global hazards - basics

Question 1

what is the global circulation system?

Answer 1

• The movement of air across the planet occurs in a specific pattern, to keep the earths temperature in balance. The whole system is driven by the equator, which is the hottest part of the Earth.
• Air rises at the equator, leading to low pressure and rainfall. When the air reaches the edge of the atmosphere, it cannot go any further and so it travels to the north and south.
• The air becomes colder and denser, and falls, creating high pressure and dry conditions at around 30° north and south of the equator. Large cells of air are created in this way.

Question 2

what kinds of climatic zones are there

Answer 2

• a hot wet climate around the equator as warm air rises where the hadley cells meet
• a hot dry climate as air sinks where the harley and ferrell cells meet, that’s why there’s deserts around the tropics
• unsettled weather at around 60° N and S as cool air mixes w warm air where the polar and ferrell cells meet, including the wet mild climate in the uk

Question 3

explain the belts of pressure

Answer 3

• air cools and sinks at the polar cells, creating a belt of high pressure and a cold dry climate
• at about 60° N and S at the ferrell cell, cold polar air mixes w warmer air and rises, creating a belt of low pressure
• cool air sinks at the harley cell, creating a belt of high pressure, as the air sinks, it becomes warmer and drier
• warm air rises, creating a belt of low pressure. as the air rises it cools, clouds form in the inter tropical convergence zone, then release precipitation. above the itcz, the air separates and moves to higher latitudes.

Question 4

what is insolation?

Answer 4

the sun radiates energy in heat and light, only some of the radiation reaches earth

Question 5

why does the equator have the potential to be the hottest part of the world, and why are the poles so cold?

Answer 5

the suns rays are strongest there, the suns rays hit earth at an angle at the poles which result in the lower temperatures

Question 6

what are some factors affecting temperatures around the world?

Answer 6

• albedo effect
• cloud cover
• winds - surface winds move heat around the world
• ocean currents - water if fluid, ocean currents move heat easily, eg the uk is warmer rhan other countries at the same latitude bc it’s warmed by the north atlantic drift, which is a warm ocean current originating in the carribean
• land and sea - on land i solar ion is concentrated on the surface, at sea it reaches deeper because water is transparent. water is slower to warm up than land, but it stays warm for longer
• altitude - higher up air pressure is lower which makes temperatures colder

Question 7

what is the albedo effect?

Answer 7

how much a surface reflects or absorbs the suns rays, eg polar ice has a high albedo as it reflects more heat and it makes the poles colder, the oceans and rainforests have a low albedo, and absorb more heat

Question 8

what is cloud cover

Answer 8

clouds reflecting the suns rays, although potential indo latino is stronger at the equator, thick clouds reduce the temperature, i dilation is acc stronger close to the tropics which are largely free from cloud cover

Question 9

what is wind?

Answer 9

the movement of air from an area of high pressure to one of low pressure, the greater the difference in pressure, the stronger the wind

• winds at ground level are slowed by friction

Question 10

what kinds of wind are there

Answer 10

• trade winds
• katabatic winds
• jet streams

Question 11

what are trade winds?

Answer 11

winds that blow from high pressure belts to low pressure belts

• trading ships used them to sail around the world

Question 12

what are katabatic winds?

Answer 12

caused by air flowing downhill

• in antarctica large ice sheets sloping gently into the sea contribute to wind speeds of it wr 320km/h

Question 13

what are jet streams?

Answer 13

winds high in the atmosphere called jet streams are very strong as there’s little to slow them down

• mf everest has jet streams

Question 14

what are tornadoes

Answer 14

very strong rotating winds

• much smaller than tropical storms and can occur over both land and sea, can be extremely hazardous and can reach 400km/h

Question 15

how do you measure wind speed and direction?

Answer 15

by anemometers, which are used to measure wind speed by counting the number of times they rotate in a minute

• wind speed and direction in a location can be shown by using a rose chart
• wind speed is measured using the beaufort scale, ranging from 0 (calm) to 12 (hurricane)

Question 16

what is precipitation?

Answer 16

when warm air rises, it carries water vapour, and as it rises the air cools and the water vapour condenses to form clouds. eventually the clouds release precipitation which falls to earth as rain sleet snow or hail

Question 17

what are the patterns of rain around the world?

Answer 17

areas of low pressure have rising air and high levels of precipitation

areas of high pressure have descending air and low precipitation

on a global scale rain falls heavily in a band around the equator, but the tropics are much drier

on a regional scale, the coasts of continents can be particularly wet

on a local scale, precipitation is influenced by altitude

Question 18

what kinds of rainfall are there?

Answer 18

• conventional rainfall
• frontal rainfall
• relief rainfall

Question 19

what is conventional rainfall

Answer 19

strong sunshine warms up the ground and air above it

pockets of warm air rise as convection currents

at high altitudes, the air cools and its water vapour condenses to form clouds

when rain falls it can be heavy, sometimes thunderstorms, this type of rain is significant at the equator where temperatures are high

Question 20

what is frontal rainfall

Answer 20

when warm air meets cool air it’s called a front, the warm air rises over the cool air and clouds are formed

• eventually there’s steady rain
• frontal rainfall is common in the uk because it’s situated where the arm air from the tropics meets cool air from the north pole

Question 21

what is relief rainfall?

Answer 21

when wind gets to mountains the warm air is forced to rise, leading to cooling, condensation and precipitation on the windward side of the mountain

when the air descends on the leeward side it will be dry, creating a rain shadow

in the uk mountains like the pennines tend to be wetter on their western sides and drier on the east