Global Wind Patterns

Hello everyone, this post is about global wind patterns. Hopefully it may help us understand this topic better! :)

Wind

A big layer of air called the atmosphere surrounds the Earth. The air within this layer moves from place to place when it warms up or cools down. This moving air is known as wind. 
All of these winds are part of a global air circulation system that acts to balance temperature and pressure around the world. In addition, winds move moisture and heat around the world and also produce much of our weather.

Cause

Energy from the Sun heats the entire Earth, but this heat is unevenly distributed across the Earth's surface. Equatorial and tropical regions receive far more solar energy than the mid-latitudes and the Polar Regions.
The tropics receive more heat radiation than they emit, while the Polar Regions emit more heat radiation than they receive. In the other words, there is a net loss of solar radiation in the higher latitudes and a net gain in the tropics. If no heat was transferred from the tropics to the polar regions, the tropics would get hotter and hotter while the poles would get colder and colder. This latitudinal heat imbalance drives the circulation of the atmosphere and oceans.  (Around 60% of the heat energy is redistributed around the planet by the atmospheric circulation and around 40% is redistributed by the ocean currents.)
As equatorial areas are heated most, the air above them warms and rises as it becomes lighter than the surrounding air, causing an area of low pressure. In cooler areas, the air sinks because it is heavier and results in an area of high pressure. Winds will blow as air is squashed out by the sinking cold air and drawn in under the rising warm air. Any difference in temperature like this will always cause a difference in air pressure – and therefore winds will blow. A good expression to remember is that:

"Winds blow from high to low" (i.e.: from high pressure to low pressure).

 Atmospheric Circulations

The following three diagrams describe the basic atmospheric circulation system.

Figure 1: Cross-section of the atmosphere with uniform horizontal atmospheric pressure.

In this first diagram (Figure 1), there is no horizontal temperature or pressure gradient and therefore no wind.

Figure 2: Development of air flow in the upper atmosphere because of surface heating.

In the second diagram (Figure 2), the potential for solar heating is added which creates contrasting surface areas of temperature and atmospheric pressure. The area to the right receives more solar radiation and the air begins to warm from heat energy transferred from the ground through conduction and convection. The vertical distance between the isobars becomes greater as the air rises. To the far left, less radiation is received because of the presence of cloud, and this area becomes relatively cooler than the area to the right. In the upper atmosphere, a pressure gradient begins to form because of the rising air and upward spreading of the isobars. The air then begins to flow in the upper atmosphere from high pressure to low pressure.

 Figure 3: Development of a closed atmospheric circulation cell because of surface heating.

Figure 3 shows the full circulation system in action. Beneath the upper atmosphere high is a thermal low pressure centre created from the heating of the ground surface. Below the upper atmosphere low is a thermal high created by the relatively cooler air temperatures and the descend air from above. Surface air temperatures are cooler here because of the obstruction of short wave radiation absorption at the Earth's surface by the cloud. At the surface, the wind blows from the high to the low pressure. Once at the low, the wind rises up to the upper air high pressure system because of thermal buoyancy and outflow in the upper atmosphere. From the upper high, the air then travels to the upper air low, and then back down to the surface high to complete the circulation cell.

Single-Circulation Cell

One way to transfer heat from the equator to the poles would be to have a single circulation cell where air moved from the tropics to the poles and back.  This  model was first proposed by Hadley in the 1700’s.   Figure 4: Single-cell circulation



Wind Cells

Since the Earth rotates, its axis is tilted and there is more land in the Northern Hemisphere than in the Southern Hemisphere, the actual global air circulation pattern is much more complicated. Instead of a single-cell circulation, the global model consists of three circulation cells in each hemisphere. These three cells are known as the Hadley cell, the Ferrell Cell and the polar cell.

                                                               Figure 5: Wind cells

1. Hadley cell - This is the cell that is closest to the equator.  It consists of winds converging and rising at the equator and then diverging north and south of the equator as it reaches the upper troposphere.  The winds then sink at 30 degrees latitude as they converge with winds in the Ferrell Cell.  They hit the surface and diverge back to the equator to complete the cell. 

2. Ferrel cell - This cell has winds sinking at 30 degrees latitude and then travelling pole-ward as they hit the ground and diverge with winds from the Hadley Cell.  These winds travel towards the poles until they converge with winds in the polar cell at 60 degrees latitude.  These winds then rise up and spread out equator-ward to complete the cell.

3. Polar cell - This cell has winds rising up at 60 degrees latitude and spreading out pole-ward as they reach the upper troposphere.  The winds sink down at the poles and then diverge towards the equator until they reach 60 degrees latitude where they rise up again to complete the cell.

                                                         Figure 6: global wind patterns
Although still oversimplified, this three cell model can describe the main features of atmospheric circulation.

Reference
http://sparce.evac.ou.edu/q_and_a/air_circulation.htm
http://people.hofstra.edu/geotrans/index.html
http://www.eoearth.org/
http://www.rcn27.dial.pipex.com/cloudsrus/home.html
http://PhysicalGeography.net

Done by: Zhexian

The Ozone Layer

I'll be posting about the Ozone Layer because I think a lot of people have slight misunderstandings of the Ozone Layer with regards to the greenhouse effect. 


To recap, the ozone layer is in the stratosphere. 

image taken from: http://www.cec.org/ods/en/module01/cec_odspolicy_m01t01p01_e.asp?print=1
The ozone layer is made up of ozone molecules, O3. The ozone layer is extremely important to us because it absorbs the very harmful UV rays from the sun, preventing them from coming down to Earth's surface, thereby protecting us. These harmful rays can cause skin cancer and many other forms of genetic problems in living organisms. 
Ozone is a greenhouse gas. Greenhouse gases absorbs heat reflected back by Earth's surface. The ozone layer absorbs heat as well. In the recent years, the increased use of chlorofluorocarbons, CFCs, has led to an increased depletion of the ozone layer. CFCs are broken into free radicals by UVt light in the stratosphere. These free radicals then break down more than ten thousand ozone molecules. Thus there are holes in the ozone layer. 
These holes allow more harmful UV rays to reach Earth's surface, dramatically increasing skin cancer/disease rates, especially in Australia which is near the hole above Antarctica. 
Although there are more UV rays entering, it does not affect the heat budget. This is because UV rays aren't considered "heat". The heat budget is dependent on the insolation (incoming solar radiation), in other words, infrared radiation, which doesn't require a medium to travel. So, with or without the hole in the ozone layer, the heat absorbed by Earth from the Sun remains the same. 


Greenhouse gases include Methane, Nitrous Oxide, Water vapor, Carbon Dioxide and Ozone. 

image taken from: http://eo.ucar.edu/kids/green/warming4.htm
The greenhouse effect refers to the greenhouse gases absorbing heat and warming up Earth, sustaining the temperature at which we can all survive in. Without the greenhouse effect, Earth would be too cold to live in. You may have heard of people saying that greenhouse effect is a bad thing, but it is not. It is just that people are concerned about the increasing amount of Carbon Dioxide, which leads to global warming. 
Global warming is the increase of Earth's temperature, mainly due to the increase in the amount of carbon dioxide. With more greenhouse gases, more incoming radiation from the Sun would be absorbed, warming Earth up even more. Thus affecting the heat budget. 
Please correct me if i made a mistake, coz i wrote these from what i understand.
CHANTAL.

Breaking news

Hey people,

I will be covering the World News worksheet based on the articles on drought in France and Australia.

What is the climate? Where is the country located? What is happening?

France is located in Europe, with a temperate climate, and a rather moderate amount of rainfall is facing water shortages due to drought and dry weather.

Australia has an arid climate, low rainfall and high temperature is facing heavy downpours. Queensland is hit by cyclone, Perth, which was threatened with cyclone, is suffering from bushfires and Sydney is suffering from heat waves.

Why? How?

France is facing the worst water shortage since 1976, due to drought and dry weather. Reservoirs and rivers are drying up so fishes and crops are dying. Fines and patrols of “water police” were put in place to enforce restrictions on irrigation and ensure that people do not waste water. Resulting in many people loses money from their farms and more people become unemployed. This could have been a result of higher amount of carbon dioxide, which causes more heat to be trapped in our atmosphere, so lakes start to evaporate and drought occurs.

Australia is facing heavy downpours. One of the biggest cyclones hit Queensland, Perth threatened with a cyclone last week is currently suffering from bush fires, while Sydney is suffering from heat waves. This could be due to the increase in evaporation from lakes due to increase heat trapped in the atmosphere, so the amount of water vapor in the atmosphere increases, causing heavy downpours.

Effects

The above would lead to the people being injured and even death. Buildings are damaged, livestock are killed and people would become homeless and suffer from hunger. The food industry will be affected, since the supply of food decreases while the demand of the people increases. If the problem persists, food prices will rise. Bushfires would damage more plants and increase the amount of carbon dioxide in the atmosphere through the burning of plants. Also, there are lesser plants to recycle carbon dioxide for oxygen. So the heat budget becomes even more imbalance as more carbon dioxide traps heat in the atmosphere. Leading to long-term effects such as temperatures rising, glaciers melting and rising of water level. 

Picture of Carbon cycle and heat budget

Done by: Lydia :)

Climate and Weather

Hey, today I will be covering the definition of Climate and Weather.

First off, I will be covering the definition of climate. Climate covers the topics of temperature, humidity, atmospheric pressure, wind, rainfall and other various factors. Climate is usually contrasted against weather. The latter is the present condition of these same elements and their variations over shorter time periods. The climate of a location is affected by its latitude, terrain, and altitude, as well as nearby water bodies and their currents. As of now, we have already studied the various climate types of tropical (Singapore), temperate (U.S.A), arid (Siberia), polar (Antarctica), mountainous (Himalayas), mediterranean (Greece).

Tropical
A tropical climate is a climate of the tropics. In the Köppen climate classification it is a non-arid climate in which all twelve months have mean temperatures above 18 °C (64 °F).  In the tropics, rainfall is relatively high and allows for the growth of tropical rainforests.

Due to the effect of sun angle on climate most areas within the tropics are hot year-round, with diurnal variations in temperature exceeding seasonal variations. Seasonal variations in tropical climate are dominated by changes in precipitation, which are largely influenced by the tropical rain belt or Intertropical Convergence Zone (ITCZ), a portion of the Hadley cell. Areas of ascending air have heavy rainfall; areas of descending air are dry. The ITCZ somewhat follows the solar equator throughout the year, but with geographical variations, and in some areas (India) is heavily influenced by local large-scale monsoon circulations.

Temperate
We all know the fact that a temperate climate usually has 4 seasons, them being summer, spring, autumn and winter. Temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold. But in continental areas, such as Asia and central North America the variations between summer and winter can be extreme. Most of the world's population live in temperate climates due to the high amounts of land mass within the areas of the polar circles and tropics.

Arid
A region of space is said to be arid when there is an absense of water sources and water bodies nearby. This lack of water bodies hinder the growth of natural vegetation and to some extent hinder the growth of animal life due to the lack of vegetation as a source of food. Environments subject to arid climates are usually called xeric or desertic. This lack of water in arid environments can defer based on where the water is present. A hot desert with alot of water vapor in the air does not allow much plant and animal life as the water is not readily assessible to living things.

Polar
The Earth's polar regions are the areas of the globe surrounding the poles known as the frigid zones. The North pole and South poles being the centers, are dominated by polar icecaps, resting respectively on the Arctic Ocean and continent of Antarctica.

Polar region receive less intensive solar radiation as the sun's energy arrives at an oblique angle, spreading over a larger area, and also travels a longer distance through the Earth's atmosphere in which it may be absorbed, scattered or reflected, which is the same thing that causes winters to be colder than the rest of the year in temperate areas.

The axial tilt of the Earth has a major effect on climate of the polar regions. Since the polar regions are the farthest from the equator, they receive the least amount of sunlight and are therefore frigid compared to the tropics. The large amount of ice and snow also reflects a large part of what little sunlight the Polar regions receive, contributing to the cold and to a certain extent, can be connected to  the topic of global warming. Polar regions are characterized by the polar climate, extremely cold temperatures, heavy glaciation wherever there is sufficient precipitation to form permanent ice, and extreme variations in daylight hours, with twenty-four hours of daylight in summer, and complete darkness at mid-winter.

Mountainous
The mountainous climate is also known as the alpine climate. In the Köppen climate classification the alpine climate is part of "Group E," along with the polar climate. Certain highland climates can also fit under hemiboreal climate or Semi-arid climate groups of climate classification. This climate gets colder the higher the elevation due to the lapse rate of air.

Mediterranean
Typically, a Mediterranean climate is found in most of the lands in the Mediterranean Basin as part of subtropical climate. Worldwide, this is where the largest area of this climate type is found. However, beyond the Mediterranean area, this climatic type prevails in much of California, in parts of Western and South Australia, in southwestern South Africa, in isolated sections of Central Asia and in parts of central Chile.

The climate is characterized by warm to hot, dry summers and mild to cool, wet winters. Mediterranean climate zones are associated with the five large subtropical high pressure cells of the oceans, the Azores High, South Atlantic High, North Pacific High, South Pacific High, and Indian Ocean High. These high pressure cells shift poleward in the summer and equator-ward in the winter, playing a major role in the formation of the world's tropical deserts and the zones of Mediterranean climate polar ward of the deserts. For example, the Azores High is associated with the Sahara Desert and the Mediterranean Basin's climate. The South Atlantic High is similarly associated with the Namib Desert and the Mediterranean climate of the western part of South Africa. The North Pacific High is related to the Sonoran Desert and California's climate, while the South Pacific High is related to the Atacama Desert and central Chile's climate, and the Indian Ocean High is related to the deserts of western Australia (Great Sandy Desert, Great Victoria Desert, and Gibson Desert) and the Mediterranean climate of southwest and south-central Australia.

And with that, I conclude on my blogpost on the Climate and basic description of weather.

Matthew.

Articles Ms Dyer gave us to read

Hi All,

I'm going to post about the articles Ms Dyer gave us to read on, about my feelings, thoughts, and general outlines for those who have not read the articles. Below are my thought processes and what I think might happen in future.

Currently, nitrogen plays a very important role in the future of Earth's 'health condition'. Its effects came in when farmers use artificial, chemical nitrogen fertilizers for their crops, as most of the time, they use an excess amount of fertilizers, which results in the release of nitrous oxide, a greenhouse gas, into the atmosphere. This release of excess nitrogen, alongside with the heavy emission of carbon into our atmosphere, causes global warming to take place, and global warming is the warming of the whole globe. This greenhouse gas in the atmosphere traps heat from the Sun inside the Earth, and causes an overall increase in Earth's temperature. Another example which claims to be a 'missing greenhouse gas', is nitrogen trifluoride, is 17000 times more potent than CO2. When plants and animals die, nitrogen is passed into the soil and the nitrogen in the soil nourishes plants on land and seas into bodies of water. Examples of these bodies of waters include the tundra's permafrost. When the arctic warms, the tundra's permafrost will thaw, and the soil releases carbon and nitrogen into the atmosphere. With too much nitrogen, eutrophication might occur, and this allows foul-smelling algae to bloom and cause toxic 'dead zones'. To counter all these problems, a Copenhagen agreement has been agreed by the EU. If the agreement is not executed well, global warming will continue to worsen. One such example is that of animals not being able to adapt to the hot environment and will die of the heat. Another example is that of the ice caps melting and causing overall water levels to rise globally, which might cause low-lying countries to be submerged underwater. We should all try to do our best to maintain current living conditions and the Earth will not be 'sick' as a result of our actions. Small actions like conserving energy by simply switching off lights and fans when they are not in use, or bigger scale actions like using a right amount of fertilizers for farmers so that excess nitrogen is not given out t the atmosphere. If everyone does their fair share, our Earth will be more alive than ever!

Benjamin

Eutrophication

Hey, everybody, my post's pretty short, but I hope it covers everything we need to know!

Eutrophication refers to an excessive amount of nutrients in a body of water, usually caused by runoff of nutrients (mainly phosphorous in freshwater and nitrogen in saltwater) from the land, which causes a dense growth of plant life, leading to a decrease in oxygen supply, which causes the death of animals.

Causes:

n By man

        -Untreated sewage and agricultural run-off carrying fertilizers

n Natural

        -When nutrients accumulate as sedimentation or when they flow into water bodies for brief periods of time

Effects:

n excessive nutrients in water bodies promote plant growth and decay (mainly in algae and plankton) which leads to

o   a drop in water quality

o   disruption of the natural ecosystem

§  E.g. lack of oxygen for shellfish and marine life (causing a drop in their population). This happens because of algal shading, which is an effect of eutrophication that prevents marine plants from receiving enough sunlight to photosynthesize. The amount of dissolved oxygen thus decreases and many marine animals cannot survive (which is what is happening in the Barnegat Bay Watershed in the USA and the Baltic sea)

o   decrease in the recreational and aesthetic value of water bodies

o   health problems when it occurs in drinking water reserves

o   coral reef decline

§  coral reefs are important as they provide habitats for marine life (which much of the ecosystem depends on) and protect the shore from erosion by storm waves

§  however, they are the most nutrient-sensitive of all habitats, requiring the lowest external inputs to trigger eutrophication

§  this can lead to the death of coral reefs and thus endanger marine reef life

How does this relate to the nitrogen cycle?



Note the eutrophication on the right side occurs due to surface runoff





As mentioned above, one of the nutrients that can cause eutrophication is nitrogen. Therefore, too much nitrogen in the atmosphere can lead to more of it in surface runoffs which go in oceans. This causes eutrophication which leads to the death of marine life due to a decline of oxygen (brought about by excessive algal growth) as well as the death of coral reefs, which are crucial in preventing erosion on shores.

Done by: Chinmayi (:

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.

-yithan