s rays are immediately reflected back into space. 20% heat the earth’s atmosphere, leaving only 50% to heat the land and oceans. If the rays don’t escape to space, the earth would be too hot for humans or animals to survive.

The carbon cycle actually interacts with heat budget. Hence, there is no balance, and the earth heats up. This leads to global warming. This would lead to harm of the environment. For example, polar ice caps would melt with global warming. When polar ice caps melt, the heat budget would also be affected because the ice helps to reflect light. Global warming would also cause strange weather. When the earth heats up, the gas would expand. As a result, it takes up more space and rises. This causes high and low pressure in the air, which results in wind.

Several cycles are present to control the climate on earth.


Heat budget system

Carbon cycle 

The water cycle

 (sry for the small pictures. the layout of the blog doesn't allow me to post bigger ones. anw, if you cant see clearly, just enlarge the whole thing :))

Some terms:
Latent heat: Energy released or absorbed to change a substance to gas.
Sensible heat: Visible to the naked eye such as steam from a cup of coffee
Albedo: Ability of an object to reflect light and radiation.


Friday, January 28, 2011

Longwave radiation and Shortwave Radiation

Hello people! I seriously don't think I'm able to write as much as Sylvia so at least you all get to read something short and sweet.
Shortwave Radiation
This isn’t in the notes
Shortwave radiation is basically radiant energy (light) in the visible, near infrared and near ultraviolet spectrum. Some of this shortwave radiation which enters the Earth is reflected to space in the end due to various means of reflection, with the others being absorbed by the surface or other things as shown in the diagram below. (The shortwave radiation is labeled with red arrows.)
The Earth-Atmosphere Energy Balance
Longwave Radiation
Longwave radiation is energy leaving the Earth as infrared energy. Although the surface of the Earth emits a large amount of longwave energy, only around 5% is directly lost to space, with the majority being absorbed by greenhouse gases and being converted to heat energy which is then emitted as atmospheric longwave radiation, resulting in the greenhouse effect. The atmospheric longwave radiation emission is split into 2 categories with 40% being lost to space, and the other 60% being transmitted to the Earth’s surface where it is absorbed and becomes heat energy. (Refer to diagram above for specific details.)

Saturday, January 22, 2011

The Carbon Cycle

Hello :) So here are the things I understood from the notes. The post would be quite lengthy, have a lot of arrows, and notes in point form. So please bear with me.
Carbon is essential as it provides energy through photosynthesis and respiration. The very presence/absence of it helps determine whether a molecule is considered organic or inorganic, and it controls the pH level in the ocean. Also, it allows carbon to be recycled and reused in the biosphere as well as in organisms, and ensures survival. As of today, the pH level of the ocean is decreasing due to the excessive uptake of carbon dioxide in the atmosphere. Carbon dioxide also increases the atmosphere's ability of hold heat, hence the name "greenhouse gas".
Carbon can be found in: carbon dioxide, limestone, diamonds, graphite, the ocean floor, the Earth's mantle etc.
The carbon cycle is a biogeochemical cycle by which carbon is exchanged, in different forms, on Earth. The cycle is divided into two subcomponents: the geological component (of which the elapsed time scale is millions of years) and the biological component (time scale spanning a few days to thousands of years). Carbon movement and exchange occur due to specific chemical, physical, geological and biological processes. Unless there are external influences (e.g. black smoker and uncontrolled deep water oil leak, both of which emit large amounts of sulfite and hydrocarbon (diff. forms of carbon compounds), respectively) that significantly increases/depletes the amount of carbon in the ocean, the cycle occurs gradually.
Difference between carbon sink and carbon source: carbon sink---more carbon enters than leaves (think 'whirlpool' and the carbons sinking); carbon source---more carbon leaves than enters (think 'origin'). Oceans are long-term sinks atmospheric carbon dioxide due to both the ability to form limestone and fossil fuels.

Linking carbon cycle to the rock cycle. (Lots of arrows here).
Forms of interaction: weathering and dissolution, precipitation of minerals, burial and subduction, volcanism

(In the atmosphere)carbonic acid reacts with carbon dioxide and water --> rain --> weakly acidic water reacts with minerals at the Earth's surface --> (chemical weathering) minerals will dissolve into their component ions --> ions will be carried in surface waters (e.g. lakes) and eventually reach the ocean, where they precipitate out as minerals like calcite (CaCO3) --> minerals sink to the bottom of the ocean
-->deposition (meaning 'removal') and burial of calcite --> (over time) limestone will be formed due to compression of sediments --> (geographical condition) subduction --> limestone and seafloor carbon heats up and melts --> carbon rises back up to oceanic surface --> interaction of molecules on oceanic surface
--> carbon dioxide released into the atmosphere

Note: Volcanic eruptions, seeps (places where liquid from the ground oozes out from the Earth surface), vents (openings at the Earth's surface where volcanic material is emitted), and carbon dioxide-rich hot springs, also release carbon dioxide into the atmosphere.
Note: Carbonic acid gas is produced by respiration, burning charcoal/other carbon compounds, when chalk/marble/limestone meets a stronger acid like sulfuric/muriatic acid, etc.

Linking carbon cycle to the hydrosphere.
1. Extreme storms (e.g. hurricanes and typhoons) --> sediments will be washed away into the oceans --> carbon/calcite minerals will be buried under ocean bed --> deposition and burial of carbon/calcite --> limestone formed --> (refer to the cycle written in the section before )
2. (Convection Current concept needed) Oceanic upwell (meaning warm oceanic water rises, cold water sinks) --> cold water on oceanic surface allows carbon from heated limestone (from subduction) and and ocean floor to be released into the atmosphere
Oceanic downwell (inverse of oceanic upwell) --> carbon dioxide from the atmosphere will be converted to dissolved carbon in oceanic water. Atmospheric carbon --> dissolved carbon dioxide.
3. Dissolved carbon dioxide reacts with water to form carbonic acid
   Carbonic acid will be in equilibrium (meaning 'reversible') with hydrogen ions + bicarbonate ions when the acid reacts with weathered rocks
   Bicarbonate ions will be in equilibrium with hydrogen ions + carbonate ions
  Carbonate ions + calcium carbonate (from shells of oceanic microorganisms like phytoplankton) will form carbonate sediments (which form limestone)
4. (Only under certain geological conditions) Organic matter buried --> (over time) deposits of carbon-containing fuels coal and oil formed (remember black smoker and uncontrolled deep-water oil well leak?). Non-calcium containing organic matter is transformed into fossil fuel.
Note: Calcium carbonate is an inorganic carbon.

Linking photosynthesis, respiration, the climate and the carbon cycle.
I'm sure you all know how carbon dioxide plays a role in both photosynthesis and respiration so I won't say much about it. :)
(During daytime) Leaves absorb sunlight --> carbon dioxide taken from the atmosphere; microorganisms consume organic carbon matter (e.g. carbohydrates) --> carbon dioxide returned to the atmosphere through respiration. Level of carbon dioxide and oxygen somewhat the same, not including external factors like extensive burning of fossil fuels, deforestation etc.
(At night) Photosynthesis stops (no solar energy); respiration continues. Atmospheric concentration of carbon dioxide is higher than oxygen's.
(During winter) Plants lose their leaves --> photosynthesis ceases --> atmospheric carbon dioxide concentration increases.
(During spring) Photosynthesis resumes --> atmospheric carbon dioxide concentration reduces.
According to data collected, the Earth's climate has oscillated between relatively warm (interglacial periods) and relatively cold (glacial periods) periods over the past 20 million years.
(Interglacial period) Atmospheric carbon dioxide concentration is relatively high. This period is where we are now, and human activities are increasing carbon dioxide concentrations higher than what have been recorded in the past interglacial periods.
(Glacial period) Atmospheric carbon dioxide concentration is relatively low.

How carbon is emitted/retained but not removed on time (due to artificial causes), consequences of excessive carbon, and solutions carried out by governments:
Sources of carbon:
1. Burning of fossil fuels. Carbon is released into the atmosphere far more rapidly than it is being removed.
2. Deforestation. The ability of photosynthesis to remove carbon dioxide from the atmosphere results in a net increase in atmospheric carbon dioxide level.
1. Rise in average sea-level due to global warming, which melts ice caps. Low-lying coastal cities or cities located by tidal rivers will be exposed, maybe submerged, even.
2. Glacial retreat and species range shifts. Trees may not be able to cope with the extent of global warming.
3. Plant growth will be affected, as some plants/shrubs respond more favorably under high level of carbon dioxide concentration. Grasslands may be invaded by carbon dioxide-responsive grass species.
4. Rise in average global temperature of approximately 1-5 degree celsius in the next half-century.
5. Major changes in precipitation patterns and land use throughout the world.
6. Change in the growth cycle of phytoplankton due to difference in atmospheric carbon dioxide concentration.

Solutions formed:
1. Intergovernmental Panel of Climate Change (IPCC) has been set up to produce reports on climate change.
2. Kyoto Protocol has been carried out to avert the negative impacts linked with human-induced climate change.

To sum up: carbon is released through:
1. Respiration
2. Decay of animal and plant matter
3. Combustion of organic material, which produces carbon dioxide
4. Production of cement (heating of limestone)
5. Volcanic eruptions, seeps, vents, carbon dioxide-rich springs

Okay this is all. Hope you have a greater understanding of the cycle!

Done by: Sylvia :)

Monday, January 17, 2011

The Nitrogen Cycle - 17/01/11

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. Nitrogen is required for all organisms as it is the essential component of DNA, RNA, and protein. However, most organisms cannot use atmospheric nitrogen hence, this cycle is important in the sense that it converts the atmospheric nitrogen into usable forms for living organisms.

(click to enlarge)

As seen from the diagram below, the carbon cycle consists of many cycles within it. These cycles consist of five important processes that are driven by microorganisms, namely:
1) Fixation
2) Uptake
3) Decomposition
4) Nitrification
5) Denitrification

Process #1 - Nitrogen Fixation
This is the process whereby N2 is converted to ammonium. Without this, organisms cannot attain nitrogen as they cannot use the atmospheric nitrogen. Ways nitrogen can be fixated in the biosphere include:
- Bacteria
- Lightning
- Rain

Process #2 - Uptake
This is the process where ammonia produced by nitrogen fixing bacteria is quickly incorporated into protein and other organic nitrogen compounds. When we eat, we are using nitrogen that has been fixed initially by nitrogen fixing bacteria.

Process #3 - Decomposition
When organisms die, or when organisms defecate, decomposers (such as bacteria and fungi) consume the organic matter or animal waste. During this decomposition process, nitrogen contained within the dead organism is converted to ammonium. Once in the form of ammonium, nitrogen is available for use by plants or for further transformation into nitrate (NO3-) through the process called nitrification.

Process #4 - Nitrification
Nitrification is whereby ammonium produced by decomposition is converted to nitrate.
Process #5 - Denitrification
The processes above remove nitrogen from the atmosphere and pass it through ecosystems. Therefore denitrification is important as it replenishes the atmosphere, by reducing nitrates to nitrogen gas.
This process can be carried out either through bacteria or the sea.


Done by: Yangting :D
Credits: 1,2,Pic

Friday, January 14, 2011

The atmosphere.

The atmosphere is made out of different layers, the troposphere, the stratosphere, the mesosphere, and the thermosphere.

The troposphere is where weather occurs and it is the only layer in the atmosphere where this happens. The stratosphere has wind, but no weather. This is because unlike the water cycle that takes place in the troposphere, the wind in the lower stratosphere travels in a parallel motion, and this phenomena is known as the "lee wave". There is also no water vapor in the other levels, an essential element in ensuring weather occurs.

The troposphere decreases in temperature as it goes higher up towards the stratosphere, where it increases in temperature again till it reaches the mesosphere. From the mesosphere, the temperature starts to drop yet again till it reaches the last layer, the thermosphere, where it increases for the last time. These changes in temperature are separated by boundaries. The first boundary between the troposphere and stratosphere is called the tropopause, the second boundary between the stratosphere and the mesosphere is called the stratopause and the last boundary between the mesosphere and thermosphere is called the mesopause. The reason for the terms given is because at the different atmospheric boundaries; the 'pauses', air starts to either decrease or increase in temperature as we go up the layers of atmosphere, hence the name.

Something interesting about the atmosphere is that despite the high temperatures at the thermosphere, if we humans were to go up to the thermosphere for example, we would not feel the heat and instead, feel cold. This is because even though the particles are of temperatures like 2500 degree celcius, they are positioned very far apart and even if one of the molecules hit us, it will simply only kill/vaporize a few cells on our body and this damage is so insignificant that we wouldn't even notice it. Therefore, because majority of our body is not in contact with any of the high temperature molecules at any one time, we feel cold instead. In simpler terms, there is no medium in the thermosphere to transfer the heat to our body. At least, not enough at any one point to let us feel the burning heat of the thermosphere. The same explanation can also be used to explain why pressure decreases as we go up the different layers, despite the increasing temperature.

Also, did you know that because the temperature at the tropopause and the lower stratosphere is nearly constant with increasing altitude, there is very little convective turbulence? This provides a good pathway for aeroplanes to fly at as this will optimize fuel burn. That is why aeroplanes have to go way up high into the sky after takeoff and not just a little high up where we are high enough to not crash and yet can still see the ground.

I hope this summarizes the lesson on 13/11 and you learnt something new as well as refreshed your memory. :)