Science 10 - Climate: Energy Flow in Global Systems

Part 2 – Distribution of Heat

Energy Transfer

Recall: Only a limited amount of the sun’s radiation is absorbed in the atmosphere while most of the radiation reaches Earth’s surface.

This means that the surface of the Earth warms up much more from the solar energy than the atmosphere and we would expect the atmosphere to very cold.

So why is the air not freezing cold?

Energy is transferred from the Earth to the atmosphere in three ways:

1. Radiation: energy emitted from the ground in waves (mostly infrared radiation). Heat from a stovetop or a microwave are examples of radiation energy transfer.

2. Conduction: collision between molecules on land in the air transfer energy from the more energetic land molecules to the air molecules. Burning your hand on a hot pot is and example of conduction.

3. Convection: Distribution of heat by moving air. Warm air rises and cooler air falls. A fan creating a wind is an example of convection.

Heat Distribution Around the Earth

Recall:Latitude: lines running parallel to the equator around the globe. Equation: 0 latitude, poles 90 latitude

Longitude: lines running pole to pole

Why do we have different weather and climates?

Different parts of the earth do not receive the same solar insolation due to the differences in the angle of incidence of solar radiation.

As we move north or south of the equator, or increase the latitude, the angle of incidence increases, and the amount of solar radiation absorbed decreases. Therefore:Near the equator or at low latitude, there is excess incoming radiation due to the high solar insolation. More energy is being absorbed from the sun than the Earth and atmosphere can emit.

At higher latitudes, closer to the poles there is a radiation deficit due to the low solar insolation. More energy is being lost by the Earth and atmosphere than is gained from the sun.

Therefore, there is a heat imbalance between the lower and higher latitudes of Earth.

This heat imbalance is responsible for most of our weather and climate.

How is heat distributed around the Earth?

The Earth, in a way, attempts to balance out the heat energy in the higher and lower latitudes as well in closer and further from the surface of the Earth.

Methods of which heat is distributed around the earth:

1. Ocean currentsWater absorbs a great amount of energy, and this is distributed around the Earth by ocean currents. Ocean currents are caused by surface winds, water’s salinity and heat content, the contours of the ocean bottom and Earth’s rotation.

2. Windsa. Convection currents

Atmospheric pressure: downward force in a given area due to the atmospheric gases above it.Warm air at the equator rises to create an area of low atmospheric pressure.Cool air descends to create an area of high atmospheric pressure.Cool air flows closer to Earth’s surface from the area of high pressure to the area of low pressure.Since the equator is the warmest, we expect air flows from the poles towards the equator.

More accurately, however, this occurs in smaller circular convection currents since risen warm air cools when it meets cooler air and cooler air will rise as it meets warmer air.

Furthermore, Earth is rotating at the same time. This momentum has an effect on the wind.

b. The Coriolis effect: apparent movement (deflection) of air and water due to the rotation of the earth.

The Coriolis effect results in the north-south direction of wind to be deflected toward the east-west direction.

c. Jet StreamsCurrents of fast moving air in the atmosphere in the top portion of the troposphereForm at the boundaries of warm and cold air.Strong and fast so move energy across continents/globally

Summarize how energy is distributed around the Earth- Ocean currents move warm and cold water around - Convection moves warm air up and cool air back down creating areas of high and low pressure.

Air will move from low to high pressure creating winds that transfer heat from warmer areas to cooler areas.

- The Coriolis effect deflects winds in east/west directions, contributing to wind patterns.- Jet streams move energy across continents/globally

Questions – check your understanding

Answer the following questions on a separate sheet of paper.

1. The land absorbs more radiation than the atmosphere. a. What type of solar radiation is not absorbed by the atmosphere?

Visible light and ultraviolet (UV)b. What type of solar radiation is absorbed by the atmosphere?

Infrared (IR)c. Which gases in the atmosphere absorb the radiation in (b)?

Greenhouse gases (CO2, H2O, O3, CH4, N2O, etc.)

d. Explain, mentioning three methods of energy transfer, how the atmosphere is warmed by the land.Conduction – air molecules hit the surface of the Earth, these collisions transfer energy from the earth to the atmosphere.Convection – Warmer air near the Earth’s surface rises and cooler air falls. Radiation – IR radiation form the Earth’s surface is emitted and absorbed by the air molecules.

2. Give an example of each of the three methods of energy transfer.Conduction – touching a hot potConvection – a fan in your home or oven moving air aroundRadiation – a microwave oven (emits microwaves that hit your food and warm it up)

3. Explain how Earth’s angle of inclination affects the amount of solar insolation the Northern Hemisphere receives throughout the year.Sometimes the northern hemisphere is tilted towards the sun and sometimes it is not. When it is tilted towards the sun it gets more direct sunlight and therefore more solar insolation as it hits the Northern Hemisphere at a lower angle of inclination. The opposite is true when the Northern Hemisphere is facing away from the sun.

4. Two cities located in the desert have the same altitude and latitude but have different surface features. The city of Rocky Peaks is surrounded by a dark rocky surface. The city of Sandy Beach is surrounded by light coloured sand. Neither city has ever had snow. Which city will have a higher temperature in the summer? Which will have a higher temperature in the winter? Explain your answers.The dark surface will have a lower albedo and therefore, will absorb more solar energy and warm up more. We would expect the rocky place to be warmer year-round.

5. a. State the prevailing direction of winds from a latitude of to 30 N to 60 N.Winds are travelling from East to West. b. Explain how the Coriolis effect determines this direction of prevailing wind.The Earth is moving faster at 30N than at 60N. Therefore, relative to the faster moving Earth at 30N the air is moving slower and at 60N relative to the Earth the air is moving faster. These relative speeds of the Earth vs. the air creates the prevailing winds.

6. State and explain any differences in temperature at different latitudes of Earth.

7. a. Define the term net radiation budget. b. On average, what is the net radiation budget for the entire Earth?

8. Describe what is responsible for most of the weather and climate on Earth.

9. Summarize how heat is distributed around the Earth. Use the following terms in your summary: ocean currents, convection currents, Coriolis effect, jet streams, wind.