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14 Cards in this Set
- Front
- Back
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What are the factors which affect temperature?
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Latitude
. Sun's rays strike the Earth at different angles . unequal distribution of heat . at lower/higher latitudes, the Sun's rays are spread over a wider surface area . thus temperatures are lower . around the equator, Sun's rays hit the Earth at a right angle . same amount of heat, concentrated in a small area, thus temperature is increased Altitude . the higher the altitude, the lower the temperature . Sun's rays strike the surface of the Earth . heat is passed on to the atmosphere . Earth is heated from the surface up . gravity also pulls water molecules towards the Earth surface . thus air is denser at lower altitudes . dense air with more water molecules can absorb more heat eg. Kota Kinabalu and Tana Laban Continental and Maritime Influence . Sun does not penetrate land surfaces as deeply as water bodies . land absorbs and loses heat faster than the sea . thus two cities along the same latitude may experience a similar angle of incidence . during summer, the city inland will have higher temperature. while the city near the coast will have a lower temperature, as they are moderated by the cooler sea . in winter, the city further inland will have a lower temp. while the cooler sea prevents the temp of the city near the sea from increasing too much eg. Sacremento (145km inland), San Francisco (coastal) Cloud cover . clouds radiates heat . in the day, clouds help to radiate part of the Sun's heat back to outer space . at night, clouds act as a blanket by radiating heat back to the Earth and preventing temperatures from dropping too low |
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Define relative humidity.
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The ratio of the actual amount of water vapour in the air to the maximum amount of water vapour a unit of air can hold at that temperature.
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How does temperature affect relative humidity?
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. temp increases, amount of water vapour it can hold increases -> RH falls
. temp drops, air has less capacity to hold water vapour -> RH rises . when the temperature decreases until the point when air cannot absorb any more water vapour -> saturation point . dew point . if temperature continues to drop, the capacity of air to hold water will be exceeded . water vapour then condesense to form clouds > basically warmer air has higher capacity than cool air |
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How is rain formed?
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. rainfall is formed by air instability (the tendency of air parcels to rise rather than remain in its original position)
. a parcel of air is heated . it expands, becomes less dense and rises . as it rises, temperature drops and air is saturated . condensation takes place after dew point . water droplets form clouds, which combine to form even bigger water droplets . they fall as rain when they become too heavy |
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Explain how convectional rain is formed.
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They are formed by air parcels which are heated, rise and condense to fall as rain.
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Explain how relief rain is formed.
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. formed when air is forced to rise over phsyical barriers such as a mountain range
. moist air parcels coming from the sea are forced to rise when they meet a mounatin along the coast . clouds form mainly on the windward side, the side where air parcels rise from eg. east coast of Peninsular MY NE Monsoon wind blows across South China sea, resulting in floods and heavy rains. However, when it crosses to the leeward side of the mountain range, west coast of MY receives little rainn eg. Death Valley, California |
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What is air pressure?
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The force exerted on one unit of the Earth's surface by the weight of a column of air above it.
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How do differences in air pressure produce wind?
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. air moves from an area of high pressure to an area of low pressure
. resulting movement is wind -> helps to balance air pressure and distribute moisture and heat |
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How are land and sea breeze produced?
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. differences in air pressure
. in the day, air over land is heated more rapidly than air over sea . warm air rises and a low pressure area is formed over land . however, sea heats up slowly, thus cooler air over sea sinks . air pressure is higher over the sea, therefore wind blows from the sea towards land . sea breeze lowers temp along the coast by 2-10 degrees . at night, land cools down faster than sea . cool air is denser, sinks . area of high pressure . opposite for sea, area of low pressure . wind blows from the land to sea, sea breeze . as cooler, denser air replaces the warmer, lighter air over the sea |
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Describe the natural and human causes of droughts.
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Natural:
. shortage of rainfall - climatic conditions cause shortages of rainfall regularly - however, unusual weather conditions may cause droughts in normally wet areas - soil moisture and water bodies dry up, resulting in droughts Human: . Increase in population - population growth increases the demand for more land to build industries, agriculture fields, housing facilities, etc - improper agricultural practices such as overgrazing and growing crops continuously without allowing land to fallow will deplete the nutrients and vegetation of the land faster than they can be replaced. hence, land can no longer be used purposefully anymore - reduction of vegetation and improper agricultural practices leads to reduction in precipitation(20%) and increased evaporation (30%) - reduction in moisture intensifies dry condition, thus worsening droughts . Climatic changes - global warming increases temperature - higher rate of evaporation - water resources depleted . Excessive use of wells and irrigation - these facilities allow people in dry areas to tap on groundwater for domestic and agricultural uses - however during a drought, excessive drawing of water leads to a decrease in the availibility of water - drought is worsened |
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What are the negative impact of droughts?
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Social:
. Health problems - increase in temp - death rate increases esp for elderly, as they are more prone to heat stroke and other health problems brought about by hot, dry weather . Disintegration of rural communities - when faced with drought, farmers may sell their land and move to cities - rural communities break up . Loss of lives - water is essential for survival and cultivation of crops - without water, decrease in food supply - widespread famine, starvation, malnutrition Economic: . Loss of income - water is essential for crop cultivation -> droughts causes crop failure - lack of food supply for livestock, livestock decreases - farmers have to borrow money to buy food and import water for their livestock, in order to keep them alive - they are unable to repay their debts and may eventually lose their farmland - higher prices for consumers as well . Devastation of economy - countries which depend heavily on the earnings of agricultural sectors - loss of main source of income - economy may collapse Environmental: . Forest fires - dry and hot conditions created by droughts lead to forest fires - 1988, Midwest and Rocky mountains of USA experienced severe forest fires, resulting in 1.6mha of Yellowstone National Park being burnt . Desertification - improper agricultural practices -> water table drops, vegetation dies - topsoil is eroded by wind and sporadic rainfall - severe dust storms and extension of desert areas eg. Sahel region in Africa, 1984, prolonged drought and human activities lead to desertification. . Reduction in aquatic life - dams and rivers dry up -> water quality declines - growth of toxic algae - unsafe drinking water - aquatic life is unable to survive the toxic environment |
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Weight the pros and cons of human adaptation to droughts.
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. Cloud Seeding
- the introduction of cooling agents to clouds through the use of aeroplanes, to encourage condensation of water droplets and create artificial rain - does not require any physical construction - may not be effective all the time . Afforestation - planting of trees on bare land - trees provide shade to the ground, lowering temperatures and decreasing the loss of moisture in the soil through evaporation - leaves and leaf litter also intercept rainfall and increase soil infiltration - trees transpire and release moisture into the air -> moisture condenses to form clouds and eventually falls as rain - long term effective measure - may be hard to convince goverments to implement this measure as they only concentrate on short term economy gains . Advanced technology - convert seawater into potable water through the process of reverse osmosis. eg. NEWater, the desalination plant in Singapore - boosts water supply - requires technical expertise and manpower . Water storage - dams can be built to accumulate water for future use during a drought - tanks can be used to store water, that would otherwise be wasted as surface runoff -> Australia, little annual rainfall, however rainwater harvesting has reduced the amount of water wastage through surface runoff by 4.5cm - canals can be connected to rivers or reservoirs to transport stored water elsewhere - however during dry periods, rivers may dry up . Remote sensing - satellite based remote sensing - used to monitor water availibility - locate presence of groundwater in different geological sites - drought surveillance - provides early warning to minimise the effects of droughts - most developing countries cannot afford the costly advanced technology . Strategic planning - water resource planning and management - conservation measures to help people prepare for a drought - water is given proper allocation for different uses - priority must be given to drinking purposes - community involvement programs and local participation in water management is important eg. Singapore: the government is always on the lookout for new sources of water. islandwide rationing exercises are also carried out, this encourages conservation of water and educates the public on the need to use water wisely. - effective long term solution - may help avoid the consequences of droughts - gov. needs to be strong politically and financially in order for the entire plan to work |
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How are monsoon winds formed?
Give examples. |
. seasonal reversals in wind direction
. caused by unequal heating of the landmasses and oceans . During summer in the northern hemisphere (June-Sep) - land in Central Asia is heated up - air over Central Asia becomes warmer and lighter - air expands and rises, thus creating an area of low pressure over Central Asia - meanwhile, it's winter in the southern hemisphere, Australia - cooler air is dense, exerts more pressure on land surface - thus creating an area of high pressure over Australia - Southeast monsoon winds blow from the area of high pressure in Australia to the area of low pressure over Central Asia - as they cross the Equator, the winds are deflected to the right and becomes Southwest monsoon winds - these winds blow across the ocean and are heavily laden with moisture - hence, they bring heavy rain to coastal areas of India -> Pakistan, Bangladesh . During winter in the northern hemisphere (Dec-Feb) - summer in Aus - air is cold and dense in Central Asia -> high pressure area - Northeast monsoon winds blow from Central Asia towards Australia - winds are dry and cold as they blow over land, thus India experiences dry and cold weather - as the winds cross the equator, they deflect to the left into the southern hemisphere - thus becoming Northwest monsoon winds |
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What is deflection?
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The invisible force, generated by the Earth turning about its axis, it alters wind direction.
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