Uplift along weather fronts; 1. Surface heating and free convection. During the daytime, the earth's surface is heated by the sun, which in turn heats the air in contact with the surface. Parcels (or bubbles) of hot air (called thermals) rise upward. As they rise upward, the thermals cool by expansion.

Frontal uplift occurs when greatly contrasting air masses meet along a weather front. For instance, when warm air collides with cool air along a warm front, the warm air is forced to rise up and over the cool air.

– Uplift along weather fronts Atmospheric Instability and Cloud Development - lifting mechanisms 2. What kind (if any) clouds will you visually observe in different stable environments? In a shallow conditionally unstable or absolutely unstable environment, one may expect clouds to develop, but their vertical growth will be limited, and may ...

Uplift along weather fronts; 1. Surface heating and free convection. During the daytime, the earth's surface is heated by the sun, which in turn heats the air in contact with the surface. However, the surface of the Earth is not heated evenly by the Sun.

Rain that occurs behind a cold front or on the cool side of a warm front is not a result of parcels rising from the surface but by rather "elevated convection". Elevated convection is the convective lifting of air that initially begins to rise starting above the planetary boundary layer.

There are five types of fronts which we need to know: Cold Front is characterized by a cold (more dense) air mass is moving into a warmer (less dense) air mass. Characterized by abrupt uplift along the frontal boundary. Cumulus (flat based or anvil-shaped) development. Short duration heavy rain & thunderstorms.

Air flowing together (convergence) will initiate lifting. Along a warm front, warm air gradually rides up and over colder surface air producing the uniform stratus like clouds. Along a cold front, warm moist air is forced up. Even in the absence of fronts warm air may form in regions of low pressure.

Fronts are boundaries between contrasting masses of air. Atmospheric scientists recognize fronts of different spatial scales. These range from the quasi-stationary fronts along which cyclones form to "weather" fronts embedded in cyclones. Fronts are three-dimensional features.

The idea of isentropic lifting is air "prefers" to move toward a region with the same density (potential temperature surfaces (a.k.a. along a constant theta surface)). Warm air resists undercutting cold air.

Lifting also occurs along frontal boundaries as air masses of different temperature and moisture content interact with eachother. For example, as the cold front advances (animation below), it lifts the warm moist air ahead of it.