GED Science Practice Test: Weather: Air Mass And Fronts

Air Mass:  In meteorology, an air mass is a volume of air defined by its temperature, water vapor content, density, and location (over land or over water). Air masses cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. Colder air masses are termed polar or arctic, while warmer air masses are deemed tropical.

Weather Front:  A front is defined as the transition zone between two air masses of different density and temperature. If warm air is moving toward cold air, it is a “warm front”. These are shown on weather maps as a red line with scallops on it. If cold air is moving toward warm air, then it is a “cold front”. Cold fronts are always shown as a blue line with arrow points on it. If neither air mass is moving very much, it is called a “stationary front”, shown as an alternating red and blue line.


The contact between two air masses at a weather front can cause a number of different weather patterns.  One weather event is pictured below, in which a cold front causes a cold and a warm air mass to meet over water.  At the weather front, clouds are formed, due to the warm air rising and water vapor condensing.



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