GED Science Practice Test: Weather and Climate

Meteorology is the study of the weather that happens in the troposphere layer of the atmosphere. Weather is the mix of events that happen each day in our atmosphere including temperature, rainfall and humidity. Weather is not the same everywhere. Perhaps it is hot, dry and sunny today where you live, but in other parts of the world it is cloudy, raining or even snowing. Everyday, weather events are recorded and predicted by meteorologists worldwide.

Climate are the consistent weather patterns in an area over a long period of time. So, the climate of Antarctica is quite different than the climate of a tropical island.   A tropical island is said to have a hot climate, because its temperatures are consistently hot, and have been for hundreds or thousands of years.

The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere “behaves” over relatively long periods of time.  Some people confuse weather and climate when discussing global warming.  For example, a person who experiences a record snowfall might wonder why scientists are worried about global warming.  After all, more snow is certainly not evidence of a warming trend.  The snowfall that the person experienced is an example of weather.  The long term changes in the weather (perhaps an increase in the average temperature by decade) are referred to as climate.

On Earth, common weather phenomena include wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as tornadoes, hurricanes, typhoons and ice storms. Almost all familiar weather phenomena occur in the troposphere.

The Earth’s Tilt and Latitudes: Weather occurs primarily due to air pressure, temperature, and moisture differences between one place to another. These differences can occur due to the sun angle at any particular spot, which varies by latitude from the tropics. In other words, the farther from the tropics one lies, the lower the sun angle is, which causes those locations to be cooler due to the indirect sunlight.

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Jet Streams: The strong temperature contrast between polar and tropical air gives rise to fast-flowing, narrow air currents called jet streams. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Weather systems in the tropics, such as monsoons or organized thunderstorm systems, are caused by different processes.

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The Earth’s Tilt and Seasons: Because the Earth’s axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, so at any given Northern Hemisphere latitude sunlight falls more directly on that spot than in December. This effect causes seasons.

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Global Wind Patterns: Global wind patterns also influence climate. Winds are named by the direction from which they blow. The globe is encircled by six major wind belts, three in each hemisphere. From pole to equator they are the polar easterlies, the westerlies and the trade winds. All six belts move north in the northern summer and south in the northern winter.

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The atmosphere is a chaotic system, so small changes to one part of the system can grow to have large effects on the system as a whole. This makes it difficult to accurately predict weather more than a few days in advance, though weather forecasters are continually working to extend this limit through the scientific study of weather, meteorology. It is theoretically impossible to make useful day-to-day predictions more than about two weeks ahead, imposing an upper limit to potential for improved prediction skill.

Ocean Currents:  The flow of water, or currents, are essential to understanding how heat energy moves between the Earth’s bodies of water, land masses, and atmosphere. The ocean covers 71 percent of the planet and holds 97 percent of its water, making the ocean a key factor in the storage and transfer of heat energy across the globe, as well as in stabilizing weather and climate patterns.

The interaction of ocean surface currents with winds in the atmosphere can influence weather events such as hurricanes, and also contribute to weather features, such as the fog and mild temperatures in San Francisco.  The following image shows some of the major ocean currents:

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Use the image below to answer question 1:

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