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The two most important properties that should be relatively homogeneous at the same altitude in an are mass are... |
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moisture content and temperature |
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An air mass from the Gulf of Mexico is called: |
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mT |
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An air mass from the Gulf of Mexico that moves northward over the U.S in winter would be labeled... |
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mTw |
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The air mass type most likely to form thunderstorms is... |
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mT |
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In North America the ______ air mass forms only in the summer. |
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cT |
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The pronounced cooling that occurs on continents at high latitudes during winter leads to the formation of ____ air masses. |
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cP |
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An ideal source region of air masses should be... |
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physically uniform |
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An mP air mass is... |
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humid and cold |
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The cP air mass in North America originates in... |
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interior Alaska and Canada |
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Characteristics of an air mass source region include... |
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uniformity of temperature and moisture |
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The air masses that have the greatest influence on weather conditions in the Midwestern United States are... |
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cP and mT |
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An air mass source region... |
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is characterized by a general stagnation of atmospheric circulation |
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Why are cT air masses of minor importance for the U.S? |
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no large source region is near the U.S |
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The typical amount of time it takes for an air mass to pass over a given area is on the order of a few... |
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days |
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An air mass is often modified as it moves over the Earth's surface. This modification is largely due to |
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contact with the ground below |
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Air mass source regions are least likely to come from... |
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middle-latitude regions |
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The coldest and driest winter air mass in North America is the... |
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cA |
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Which of the following is not an air mass that influences North America? |
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mA |
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Air mass source regions tend to be dominated by... |
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slow moving anticyclones |
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The ____ air mass often originates as a different air mass in Siberia and is subsequently altered. |
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mP |
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Why are maritime air masses from the north Atlantic of only limited concern for weather in the U.S? |
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prevailing winds move them away from the U.S |
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The _____ air mass provides much of the moisture for precipitation in the central and eastern United States. |
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mT |
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Which of the following occurs only in summer in North America? |
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cT |
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Most of the precipitation for the region east of the Rocky Mountains comes from... |
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mT air masses |
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A cT air mass is... |
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warm and dry |
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Which of these is not a process by which air masses are modified? |
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calm winds |
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"Lake-effect" snow is associated with the ____ air mass. |
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cP |
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The ____ air mass may produce an occasional "northeaster" in the winter. |
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mP |
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An air mass is a body of air with... |
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similar values of temperature and moisture in the horizontal |
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The stability of an air mass can be affected by... |
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a, b, and c |
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When an air mass is warmer than the surface over which it is moving... |
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the air becomes more stable |
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When an area is experiencing several consecutive days of rather constant weather, it is experiencing... |
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air mass weather |
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