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Biosphere Chapter 59 Effects of Sun, Wind, Water Biosphere includes all living communities on Earth Global patterns of life on Earth are influenced by – The amount of solar radiation that reaches different areas (temperature) – Patterns of global atmospheric circulation which influence oceanic circulation (temperature and precipitation) The atmosphere and climate Weather - A description of physical conditions of the atmosphere Climate - A description of the long-term weather pattern in a particular area – Weather and climate are primary determinants of biomes and ecosystem distribution Distribution of biomes Temperature and precipitation are controlled by: – Solar heat – Global atmospheric circulation – Prevailing winds – Topography – Latitude – Elevation – Ocean currents Areas differ in solar energy Differences due to angle of incidence Earth’s tilt causes seasonality Air circulation patterns Global circulation patterns – Hot air rises relative to cooler air – Heating at the equator causes air to rise from the surface to high in the atmosphere – Rising air is rich in water vapor Warm air holds more water than cold Intense solar radiation at the equator provides the heat needed for water to evaporate Global air circulation After the warm moist air moves from the surface at the equator – Warm air moves north and south – Cooler air flows toward the equator from both hemispheres – Air descends at 30˚ latitude-desert regions of the earth – At 60˚ latitude air begins to rise again Global atmospheric circulation Creates areas low rainfall about 20° to 40° north and south of the equator Prevailing winds Areas far from oceans - in a windward direction are usually relatively dry Regional climates Monsoon areas in southern Asia and India caused by winds blowing off the cool land to the warm sea in summer and reversing direction in winter, causing rain Topography Mountains act as cloud formers and rain catchers Rainshadow effect Rain shadows Air sweeps up the windward side of a mountain, pressure decreases, and the air cools Eventually saturation point is reached, and moisture in the air condenses Rain falls on the mountaintop Cool, dry air descends and warms, absorbing moisture from other sources – Rain shadow Mt Waialeale windward side receives 12 m/year, while the leeward side receives 46 cm Windward Rainshadow Latitude Elevation Air temperature falls about 6˚C for every 1000m increase in elevation Ocean currents Warm and cold ocean currents strongly influence climate conditions on land – As surface water moves, deep water wells up to replace it Ocean currents are driven by winds Ocean currents distribute heat Upwelling Upward movement of water along a coast; replaces surface waters that move away from shore El Niño (ENSO) El Niño Southern Oscillation Climactic event that involves changes in sea surface temperature and air circulation patterns in the equatorial Pacific Ocean El Niño southern oscillation (ENSO) Large pool of warm surface water in Pacific Ocean moves back and forth between Indonesia and South America – Most years, the pool is held in western Pacific by steady equatorial trade winds Every 3-7 years the Indonesian low collapses and the mass of warm surface water surges back east Between ENSOs Warm water and heavy rainfall move west across the Pacific Warm moist air rises in the western Pacific causing storms Upwelling of cool water along western coasts Between ENSO During an ENSO Trade winds weaken and warm water flows east across the Pacific Sea surface temperatures rise Upwelling along western coasts ceases Heavy rainfall occurs along coasts, droughts elsewhere During ENSO During an El Niño year, the northern jet stream pulls moist air from the Pacific over the U.S. – Intense storms and heavy rains El Niño from 1991-1995 caused floods of the century in Mississippi Valley Sea temperature Cholera Connection Cholera outbreaks are correlated with rises in sea temperature Dormant stage of causative organism lives in copepods Copepod population increases when phytoplankton increase in warming seas
