Final answer:
Maritime air masses have a high water vapor content due to their formation over the oceans, which are a significant source of moisture.
Step-by-step explanation:
Maritime air masses have a high water vapor content because they form over the oceans, which are a major source of moisture. The warm sea surface temperatures cause the air in these masses to become saturated with water vapor. As the air mass moves over land, it can bring this moisture with it, resulting in potentially cloudy and rainy weather.
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