natural hazards - weather Flashcards
global atmospheric circulation
circular air movements called cells which join together to form the overall circulation of earth’s atmosphere
sinking air creates high pressure
rising air creates low pressure - ground winds moves towards low pressure areas
ground winds distorted by earth’s rotation
surface winds transfer heat and moisture
pressure belts and winds affected by seasonal changes - tilt and rotation, winds move north in summer, south in winter
cloudy and wet weather in uk
uk is close to boundary of cold polar air moving down from north and warm tropical air moving up from south
boundary is unstable. rising air and low-pressure belts on ground - rising air cools , condenses and forms cloud and rain
hot and dry weather in the desert
air is sinking, belt of high pressure, no rising air so few clouds and little rainfall, hot during day, cold at night as heat is lost quickly from ground
hot and wet weather at the equator
rising air, low pressure belt, sun directly overhead so a lot hotter than UK, cloudy and high rainfall, humid
where do tropical storms form
need warm oceans with temperatures over 27C so only over tropical oceans
summer and autumn when sea temperatures are highest
5-15 degrees north and south of equator - sufficient spin caused by earth’s rotation (coriolis effect), no spin at equator
unstable air in equatorial regions as intense heat so rises rapidly, condenses, forms storm clouds
trade winds responsible for mostly east to west storm paths - caused by air flowing over earth’s surface from sub-tropical high-pressure to equatorial low pressure belts
how do tropical storms form
warm oceans, coriolis effect, unstable conditions in equatorial regions
rapid rates of evaporation transfers huge quantities of warm water vapor into air, rises rapidly, cools, condenses to form towering thunderstorm clouds, an eye is formed down the centre where air descends rapidly, most intense conditions at eye wall
storm carried by prevailing winds
loses energy source when it hits land, friction with land slows it down and it weakens
structure and features of a tropical storm
eye - at the centre, column of rapidly sinking cool air, no clouds, calm
eye wall - most severe conditions, strong winds, torrential rainfall
cumulonimbus clouds - can reach heights of 15 okm
several bands of rain associated with clouds swirling
could have a diameter of 500km - large enough to cover england
move quite slowly - high rainfall, flooding, landslides
affect of climate change on tropical storm distribution
more tropical storms originating in north atlantic and central pacific - change annually very small though - oceans becoming warmer
less storm in southern indian ocean and western north pacific - oceans and atmosphere warmed, reduces temperature range, more stable atmospheric conditions, formation less likely
effect of climate change on tropical storm frequency
no obvious trend of an increase or decrease in frequency by there is expected to be an increase in number of intense storms
effect of climate change on tropical storm intensity
increased due to to climate change - warmer moist rising air providing extra energy for formation
increasing sea surface temperature
cyclone idai
14-15 march 2019
mozambique
africa’s deadliest tropical cyclone on record - category 2
primary effects of cyclone idai
1300 killed - drowned, flying debris
90% of beira destroyed
heavy rains flooded agricultural fields and houses - no food or shelter
secondary effects of cyclone idai
dams collapsed, two hydro-electric power plants damages
400 cases of cholera in beira - lack of sanitation and clean water
several rivers overflowed - washed away roads and bridges
immediate responses to cyclone idai
over 140 evacuation centres set up in mozambique to cope with displaced people
UN dropped food and volunteers
uk governments provided £18 million of aid in form of food, water and shelter kits
long term responses to cyclone idai
water supplies restored in beira
improvements to early warning system to increase awareness and preparedness
£2 million towards supporting families and communities rebuild lives
monitoring and predicting tropical storms
satellites, radar, weather charts
hurricane watch - hurricane conditions possible, wide area
hurricane warning - hurricane conditions expected, take immediate action, specific area
predicted track of cyclone idai quite accurate - poor communication systems
protection from tropical storms
cyclone shelters - on stilts, raised ground, multipurpose, strong concrete, window shutters, stairs to first floor safety
sea walls built to protect from storm surges
windows doors roofs reinforces - strengthen
planning for tropical storms
raising awareness, national hurricane preparedness week in USA, families should devise action plan, hurricane evacuation routes
uk weather hazards
thunderstorms - august 2020, electrical storms, 35000 lightning strikes
prolonged rainfall - lead to river floods, common
drough and extreme heat - rivers dry up, affects water supply, dangerous to elderly, over 20000 people died in 2003 in europe
heavy snow - less common can cause difficulty
strong winds - remnants of hurricanes, disruption to power, fallen trees
why is there extreme weather in uk
meeting point of several types of weather from different directions - explains varied weather, occasional extreme weather
evidence for extreme weather in uk
floods in 2007 - people died, homeless, hull, gloucestershire
heavy snow in 2010 - december, record -18.7 degrees C in northern ireland
strong winds in 2017 - power cuts, transport disruption, ireland, west britain
heat in 2019 - highest temperature in cambridge
(38.7 degrees C) in july
2014 somerset levels floods
wetlands, drained by several rivers, developed for farming and settlements - at risk of severe flooding
cause of somerset floods
wettest january on record - 350mm in jan and feb, 100mm above average
high tides and storm surges - from bristol channel, fresh water spilled over banks
rivers not dredged - at least 20 years, clogged
social effects of somerset floods
over 600 houses flooded
16 farms evacuated
power supplies cut off for many
