The polar air masses are air masses that form on the high latitudes, in the polar regions. The tropical air masses are air masses that form on the low latitudes, around the equator.
The polar air masses are cold air masses. They are also dry, very dense, and have much higher air pressure. The tropical air masses are warm air masses. Depending have they formed over land or over sea, they can be either dry or moist, and they have low air pressure as they are much less dense.
A typical polar air mass brings in cold and dry weather, while the tropical air mass brings in warm weather, with either lot of precipitation, or being very dry.
The polar air masses are moving from the high latitudes toward the lower latitudes, while the tropical air masses are moving from the lower latitudes toward the higher latitudes.
