Answer: A source region must have certain temperature and humidity properties that can remain fixed for a substantial length of time to affect air masses above it. above it. Air mass source regions occur only in the high or low latitudes; middle latitudes are too variable. An air mass is a huge body of air with similar temperature and humidity characteristics. ... The air masses obtain their characteristic temperature and humidity by sitting at a location on earth for a period of time. This location is the source region. Air masses are NAMED by their temperature and humidity characteristics. A good source region for an air mass would be: generally flat areas of uniform composition with light surface winds. The origin of cP and cA air masses that enter the United States is: Northern Canada and Alaska.
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