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Lecture 4

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Political Science

IDSB02- Development and the Environment st Lecture 4: January 31 2012 LAST WEEK OVERVIEW Breaking the Sod  Soil erosion (3 ways- plough, intensification of agriculture etc.  Soil management  Soil knowledge  How soils are formed (weathering- physical, chemical etc.)  Five soil forming factors? Climate etc.  Classification of soils by texture (sand, silt, clay – differences between them; clay have a net negative charge effecting CEC and clay has internal layers giving it a massive surface area)  Soil structure and stability: discourage erosion biological material etc.  Tropical soils – ferralsols; red soils phosphorus less available (phosphorus fixation etc.)  Temperate soils vs. tropical soils (know the characteristics) NEW LECTURE  AT the equator has high inputs of energy so air rises giving a zone of low pressure; and through high pressure zones that move into the low pressure zones  3 cells: Hadley, ferrel, and polar  General circulation  Knowledge of forces (Pressure gradient force + Coriolis effect and friction) allows us to construct a basic model of how air moves  Air moves north in the northern hemisphere and south in southern hemisphere- when it hits the colder zones it descends and contracts (dries) to the surface – creates a high pressure zone; the air then flows from high pressure to low pressure zones  Sub-tropical high pressures zone is where the air is drying; where we find deserts  Where the air is rising is where there are tropical rainforests and tropical rain  Explains why there is cloud cover circling the equator  STHPZ- sub tropical high pressure zone  Air moving north form the STHPZ increases in momentum and creates a strong belt of winds moving from W ->E creating westerlies winds  At poles eventually the air sinks with colder temperatures = polar cells   ITCZ- inter tropical convergences zone there is an equatorial low in this area;  High pressure zones are more stable (less rain etc.)  Low pressure zones unstable  Know where these things are on a map!  Hurricanes/monsoons  Hurricanes are tropical cyclones: major source of water inputs  Monsoons are seasonal changes in atmospheric circulation and precipitation (wet seasons/monsoon rain):  Regional climates (broadly describes because of the weather patterns)  Wet tropics – rainforests; little variation in temperature or precipitation (very stable in that sense)- very hot and very rainy; deciduous vegetation; shifting agriculture possible but needs long fallow periods because the soils are highly weathered- low fertility and CEC; rice paddy agriculture very good  Savannah (semi-arid climate)  Regions right at the edge of the ITCZ  Just before the high pressure zones  Long dry seasons and fast quick wet seasons  Wa
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