Lecture 5– Climate

1. Lecture 5– Climate

2. Meteorology: Study of climate and weather • Weather: daily variations in precipitation, winds, temperature, etc. Climate: overall combination of temperature, precipitation, winds etc. of an area/region • Subject to many factors: • microclimate Climate Impacts life forms

3. Heating of the Earth • Shortwave radiations most energetic • about 51% reaches earth surface • Albedo – surface reflectivity of earth • Clouds • Polar ice caps • Deserts • Greenhouse effect: trapped energy not re-radiated to space • Clouds • Atmospheric gasses (chapter 30)

4. Incoming radiation: short wave (high temperature) • Reflected radiations from earth: long wave (low temperature)

5. The sun emits electromagnetic radiation of a wide range of wavelengths • The wavelengths of 400 to 700 nanometers (nm) make up visible light • One nanometer is one-billionth of a meter (1 nm = 0.000000001 m) • These same wavelengths are also called photosynthetically active radiation (PAR) • Used by plants to power photosynthesis

6. Seasons due to tilt of earth • Uneven heating drives air circulation/ppt patterns • Warm, moist air rises. • Adiabatic cooling: moisture condenses and falls as rain. • Cooler, dry air falls back to surface. • Rainforests found near equator. • Major deserts found near 30o N / S.

7. Northern hemisphere annual variations in solar radiation and temperature

8. Adiabatic temperature changes: changes in air temperature which occur without a gain or loss of heat energy – due to expansion/contraction of air with altitude • Air cools as it rises: for dry air ~ 10C/1000 meters • Slower for moist air ~ 6C/1000 meters

9. Uneven atmospheric heating  global air circulation and precipitation patterns • Hadley cells • Ferrell cells • Polar cells • ITCZ – Inter-tropical convergence zone – area over equator where Hadley cells converge

10. Solar-Driven Air Circulation h

11. Coriolis effect – prevailing wind/water movements • caused by moving N or S on rotating Earth • earth is rotating from left to right (eastwards) • Motion faster at equator than towards poles (think parabola) • so as one moves toward equator, one enters a faster region from a slower one • objects in motion seem to be deflected to left as they are moving slower (to the right) than their surroundings • moving away from equator, one enters a slower region from a faster one • objects in motion seem to be deflected to right as they are moving faster (to the right) than their surroundings

12. Relative humidity - amount of water vapor in air relative to the amount it can actually hold at that temperature • Affects living things through evaporation and condensation RH = current water vapor pressure saturation water vapor pressure(X 100)

13. Ocean Currents: movement of large masses of water • Driven by: • Uneven heating • Steady winds, interrupted by land masses • Thermohaline differences • Gyres: large circular movements that circulate around an oceanic basin • counterclockwise in southern hemisphere • clockwise in northern hemisphere

15. Impact of Gyres • move warm waters northward or southward  warm the climate of the land • example is the Gulf Stream in the North Atlantic, which so warms western Europe that palm trees grow in southern Ireland • move cool water south • Example: California Current cools west coastal climate

16. Rain shadow effect

17. Water in Air • Evaporation: water converted from liquid to gas as it enters air • Energy requiring process (heat) • Condensation: reverse • Vapor pressure: pressure water exerts as an independent component of the atmosphere • ‘saturated’ atmosphere: • evaporation = condensation • Saturation vapor pressure (water vapor capacity of air) = maximum amount of water that can enter the atmosphere • Function of temperature

18. Fog: a visible aggregate of tiny water droplets suspended in the air near the ground • Important to many species: • California coastal redwood • Soft or maritime chaparral community • Human uses – fog nets

19. Saturation vapor pressure: function of temperature • As temp. drops amount of water that can be held in the atmosphere drops – precipitation forms