Atmosphere and Weathering

managing impacts of global warming

Kyoto Protocol (1997) did not cover all countries. It gave all MEDCs legally binding targets for cuts in emissions from the 1990 level by 2008-2012. This was extended to 2017. The EU agreed to cut emissions by 8% and Japan by 7%. According to the Stern Report (2006), global warming could deliver an economic blow of between 5% and 20% of GDP to world economies. Dealing with the problem, by comparison, will cost just 1% of GDP, equivalent to £184 billion

land and sea breezes

On a warm summer day along the coast, this differential heating of land and sea leads to the development of local winds called sea breezes. The land is heated quicker than the sea and so the air above the land is warmer than the air above the sea during the day. As air above the land surface is heated by radiation from the Sun, it expands and begins to rise, being lighter than the surrounding air. To replace the rising air, cooler air is drawn in from above the surface of the sea. This is the sea breeze, and can offer a pleasant cooling influence on hot summer afternoons. A land breeze occurs at night when the land cools faster than the sea at night. This creates a situation which is the opposite to day time - where the air above the sea is actually warmer at night than the air above the land. In this case, it is air above the warmer surface water that is heated and rises, pulling in air from the cooler land surface.

enhanced greenhouse effect Climate change is caused by an enhancement of a natural process called the Greenhouse Effect, Without the Greenhouse effect , life could not survive here on earth

build up of certain greenhouse gases as a result of human activity greenhouse gases, such as water vapour, CO2, methane, ozone, nitrous oxides and chlorofluorocarbons (CFCs), like the glass on a greenhouse, allow short-wave radiation from the Sun to pass through, but they trap outgoing long-wave radiation, thereby raising the temperature of the lower atmosphere

understand which places on Earth gain more heat than they lose, and vice versa

receipt of solar radiation varies with latitude and season result is an imbalance: positive budget in the tropics, negative one at the poles, however, neither region is getting progressively hotter or colder due to an important second energy budget in the atmosphere - this is the horizontal transfer between low latitudes and high latitudes to compensate for differences in global insolation - takes place by winds and ocean currents

understand how such imbalances are overcome by heat being transferred around the Earth i.e. the global circulation of the atmosphere involving - rossby waves - jet streams - three cell model

rossby waves (early 20th century): - large-scale fast "rivers of air" formed by westerly winds which follow a ridge and trough like pattern - affected by major topographic barriers such as the rockies and the andes - form when air has to loop around and above these blocking features - shape varies over a 6 weeks cycle from a low zonal index to a high zonal index - troughs: low pressure systems - ridges: high pressure systems jet streams: - strong and regular winds which blow in the upper atmosphere about 10km above the surface as part of the rossby waves - 100-300 km per hour - two streams in each hemisphere 1. 30-50o: polar jet 2. 20-20o: sub-tropical jet - caused by differences in polar and sub-tropical air - greater the temperature difference, the stronger the jet stream

daytime energy budget understand how energy comes to and leaves Earth in the daytime, e.g. incoming solar radiation, reflected solar radiation, energy absorbed into the surface and subsurface, sensible heat transfer, long wave earth radiation, latent heat transfer - evaporation.

six components: 1. incoming solar radiation (insolation): - main energy input - affected by latitude, season and cloud cover - less/higher cloud, more radiation reaches Earth's surface 2. reflected solar radiation (albedo) - varies with colour, grass average albedo of 20-30%, meaning that it reflects back about 20-30% of the radiation it receives 3. surface absorption - if the surface can conduct heat to lower layers, the surface will remain cool - if the energy is concentrated at the surface, the surface warms up 4. sensible heat transfer - movement of parcels of air into and out from the area being studied - e.g. air that is warmed by the surface may begin to rise and be replaced by cooler air (convection transfer) 5. long-wave radiation - radiation of energy from the earth (a cold body) into the atmosphere and, for some of it, eventually into space - also, downward movement of long-wave radiation from particles in the atmosphere - difference between the two flows is known as the net radiation balance 6. latent heat transfer (evaporation) - heat energy is used to turn liquid water into water vapour. - when water present at a surface, energy is used to evaporate it, hence less energy available to raise temperature

energy budget

the amount of energy entering a system, the amount leaving the system, and the transfer of energy within the system

dew point

the temperature at which relative humidity is 100%

three cell model

tri-cell model names the equator (ITCZ) as the start of the circulation: hadley cell: - sun shines directly at equator and warms earth's surface - warm air rises creating an area of low pressure - air sinks at sub-tropics (20-30o North and South) because it is colder and denser - returns to the tropics to replace the rising air polar cell: - warmer air rises at lower latitudes and moves pole ward - when the air reaches the polar areas, it has cooled considerably, and descends as a cold, dry high pressure area ferrell cell. - exists due to the other two cells and it mirrors the other cells movements - transfers warm air to high latitudes and shifts cold air back to the subtropics, where it is warmed

characteristic of urban climate: more intense storms

- greater instability and stronger convection above urban areas - concentration of hygroscopic particles accelerates the onset of condensation

characteristic of urban climate: hotter than surrounding areas

- heat produced by human activity - greater surface area to absorb heat - high albedo?? (less reflected insolation) of tarmac and concrete - buildings high thermal capacity (absorb large quantities of heat and release them at night) - little energy used for evapotranspiration - pollutants help trap radiation - fewer bodies of open water (therefore less evaporation)

characteristic of urban climate: less snowfall

- higher temperatures

characteristic of urban climate: less moisture and lower relative humidity

- lack of vegetation so less transpiration - high drainage density (drains) which remove water

characteristic of urban climate: slower winds unless they are tunneled between buildings

- winds deflected over buildings - large buildings can produce eddying - deep, narrow streets are much calmer unless aligned with prevailing winds to funnel flows along them - the 'canyon effect'

understand how lapse rates relate to latent heat release and the state of the atmosphere: - stable - unstable - conditionally unstable be able to draw or interpret simple graphs to show stability and lapse rates

Stable conditions (stability) in the atmosphere exist when a rising parcel of air cools more quickly than the air surrounding it . If air is displaced upwards it immediately gets cooled, denser and sinks. (ELR at 6oC is lower than DALR at 10oC) Because the air cools quickly it sinks and no clouds or precipitation is formed, bringing dry and calm weather. Unstable conditions (instability) in the atmosphere exist when a rising parcel of air cools more slowly than the air surrounding it (ELR is greater than DALR or SALR) Because the air is warmer than the surrounding air it continues to rise forming clouds and precipitation Conditional instability in the atmosphere exist when air parcels are stable if they are dry and unstable if they are saturated. So ELR is less than DALR but greater than SALR Air would be stable if it is dry and would sink to the ground, but if it becomes saturated it is forced to rise and may become unstable

surface wind belts

Winds between the tropics converge on a line known as the inter-tropical convergence zone (ITCZ) or equatorial trough inter-tropical convergence zone is a band a few hundred kilometres wide in which winds from the tropics blow inwards, converge and then rise, forming an area of low-pressure Latitudinal variations in the ITCZ occur as a result of the movement of the overhead sun. l In June the ITCZ lies further north, whereas in December it lies in the southern hemisphere. l The seasonal variation in the ITCZ is greatest over large land masses (e.g. Asia). l By contrast, over the Atlantic and Pacific Oceans its movement is far less. The word monsoon means reverse and refers to a seasonal reversal of wind direction. l The monsoon is induced by Asia - the world's largest continent - which causes winds to blow outwards from high pressure in winter but pulls the southern trades into low pressure in the summer. l The monsoon is therefore influenced by the reversal of land and sea temperatures between Asia and the Pacific during the summer and winter. l In winter surface temperatures in Asia can be as low as -20°C. By contrast the surrounding oceans have temperatures of 20°C. l During the summer the land heats up quickly and may reach 40°C. By contrast the sea remains cooler at about 27°C. This initiates a land-sea breeze blowing from the cooler sea (high pressure) in summer to the warmer land (low pressure), whereas in winter air flows out of the cold land mass (high pressure) to the warm water (low pressure). The uneven pattern in Figure 2.5 is the result of seasonal variations in the overhead sun. Summer in the southern hemisphere means that there is a cooling in the northern hemisphere, thereby increasing the temperature differences between polar and equatorial air. Consequently, the high-level westerlies are stronger in the northern hemisphere in winter. factors affecting air movement: Pressure and wind The basic cause of air motion is the unequal heating of the Earth's surface. The major equalising factor is the transfer of heat by air movement. Variable heating of the earth causes variations in pressure and this in turn sets the air in motion. There is thus a basic correlation between winds and pressure. Pressure gradient The driving force is the pressure gradient, i.e. the difference in pressure between any two points. Air blows from high pressure to low pressure (Figure 2.5). Globally, very high-pressure conditions exist over Asia in winter due to the low temperatures. By contrast, the mean sea-level pressure is low over continents in summer. High surface temperatures produce atmospheric expansion and therefore a reduction in air pressure.

effects of global warming

a rise in sea levels, causing flooding in low-lying areas such as the Netherlands, Egypt and Bangladesh - up to 200 million people could be displaced l an increase in storm activity, such as more frequent and intense hurricanes (owing to more atmospheric energy) l 4 billion people suffering from water shortage if temperatures rise by 2°C l 35% drop in crop yields across Africa and the Middle East if temperatures rise by 3°C l 200 million more people could be exposed to hunger if world temperatures rise by 2°C, 550 million if temperatures rise by 3°C l extinction of up to 40% of species of wildlife if temperatures rise by 2°C

mist and fog

cloud at ground level condensation nuclei, such as dust and salt, are needed mist: visibility between 1000 m and 5000 m and relative humidity is over 93% fog: visibility below 1000 m dense fog: visibility below 200 m formed in two major ways: 1. air is cooled - cooling of air is quite common (orographic, frontal and convectional uplift) - contact cooling at a cold ground surface may produce saturation. As warm moist air passes over a cold surface it is chilled. Condensation takes place as the temperature of the air is reduced and the air reaches dew point . When warm air flows over a cold surface advection fog is formed. For example, near the Grand Banks off Newfoundland warm air from the Gulf Stream passes over the waters of the Labrador Current, which is 8-11°C cooler because it brings with it meltwater from the disintegrating pack-ice further north. This creates dense fog for 70-100 days each year. - radiation fog occurs when the ground loses heat at night by long-wave radiation. This occurs during high-pressure conditions associated with clear skies. 2. more water is added to the atmosphere - occur over warm surfaces such as the Great Lakes in North America or over the Arctic Ocean. Water evaporates from the relatively warm surface and condenses into the cold air above

dew

condensation on a surface air is saturated - because the temperature of the surface has dropped enough to cause condensation - or because more moisture is introduced while temperature remains constant, for example by a sea breeze

global energy budget

energy budget considered at a global scale (macro-scale)

local energy budget

energy budget considered at a local scale (micro-scale)

night-time energy budget understand how energy comes to and leaves Earth in the night

four components: 1. long wave earth radiation - clouds reduce loss of energy as long-wave radiation by returning some to the surface 2. latent heat transfer (dew/condensation) - released when water condenses - during the night, air near the cold surface is cooled and can condense to form water 3. absorbed energy returned to earth (sub-surface supply) - heat transferred to the soil and bedrock during the day, which is released back to the surface at night - can partly offset the night-time cooling at the surface 4. sensible heat transfer - air movement - cold air moving into an area may reduce temperatures - warm air may supply energy and raise temperatures

weather processes phenomena

know how moisture occurs in the atmosphere (vapour, liquid, solid) describe the processes that alter these states i.e. evaporation, condensation, freezing, melting, deposition and sublimation describe and understand what causes air to rise (convection and orographic uplift) and then cool • • understand how the above relates to precipitation (including ideas of relative humidity, saturation, dew point, condensation level, condensation nuclei) •

understand the influence on these patterns of - latitude - land/sea distribution - ocean currents

latitude: - initiates a land-sea breeze - summer: blowing from the cooler sea (high pressure) to the warmer land (low pressure) - winter: air flows out of the cold land mass (high pressure) to the warm water (low pressure) - summer in the southern hemisphere means that there is a cooling in the northern hemisphere, thereby increasing the temperature differences between polar and equatorial air - high-level westerlies are stronger in the northern hemisphere in winter - near the poles insolation has more atmosphere to pass through - insolation concentrated at equator - insolation dispersed at poles distribution of land and sea: -land heats and cools more quickly than water due to: 1. sea having greater heat capacity 2. sea being clear, so the sun's rays penetrate to a greater depth (distributing energy over a larger volume) 3. tides and currents cause the heat to be further distributed - winter: mid- latitudes, sea air is much warmer than the land air, so onshore winds bring heat to the coastal lands - summer: coastal areas remain much cooler than inland sites - areas with a coastal influence are termed maritime or oceanic - inland areas are called continental. ocean (sea) currents - winter: warm currents from equatorial regions raise the temperatures of polar areas (with the aid of prevailing westerly winds) - e.g. north atlantic drift raises winter temperatures of northwest europe - summer: cold currents, such as the labrador current off the northeast coast of north america can reduce temperature

climate change is the correct term, for the common term Global Warming. It is the process of the average global temperature rising

natural causes include: l variations in the Earth's orbit around the Sun l variations in the tilt of the Earth's axis l variations in solar output (sunspot activity) l changes in the amount of dust in the atmosphere (partly due to volcanic activity) l changes in the Earth's ocean currents as a result of continental drift

temperature (radiation/nocturnal) inversion

normally air temperature decreases with altitude relative increase in temperature with height in the lower part of the atmosphere - cold air near the ground is dense and tends t stay near the earth's surface - during calm, high-pressure conditions the band of cooled air may extend a few metres before the warmer air is reached - a temperature inversion will act like a lid on pollutants, causing them to remain in the lower atmosphere next to the Earth's surface - only when the surface begins to heat up, and in turn warms the air above it, will the warm air be able to rise and with it any pollutants that it may contain common in depressions and valleys urban areas surrounded by high ground, such as Mexico City and Los Angeles, are also vulnerable as cold air sinks from the mountains down to lower altitudes

describe and understand world patterns of: - temperature - pressure - winds

pressure variations: - Sea-level pressure conditions show marked differences between the hemispheres. In the northern hemisphere there are greater seasonal contrasts whereas in the southern hemisphere more stable average conditions exist . The differences are largely related to unequal distribution of land and sea, because ocean areas are much more equable in terms of temperature and pressure variations Subtropical high-pressure belts (STHP) are a permanent feature, especially over ocean areas. - In the southern hemisphere this is almost continuous at about 30° latitude. l In the northern hemisphere, by contrast, at 30° the belt is much more discontinuous because of the land. - Over the oceans high pressure occurs as discrete cells, such as the Azores and Pacific Highs. - Over continental areas, such as southwest USA, southern Asia and the Sahara, major fluctuations occur: high pressure in winter and summer lows because of overheating. - Over the equatorial trough pressure is low, at around 1008-1010 mb. - The trough coincides with the zone of maximum insolation. - In the northern hemisphere in July it is well north of the equator (25° over India), whereas in the southern hemisphere (January) it is just south of the equator because land masses in the southern hemisphere are not of sufficient size to displace it southwards. - In temperate latitudes pressure is generally lower than in subtropical areas. - The most unique feature is the large number of depressions (low pressure) and anticyclones (high pressure), which do not show up on a map of mean pressure. - In the northern hemisphere there are strong winter low pressure zones over Icelandic and oceanic areas, but over Canada and Siberia high pressure dominates, due to the coldness of the land. - In summer, high pressure is reduced, especially over continental areas. - In polar areas pressure is relatively high throughout the year, especially over Antarctica, because of the coldness of the land mass.