2. Energy Input: Solar Radiation decreases poleward reduced in areas of frequent cloud total energy input to atmosphere highest at equator, but highest insolation at surface in subtropical deserts Global Range in Average Annual Solar Radiation Intensity <80 W/m 2 in frequently cloudy portions of Arctic/Antarctic  150 W/m 2 in Lethbridge (greatest # of hours of sunshine in Canada) >280 W/m 2 in subtropical deserts

3. Short-wave Energy Loss: Albedo Proportion of insolation that is reflected (31% global avg.) Energy may reflect back to space without being absorbed Darker colours have lower albedo Water: low albedo for high solar alitude (calm seas) high albedo for low solar altitude (calm seas) rough seas moderate this pattern Cloud-albedo forcing reduces available solar energy Partially compensated by absorption of longwave energy emitted by the Earth (cloud-greenhouse forcing)

4. Albedo of Water

5. Scattering Gas molecules, dust particles, pollutants, ice and cloud droplets scatter incoming solar radiation. This results in diffuse radiation Absorption 69% of top-of-atmosphere solar radiation is absorbed Earth’s surfaces (45%) Atmosphere (24%) Heats surface or converted to chemical energy in photosynthesis

6. Conduction, Convection and Advection Conduction heat is diffused to cooler material as radiation absorbed land heats more quickly than water Why ? Thermal mixing and higher heat capacity of water Solids (land) are better conductors than gases (atmosphere). Convection physical mixing with a strong vertical motion in gaseous or liquid media As land heats up, the air immediately above warms too Warm air rises (less dense) while cooler air falls (more dense) Advection Lateral heat transfer

7. Energy Output: Earth Re-radiation (longwave) The Earth and its atmosphere emit longwave radiation Greenhouse Effect: Some L  is absorbed by CO 2, H 2 O, CH 4, NO x and CFC’s in the lower atmosphere Re-radiated in all directions (some toward Earth) Human-Induced Climate Change: Greenhouse gas emissions (eg. fossil fuel burning) Increased absorption of L  Effect of Clouds: High clouds cause cloud-greenhouse forcing Low clouds cause cloud-albedo forcing

8. Tropics Energy surpluses due to high solar altitude (incoming energy exceeds outgoing loss) Mid-latitudes Surpluses and deficits occur seasonally Deficits dominate (annual balance at  36° latitude) Polar regions Deficit (outgoing loss exceeds incoming energy gain) Result: Net poleward transport of energy surplus through atmospheric and oceanic currents Latitudinal Energy Balance Distribution (Fig 3-10)

9. Net Radiation Q * = K  - K  + L  - L  (Fig. 3-9) K  is solar radiation incident upon the surface K  is solar radiation reflected from the surface L  is infrared radiation reradiated to the surface L  is infrared radiation emitted from the surface Net radiation, Q* is expended from a non-vegetated surface through one of three pathways: 1.Latent heat of evaporation (stored as water vapour) 2.Sensible heat 3.Ground heating and cooling (zero annually)

10. A lake Notice the low K  values

11. What do you think the surface type is for this plot ? Why ?

12. Energy at Earth's Surface Daily radiation pattern is symmetrical Temperature lags behind insolation curve When would you expect the coolest/warmest part of the day? So far today… (Sept 10, 2003)

14. Radiation vs. Energy Balance Overall, the surface receives more K  and L  than it expends as K  and L  Why does the surface not just get hotter and hotter ? Energy is expended Sensible heat (convection and conduction) Latent heat of evaporation Ground heating at depth

15. Source: NOAA ABSORPTION K  TO SPACE=31 L  <K  !! Heat transfer 7+24=31 ! Compensates for radiation imbalance at surface L 46+19+4=69 L  TO SPACE=69 100 46-15=31 100-31-69=0

16. Temperature Measured in degrees Celsius or Kelvin Types of Thermometers Thermisters Thermocouples Alcohol Thermometers Mercury Thermometers Global Climate Observing System 15,400 known weather stations worldwide Daily mean temperature (average of min and max) Monthly mean temperature (average of daily means) Gill Radiation Shield Basis: temperature alters electrical resistance

17. Temperature Controls Latitude Variation in insolation Altitude temperature decreases with altitude ‘Parcel’ of air expands as pressure reduced Mountainous areas are colder than locations near sea level Surfaces gain and lose heat rapidly to atmosphere at high elevation (air is has less mass per unit area) Permanent equatorial icefields and glaciers at high altitude Snowline closer to the ground with increasing latitude (and/or precipitation)

18. Cloud Cover Reflect and absorb solar radiation (surface cooling) Absorb, and (re-)radiate longwave radiation (surface warming) Overall effect is a slight cooling (mainly low cloud) Land-Water Heating Differences 1.Ocean: energy lost to evaporation Heat energy absorbed (latent heat of phase change) Land: (more heating expended as sensible heat) 2.Water is transparent; ground is opaque Ground absorbs insolation at Earth-Atmosphere interface

19. 3.Solar insolation distributed to much greater depth in water (photic layer) Water has higher specific heat (same volume can hold more heat) 4.Water movement - mixing spreads heat over a greater volume Surface waters and deep waters mix