2.2 The global energy budget

Question 1

What is the global energy budget?

Answer 1

The atmosphere is an open energy system receiving energy from both Sun and Earth

Question 2

What are the variations in the receipt of solar radiation and why?

Answer 2

• Due to the tilt of the Earth and its orbiting around the Sun, with latitude, there is a positive budget in the tropics and negative at the poles
• It is also due to the tilt of the Earth that the Southern hemisphere in January is summer, July winter and vice versa.

Question 3

Define thermal equator

Answer 3

An imaginary line round the earth running through the point on each meridian with the highest average temperature

Question 4

What is the annual temperature pattern (thermal equator)?

Answer 4

• In January, the thermal equator is further South
• In July, the thermal equator is closer to the actual equator
• In general, there’s a decline in temperatures northwards from the Tropic of Capricorn

Question 5

How is balance achieved between the negative energy budget (at the poles) and positive energy budget (at the tropics)?

Answer 5

By the horizontal transfer of energy from the equator to both poles by winds and ocean current to compensate for differences in global insolation. Warm air rises at the equator, spreads northwards and southwards and then sinks

Question 6

What does the surface pressure belt consist of?

Answer 6

• Equatorial low pressure trough
• Sub-tropical high pressure belt
• Sub-Antarctic and sub-Polar areas
• Polar highs

Question 7

Why does the equatorial low pressure trough have low pressure?

Answer 7

This is an area of low pressure because it is an area of high temperature and humidity due to the sun heating it directly. In the northern hemisphere in July, the belt is north of the equator whereas in the southern hemisphere during January

Question 8

Define Intertropical Convergence Zone (ITCZ)

Answer 8

• The area encircling the earth near the equator where the northeast and southeast trade winds come together.
• The convergence of warm, moist air over the equator transports large volumes of air aloft, to the top of the troposphere. This air is confined vertically by the base of the stratosphere and thus spreads out north and south toward the poles

Question 9

Define doldrum

Answer 9

Refers to the part of Atlantic ocean/Pacific affected by ITCZ

Question 10

How does pressure vary at the sub-tropical high pressure belts (30 degrees N and S)?

Answer 10

• In SH continuous about 30 degrees latitude
• In NH discontinuous because of the land
• Over oceans, high pressure occurs as discrete cells, the Azores and Pacific Highs
• Over continental areas, southwest USA, southern Asia and Sahara, major fluctuations: high pressure in winter and low in summer due to overheating

Question 11

How does pressure vary at the sub-Arctic or sub-Polar areas (temperate latitudes)?

Answer 11

• In the northern hemisphere, there are strong winter low pressure zones over Icelandic and oceanic areas but over Canada and Siberia, there is high pressure due to the coldness of the land.
• In summer, high pressure is reduced, especially over continental areas
• In SH, it does not vary as much because here is more ocean in the Southern Hemisphere- and oceans do not vary in pressure or temperature as much as land does

Question 12

What’s the pressure at the poles?

Answer 12

• Polar highs

- Pressure is high relatively throughout the year, especially over Antarctica due to the coldness over the landmass

Question 13

How does the wind move?

Answer 13

From high pressure to low pressure and also due to the Coriolis effect, tends to follow more east-west trends rather than north-south trends.

Question 14

Define Trade Winds

Answer 14

• In the NH, air blows from the northeast to the southwest
• In the SH, blow from the southeast toward the northwest
• These are Trade Winds

Question 15

Define monsoon

Answer 15

Reversing wind systems/direction

Question 16

How is monsoon induced?

Answer 16

• Induced by Asia which causes wind to blow outwards from high pressure in winter but pulls the southern trades into low pressure in summer => influenced by the reversal of land and sea temperatures between Asia and Pacific during winter and summer
• In winter, surface in Asia can be as low as -20 degrees and surrounding oceans have temp of 20 degrees
• During summer, land heats up more quickly => 40 degrees while summer 27 degrees

Question 17

Define Upper Westerlies

Answer 17

Prevailing winds at the upper latitudes (between 30 and 60) that travels from west to east

Question 18

Define Easterlies

Answer 18

Winds that travel from east to west

Question 19

How is land-sea breeze induced?

Answer 19

• Blowing from the cooler sea (high pressure) in summer to warmer land (low pressure)
• In winter, air flows out of the cold land mass (high pressure) to warm water (low pressure)

Question 20

What are the 3 cells the tri-cellular model consist of?

Answer 20

• Polar
• Ferrell
• Hadley

Question 21

What happens in the Hadley cell?

Answer 21

• At the equator the sun shines directly and warms the surface => warm air rises => low pressure
• In the subtropics (20-30 N and S) air sinks because it’s colder and denser, it then returns to the tropics to replace rising air. Cycle repeats.

Question 22

What happens in the Polar cell?

Answer 22

Warm air rises at lower latitudes and moves pole wards. Air reaches the polar areas cooled considerably and descend as cold dry high pressure area

Question 23

What happens in the Ferrell cell?

Answer 23

• Warm air is transferred to high latitudes and shifts cold air back to the subtropics where it is warmed
• It exists due to the other 2 cells and it mirrors the other cell movements

Question 24

What is the Coriolis effect?

Answer 24

The deflection of moving objects caused by easterly (West to East) rotation of the Earth

Question 25

Explanation of the Coriolis effect

Answer 25

• Near the equator where the Earth is widest, the outer edge of the Earth’s atmosphere is moving faster than it does around the poles => atmosphere gains a more west to east spin at the equator
• Flies upwards to the NH => to the right/east (nhin tu pole xuong equator)
• Flies downwards to the SH => to the left/west

Question 26

Define jetstreams

Answer 26

Strong, regular winds which blow in the upper atmosphere (abt 10 km above the surface), they blow between the poles and tropics at speed from 100-300km/h

Question 27

Define Rossby waves

Answer 27

Meandering rivers of air formed by westerly winds. They are formed by major relief barriers such as the Rockies, the Andes by thermal differences and uneven land-sea interfaces

Question 28

How does the Rossby wave work?

Answer 28

1. Tropical air moves towards the Poles because heat tends to flow from low to high latitudes
2. When air hits a barrier, usually a mountain, this changes its trajectory-heading north
3. Due to Coriolis effect, the air moves South and then North again

Question 29

Why are jetstreams and Rossby waves important?

Answer 29

Mixing warm and cold air

Question 30

Factors affecting the climate

Answer 30

• Altitude
• Latitude
• Distance from sea
• Ocean currents
• Prevailing winds and air circulations

Question 31

How does latitude affect the climate?

Answer 31

• High temps are recorded at low latitudes in the tropics N & S of the equator
• A decrease in temp between Equator and poles
• Explanation: The sun’s ray are more concentrated at the Equator because they hit the Earth directly. As you go away from the equator, the curve of the earth means that the same rays have to spread over a larger surface area => doesn’t heat up as much

Question 32

How does ocean currents affect the climate?

Answer 32

• Warm currents from equatorial regions raise the temps of polar areas (with the aid of prevailing westerly winds). However, only noticeable in winter. e.g. North Atlantic Drift raises temp of northwest Europe
• Areas made colder by ocean currents. e.g. Labrador current off the northeast coast of North America reduce summer temp, if only winds blows from sea to land

Question 33

Define gyres

Answer 33

The dominant pattern of surface ocean currents that is a roughly circular flow. Pattern is clockwise in NH and vice versa

Question 34

What’s the general movement of currents?

Answer 34

• Warm - away from equator

- Cold - towards the equator

Question 35

How does distance from the sea affect the climate?

Answer 35

• Difference in the specific heat capacity/continentality
• Land heats up and cools more quickly than sea
• In land: warm summer, cool winter
• In coastal areas: cool summer, warm winter

Question 36

How does altitude affect the climate?

Answer 36

• For every 100m you ascend, the air temp drops by 1 degree
• Temperature decreases with height because most of the solar radiation passes through the atmosphere with little or no effect - that radiation is absorbed by the solid Earth surface and is transferred to the air above the surface by conduction.

Question 37

How does air circulation affect the climate?

Answer 37

• Air rises at the equator due to the amount of insolation received
• As air rises, it makes cumulonimbus (thunder and rain) as it cools down in the tropical areas
• Once it has cooled it becomes denser and sinks making an area with high pressure and no clouds - deserts
• In temperate zones, warm air (equatorial regions) meets cool air (polar regions) , the warm air slowly rises above the cold air, forming a low pressure zone. As the rising warm air reaches higher elevations, the liquid in it condenses and forms clouds and rain. Cool air rushes in to fill the low pressure zone, pushing more warm air up and creating a cycle that can result in high winds and storms.