Biology 2014-2015

The Role of Climate
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Section 4-1

What Is Climate?

       In the atmosphere, temperature, precipitation, and other environmental factors combine to produce weather and climate.

       Weather is the day-to-day condition of Earth’s atmosphere at a particular time and place.

       Climate refers to the average, year-to-year conditions of temperature and precipitation in a particular region.

       Climate is caused by:

       the trapping of heat by the atmosphere

       the latitude

       the transport of heat by winds and ocean currents

       the amount of precipitation

       the shape and elevation of land masses

       The energy of incoming sunlight drives Earth’s weather and helps determine climate.

 

The Greenhouse Effect

       The atmosphere is a natural insulating blanket, which keeps the Earth’s temperatures within a suitable range to sustain life.

       Carbon dioxide, methane, water vapor, and a few other atmospheric gases trap heat energy and maintain Earth’s temperature range.

       The gases function like the glass windows of a green house trapping the heat energy of sunlight inside Earth’s atmosphere.

       The greenhouse effect is when a layer of greenhouse gases retains heat. 

       How does this work?

1.       Greenhouse gases allow solar energy to penetrate the atmosphere in the form of sunlight.

2.       The sunlight hits the Earth’s surface and converted to heat energy and then radiated back into the atmosphere.

3.       The same gases do not allow heat energy to pass out of the atmosphere as readily as light energy enters it.

4.       The gases trap heat inside Earth’s atmosphere.

       If these gases were not present, the Earth would be 30 Celsius degrees cooler.

 

The Effect of Latitude on Climate

       Due to the Earth being tilted, solar radiation strikes the Earth’s surface at an angle that varies throughout the year.

       At the equator, the sun is almost directly overhead.

       At the North and South poles, the sun is much lower in the sky for months at a time.

       As a result of differences in latitude and the angle of heating, the Earth has three main climate zones: polar, temperate, and tropical.

Polar Zones

v      The polar zones are cold areas where the sun’s rays strike Earth at a very low angle.

v      These zones are located in areas around the North and South poles between 66.5o and 90o North and South latitudes.

Temperate Zones

v      The temperate zones sit between the polar zones and the tropics.

v      The climates in these zones range from hot to cold, depending on the season.

Tropical Zones

v      The tropical zone, or tropics, is near the equator, between 23.5o North and 23.5o South latitudes.

v      The tropics receive direct or nearly direct sunlight year-round, making the climate almost always warm.

 

Heat Transport in the Biosphere

       The unequal heating of Earth’s surface drives winds and ocean currents, which transport heat throughout the biosphere.

       Winds form because warm air tends to rise and cool air tends to sink.

       Air that is heated near the equator rises and cool air near the poles sinks.

       The upward and downward movement of the air creates air currents, or winds that move heat throughout the atmosphere.

       Similar patterns of heating and cooling occur in the Earth’s oceans.

       Cold water near the poles sinks and flows parallel to the ocean bottom, rising again in warmer regions.

       Surface water is moved by winds.

       The water flow creates currents, which transport heat energy.

       Surface ocean currents warm or cool the air above them affecting the weather and climate of nearby landmasses.

       Landmasses can interfere with the movement of air masses.

       A mountain range causes a moist air mass to rise, and as this happens, the air mass cools and moisture condenses, forming clouds that brings precipitation.

       Once the air mass reaches the far side of the mountains, it has lost much of its moisture resulting in a rain shadow – an area with a dry climate – on the far side of the mountain.