Structure

Introduction: (upto 30 words) Define airmasses and fornts

Body: (upto 100 words) After explaining frontogenesis, classify the different types of fronts that can develop.

Conclusion: (upto 30 words) Conclude by writing that, the characteristics of the Air masses will be depend upon the source region over which it is formed and will affect frontogenesis accordingly.

Supporting Points:

Air mass is a volume of air defined by its temperature and water vapour content. An air mass may be of many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. An air mass can be so extensive that it may cover the large portion of a continent below it and may be vertically so thick that may cover the troposphere. The vertical distribution of the temperature in an air mass and moisture content of the air are the two properties of air air mass which control the weather conditions of an area under that particular air mass. The air mass is considered to be cold air mass if its temperature is lower than the underlying surface, while an air mass is terms warm air mass when its temperature is higher than the underlying surface. The boundary between the two air masses is called the front.

The process of formation of a front is known as Frontogenesis (war between two air masses), and dissipation of a front is known as Frontolysis (one of the air masses win against the other). Frontogenesis involves convergence of two distinct air masses. Frontolysis involves overriding of one of the air mass by another.

Classification of fronts:

Based on the mechanism of frontogenesis and the associated weather, the fronts can be studied under the following types.

Stationary Front:

1. When the surface position of a front does not change, a stationary front is formed.
2. The wind motion on both sides of the front is parallel to the front.
3. Overrunning of warm air along such a front causes frontal precipitation.
4. Warm or cold front stops moving, so the name stationary front.
5. Once this boundary resumes its forward motion, becomes a warm front or cold front.
6. Cyclones migrating along a stationary front can dump heavy amounts of precipitation, resulting in significant flooding along the front.

Cold Front:

1. Such a front is formed when a cold air mass replaces a warm air mass by advancing into it or that the warm air mass retreats and cold air mass advances.
2. In such a situation, the transition zone between the two is a cold front.
3. The weather along such a front depends on a narrow band of cloudiness and precipitation.
4. During the summer months thunderstorms are common in warm sector.
5. In some regions like USA tornadoes occur in warm sector.
6. Possibility of severe storms.
7. Temperatures can drop more than 15 degrees within the first hour.
8. Produce sharper changes in weather
9. Move up to twice as quickly as warm fronts
10. The approach of a cold front is marked by increased wind activity in warm sector and the appearance of cirrus clouds, followed by lower, denser altocumulous and altostratus.
11. At actual front, dark nimbus clouds cause heavy showers. A cold front passes off rapidly, but the weather along it is violent.

Warm Front:

1. This is actually a sloping frontal surface along which active movement of warm air over cold air takes place.
2. As the warm air moves up the slope, it condenses and causes precipitation but, unlike a cold front, the temperature and wind direction changes are gradual.
3. With the approach, the hierarchy of clouds is - cirrus, stratus and nimbus.
4. Cirrostratus clouds ahead of the warm front create a halo around sun and moon.
5. Such fronts cause moderate to gentle precipitation over a large area, over several hours.
6. The passage of warm front is marked by rise in temperature, pressure and change in weather.

Occluded Front:

1. Such a front is formed when a cold air mass overtakes a warm air mass and goes underneath it.
2. The warm sector diminishes and the cold air mass completely undertakes the warm sector on ground.
3. Thus, a long and backward swinging occluded front is formed which could be a warm front type or cold front type occlusion.
4. Weather along an occluded front is complex—a mixture of cold front type and warm front type weather. Such fronts are common in west Europe.