3.1.1.3 Weather Hazards - Global Atmospheric Circulation

Question 1

What does global atmospheric circulation help to do?

Answer 1

global atmospheric circulation helps to determine patters of weather and climate

Question 2

How does the curvature of the earth affect weather patterns?

Answer 2

• due to curvature of the earth, some parts receive much higher insolation than others e.g. the equator, for example receives more than the poles
• more heat E per km2 at equator has suns rays hit earth at 90 degree angle at Equator (so is more concentrated) unlike in polar regions where heat E distributed over larger area so less heat E per km2
• due to curvature of the earth the different cells are affected by seasonal changes
• in the winter the cells move further north meaning we have more low pressure weather and in the summer they move south, meaning we have more high pressure weather

Question 3

What can the amount of insolation be affected by?

Answer 3

• Cloud cover
• Albedo (surface reflectivity)
• Land/Sea (Sea has a lower albedo)

Question 4

Global atmospheric circulation diagram:

Answer 4

Question 5

What drives global atmospheric circulation?

Answer 5

• Because of the curved nature of the earth, some parts receive much higher insolation than others e.g. the equator receives more than the poles
• Due to the curved nature of the earth, the different cells are affected by seasonal changes
• In the winter the cells move further north meaning we have more low pressure weather and in the summer they move south, meaning we have more high pressure weather

Question 6

What are winds and what are they part of?

Answer 6

• large scale movements of air (when air particles move) due to differences in pressure - move from an area of high pressure to an area of low pressure
• winds are part of global atmospheric circulation loops (or cells)
• these loops have warm rising air which creates a low pressure belt, and cool falling air which creates a high pressure belt

Question 7

What are surface winds important in?

Answer 7

surface winds are important in transferring heat and moisture from one another

Question 8

What are differences in air pressure caused by?

Answer 8

• air circulations create different areas of pressure
• caused by differences in temperature between the equator and the poles
• winds move from the areas of high pressure to areas of low pressure

Question 9

How do seasonal changes impact global atmospheric circulation?

Answer 9

• the patterns of pressure belts (such as the polar high) and winds are affected by seasonal changes
• the tilt and rotation of the Earth causes relative changes in the position of the overhead Sun
• these seasonal changes cause pressure belts and winds to move north during our summer and south during our winter

Question 10

What causes low pressure and what is low pressure weather like?

Answer 10

• Air that is rising from the ground surface causes low pressure weather
• Low pressure weather can be unsettled, meaning it can easily change
• Low pressure weather can be increasingly wet and showery
• Winds on the ground move towards these areas of low pressure

Question 11

What causes high pressure and what is high pressure weather like?

Answer 11

• Air that is sinking to the ground surface causes high pressure weather
• High pressure weather is more settled, meaning you can expect days of relatively similar weather
• High pressure weather is generally rain free/cloud free
• Winds on the ground move outwards from these areas

Question 12

Where is low pressure found on Earth?

Answer 12

• low pressure at the equator and at 60 degrees either side due to the air rising here
• it rises here the most due to the heat from the sun’s heat being most concentrated along the equator

Question 13

Where is high pressure found on Earth?

Answer 13

• there is high pressure at the poles and 30 degrees either side of the equator due to air sinking here
• due to the air being colder there as it’s further away from the sun so it is heated less

Question 14

What is the Coriolis effect?

Answer 14

• winds do not move in a straight line across the Earth
• the winds are deflected in different directions
• due to the Earth’s spinning and due to the Earth’s surface rotating faster at the equator than at the poles (as it is wider so has further to travel for one full rotation) so the winds end up travelling in a curved direction
• winds are deflected right in the Northern hemisphere and left in the Southern hemisphere

Question 15

What impacts temperature and humidity?

Answer 15

pressure belts and surface winds impact the temperature and humidity in regions throughout the world

Question 16

How does atmospheric circulation impact the climate at the equator?

Answer 16

• sunlight hits the equator at a 90 degree angle
• consistently warmer as the heat energy is per km2 is greater as the sunlight is concentrated along the equator unlike the poles where the heat energy from the Sun has to be spread over a larger area
• moist air rises here creating an area of low pressure (equatorial low)
• when the air rises it condenses to form rain
• causes climate at the equator to be very humid and rainy
• tropical rainforests are found here due to the warm and wet weather

Question 17

How does atmospheric circulation impact the climate at the subtropics?

Answer 17

• dry air sinks at the subtropics, meaning it forms an area of high pressure 9high pressure belt - sub-tropical high)
• clouds do not form here as the air isn’t rising, so it is very dry with little precipitation
• this is where we find many of the world’s deserts
• it is very hot in the day because of the intense sunlight, but very cold at night because there are no clouds to retain heat and it is quickly lost from the ground

Question 18

How does atmospheric circulation impact the climate at sub-polar latitudes?

Answer 18

• at around 60 degrees north or south of the equator there is a low pressure belt, causing the climate to be cloudy and wet
• the climate here is not as warm as the sun shines less directly than at the equator

Question 19

How does atmospheric circulation impact the climate of the UK?

Answer 19

• UK located about 55 degrees N just below the 60 degrees N line of latitude
• puts the UK closer to the boundary of cold polar air moving down from the norther and warm sub-tropical air moving up from the south
• the boundary between these 2 air masses is unstable
• here there is rising air and low-pressure belts (the sub-polar low) on the ground
• rising air cools, condenses and forms clouds and rain - explains why it is often cloudy and wet in the UK
• sometimes the cold polar air from the N moves down over the UK bringing snow and very cold winter weather

Question 20

Albedo:

Answer 20

• the reflectivity of the Earth’s surface
• the higher the figure the more reflective it is (it absorbs less)

Question 21

Insolation:

Answer 21

the amount of solar radiation absorbed by the Earth’s surface

Question 22

Latitude:

Answer 22

the imaginary lines that go around the Earth to help locate places e.g. the equator

Question 23

Where are the Hadley cells found?

Answer 23

this is the largest cell and extends from the Equator to 30˚ North/South

Question 24

What happens at the Hadley cells and what is the climate like there?

Answer 24

• It is a high pressure area, home to the majority of the worlds deserts
• There is intense heating at the equator (because of the high levels of insolation) causing the air to rise to very high altitudes
• When the air rises to the high altitudes it moves back towards the poles

Question 25

Where are the Ferrel cells found?

Answer 25

the Ferrel cells are found in between the Polar and Hadley cells

Question 26

What happens at the Ferrel cells and what is the climate like there?

Answer 26

• The cooler air from the poles meets the warmer air from the tropics causing the air to rise (more low pressure)
• unsettled weather

Question 27

Where are the Polar cells found?

Answer 27

The Polar Cell is found between the poles 60˚ North and South

Question 28

What happens at the Polar cells and what is the climate like there?

Answer 28

• The cold dense air sinks at the higher latitudes and moves to the lower latitudes
• As it moves closer to the equator the air warms and rises and causes a low pressure front known as a polar front