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Chap. 2 – Climate The Physical Environment Habitability – the ability of the physical environment to support life Organisms interact w/ physical environment over two very different timescales o Over many generations the physical environment is a guiding force for natural selection o Over shorter periods the physical environment influences an organism’s physiology + resource availability (Ex. 60 degrees in Jan. vs 60 degrees in July) Weather – combination of temperature, humidity, precipitation, wind, cloudiness, and other atmospheric conditions occurring at a specific place + time Climate – long term average pattern of weather o Local o Regional o Global o East + West gradient reflects decrease in annual precipitation o Equatorial to polar regions reflect a decrease in annual temperatures Earth Intercepts Solar Radiation Weather patterns influenced by solar radiation intercepted by Earth’s atmosphere + rotation solar radiation – electromagnetic energy or stream of photons produced by the sun all objects emit radiant energy
o energy emitted depends on temperature of object it is coming from o hotter object = more energetic o shortwave radiation = more energetic o longwave radiation = less energetic Earth receives solar radiation + emits its own longwave radiation o Energy emitted by Earth’s surface exceeds the solar radiation absorbed o Solar is only during the day Greenhouse Effect – Earth’s atmosphere captures most of the radiation emitted by Earth + radiated back to Earth o Longwave radiation is easier to reflect Photosynthetically Active Radiation (PAR) – visible light spectrum used by plants to power photosynthesis Intercepted Solar Radiation Varies Seasonally Amount of solar radiation intercepted at any point on Earth’s surface varies by latitude w/ a gradient of decreasing temperature from equator to the poles At higher latitudes, solar radiation hits Earth’s surface at a steeper angle o Sunlight is spread over a larger area Less intensity o Tropics are warmer because more direct light goes through the atmosphere Seasons are a result of: o Earth’s tilt of 23.5 degrees
o Less warming radiation from Earth (longwave radiation is dissipated as it moves from the surface to a higher altitude) Atmospheric regions (from closest to surface to furthest from surface) o Troposphere o Stratosphere (ozone layer is here) o Mesosphere o Thermosphere Adiabatic cooling – decrease in air temperature through expansion rather than heat loss o Air is allowed to expand so the volume increases causing a loss of internal energy, and thus temperature o Rate of adiabatic cooling depends on moisture of the air + slows w/ an increase in moisture Air Masses Circulate Globally Air heated in the equatorial region rises to the top of the troposphere As the air rises away from Earth, an area of low pressure establishes at the surface Coriolis Effect – deflection in the pattern of air flow due to differences in rotation speed o Different areas of the Earth experience different rotation speed o Creates a series of belts of prevailing winds + breaks up simple flow of surface air from equator to poles o Belts + cells of air are formed in the Northern Hemisphere + Southern hemisphere
Northern hemisphere – air deflects right Southern hemisphere – air deflects left Westerlies – currents that move towards the poles + diverted to the right o West -> East Trade Winds (Easterlies) – currents move toward the equator + directed right o East -> West Polar easterlies are formed as air moves away from poles + air deflected right Solar Energy, Wind, + Earth Rotation Create Ocean Current Currents – systematic pattern of water movement o Determined by global pattern of prevailing winds Two circular water motions (gyres) o Ocean moves clockwise in the Northern hemisphere o Ocean moves counter clockwise in the Southern hemisphere Temperature Influences Moisture Content of Air General rainfall patterns exist o Precipitation is highest in equatorial regions + declines as you move North + South o Declines are not continuous because of prevailing wind effects Intertropical Convergence Zone (ITCZ) – region that forms where the trade winds meet + is characterized by high amounts of precipitation
La Niña Event o Surface of Eastern Pacific cools more than usual causing droughts in South America + heavy rain in Eastern Australia o Strong Trade Winds Most Organisms Live in Microclimates Most organisms live in local conditions that do not match the general climate profile of the larger region surrounding them Microclimates – the conditions an organism lives in (Ex. Light, heat o Always at a veery specific place (Ex. Under a rock) Topography influences local climatic conditions Aspect – direction that a slope faces o Northern hemisphere: South – facing slopes are warm + dry + variable conditions North – facing slopes are cool, moist, + more uniform Ecological Issues: Urban Microclimates Urban areas create their own microclimates Urban heat islands – urban areas that are generally several degrees hotter than surrounding countryside Warmer because: o Less vegetation o Non porous landscape
o More buildings, streets, walkways absorb solar radiation + reradiate heat o Construction materials The Heat Island Effect o Can raise temperatures by 5-10 degrees C o Negative impact on air quality Humidity traps particulate matter Smog + pollution
