willy teleconnect
climatology
earth receives radiation from the sun in the form of short wave solar radiation, and emits long wave terrestial radiation.
the greenhouse effect comes about because our atmosphere is opaque to long wave radiation but absorptive to short wave radiation. this means that while it tends to allow insolation to reach earth's surface, it has a tendency to trap outgoing radiation so that the heat is circulated within the atmosphere.
the tropics receives the greatest amount of insolation while the poles receives the least. this is because the insolation is more concentrated when the sun is more high-angled. the amount of atmosphere that insolation passes through also increases towards the poles, implying more scattering, reflection, and absorption by the atmosphere and hence less heat received by the ground. as such, there is a net flow of energy from the tropics towards the poles.
five factors affecting regional temperature variations:
1. proximity to sea
2. altitude
3. ocean currents
4. cloud cover
5. aspect
the tri-cellular model:
1.ITCZ, horse latitudes, polar fronts
2. hadley cell, ferrel cell, polar cell
3. trade winds, westerlies, easterlies (surface winds)
pressure gradient force drives the movement of air, simply because of a pressure difference. the coriolis force affects direction of air movement. always acting perpendicular to direction of flow and increasing in strength with higher wind speed, the coriolis force deflects winds towards the right in the northern hemisphere, and towards the left in the southern hemisphere. the coriolis force is the strongest at the poles, and zero at the equator.
aloft, there is little friction to air movement, and thus coriolis force results in purely westerly flows. near the ground, friction slows down the winds, and thus coriolis force is limited. as such, surface winds follow a diagonal path.
at the ITCZ is a zone of low pressure, because air over that area is being lifted via convection. at the horse latitudes we find zones of high pressure, and deserts are common here. this is because the descending air, lacking in moisture (shed over the ITCZ), heats up adiabatically as it contracts, causing a further drop in relative humidity, and making it even harder to reach dew point.
because of the tilt of the earth and its revolution around the sun, places polewards of the tropics will experience changes in seasonality. on the solstices, the sun is directly overhead the tropics, and on the equinoxes, the sun is directly overhead the equator. this affects the length of day and night at different latitudes.
in the westerlies aloft, there exist narrow strips of high-speed winds called jet streams. these arise because of a stark contrast in temperatures of the air masses that meet at the ground surface. jet streams have been associated with tonradoes and hurricanes, because they are believed to aid in removing air from the centre of these storms, causing a continual drawing in of air at the surface. jet strems are also known to lock high pressure cells over regions, and cause anomalous weather patterns.
to form precipitation, there must be condensation occuring. this happens if air is saturated and in the presence of condensation nuclei. three types of lifting: convective, frontal, orographic.
we examine the precipitation and temperature characteristics of four climatic zones:
1. tropical rainforest (singapore)
2. tropical monsoon (monrovia, liberia)
3. tropical savanna (bamako, mali)
4. subtropical desert (cairo)
(consider annual temperature range, diurnal temperature range, annual rainfall, annual rainfall variability, and vegetation. these change with latitude, cloud cover, type of rain, etc.)
global dimming. see 13th november 2005 post.
cyclones form over warm seas between 5 to 15 degrees north and south of the equator. these are circular tropical storms characterised by high wind speeds of above 119km/hr. there are three types of cyclone damages: storm surge, wind damage, and inland freshwater flooding.
case studies for cyclones:
1. hurricane andrew
2. hurricane mitch
3. hurricane agnes
the strength of cyclones is measured on the safir-simpson scale. efforts at predicting and monitoring cyclones include the use of satellites, aircraft reconnaissance, radar, warning systems, evacuation exercises, and first aid strategies.
the earth is currently in an ice age. the pleistocene ice age has been punctuated by several alternating glacial and interglacial periods. studies show that we are on a deglaciation period.
five evidences for climate change:
1. tillites and striae
2. deep-sea sediment - foram and oxygen isotope analysis
3. ice core - carbon dioxide and oxygen isotope analysis
4. tree ring analysis
5. pollen analysis
natural causes of climate change:
1. milankovitch cycles
2. sunspot activity
3. volcanic activity
4. plate tectonics
cities are known to be hotter than the countryside because of the ubran heat island effect. there are six causes: higher thermal capacity, urban structure, sensible heat transfer, pollutants, heat from combustion, and lower wind speed.
other changes in the urban climate include the urban-induced precipitation, reduction in solar radiation, lowered relative humidity, and country breeze.
global warming is likely to be caused by humans, although there are some who argue that the earth is simply reaching an interglacial period. the increase in atmospheric concentrations of carbon dioxide, methane, water vapour, and other greenhouse gases due to human activities causes more long wave terrestrial radiation to get absorbed.
the heating up of earth produces some positive and negative feedback mechanisms:
1. with higher temperatures, water vapour concentrations will increase due to higher evaporation rates. this would serve to trap more heat.
2. with higher temperatures, polar ice caps will melt, and the albedo of the ice caps will decrease, causing less reflection of insolation. this would increase the radiation, and thus heat, received.
3. with higher temperatures, more clouds would be formed. the clouds could either trap heat from escaping the earth, or reflect insolation from the sun. studies show the latter effect is more dominant, implying a negative feedback mechanism.
4. with higher temperatures, marine life would fluorish. increased rate of photosynthesis by phytoplankton can help to absorb much carbon dioxide into the ocean, and thus marine food chain, which would eventually become part of the seabed.
5. with higher temperatures, icebergs will be released into the oceans from the ice caps. these ice bags contain mineral-rich dust that has accumulated over millions of years, and are capable of supporting microscopic marine life. this can attract and set up an entire marine ecosystem at the iceberg, and thus help to remove carbon dioxide from the atmosphere.
consequences of global warming:
1. increased sea levels
2. plant migration
3. intense storms
4. poleward migration of tropical diseases
5. changing patterns of tourism
6. drought
7. changing agricultural productivity
el nino southern oscillation is the term for the cyclic changes that occur in the walker circulation over the pacific ocean. during normal years, the circulation pattern is such that there is high pressure and thus stable conditions over peru, and there is low pressure and rain over indoaustralia. during an el nino event, the circulation is reversed so that indoaustralia experiences drought and peru gets rain.
el nino has great economic impacts on peru, mostly because it causes the humboldt current to be weakened, bringing less nutrients to the waters near peru. the fishing industry is thus affected. also, the guano industry is affected because the birds that feed on the fish are not able to survive. during el nino, some parts of peru also receive rain and thus cotton fields experience greater yield.
the 1982-3 el nino event caused heavy rains and flooding in peru, drought in asutralia, india and africa, and hurricanes in tahiti and the philippines. cost of $40 billion worldwide. the 1997 el nino brought severe drought to indonesia, and coupled with the forest-burning schemes caused haze pollution to the south-east asian region.
drought. refer to the cheater essays.
-fin
earth receives radiation from the sun in the form of short wave solar radiation, and emits long wave terrestial radiation.
the greenhouse effect comes about because our atmosphere is opaque to long wave radiation but absorptive to short wave radiation. this means that while it tends to allow insolation to reach earth's surface, it has a tendency to trap outgoing radiation so that the heat is circulated within the atmosphere.
the tropics receives the greatest amount of insolation while the poles receives the least. this is because the insolation is more concentrated when the sun is more high-angled. the amount of atmosphere that insolation passes through also increases towards the poles, implying more scattering, reflection, and absorption by the atmosphere and hence less heat received by the ground. as such, there is a net flow of energy from the tropics towards the poles.
five factors affecting regional temperature variations:
1. proximity to sea
2. altitude
3. ocean currents
4. cloud cover
5. aspect
the tri-cellular model:
1.ITCZ, horse latitudes, polar fronts
2. hadley cell, ferrel cell, polar cell
3. trade winds, westerlies, easterlies (surface winds)
pressure gradient force drives the movement of air, simply because of a pressure difference. the coriolis force affects direction of air movement. always acting perpendicular to direction of flow and increasing in strength with higher wind speed, the coriolis force deflects winds towards the right in the northern hemisphere, and towards the left in the southern hemisphere. the coriolis force is the strongest at the poles, and zero at the equator.
aloft, there is little friction to air movement, and thus coriolis force results in purely westerly flows. near the ground, friction slows down the winds, and thus coriolis force is limited. as such, surface winds follow a diagonal path.
at the ITCZ is a zone of low pressure, because air over that area is being lifted via convection. at the horse latitudes we find zones of high pressure, and deserts are common here. this is because the descending air, lacking in moisture (shed over the ITCZ), heats up adiabatically as it contracts, causing a further drop in relative humidity, and making it even harder to reach dew point.
because of the tilt of the earth and its revolution around the sun, places polewards of the tropics will experience changes in seasonality. on the solstices, the sun is directly overhead the tropics, and on the equinoxes, the sun is directly overhead the equator. this affects the length of day and night at different latitudes.
in the westerlies aloft, there exist narrow strips of high-speed winds called jet streams. these arise because of a stark contrast in temperatures of the air masses that meet at the ground surface. jet streams have been associated with tonradoes and hurricanes, because they are believed to aid in removing air from the centre of these storms, causing a continual drawing in of air at the surface. jet strems are also known to lock high pressure cells over regions, and cause anomalous weather patterns.
to form precipitation, there must be condensation occuring. this happens if air is saturated and in the presence of condensation nuclei. three types of lifting: convective, frontal, orographic.
we examine the precipitation and temperature characteristics of four climatic zones:
1. tropical rainforest (singapore)
2. tropical monsoon (monrovia, liberia)
3. tropical savanna (bamako, mali)
4. subtropical desert (cairo)
(consider annual temperature range, diurnal temperature range, annual rainfall, annual rainfall variability, and vegetation. these change with latitude, cloud cover, type of rain, etc.)
global dimming. see 13th november 2005 post.
cyclones form over warm seas between 5 to 15 degrees north and south of the equator. these are circular tropical storms characterised by high wind speeds of above 119km/hr. there are three types of cyclone damages: storm surge, wind damage, and inland freshwater flooding.
case studies for cyclones:
1. hurricane andrew
2. hurricane mitch
3. hurricane agnes
the strength of cyclones is measured on the safir-simpson scale. efforts at predicting and monitoring cyclones include the use of satellites, aircraft reconnaissance, radar, warning systems, evacuation exercises, and first aid strategies.
the earth is currently in an ice age. the pleistocene ice age has been punctuated by several alternating glacial and interglacial periods. studies show that we are on a deglaciation period.
five evidences for climate change:
1. tillites and striae
2. deep-sea sediment - foram and oxygen isotope analysis
3. ice core - carbon dioxide and oxygen isotope analysis
4. tree ring analysis
5. pollen analysis
natural causes of climate change:
1. milankovitch cycles
2. sunspot activity
3. volcanic activity
4. plate tectonics
cities are known to be hotter than the countryside because of the ubran heat island effect. there are six causes: higher thermal capacity, urban structure, sensible heat transfer, pollutants, heat from combustion, and lower wind speed.
other changes in the urban climate include the urban-induced precipitation, reduction in solar radiation, lowered relative humidity, and country breeze.
global warming is likely to be caused by humans, although there are some who argue that the earth is simply reaching an interglacial period. the increase in atmospheric concentrations of carbon dioxide, methane, water vapour, and other greenhouse gases due to human activities causes more long wave terrestrial radiation to get absorbed.
the heating up of earth produces some positive and negative feedback mechanisms:
1. with higher temperatures, water vapour concentrations will increase due to higher evaporation rates. this would serve to trap more heat.
2. with higher temperatures, polar ice caps will melt, and the albedo of the ice caps will decrease, causing less reflection of insolation. this would increase the radiation, and thus heat, received.
3. with higher temperatures, more clouds would be formed. the clouds could either trap heat from escaping the earth, or reflect insolation from the sun. studies show the latter effect is more dominant, implying a negative feedback mechanism.
4. with higher temperatures, marine life would fluorish. increased rate of photosynthesis by phytoplankton can help to absorb much carbon dioxide into the ocean, and thus marine food chain, which would eventually become part of the seabed.
5. with higher temperatures, icebergs will be released into the oceans from the ice caps. these ice bags contain mineral-rich dust that has accumulated over millions of years, and are capable of supporting microscopic marine life. this can attract and set up an entire marine ecosystem at the iceberg, and thus help to remove carbon dioxide from the atmosphere.
consequences of global warming:
1. increased sea levels
2. plant migration
3. intense storms
4. poleward migration of tropical diseases
5. changing patterns of tourism
6. drought
7. changing agricultural productivity
el nino southern oscillation is the term for the cyclic changes that occur in the walker circulation over the pacific ocean. during normal years, the circulation pattern is such that there is high pressure and thus stable conditions over peru, and there is low pressure and rain over indoaustralia. during an el nino event, the circulation is reversed so that indoaustralia experiences drought and peru gets rain.
el nino has great economic impacts on peru, mostly because it causes the humboldt current to be weakened, bringing less nutrients to the waters near peru. the fishing industry is thus affected. also, the guano industry is affected because the birds that feed on the fish are not able to survive. during el nino, some parts of peru also receive rain and thus cotton fields experience greater yield.
the 1982-3 el nino event caused heavy rains and flooding in peru, drought in asutralia, india and africa, and hurricanes in tahiti and the philippines. cost of $40 billion worldwide. the 1997 el nino brought severe drought to indonesia, and coupled with the forest-burning schemes caused haze pollution to the south-east asian region.
drought. refer to the cheater essays.
-fin
posted by ivan at 1:30 AM
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