Chapter 6

Chapter 6 - Intro to Oceanography: Chapter 6 I. What Causes...

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Intro to Oceanography : Chapter 6 I. What Causes Earth’s Seasons? a. Ecliptic – the plane traced by Earth’s orbit (elliptical) b. Earth’s axis of rotation is not perpendicular (upright); tilted at 23.5 degrees c. Earth’s axis points to the Polaris, the North Star d. Four seasons i. Spring (vernal equinox) 1. Occurs on or about March 21 2. The sun is directly overhead along the equator 3. Equal lengths of night and day (equinox) ii. Summer (summer solstice) 1. Occurs on or about June 21 2. The sun reaches its most northerly point in the sky, directly overhead along the Tropic of Cancer, at 23.5 degrees north latitude 3. Reaches northernmost of southernmost and pauses (solstice) iii. Autumn (autumnal equinox) 1. Occurs on or about September 23 2. The sun is directly overhead along the equator again. iv. Winter (winter solstice) 1. Occurs on or about December 22 2. The sun is directly overhead along the Tropic of Capricorn, at 23.5 degrees south latitude 3. In the Southern Hemisphere, the seasons are reversed e. Declination – angular distance from the equatorial plane f. Areas in the Arctic Circle and the Antarctic Circle (66.5 degrees north and south latitude) have areas where they receive either light or dark up to six months and reverse II. How Does Uneven Solar Heating Affect Earth? a. Distribution of Solar Energy i. Sunlight strikes low latitudes at a high angle, so the radiation is concentrated in a relatively small area ii. Sunlight strike high latitudes at a low angle, so the same amount of radiation is spread over a larger area iii. Earth’s atmosphere absorbs some radiation, so less radiation strikes Earth at high latitudes than at low latitudes, because sunlight passes through more of the atmosphere at high latitudes iv. Albedo – the percentage of incident radiation that is reflected back to space (avg ~ 30%) (More is reflected back at high latitudes because ice has high albedo than soil or vegetation) v. The ocean reflects more radiation at high latitudes than at low latitudes b. Oceanic Heat Flow i. Between 35 degrees north latitude and 40 degrees south latitude sunlight strikes at much higher angles and more energy is absorbed III. What Physical Properties Does the Atmosphere Possess?
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a. Composition i. Atmosphere consists mostly of N 2 and O 2 . ii. Other trace elements trap significant amounts of heat within the atmosphere b. Temperature i. Troposphere – surface to 12 km (where all weather is produced) ii. At high altitudes, air temp is well below freezing c. Density i. At higher temps, air molecules move more quickly, take up more space, and density is decreased ii. Warm air is less dense, so it rises iii. Cool air is more dense, so it sinks d. Water Vapor Content i. Warm air can hold more water vapor because the air molecule are moving more quickly and come into contact with more water vapor ii. The addition of water vapor decreases the density of air because water vapor has a lower density than air e. Pressure i. Atmospheric pressure is 1.0 atmosphere (14.7 lbs per sq in) at sea level
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Chapter 6 - Intro to Oceanography: Chapter 6 I. What Causes...

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