Which type of air mass is typically warm and moist, originating over oceans?

The type of air mass that is typically warm and moist, originating over oceans, is maritime tropical. This classification comes from the nature of the air mass, which picks up moisture from the warm ocean waters as it travels over them. The warm temperatures are a result of its origin in tropical regions where the climate is generally hot, enabling the air to hold more moisture. This leads to the characteristic humid conditions associated with maritime tropical air masses, making them key players in weather patterns, particularly when they move over land and interact with other air masses.

Continental polar air masses, on the other hand, originate over land in polar regions and are cold and dry. Continental tropical air masses are warm as well but originate over land in tropical regions, making them typically dry due to the lack of moisture. Maritime polar air masses are cool and moist, arising over the oceans in higher latitudes, but they do not have the warm characteristics typical of maritime tropical air masses. Thus, the maritime tropical air mass uniquely exemplifies the combination of warmth and moisture derived from its oceanic origins.