O Level Notes : Geography - Weather and climate - Frontal Systems
When two different air masses meet they do not mix but they remain separated by a zone called a front. A front is therefore a boundary or zone separating two air masses. For example, when the tropical and polar air masses meet, they do not mix but they form a front between them.
There are different types of fronts and these are named according to the air pushing behind them. The process by which fronts are formed is called frontogenesis. Frontogenesis occurs where two air masses are pushing against each other as if waging a war. A front does not exist forever but will disperse or dissipate in a process called frontolysis. One of the air masses at the front would have lost the battle. Frontogenesis is the convergence of two air masses while under frontolysis one mass is over riding the other air mass.
Types of fronts and weather conditions
- Cold front
A cold front is the situation that occurs when cold air is pushing behind the front. The cold air therefore advances into the warm air replacing it at the surface. When the cold front completely uplifts the warm air from the surface, frontolysis begins. Cold front move faster than warm front and has steep gradient of 1: 100.
The cold front
Weather conditions associated with a cold front include:
- Storms during the summer
- The approaching front is marked by cirrus clouds
- Cirrus clouds are followed by altocumulus clouds
- Heavy showers
- Violent weather along the front
- Thunderstorms and thick clouds
- The warm front
This occurs when the warm air is pushing behind the front. The warm air is therefore replacing the cold air at the surface. Warm front has a gentle gradient . It moves slowly and is less violent.
The warm front
Weather conditions along the warm front include:
- Moderate precipitation
- Arise in temperature due to passing of warm front
- Awarm front is associated with cirrus, stratus and nimbostratus clouds
A cold front and a warm front on a synoptic map
- Occluded front
The cold front moves faster than the warm front. The cold front catches up with the warm front such that the warm air is completely lifted from the surface. The cold air ends up overtaking the warm air and goes underneath it. The process of frontolysis begins when an occluded front is formed.
An occluded front
Weather conditions associated with an occluded front
An occluded front comprises of cold and warm front mixing so it is associated with a mixture of warm and cold front weather conditions. Cumulonimbus clouds, cirrus and nimbostratus are all mixed up.
- Stationary front
This front occurs when a frontal system stops moving forward. Such a front can remain stationary for several days. When it starts moving it may be either be a cold or a warm front. The temperatures may weaken and the front just disappears. The front is associated with gentle winds.
What's Your Reaction?
