Lecture 2A - Global Winds and Pressure Systems

Lecture 2A - Global Winds and Pressure Systems - GEOG 100...

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GEOG 100 – SUMMER 2007 2A – SECOND WEEK, SECOND LECTURE LECTURE 2A EARTH PRESSURE SYSTEMS and GLOBAL WINDS (IMPORTANT NOTE – SEE 2 DIAGRAMS FOR THIS LECTURE IN THE CONTENT SECTION. LOOK UNDER “GRAPHS, DIAGRAMS AND MAPS”) I. PRESSURE SYSTEMS – HIGHS AND LOWS – THESE ARE MAJOR DETERMINANTS OF CLIMATE, WHICH IS THE MAJOR DETERMINAT OF CLIMATE, WHICH DETERMINES THE WORLD BIOMES (A)High Pressure – High pressure is characterized by air descending, which is getting drier as it descend. It therefore is a zone of little precipitation. High pressure zones can be in hot regions (subtropical highs) or cold regions (polar highs or cold core highs). Surface air flow moves out of, or diverges, from a high pressure system. This is because air always flows from High to Low Pressure. So High Pressure systems, or Highs as they are sometimes called, are characterized by diverging air at the surface. However, there is convergence aloft to feed the air that is descending into the surface low. (B) Low Pressure – Low pressure is air characterized by ascending (rising) air, which is getting more humid as it rises. This is because as air rises, it cools, and cool air has less ability to hold moisture than warm air. So, as air rises it tends to reach the dew point, or temperature at which it becomes saturated and cannot hold any more moisture. With the right conditions and the presence of condensation nuclei for raindrops, precipitation can then occur. Low pressure zones of rising air, then, are characterized by a zone of clouds and precipitation. These low pressure systems, or Lows as the are sometimes called, can be located in Hot regions (equatorial low) or cold (sub-polar low) regions. Because air moves from High to Low pressure, the surface air flow will always be into a low pressure system. Thus air converges, or movies into, into a Low pressure systems. However, after the converging air rises to higher elevations, into will eventually move away from the low. Hence, low pressure systems have convergence at the surface, but have divergence aloft as the rising air moves away from the system. The opposite is true of a High Pressure system, which is characterized by divergence of air at the surface and convergence aloft. IMPORTANT NOTE. LOOK AT 2 IMPORTANT DIAGRAMS ON D2L THAT ARE THE SUBJECT OF THIS LECTURE. UNDER “CONTENT” UNDERNEATH ALL THE LECTURES LOOK FOR “GRAPHS, DIAGRAMS, AND MAPS” – UNDER THIS LOOK FOR 1. “HIGH AND LOW PRESSURE CIRCULATION”
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2. “GLOBAL WINDS” 3. “GLOBAL PRESSURE AND PREVAILING WINDS” – which is shown below II. THE EARTH’S PRESSURE SYSTEMS – There are four major pressures systems in the world. The 0, 30, 60, 90 rules lets you know where these systems are regarding latitude. Lows and Highs alternate starting at 0 degrees and going to 90 degrees. (A)
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Lecture 2A - Global Winds and Pressure Systems - GEOG 100...

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