Transferring energy in the atmosphere (Conduction, convection and latent heat)
Why evaporation and condensation are important phase changes of water.
600 cal per gram, they have larger latent heat and so can provide more energy (than freezing and melting)
Thermal conductivity
Ability of a substance to conduct heat by molecular motions.
Energy needed for evaporation
About 7 times the amount needed to melt ice.
Poor conductor of heat
Air (when it is not moving)
Latent heat of melting
Amount of energy absorbed by water to change 1 gram of ice into water. Equal to 80 cal for each gram of ice.
Latent heat of condensation
Amount of energy released when water vapour condenses into liquid water
Latent heat of vaporization (evaporation)
Amount of heat required to evaporate 1 gram of liquid water.
Convection in areas where the ground is warmer than the air above it
Convection is an important systems of moving heat vertically.
Adding or removing energy from a substance
Changes the temperature of that substance
Consequence of air being a poor heat conductor
Conduction isn't an efficient mechanism for transferring energy in the atmosphere over global scales. Conduction is only good for energy transfer over small scales.
Amount of energy transferred by conduction
Depends on the temperature difference of the two objects and their thermal conductivity.
Phase change - liquid water to ice
Energy is released.
Phase change - ice to liquid water
Energy must be added to ice to break the intermolecular attractions and create liquid water
Changing phase of water is an efficient method of
Energy transfer and provides energy for much of the weather.
Latent heat
Heat absorbed or released per unit mass when water changes phase.
Temperature advection
Horizontal transport of energy.
Factors that affect the rate of energy transfer by convection in the atmosphere
How hot the rising air parcel is and the vertical temperature pattern of the surrounding atmosphere.
Sublimation
Ice directly entering the gas phase without melting
Convection in the atmosphere
If the ground is hot, energy is transferred to the air molecules by conduction. Heated air parcel will rise and cooler air sinks to replace the rising hot air. Heat rises upwards away from the surface because of the movement of fluid (air) and not due to contact.
Change of phases doesn't result in what?
Increase in water temperature (adding heat will melt an ice cube to water, but doesn't always make it hotter)
Convection in polar regions
Inefficient mode of heat transfer as the surface is usually cooler than the air above it.
Why metal feels cooler than wood
Metal has a high thermal conductivity and so heat is transferred quickly from your finger to the metal.
Conduction is an important energy transfer system
Near the ground.
Conduction
Process of heat transfer from molecule to molecule, energy transfer by conduction requires contact.
680 cals
Required to change 1 gram of ice to water vapour (and vice versa). Evaporation/condensation (600) + freezing/melting (80)
Changing phases of a substance
Requires or releases energy
Convection in deserts
Strong during summer, where heat from the sun rapidly warms the sun.
Evaporation cold water
Takes slightly more energy than evaporation warmer water.
Latent heat of fusion
The amount of energy released into the environment when water freezes. Equal to 80 cal for each gram of ice.
The latent heat of sublimation equals
The latent heat of deposition
Convection
The transfer of energy by movements of masses in a liquid or a mass. In meteorology the energy transfer is vertical.
Advection important in
Troposphere - especially earth's surface
Warm air advection
Warm air replaces cool air
Good conductor of heat
Water
Evaporation (vapourization)
Water from the liquid phase to the gas phase. Molecules of a gas are free of each other and have no bonds. Sizeable amount of energy is needed to break the bonds of the liquid state.
Ice phase structure
Water molecules are bond together by molecular forces. The water molecules have low enough kinetic energies that intermolecular attractions bind them into a highly ordered and cyrstalline form.
Water exists in three phases in the atmosphere
Water vapour (gas), liquid water (liquid) and ice (solid).
Deposition
Water vapour changes directly to ice particles.
Condensation
Water vapour cools and energy is released to form liquid water.
