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58 Cards in this Set
- Front
- Back
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what are anticyclones? |
a region of hig h pressue bringing calm donditions.
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in summer, what do anticyclones do? |
In an anticyclone, air is descending. As it descends it warms up, causing water vapour in the air to evaporate. This prevents clouds from forming. - cloudless skies mean that all the suns energy reaches the earth's surface, raising ground temperature dramatically. If the anticyclone stays stationery, it produces a heatwave. |
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in winter, what do anticyclones do ? |
the cloudless skies associated with anticyclones allow heat to escape into the atmosphere, cooling the ground quickly at night and leading to the formation of frost. Water vapour condenses into droplets, causing fog which can linger into the day until the heat of the sun evaporates it. |
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what are synoptic charts? |
synoptic charts, or weather maps are used to plot the weather conditions of certain areas at a single point in time. |
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what are depressions? |
a region of low atmospheric pressure which form over the Atlantic ocean when warm air from the tropics meets cold air from polar regions. its rising air brings windy conditions and precipitation. |
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how do depressions develop? |
1) cold air flowing down from the polar regions meets warm air flowing up from the tropics. The warm tropical air is less dense than the cold polar air, so it starts to rise over it, creating low air pressure. 2)The warm air is sucked into the low pressure area, creating a warm section. The cold air is sucked in behind the warm air. The whole air mass starts to spiral anticlockwise. 3)where the warm air rises over the cold air- it is a warm front. As the air rises, it cools and condenses, resulting is clouds and precipitation. 3)where the cold air pushes in behind the warm- it is a cold front. This forces the warm air to rise- resulting in thick clouds and heavy rainfall. 4) the warm sector starts to climb above the cold air because it is buoyant. Below the rising air the cold front catches up with warm front, it lifts the warm sector off the ground. Where the warm sector is lifted - it is a occluded front. 5) cold air replaces the warm sector on the ground, the temperatures even out and fronts and depression disappears. |
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in the northern hemisphere, what direction is the spiralling inward pattern of air movement? |
in the northern hemisphere, the spiral turns anticlockwise |
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in the southern hemisphere, what direction is the spirally inward pattern of air movement? |
in the southern hemipshere, the spiral turns clockwise |
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how do hurricanes form? |
1) tropical storms begin when thunderstorms move over tropical ocean water. 2) tropical oceans(these are ITCZ zones where sea temperatures are above 26C and air humidity over 75%) warms the air above it. 3) this warm moist air starts to rise 4) because this air is evaportating,there is less air left near the surfacr.This creates an area of low air pressure. 5)low air pressue pulls denser colder air from surronding areas, creating an anticlockwise upward spiral of increasing wind speeds. 6)water vapour evaporated from the ocean below rises and cools off, creating a massive wall of cumulosnumbus cloud around the central eye. 7) condensation releases latent heat, which increases energy and sind speed still further, pushing the rusing air up to an altitude of 10km above sea level. 8)at the top of the hurricane, the cooling air spreads outwards, creating a thick canopy of cirrus clouds up to 1,500 km across - torrential rain and massive storm waves are produced |
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what does the eye of a hurricane have? |
the eye has an area of calm winds which are surronded by the deadly eye wall of high winds and heavy rain. |
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in what months and where do hurricane normally form? what are these areas like? |
most hurricanes form north of the equator between july and october in low pressue areas. Here the trade winds meet over the warm oceans. In this ITCZ's, where sea temperatures are above 26C |
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what brings uk, its weather? |
westerly airstreams bring our weather to us from across the Atlantic. This maritime air is often unstable and when it meets with colder, dense air it rises and cools, bringing depressions and wet or windy weather. |
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uk weather what is the blocked phase? examples? |
1) in a "normal" summer, westerlies are blocked by anticyclonic systems over Europe and the jet stream directs storms north of the UK, bringing us more settled, stable conditions e.g heatwave in france 2003, dry conditions 2006 in UK |
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uk weather what is the progressive phasE? |
The jet stream flows across the south of the UK, allowing deep Atlantic depressions to increase the risk of storms, storm surges and flooding. e.g spring and summer 2007 UK |
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mechasims behind extreme weather in the mid latitudes? |
as the earth spins, meandering flows of air move towards us from the west. Some 10km above the polar front these waves drive the fast moving current of air called the polar jet stream, which seems to determine the surface pattern of high and low pressure systems below. |
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what are jet streams? |
a meandering ribbon of air in the upper atmosphere above the polar front which flows eastwards at hurricane speeds, determining the pattern of high and low pressure areas below. |
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what are hurricanes? |
hrricanes are tropical cyclones in which the maximum sustined wind speed ranges for 39mph to 73 mph. |
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what are inter tropical convergence zone?(ITCZ) |
a zone of low atmospheric pressure near the equator. This migrates seasonally, sea temperatures 26C, air humidity over 75%. |
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during the atlantic hurricane season, what do tropical storms do? |
tropical storms do not remain stationery, from 15th may to 30th november, they move northwesterds across the caribeen and gulf states gathering speed and strength. They are deflected in this direction by the spin of the earth - the coriolis effect. |
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where does drought mostly happen? |
drought happens most in arid or semi arid areas where the unreliable nature of rainfall is as much as issue as the low amount. |
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what does the impact of weather hazard depend on? |
scale, intensity, predictability and duration of each hazard, also on the nature of the palces and communities invovled. |
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how to predict droughts? |
1) use weather records to forecast two fundamental meterological variables: precippation and temperauture. - the PSDI is the most effective index in place in derterming long term drought. ( a value of 0 means conditions are normal, and negative values represnets the severity of the droughts. - the historical frequency,duration and spartial extent of previous droughts will help people to prepare better by projecting possible situations. disadvantages: method only works for long term periods and is of little use of predicting short term droughts. - prediction accuracy varies between region |
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two global warming systems in place to anticipate crop failure and food shortages?
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Un sponsored global information and early warming system(GIEWS) + USA- sponsored famine early warming system - both systems reply multi agency support and focus on large scale monioring and forecasting activities to support potential internevtion at a more local level. - the primary data they get comes from satallities that produce near real time images on a 10 day basis. The rainfall and vegation estamites are then processed into maps of current and forecasted conditions for staple food and crops and pasture land. These reports are produced reguarly and when danger threatens, local field reports willl be done to assess the situation at hand. disadvnatges: this large scale system is not able to detect food security issues at the sub national or local levels, when the prompt detection of failing supplies is nesscary to prompt swift reactions from donors |
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disturbution of tropical cyclones? |
the tropics and sub tropics- mainly in the north atlantic and north pacific oceans, and the western pacific |
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disturbution of river floods? |
widespread. - flooding is most common in climates with wet seasons and where rivers drain high hills and mountains |
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disturbution in tornadoes? |
middle- high latitudes, between 35C and 70C |
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disturbution of blizzards? |
high latitudes and mountains regions |
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disturbution of heat waves? |
middle latitudes in summer |
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distubution of wildfires? |
regions with prolonged dry seaosons, and dense vegatation |
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disturbution of drought? |
widespread but most common in the sub tropics, continential interiors and the medditrerian. |
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how should weather changes associated with depressions be measured? |
- weather changes should be measured and recorded at the approch and passage of the warm and cold fronts either through direct observation, or through hourly data published online met office weather stations. |
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when is an air mass stable? |
when the air temperature near the ground is lower than the air temp. above. So air near the ground displaced vertically will return to its original position . |
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when is an air mass unstable? |
when the air temp. near the ground is higher than the air temp above. air near the ground displaced vertically will not return to its original position. |
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favourable weather conditions and ocean conditions for develoment of tropical cylones? |
- high humidity, supplying abundant water vapur - light winds to allow vertical cloud development - sea surface temp. of at least 26-27C and a deep water layer of 60-70C( to prevent cold rising to the surface and killing the system) |
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causes of blizzards? |
blizzards develop when heavy snowfall is driven by strong winds. - caused by deep depressions and frontal systems during spells of sub zero temp. |
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prolonged cold spells in western europe causes? |
blocking anti cyclones e.g in 2009-2010 the normal westerly circulation over the uk broke down and high pressue from eastern europe and siberioa extended westwards, flooding western europe with freezing arctic air. |
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factors hat influnce the severity of impact of extreme weather? |
- scale and magnitude of the hazadourous event - nuber of people exposed to the risk in the effected area - the vulnerability of a population and its level prepardness |
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scale and magnitude for tropical cyclones example, measurement |
more powerful and intense a weathe event, generally the more severe its impacts. - saffir simpson scale grades hurricanes from 1 to 5 e.g hurricane katrina a C5 hurricane devastated the gulf coast of louisiani in august 2005. |
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scale and magnitude for tornadoes? measurement |
their impact depends on their intensity, winds in tornadoes can reach 500km - the fujita tornadic damage scale provides an indication of the power of tornadoes. |
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extreme rainfall in uk exmaple? |
long sequences of deep Atlantic depressions can reuslt in exceptional rainfall events e.g in late autumn 2009, november 2009 was the wettest month on record in uk, with rainfall averaging 217mm across the whole country. - the heaviestt rain intentisified by the lakeland hills, and rivers derwent and cocker burst their banks and caused widespread flooding throughout the county. |
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population at risk: case study of trpical cyclon in bangladesh and india |
e.g in 1970 and 1991, tropical cyclones caused huge loss of life in the ganges brahmaputra delta of bangladesh and india. - 600 000 deaths -the delta is home to up to 140 million. |
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in the usa, how is vulnearbility to hurricanes reduced? |
- hard enginerring strcutures such as levees and flood gates protecting the areas of higher risk - planned evacuation by us state goverments and federal agiences emergency relif plans - monitotring and tracking of hurricanes by the US national hurricane cneter |
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natural causes of global increase in the frequency of extreme weather events? |
natural causes: more extreme and more frequent high temp. result in an increasing no. of heat waves and related hazards. e.g examples include 2003 heat wave. extreme rainfall and flooding also occur with more frequency. - because global tempearatures have increased, warmer atmosphere contains more moisture. one outcome is that torrential rainfall events are more frequent. e.g in 2012 the uk recordded its wettest ever april- june. |
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human causes of global increase in the frequency of extreme weather events? |
- GRowth of population and settlement on floodplains and delatas increases exposure to and risks to flooding. e.g hurricane katrina huge impact was not due to maginitude of the storm but: - the fact that 12 million people inhibit the coastal countries between louisiana and floria along the gulf of mexico - rapid population growth, which had taken place in these communities in the previous 50 years |
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how does land management cause the global increase in the freuency of extreme weather events? |
- poor land managment such as deforestration increases runoff and the flood risk. e.g the floods caused by hurricane mitch in honduras and nicaragua in 1990 were triggered by torrential rain, and extensive defortration of upland catchments by farmers, loggers - urban growth covers the ground with impermable surfaces that accelarate runoff and raise peak river flows. The encroachment of towns and cities into the countryside contributes to the los of watlands and lakes. |
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short term responses to hurricane hazards in the usa? |
- weather forecasts, updates and warnings are issued by agencies such as national hurricane center - early warning of immient storms may trigger mass evacuations such as new orleans in 2005(hurricane katrina) |
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long term respnses to hurricane hazards in the usa? |
- strengthening levees, sea walls to protect people and property - reducing the risk of flooding from storm surges by land use zoning , conserving wetlands - the fema who mission includes responsing to, aiding from, and helping to mitigate natural disasters |
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short term responses to river floods in the uk? |
- the enviroment agency operates a flood warning system. warning can be telopphone, email - people in areas at high flood risk can evacuate to higher ground, mvoe belondings to upper storeys, sandbags |
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long term responses to river floods in the uk? |
- flood insurance to compensate householders for damaged property and repairs - land use planning - restricting development in areas of high flood risk - soft engineering to reduce rainfall - runoff ratios e.g conservation of wetlands |
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how can technology improve preparness and reduce impacts? |
weather forecasting - use of sattellites and automated weather stations has greatly increased the accuracy of weather forecasts over the past 40 years. - extreme weather phenomena are monitored by sattlllites images. - information is used to forecasts and warnings of extreme weather events flood forecasting - in the uk, enviroment agency issues flood warnings, they dely on data from weather forecasts, river catchment models and histrorical hydrological data that relate precipation events to river discharge drought resistant crops - scientists have improved crop yields in drought pront areas by developing new crops that either more resistant to drought or that mature earlier. this has been archieved by selective plant bleeding and genetic enginerring. managing drought - water management and aapting farming techniques are options for tackling the problem of drought |
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possible responses to increased aridity to farming? |
- extending the area of irrigated cropland -trickle irrigation, which is more water efficient and produces higher yieleds than spray irrigation - zero tillage - which is planting crops in unploughed soils, zero tillage reduces moisture losses to evaporation |
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investagating air masses from fieldwork and secondary might include: |
- deciding whether the air mass is stable or unstable - identifiting the type of air mass affecting the uk or region of observation - observing and recording information on temp. cloud cover over several hours |
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weather observations of anticylones? |
- general synoptic situation shwon on weather charts - monitoring of cloud types and cloud cover. Some anticylones bring clear skies others overcast conditions - measurments of temp., extreme temp. are possible under clear skies |
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what does the abillity of predicting drought depend on/? |
predicting drought depends on the ability to forecast two fundamental meteorological surface paramets, precipation, and temp. |
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weather observatons for anticyclones |
- monitoring cloud types and cloud cover - measuremnts of temperature |
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causes of drought? |
- - in western europe persistant anticlyones, block the passage of depressions - deforesration may also contriute to desertification - seasonal rain failing |
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drought impacts? direct and idnrect |
direct impacts: - reduced crop and water shortages indirect impacts: indrect impacts: -consequences fr farmers and businesses and migration |
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investigating air masses from fiedlwork and secondry data include? |
- identifying the type of air mass affecting the uk or the region of observation - decideing whether the air is stable or unstable |
