1. Lab 2 – September 11, 2013 More on Radiation, The Four Seasons, Solstice and Equinox, Sun Angle and the Surface, Seasonality

2. Radiation Review Everything emits radiation (T>0 Kelvin) Stefan-Boltzmann Law: E = σ T 4 Stefan-Boltzmann Constant σ = 0.0000000567 W/(m 2 K 4 ) Energy Emitted ∝ Temperature (to the fourth power) Where is the greatest radiation measurement? The least? Note: Temp of Clouds < Temp of Surface

3. Downwelling Radiation Downward emission of infrared energy (in our case, from clouds) Results in higher surface temperatures e.g. Cloudy nights are typically warmer than clear nights Intensity of downwelling radiationIncreased surface temperatures

4. Incoming Solar Radiation and the Atmosphere Some solar radiation traveling through the atmosphere is back-scattered Solar radiation striking the earth at an angle travels through more atmosphere Clouds in the atmosphere back-scatter a lot of incoming sunlight Which person experiences more intense sunlight?

5. The Four Seasons Earth’s axis always points in the same direction in space Time-lapse photography showing concentric, circular star trails What astronomical feature is in the center?

6. The Four Seasons Variations in seasonal temperatures is a result of the Earth’s tilt Sun Directly over- head at 23.5° S Sun Directly over- head at 0° Sun Directly over- head at 23.5° N

7. Solstice and Equinox (Northern Hemisphere) DateLatitude of Direct Sunlight Summer SolsticeJune 2123.5° N (Tropic of Cancer) Winter SolsticeDecember 21 or 2223.5° S (Tropic of Capricorn) Autumnal EquinoxSeptember 220° (Equator) Vernal (Spring) EquinoxMarch 200° (Equator) Note: Solstices are reversed for Southern Hemisphere

8. Sun Angle and the Surface The greater the sun angle, the more concentrated the radiation is when it strikes the surface

9. Seasonality Annual range of temperature at a location i.e. swings in temperature between summer and winter Major controllers in seasonality: ◦ Latitude ◦ Proximity to large bodies of water

10. Seasonality (Latitude) Higher latitudes receive widely varying solar radiation throughout the year Think about hours of daylight in each season ◦ North Pole? ◦ Equator?

11. Seasonality (Bodies of Water) Heat Capacity – a measure of the ratio of the amount of energy absorbed (or released) by a substance to the corresponding temperature increase (or decrease) If it requires 40 units of energy to increase the temperature of one gram of dirt by one Kelvin and requires 120 units of energy to increase the temperature of one gram of water one Kelvin, which substance has a higher heat capacity? H.C. Water > H.C. Land

12. Seasonality (Bodies of Water)

14. Lab 2 Problems 2.7a,b 2.10a,b 2.11a,b 2.13a,c,d 3.1 3.4 3.6 3.9a,b,c DUE FRIDAY BEFORE CLASS