Biol 301 1nd EditionExam # 4 Study Guide Lectures: 17 - 20Lecture 17- Greenhouse Effect – the process of solar radiation striking Earth, being converted to infraredradiation, and being absorbed and re-emitted by atmospheric gases.- Greenhouse Gases – Greenhouse gases are those that absorb and re-emit infrared radiation and contribute to the greenhouse effect. These gases comprise only a small fraction of the atmosphere. - Natural Effects – H2O and CO2 are the two most prevalent greenhouse gases, derived from the transpiration of plants, decomposition, respiration, and volcanic eruptions. Other gases, such as nitrous oxide (N2O), methane (CH4), and ozone (O3) are naturally derived and contribute to the greenhouse effect. The naturally occurring greenhouse effect is beneficial to organisms.- Human Effects – The concentration of CO2 has increased over the past two centuries due to combustion of fossil fuels. Agriculture, landfills, and fossil fuel combustion have also increased concentrations of CH4 and N2O. Humans have produced unnatural gases (e.g., chlorofluorocarbons) that exist at low concentrations but absorb relatively more infrared radiation and persist in the atmosphere for hundreds of years. Increases in greenhouse gases could cause an increase in the average temperature of Earth. Some regions may become cooler; some regions may become up to 4°C warmer.- Unequal heating - Differences in temperature around the globe are the result of how much solar radiation strikes Earth at a given location.o Sunlight intensity – The distance travelled through the atmosphere is shorter at the equator than at the poles, so less solar energy is removed by the atmosphere and more strikes the ground. The Sun’s rays strike the poles at an angle, spreading radiation over a much larger area than at the equator. Hence, Earth’s surface at the equator receives more direct and more intense sunlight.o Albedo – the fraction of solar energy reflected by an object. Some surfaces have higher albedo than others; light-colored surfaces reflect more light than dark-coloredsurfaces. The low albedo of forests causes the tropics at the equator and increases average temperatures. The high albedo of snow at the poles decreases average temperatures.o Seasonal Heating – The axis of Earth is tilted 23.5° with respect to the path it follows around the Sun. During the March and September equinoxes, the Sun is directly overthe equator. During the June solstice, the Sun is directly over 23.5°N (i.e., Tropic of Cancer); during the December solstice it is over 23.5°S (i.e., Tropic of Capricorn). Solar equator: the latitude receiving the most direct rays of the Sun. Temporal variation of the solar equator from 23.5°N and 23.5°S changes solar intensity throughout the globe, and creates seasons.- Air Currents – o Convection – the circulation of air between the surface of Earth and the atmosphere;caused by properties of air. As air temperature increases, it can hold more water vapor.o Saturation – the limit of the amount of water vapor that air can contain. If vapor content exceeds saturation, water condenses to liquid or ice, and produces clouds or precipitation. Condensation occurs when the temperature of saturated air decreases.o Adiabatic cooling – the cooling effect of reduced pressure on air as it rises higher in the atmosphere and expands. o Adiabatic heating - he heating effect of increased pressure on air as it sinks toward the surface of Earth and decreases in volume.o Weather cells – Hadley cells: the two circulation cells of air between the equator and30°N and 30°S latitudes. Polar cells: atmospheric convection currents between 60° and 90° latitudes that are similar to Hadley cells. At 60°N and 60°S latitudes, air rises and drops moisture; air moves toward the poles and sinks back to Earth at 90°N and 90°S. Air between Hadley cells and polar cells (i.e., from ~30° to 60°) lack distinct convection currents. This region can have dramatic fluctuations in wind direction,temperature, and precipitation. Winds generally move from west to east, leading to warmer conditions on the west coast.o Coriolis effect – Wind direction is also affected by the speed of Earth’s rotation, which changes with latitude. Since the circumference of the planet at the equator is larger than at the poles, the speed of rotation is faster at the equator. The different rotation speeds deflect the direction of surface air circulation in the Hadley and polarcells. Coriolis effect: the deflection of an object’s path due to the rotation of Earth. Air moving along the surface of Earth within the northern Hadley cell is deflected so that it moves from the northeast to the southwest; these winds are known as northeast trade winds. Similarly, air moving along the surface within the southern Hadley cell is deflected to the northwest; these winds are known as southeast trade winds. Winds in the mid-latitudes tend to move from west to east and are known as westerlies.- Ocean Currents – Ocean currents distribute unequal heating of Earth’s water and influence the location of different climates. In general, warm tropical water circulates up along western reaches of ocean basins toward the poles, and cold polar water circulates down along eastern reaches. Many factors create these currents, including unequal heating, Coriolis effects, wind directions, ocean basin topography, and salinity.o Gyre – a large-scale water circulation pattern between continents. Ocean water near the equator expands as it warms, causing water to be ~8 cm higher in elevation than water at mid-latitudes. Gravity pulls the higher water away from the equator. Corioliseffects and prevailing trade winds push surface water east to west in the Northern Hemisphere and west to east in the south. Continents change the direction of current, and westerlies at mid-latitudes push water in the opposite direction. Currents flow clockwise in the Northern Hemisphere, and counterclockwise in the Southern Hemisphere. Gyres redistribute heat energy and influence global climates.o Upwellings – an upward movement of ocean water. Upwelling occurs in locations along continents where surface currents move away from the coastline. As water moves away, cold water from ocean depths is drawn upward. Since deep water tendsto be high in nutrients, upwelling zones are often areas of high biological productivityand fish biomass.o Thermohaline circulation -