Which front serves to replace colder air with warmer air?

A warm front is characterized by the movement of warm air into an area that was previously occupied by cooler air. When a warm front approaches, the lighter, warmer air rises over the denser, colder air. This process often leads to the formation of clouds and precipitation as the moisture in the rising warm air cools and condenses.

The warm front typically brings more gradual changes in weather, such as an increase in temperature and a transition from overcast skies to clearer conditions as the warm air replaces the colder air. This is in contrast with a cold front, which brings more sudden changes, including sharp drops in temperature and more intense storms.

Stationary fronts do not actively replace one type of air with another; instead, they occur when two air masses meet but neither is strong enough to replace the other. An occluded front involves the interaction of two different air masses, but it does not primarily function to replace cold air with warm air. Thus, the warm front is clearly the correct choice for the process of replacing colder air with warmer air.