Lecture 5– Climate

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

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)

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

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 = m) These same wavelengths are also called photosynthetically active radiation (PAR) –Used by plants to power photosynthesis

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 30 o N / S.

Northern hemisphere annual variations in solar radiation and temperature

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

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

Solar-Driven Air Circulation h

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

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)

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

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

Rain shadow effect

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

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

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