Ch 9 Flashcards
Weather
short-term processes
Climate
long-term processes
External sources of energy
Solar radiation
- ~4000x interior energy
- Some from Earth, moon, and sun tides
Sun’s electromagnetic radiation:
Radiowaves through visible, X-rays to gamma rays
- Visible light = 43% of light at the surface
Solar radiation received by Earth
Reflected/absorbed varies with latitude (30/70 avg ratio)
Equatorial belt:
- 38N, 38 S
- 2.4x polar region absorption
- net heating
Polar regions:
- net cooling
Heat and energy transfer from
equator to poles
Circulation patterns determine weather and climate:
Earth’s orbit:
- seasons - variable heating with latitude
Earth’s rotation and gravity:
- Oceanic and atmospheric circulation
The greenhouse effect raises Earth’s surface temp
Solar radiation
- short wavelength
- raises Earth’s surface temp
Excess heat re-radiated
- long wavelength (tends to get trapped like short wavelengths)
- absorbed by GHGs
- raises Earth’s surface temp
Albedo
- direct reflection of solar radiation
- 30% for whole earth
- ice cover increases albedo (keeps poles cold)
- liquid water decreases albedo (accelerates melting)
ice albedo: 70-90%
The hydrologic cycle
1) H2O evaporates from oceans and plant transpiration (rises as vapour in atmosphere)
2) vapour condenses (falls as precipitation)
3) gravity returns H2O to oceans (continuously operating, distillation and filter system, ~1/4 solar energy drives water evaporation)
Extraordinary properties of H2O
Highest: heat capacity of all solids, heat conduction of all liquids, latent heat of vaporization, dielectric constant of all liquids, surface tension
2nd highest: latent heat of fusion
- Bipolar molecule
Water vapour and humidity
By vol, atmosphere is 0-4% H2O vapour
Humidity: amount of H2O vapour in air
Saturation humidity: max vapour content
Relative humidity: ratio of humidity and saturation humidity
- If temp of air is lowered without changing humidity, it will reach 100% relative humidity
- When 100% relative humidity, excess H2O vapour condense to liquid water -> temp = dew point
- Temp “felt” depends on relative humidity -> heat index
Latent heat
- H2O absorbs, stores, and releases energy when changing phases
- Stored or released energy = latent heat
- Water to ice: releases heat
- Ice to water: absorbs heat
- Evaporating water: heat absorbed
- Condensing water: heat released
Differential heating of land and water
Low heat capacity of rock = heats up and cools down quickly
Winter heating of land and water
- Land cools quickly, cool air sinks toward ground -> high pressure region
- Oceans retain warmth, warm moist air rises, cools, condenses, rains over oceans
- Land retains less heat but can return it faster
- Ocean retains more heat but takes longer to return
Summer heating of land and water
- Land heats up quickly, hot, dry air rises -> low pressure
- Ocean warms slowly - cool and moist air over ocean
- Warm land draws cool, moist air from oceans -> warms, rises, cools, condenses, rains over land
- Land surface heats up faster compared to ocean, so circulation reverses -> precip on land