Atmospheric Lifting Mechanisms

Atmospheric Lifting Mechanisms

1) convergent - air flows towards an area of low pressure; characteristic in low latitudes

2) convectional - caused by surface heating; associated with warm parts of the world or warm

season of the year

3) frontal - along the leading edges of contrasting air masses; most characteristic in midlatitudes

4) orographic - air is forced over a barrier (ex: mt. range); produces a rain shadow on the leeward slope; least dominant worldwide

Front - boundary bet. 2 different air masses; leading edge of an advancing air mass

Discontinuities

a) abrupt - narrow front

b) gradual - broad & diffuse front

1) temperature

2) dew point & T-DP spread

3) wind w.r.t. direction &/or speed

4) pressure - rise going into cold

- fall going into warm

Types of Fronts

1) cold - leading edge of cold air mass; at the surface, cold air is replacing warm air; steep slope

2) warm - leading edge of warm air mass; warm air slides up & over cold air; gradual slope;

move ~½ as fast as cold fronts;

3) stationary - neither air mass is replacing the other; wind is parallel to the front;

4) occluded - when a cold front & warm front catch up to each other;

Squall Line - a line of intense thunderstorms slightly ahead of a fast-advancing cold front

Frontal Weather depends on:

1) amount of moisture available - determines if clouds will form

2) degree of stability of the air that is forced upward - determines type of clouds

3) slope of the front

4) speed of the frontal movement

5) upper wind flow - determines amount of cloudiness & rain accompanying a frontal system & the movement of the front