Temperature And Heat Exchange Processes

Question 1

Describe the temperature reference points of the centigrade scale used in NZ aviation.

Answer 1

• 0degrees Celsius = water freezing or ice melting
• 100degrees Celsius = waters boiling point
• These numbers only work at 1013.25hPa - SEA LEVEL
• If pressure is reduced water will boil at a lower temperature

Question 2

Explain the factors that influence the amount of solar radiation received at the earth’s surface.

Answer 2

• Cloud cover
• Sun’s angle of incidence to the surface (season/latitude/time of day)
• Mountains
• Albedo

Question 3

Explain the warming or cooling of the atmosphere with reference to solar and terrestrial radiation.

Answer 3

• Daytime = Earth receives more energy than it emits, heating the atmosphere
• Night time = Earth emits more energy than it receives, cooling the atmosphere.

Question 4

Describe conduction.

Answer 4

• Transfer of heat by touch
• Occurs faster in solids and liquids than gas
• Will only heat the first 10cm of air

Question 5

Describe convection.

Answer 5

• Requires the air too be heated by conduction first
• Warm air becomes less dense and rises
• Cool air above is more dense and sinks
• This cool air can then be heated by conduction and rise

Question 6

Describe advection.

Answer 6

• Horizontal transfer of heat or matter
• Also requires conduction to heat the lower parts of air
• Wind then blows the warm air through cold air and mixes

Question 7

Explain how the atmosphere is warmed or cooled by conduction.

Answer 7

• Heats the surface
• Transferred by convection, turbulence or wind into the atmosphere.
• Over ice the cooling can only be spread by turbulence and wind.

Question 8

Explain how the atmosphere is warmed or cooled by convection.

Answer 8

• Transfers warm air from the surface to the upper troposphere
• As the warm air rises, cooling air sinks creating a convective current.

Question 9

Explain how the atmosphere is warmed or cooled by advection.

Answer 9

• Warm advection = warm air moving to colder areas
• Cold advection = cold air moving to warmer areas

Question 10

Define the term ‘specific heat’

Answer 10

• The amount of solar radiation (or energy) required to increase temperature by 1degree Celsius.
• If it requires large amounts of solar radiation= high specific heat
• If it requires low amounts of solar radiation = low specific heat.

Question 11

What is the specific heat of water and land?

Answer 11

• Water = 1
• Land = 0.2

Question 12

Define the term ‘albedo’

Answer 12

• How reflective something is to solar radiation
• Reflects large amounts/lighter colours = high albedo
• Reflects small amounts/darker colours = low albedo

Question 13

Explain the significance of the heating at Earth’s surface, in terms of specific heat.

Answer 13

• Land has a low specific heat
• Ocean has a high specific heat
• Land heats/cools faster than the ocean
• Creates pressure differential which creates a sea breeze or land breeze.

Question 14

Explain the significance of the heating at Earth’s surface, in terms of albedo.

Answer 14

• Mountains covered in snow reflect solar radiation keeping them cool
• Dark roads absorb solar radiation and heat up faster
• Dark sand beaches absorb more radiation than light sand beaches
• Ocean waves make heating harder as sun angle is always changing.

Question 15

Explain the significance of the heating at Earth’s surface, in terms of insolation.

Answer 15

• Means amount of solar radiation which strikes the Earths surface.
• Depends on: the angle of incidence of the sun’s rays
• Duration of day and distance from sun
• Transparency of the atmosphere

Question 16

Describe Celsius.

Answer 16

• 0degrees = freezing point of water
• 100degrees = boiling point of water
• Named after Swedish astronomer Anders Celsius.

Question 17

Describe Fahrenheit.

Answer 17

• 0degrees = freezing point of a mixture of water ice and ammonium chloride
• 100degrees = best estimate of human body temperature
• Named after Daniel Gabriel Fahrenheit
• 32degrees = water freezing
• 212degrees = water boiling

Question 18

Describe Absolute (Kelvin)

Answer 18

• SI unit for temperature
• Uses absolute zero as its starting point
• No molecular movement at absolute zero
• Not written as a degree

Question 19

What is the formula to convert Fahrenheit to Celsius?

Answer 19

(F - 32) x 5/9 = C

Question 20

What is the formula to convert Celsius to Fahrenheit?

Answer 20

(C x 9/5) + 32 = F

Question 21

What is the formula to convert Kelvin to Celsius?

Answer 21

0 K = -273.15 °C

Question 22

What is the formula to convert Celsius to Kelvin?

Answer 22

0degrees Celsius = 273 K

Question 23

Explain solar radiation.

Answer 23

• Solar radiation = electromagnetic radiation emitted from the Sun

Radiation is not hot but produces heat on contact.
Net gain of insolation during the day and loss at night.

Question 24

Explain terrestrial radiation.

Answer 24

• Terrestrial radiation = electromagnetic radiation emitted from Earth.

Radiation is not hot but produces heat on contact.
Net gain of insolation during the day and loss at night.

Question 25

State the wave length of solar radiation.

Answer 25

- Solar radiation = 0.4 - 4 micrometres

Question 26

State the wave length of terrestrial radiation.

Answer 26

- Terrestrial radiation = 4 - 80 micrometres

Question 27

Describe the effect of the sun angle on the amount of solar radiation received at the surface of the Earth.

Answer 27

- Sun’s angle at 90degrees to the Earth’s surface = maximum radiation received. - Occurs near the equator - High latitudes the angle reduces, spreading the same amount of radiation over a larger area - Higher latitudes = less heating

Question 28

Describe the effect of the length of day on the amount of solar radiation received at the surface of the Earth.

Answer 28

- Longer days = more solar radiation received - Due to the delay of heating air, hottest time of day is mid afternoon - Longer days also mean shorter nights

Question 29

Describe the effect of seasons on the amount of solar radiation received at the surface of the Earth.

Answer 29

- Summer = most solar radiation received - Winter = lowest amounts of solar radiation received - Due to Earth’s tilted rotational axis at 23.5degrees orbit around the sun

Question 30

Define the term solstice.

Answer 30

- Sun reaches most northerly or southerly latitude for the year. - Represent the longest and shortest day - June 20th or 21st = shortest day in SH - Dec 21st or 22nd = longest day in SH OPPOSITE applies for NH

Question 31

Define the term equinox.

Answer 31

- Centre of Sun directly over the equator - Day will be equal length in NH and SH - March 20th and September 22nd or 23rd

Question 32

State the significance of a solstice.

Answer 32

- June = Sun at most northern latitude (no sunlight at the South Pole. - December = Sun at most southern latitude (no sunlight at the North Pole) - Solar radiation for SH largest in Sep - Mar - Lowest from Mar - Sep

Question 33

State the significance of an equinox

Answer 33

- Only time when NH and SH have equal day length. - Occurs twice a year