Ch 6 - Air and Sea Interaction (Slides 1 - 10)

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Ch 6 - Air and Sea Interaction (Slides 1 - 10)

  1. 1. Chapter VI: Air-Sea InteractionEssentials of Oceanography, Thurman and Trujillo
  2. 2. Earth’s seasons• Earth’s axis is tilted 23½º from vertical (tropic of Capricorn/Cancer)• Northern and Southern Hemispheres are alternately tilted toward and away from the Sun (6 months apart)• Earth is tilted the same direction during entire sun orbit (precession is the slow turning of the direction)• Causes longer days and more intense solar radiation during summer Earth Sun Animation Figure 6-1
  3. 3. Uneven solar heating on Earth• Solar energy in high latitudes: – Has a larger “footprint” – Is reflected to a greater extent (albedo) – Passes through more atmosphere – Is less than that received in low latitudes• Temperature is constant over longer periods of time. Heat must be transferred from low latitudes to high.• All weather is the result of this transfer of Figure 6-1 heat
  4. 4. Oceanic and Atmospheric heat flowA net heat gain isexperienced in low latitudesA net heat loss isexperienced in highlatitudesHeat gain and loss arebalanced by oceanic andatmospheric circulationNet heat is the differencebetween incomingshortwave radiation (sun)and outgoing longwave(black body) radiation. Figure 6-3
  5. 5. Table 6.2
  6. 6. Physical properties of the atmosphere: Temperature• Troposphere is: – Lowermost part of the atmosphere – Where most weather occurs – Contains all earth’s surface• Temperature of troposphere cools with increasing Figure 6-4 altitude• Troposphere is ripe for convection!• Stratosphere is: – contains ozone layer – Temperature of stratosphere warms with increasing altitude• Tropopause is the boundary between the two
  7. 7. Physical properties of the atmosphere: Density• Warm, low density air rises (why heaters are near the floor)• Warm air holds moisture, as it rises it cools, can’t hold the same moisture, rains• Cool, high density air sinks (why air conditioner outlets should be near the ceiling)• Cold air can’t hold the Figure 6-5 moisture. Descending air warms, can hold more moisture, doesn’t rain.• Creates circular- moving loop of air (convection cell)
  8. 8. Physical properties of the atmosphere: Pressure• A column of warm, less dense air causes low pressure at the surface, which will lead to rising air (High pressure above)• As air rises, air is replaced with air along the earths surface• A column of cool, dense air causes high pressure at the surface, which will lead to sinking air (low pressure above)• Air moves horizontally from H go L pressure Figure 6-6
  9. 9. Physical properties of the atmosphere: Water vapor • Cool air cannot hold much water vapor, so is typically dry (Cool air is a HIGH pressure) – Descending air is cool (does not hold vapor) • Warm air can hold more water vapor, so is typically moist (Warmer air is a LOW pressure) – Ascending air is warm (does hold vapor) • Water vapor decreases the density of air (this is sort of strange, but water vapor is light! H2O vs N2 vs O2) – So even if same temperature, wet air will rise
  10. 10. Physical properties of the atmosphere: Movement • Air INITIALLY flows Summer/day horizontally from high- pressure regions toward low-pressure regions – Moving air is called wind – Sea Breeze in San Diego • San Diego’s air conditioner – Sea Breeze is quickly reduced as you move inland (and with it the cooler temps) – So where is the High Winter/night Pressure ? Figure 6.13

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