Weather Hazards Flashcards
(38 cards)
Define the atmosphere
the complex mass of gases, liquids and solids surrounding the earth
Define weather
day to day conditions of temperature, cloud, precipitation, fog/visibility, wind + sunshine
What causes wind?
Air moves from an area of high pressure to low pressure. The low pressure means that air is rising, there is less air
Order of Cells from Equator up in the global atmospheric circulation
Hadley Cell, Ferrel Cell, Polar cell.
between Hadley and Ferrel = High pressure descending air
between ferrel and polar = low pressure rising air
Describe the global atmospheric circulation
Sinking air creates high pressure, and rising air creates low pressure.
Surface winds move from high to low pressure, transferring heat and moisture from one to another.
These winds curve due to the earth’s rotation and change seasonally as the tilt and rotation of the earth causes relative changes in the position of the overhead sun.
How does global circulation affect the world’s weather?
Cloudy and wet in the UK – we are 60o north and this is close to where cold polar air from the north meets the warm subtropical air from the south. So since the boundary is unstable, the rising air cools and condenses forming clouds and rain.
Hot and dry in the desert – there they are 30o north or south of the equator, where the sinking air means that there is high pressure, little rain, hot daytime temperatures and very cold nights. Since no air is rising there are no clouds forming and therefore little rain.
Hot and sweaty at the equator – there the air is rising and there is another pressure belt called the equatorial low. It’s much hotter here since the sun is directly overhead, so it is often cloudy with high rainfall. This is where tropical rainforests are often found.
Define Tropical Storms
a huge storm that developed in the tropics, they can be called hurricanes (US and Caribbean), cyclones (south-east Asia, Australia) and typhoons (japan and Philippines).
How do Tropical Storms form?
- Rising air draws evaporated water vapour up from the warm ocean surface which cools and condenses to form towering thunderstorm clouds.
- The condensing releases heat which powers the storm and only draws up more water vapour.
- Multiple thunderstorms join to form a giant rotating storm.
- The Earth’s rotation spin the cloud an over 120 km/h creating a vast cloud spiral with a central, calm eye of rapidly descending air.
- Prevailing winds drift the storm over the ocean surfaces like a spinning top, gathering energy and strength.
- On reaching land the energy supply of evaporated water is cut off and the storm will weaken.
Conditions for Tropical Storms
- mainly formed in Summer and Autumn
- Warm oceans supply the energy
- Need to be at least 26.5degreesCelsius
- Oceans take months towarm up
- Around 5-15o north or south of the equator as there the Coriolis effect (the effect of the earth’s rotation) is stronger.
- Intense heat and humidity in the tropics makes the air unstable
Structure and feature of Tropical Storms
- 500-2000km long
- height = about 12km
- Eye = clearly visible, small area where relatively cold air sinks towards the ground and warms up
= no clouds and conditions are calm. - Eye wall = bank of cloud; strong in excess of 120km/h; heavy torrential rain; thunder and lightning
- Beyond the eye wall there are further banks of clouds with thunderstorms and occasional tornadoes
= strong gusty winds
= heavy rain
Description of the Hadley Cell
Since it is at the equator, the sun is directly overhead, there are vast quantities of warm, moist air. This rises to about 30degrees north or south where it is cooled down again and goes back towards the equator where it is heated up again with the concentrated sun rays.
Conditions near the equator
- very humid
- hot
- wet
- high rainfall
- Tropical Rainforest
General direction of Tropical storms
- overall most go from east to west
- never cross the quator
- Northern Hemisphere go up north
- Southern Hemisphere go down south
How do the tropical storms move thousands of miles
- the prevailing wind pushes the storm along as wells as ocean currents
- the Earth’s rotation from east to west.
Under what conditions do tropical storms lose or gain intensity?
Lose intensity:
- cooler ocean
- moving on land
Gain intensity
- warmer ocean
- not over land
- Time = takes days to build
How will climate change affect tropical storms?
Distribution
The sea surface temps have increased by 0.25 – 0.5o in the tropics so it is easier for them to form and affect the distribution. Therefore, areas which are now outside the hazard zone may become affected. The storms can also become more powerful.
Frequency
Six of the ten most active years in the north Atlantic since the 1950 have happened since the mid-1990s.
Intensity
In the last 20 years, hurricane intensity has increased, this is linked with sea surface temperatures.
Locational detail of the Philippines
- South East Asia
- Archipelago
- Pacific Ocean to the East
South China sea to the west - Population: 99.9 million
Overview of Typhoon Haiyan
It was one of the strongest category 5 storms ever recorded. There was very low air pressure which caused a 5m storm surge which was swept on shore by winds of up to 275km/h. coastal devastation included 90% of Tacloban destroyed by the storm surge.
Primary Effects of the Typhoon Haiyan
About 6300 killed, most in storm surge.
Over 600 000 displaces and 40 000 homes damaged or flattened.
Over 400mm of rain caused widespread flooding.
30 000 fishing boats destroyed.
Airport terminal badly damaged.
Wind damage to buildings, power lines and crops.
Secondary Effects of Typhoon Haiyan
14 million affected including 6 million lost jobs.
Landslides and blocked roads due to flooding.
Power supplies cut off for a month in certain areas.
Shortages of power, water, food and shelter, leading to outbreaks of disease.
Looting and violence in Tacloban.
Immediate Responses of Typhoon Haiyan
Rapid overseas aid.
US aircraft carrier ‘George Washington’ assisted with the search and rescue and delivery of aid.
Over 1200 evacuation centres set up.
Field hospitals helped injured.
Long Term Responses of Typhoon Haiyan
UN and international financial aid, supplies and medical support.
Rebuilding of infrastructure.
Rice farming and fishing quickly re-established.
Homes rebuilt in safer areas.
More cyclone shelters built.
Tropical Storms : Monitoring and Prediction
Tropical storms can’t be prevented, but they can be monitored and their tracks can be predicted so warnings can be given out and people can prepare and know what to expect.
- computer models
e.g. National Hurricane center in Miami warns people.
Tropical Storms : Protection
- Cyclone shelters = very expensive but highly effective
- Storm drains = preventing flooding, cheaper option
- Sea walls to protect key properties from storm surge
- Houses on stilts = if made with strong material (expensive) but can be very effective.
