Meteorology - Temperature Flashcards
What is temperature a measure of?
Temperature is a measure of the level of molecular activity within a substance.
Is temperature a direct measure of heat energy?
No, temperature is not a direct measure of the amount of heat energy present.
Can small objects with high temperatures contain little heat energy?
Yes, very hot small objects can contain little heat energy.
Can large warm objects contain huge amounts of heat energy?
Yes, large warm objects can contain huge amounts of heat energy.
What happens to molecular activity at absolute zero (-273°C or 0 Kelvin)?
All molecular activity ceases, and the object contains no heat energy.
What happens to temperature when heat energy is added?
The temperature goes up.
What does the temperature increase depend on?
The temperature increase depends on the material being heated.
How do we define the units of heat energy?
By reference to the behavior of water.
What is a calorie (cal)?
The amount of heat needed to raise one gram of water by one degree centigrade (or one Kelvin).
How much does the temperature of 1 gram of water rise if 10 calories are added?
The temperature will rise by 10°C.
How much does the temperature of 100 grams of water rise if 10 calories are added?
The temperature will rise by 0.1°C.
Which substance has the highest ability to absorb heat among common substances?
Water.
What is specific heat?
The ratio of the amounts of heat required for the same temperature rise.
What is the specific heat of water?
1
What is the approximate specific heat of ice?
0.5
What is the approximate specific heat of rock?
About 0.25, depending on its composition.
How much energy is needed to raise the temperature of 1 gram of water by 1 degree Celsius?
One calorie.
How much energy is needed to raise the temperature of 1 gram of ice by 1 degree Celsius?
½ calorie.
How much energy is needed to raise the temperature of 1 gram of rock by 1 degree Celsius?
¼ calorie.
How does the specific heat affect oceans and land masses?
Oceans stay at a more or less constant temperature while night and day, winter and summer, but land heats up quickly and cools down quickly.
What is needed to loosen the bonds that hold molecules together and change solids to liquids and liquids to gases?
Energy is needed to loosen the bonds that hold molecules together and change states of aggregation.
What happens to the temperature when energy is input to change the state of aggregation?
The temperature does not rise; the energy remains hidden (latent).
How many calories are needed to change 1 gram of ice at 0°C to water at 0°C?
80 calories.
How many calories are needed to change 1 gram of liquid water to water vapour at 100°C?
540 calories.
What happens when 1 gram of water vapour condenses into water?
540 calories are released into the surroundings.
How many calories are released when 1 gram of water freezes to ice?
80 calories are released into the surroundings.
What are the latent heat of fusion and latent heat of evaporation?
Latent heat of fusion is melting/solidification and latent heat of evaporation is condensation.
How much total heat is needed to bring 1 gram of ice at -273°C to water vapour at 100°C?
857 calories (137 cal to bring ice to 0°C, 80 cal to change to water, 100 cal to bring water to 100°C, 540 cal to change water to vapour).
How much heat is released when water vapour changes back to water at 100°C?
540 calories per gram.
Can water evaporate at temperatures below 100°C?
Yes, but the process is slower and requires more calories.
What is sublimation in terms of state changes?
Sublimation is when water vapour goes straight to ice or ice goes to water vapour without passing through the liquid stage.
How many calories are involved in sublimation?
About 680 calories, the sum of the two normal stages.
How do cloud and fog droplets form?
By condensation of water vapour from the atmosphere onto small particles called condensation nuclei.
What role do condensation nuclei play besides forming cloud and fog droplets?
They affect the optical properties of the atmosphere and play an important role in atmospheric electricity.
When will droplet cloud formation occur in a dust-free sample of air saturated with water vapour?
When the air is rapidly expanded so that adiabatic cooling occurs and the expansion ratio is high enough to produce several hundred percent supersaturation.
At what level of supersaturation can condensation occur if particles are present in the air?
At much lower supersaturations (a few tenths of a percent).
What determines the effectiveness of a particle as a condensation nucleus?
Whether it is hygroscopic (water attracting) or hydrophobic (water repelling).
How can small water droplets be supercooled?
They can be supercooled to temperatures as low as -40°C.
What happens in the presence of freezing and sublimation nuclei?
The formation of ice crystals occurs at much warmer temperatures.
What is the energy impact of changes of state of aggregation?
The energy released by changes of state of aggregation is extraordinary.
Give an example of the impact of latent heat of condensation.
Over the Amazon basin on a typical day, rising moist air forms convective clouds aloft and heavy rain falls, releasing latent heat of condensation, which can raise the mean temperature of the troposphere overhead by 10°C.
What is a powerful factor involved in the global movement of heat energy?
The process of evaporation and condensation.
What is insolation?
Insolation is a measure of solar radiation energy received on a given surface area in a given time.
How is radiation defined?
Radiation is defined as the emission and propagation of energy in the form of rays or waves; the energy radiated or transmitted in the form of rays, waves, or particles; and a stream of particles or electromagnetic waves emitted by the atoms and molecules of a radioactive substance as a result of nuclear decay.
How is solar energy created at the core of the Sun?
Solar energy is created when hydrogen atoms are fused into helium by nuclear fusion.
What is the average temperature of the Sun’s photosphere?
About 5800 Kelvins.
In which bands does the Sun emit electromagnetic radiation?
Most radiation is emitted in the visible band centered at 500 nm, but the Sun also emits significant energy in the ultraviolet and infrared bands, and small amounts of energy in the radio, microwave, X-ray, and gamma ray bands.
What is the total quantity of energy emitted from the Sun’s surface?
Approximately 63,000,000 Watts per square meter (W/m² or Wm⁻²).
What happens to the energy emitted by the Sun?
It passes through space until it is intercepted by planets, other celestial objects, or interstellar gas and dust.
How long does the trip from the Sun’s surface to the Earth take?
About 8 minutes.
What happens to a lot of the Sun’s energy as it reaches the atmosphere?
It is diverted, scattered, and reflected high in the atmosphere, and much of the ultraviolet is absorbed in the ozone layer.
How much of the Sun’s energy is scattered or absorbed in the troposphere?
About 15%.
How does the Sun’s radiation affect the Earth and troposphere?
The Sun’s radiation passes through the troposphere to heat the Earth, and the Earth then heats the troposphere.
What factors influence the intensity of radiant energy from the Sun that hits the Earth?
The angle of arrival, which depends on the Earth’s latitude, the season, the tilt of the Earth’s axis in relation to the Sun, and the time of day.
How does the intensity of radiation change when it hits different points on the Earth’s surface?
The same intensity of radiation covers more surface area at points A and C than at point B, reducing the intensity of radiation on the surface at A and C.
What additional factor reduces the intensity of radiation on the Earth’s surface?
The extra distance that radiation at A and C has to pass through the atmosphere slightly reduces the intensity on the surface.
What happens to radiation when it arrives at the Earth’s surface?
Some of it is absorbed, and some is reflected back out to the troposphere and to space.
What determines how much radiation is absorbed and how much is reflected?
It depends primarily on the type of surface.
Which surfaces absorb radiation energy readily?
Forests and ploughed land absorb radiation energy readily.
Which surfaces reflect radiation energy back?
Snow and desert sand reflect radiation energy back.
How do oceans absorb and reflect radiation?
Oceans absorb radiation that arrives at high angles of incidence (e.g., in the tropics) but reflect more when the angle of arrival is low.
What overall factors determine the percentage of incident radiation energy absorbed by the Earth?
The type of surface and the angle of arrival of the radiation.
What happens to the Earth’s temperature when it absorbs radiant energy from the Sun?
The Earth’s temperature rises.
What influences the rise in temperature for any given quantity of heat energy absorbed by the Earth’s surface?
The specific heat of the surface material.
Which surface material shows the lowest temperature rise?
Water, with a specific heat of 1.0.
Which surface materials show the greatest rise in temperature?
Materials like rock and concrete, found in cities.
Why do flagstones by a swimming pool burn your feet in the sunshine when the pool water is cold?
Because flagstones have a higher temperature rise due to their specific heat compared to water.
Why is the temperature rise in oceans limited?
The deep penetration of radiation and circulation of the water mix surface water with the stable mass of cold deep water.
What determines how much the Earth heats the troposphere?
The temperature of the Earth’s surface.
What fundamental factors determine the behavior of the weather system?
The temperature of the Earth’s surface and its influence on the troposphere.
How do oceans and land masses differ in terms of temperature stability?
Oceans maintain stable temperatures, while land masses rapidly heat up and cool down.
How is the atmosphere warmed?
By absorption of infrared thermal radiation from the underlying surface, absorption of shorter wavelength radiant energy from the Sun, and convective heat from the surface.
What happens to the energy radiated by gases in the atmosphere?
Some of it is directed back down to the surface and lower atmosphere, thereby warming these areas.
What is the greenhouse effect?
The process by which radiation from gases in the atmosphere warms the Earth’s surface to a temperature above what it would be without its atmosphere.
What are the four major gases contributing to the greenhouse effect and their percentage contributions?
Water vapour (36-70%), CO₂ (9-26%), methane (4-9%), ozone (3-7%).
Why can’t specific percentages be assigned to each greenhouse gas?
Because the absorption and emission bands of the gases overlap.
What is the major non-gas contributor to Earth’s greenhouse effect?
Clouds, as they absorb and emit infrared radiation and affect the radiative properties of the atmosphere.
Why does the Earth radiate energy at a much longer wavelength than the Sun?
Because the Earth has a much lower temperature than the Sun.
At what wavelength does the Earth radiate energy?
In the 10 micron band.
What absorbs radiation at the Earth’s wavelength?
Water vapour, carbon dioxide, and clouds.
Where in the troposphere is the heating effect of radiation most significant?
In the lower troposphere, where clouds and water vapour are at a maximum.
What happens to long wave radiation in overcast conditions?
It is re-radiated and reflected back to the Earth at a maximum rate.
How does the Sun heat the Earth?
By radiation.
How does the Earth heat the atmosphere?
By radiation, conduction, and convection.
How does heat exchange take place at the surface in contact with the troposphere?
By conduction, which can go either way depending on whether the surface is warmer or colder than the air.
How does conduction work?
Conduction works by contact; heat is conducted along a medium.
Is air a good conductor of heat?
No, air is not a good conductor of heat.
What happens to the heat distribution in the absence of a method for distributing it aloft?
The effect is confined to a very shallow layer at low level, especially on very still days or nights.
What happens if the airflow in the lower troposphere is turbulent?
It can transfer heat from the surface through the lower troposphere, a method referred to as turbulence heating.
What is the method for the transfer of heat aloft?
Convection, which is the vertical movement of air.
What are the types of convection?
Forced convection (air forced up over mountains or through mechanical turbulence) and thermal convection (where heated air rises due to lower density).
What does the rising air carry aloft?
Energy in two forms: ordinary heat energy and latent energy.
What happens to water vapour as the air rises and cools?
It may condense to form clouds, releasing its latent heat of condensation.
What is the purpose of the diagrams related to short and long-wave radiation?
To give a general feel for the system; they are not meant to be memorized.
What happens to short wave radiation from the Sun when it enters the atmosphere?
Some of it is reflected, and some is absorbed.
What does long wave radiation do in the troposphere?
It transfers a large amount of heat out to the troposphere, but a large amount is also re-radiated back to the surface.
What percentage of energy transferred from the surface to the troposphere is accounted for by net long wave radiation?
42%.
What percentage of energy transfer is accounted for by warm air convection?
12%.
What percentage of energy transfer is accounted for by latent heat convection?
46%.
Where does long wave radiation out to space occur from?
The upper troposphere.
Why are temperatures aloft low?
Because long wave radiation out to space occurs from the upper troposphere.
What is advection?
Advection is the horizontal movement of air, wind. It transfers energy horizontally and is not responsible for heating the troposphere, only for redistributing the energy within it.
What effect does advection have on the stability of the air?
Advection has a substantial effect on the stability of the air.
What are the two types of thermal advection?
Warm Air Advection (WAA) and Cold Air Advection (CAA).
What is Warm Air Advection (WAA)?
WAA is the movement of warmer air toward a fixed point on a horizontal plane, common behind warm fronts and ahead of cold fronts.
Why does WAA contribute to rising air?
Because warm air is less dense than cold air. As warmer air expands to a larger volume than cold air, this expansion in the low levels pushes the air above the low levels up.
How does the rate of upward motion in WAA compare to the rate of air rising in an updraft of a thunderstorm?
The rate of upward motion in WAA is much slower than the rate of air rising in an updraft of a thunderstorm.
What is Cold Air Advection (CAA)?
CAA is the movement of colder air toward a fixed point on a horizontal plane, common behind cold fronts.
Why does CAA contribute to sinking air?
Because cold air is denser than warm air. Cooler air contracts more than warmer air, forcing a sinking motion aloft to compensate for the reduction of volume in the lower levels.
What happens to the skies behind cold fronts due to CAA?
In the ideal case, the skies will clear behind cold fronts.
Why is there no direct relationship between thermal advection and resultant vertical motion in the atmosphere?
Because other lifting and sinking mechanisms can complicate the picture.
What factors can contaminate thermal advection?
Evaporative cooling, condensation warming, solar heating, complex topography, and radiational cooling.
How do forecasters determine the actual magnitude of resultant thermal advection?
By examining the contaminating factors.
How does precipitation affect WAA?
The warming and uplift from WAA will be reduced when precipitation falls into the low levels and cools the air through evaporation.
What causes surface temperature to vary widely?
The place, time of day, and season.
When do the diagrams show the world mean surface temperatures?
In January and July.
How are the land masses in the Northern Hemisphere in January?
Extremely cold.
How are the land masses in the Southern Hemisphere in January?
Hot.
What effects are noted in January related to sea currents?
The effects of cold sea currents off the west coasts of Africa and South America, and warm sea currents in the North Atlantic and North Pacific oceans.
How does the surface temperature change in July?
North America and Siberia have warmed up (Siberia reaching 20°C), while the land masses in the Southern Hemisphere have cooled down.
Which regions are very hot in July?
Mexico, the Sahara, and the Tibetan plateau.
How do the effects of cold currents off Peru and South Africa appear in July?
They can still be seen.
How is the sea temperature in the North Atlantic in July?
About the same as the land temperature, with less obvious contrast.
How is the sea temperature in the North Pacific in July?
Colder than the land temperature, remaining relatively constant.
How is the sea temperature off California throughout the year?
More or less the same all year round.
What plays a major part in the distribution of heat at low levels?
Sea currents and global winds.
How do warm winds over the Gulf Stream move heat?
Horizontally by a process of advection, carrying heat in the same way that convection does, as warm air and latent heat.
What happens when warm moist air drifts over cold surfaces and forms advection fog?
It carries out the same process as convection and cloud formation but horizontally instead of vertically
What is the diurnal variation of surface temperature?
The daily variation in surface temperature.
Why is the diurnal variation of surface temperature important?
It affects the formation of radiation fog, land and sea breezes, and the development of convective cloud during the day.
When is the balance between incoming and outgoing radiation shown?
For a typical day over land in May or September in the middle latitudes, with sunrise at 0600 local mean time (LMT) and sunset at 1800LMT.
What happens to surface temperature during radiation deficit?
It falls.
What happens to surface temperature when net radiation goes into surplus?
It rises.
What additional factors affect surface temperature besides radiation?
Thermal convection and turbulent mixing of the air by winds.
What occurs on a calm night regarding surface cooling?
Maximum surface cooling can take place.
How does a windy night affect surface temperatures?
Warmer air is mixed downward to the surface, preventing temperatures from dropping as quickly as on a clear night.
What effect do sea breezes near the coast have?
They bring the sea’s stabilizing effect into play.
How do clouds affect incoming and outgoing radiation?
Clouds give a blanket effect, limiting incoming radiation and reflecting back outgoing radiation, reducing temperature variation.
Which type of clouds are more effective in reducing temperature variation?
Thick clouds are more effective than thin clouds.
Which clouds are most efficient in reducing daytime maximum temperature and diurnal temperature range (DTR)?
Clouds with low bases.
What is the overall effect of cloud cover on surface temperature?
It reduces the diurnal variation of surface temperature.
When do minimum surface temperatures occur?
About 30 minutes after sunrise.
When do maximum surface temperatures occur?
Two to three hours after mid-day
