Table of Contents
Fronts
The Front is an inclined zone formed by the convergence of two opposing air masses with contrasting characteristics in terms of air temperature, humidity, density, and pressure. A frontal zone is a large transitional zone between two converging Air Masses. The frontal zone is inclined to the Earth’s surface at a low angle. They are distinguished by features such as large differences in air temperature across the convergence zone and bending isobars.
It is also a zone of low-pressure intensification, cooling of rising hot and humid air, condensation, cloud formation, and Precipitation. The process of forming a new front is referred to as frontogenesis. Frontolysis is the process of destroying, dying or dissolving the front. Due to the Coriolis effect, frontogenesis occurs in the northern hemisphere in an anti-clockwise direction and in the southern hemisphere in a clockwise direction.
Front Meaning
When two different air masses meet, the boundary zone between them is called a Front. The cold air mass tends to sink, and the warm air mass tends to rise and this explains why fronts are always inclined. Front development can mostly be found in the mid-latitude region i.e. between 30-65 degrees in both hemispheres.
The process of formation of the fronts is known as frontogenesis. The process of dissipation of a front is known as Frontolysis. The concept of fronts was propounded by the Norwegian meteorologists- V Bjerkens and J Bjerkens during World War I. Fonts can be broadly classified into four types depending on their interaction.
Frontogenesis
Frontogenesis (war between two air masses) is the process of forming a front, and Frontolysis (dissipation of a front) is the process of dissipating a front (one of the air masses wins against the other).
Frontogenesis occurs when two distinct air masses collide. Frontolysis is the replacement of one air mass by another. Frontogenesis (air mass convergence) occurs anticlockwise in the northern hemisphere and clockwise in the southern hemisphere. This is because of the Coriolis effect. Frontogenesis causes mid-latitude cyclones or temperate cyclones or extratropical cyclones.
Frontogenesis Necessary Conditions
- It is critical to have two opposing air masses with contrasting air temperatures, pressure, density, and humidity.
- Two opposing air masses must have contrasting temperatures, with one being dry and heavier and the other being hot, humid, and light.
- In such cases, the heavier cold and denser air mass invade the area of the lighter warm air mass.
- The two masses must either move in the same direction or converge.
- When air masses separate, they move in opposite directions, and no frontogenesis occurs.
Read More: Tropical Cyclone
Fronts Diagram
On weather maps, the cold front is depicted by blue lines with protruding “teeth” that point in the wind’s direction. Orange lines with rounded bumps pointing in the wind direction represent a warm front.
Read More: Evaporation and Condensation
Front Types
Stationary fronts, Cold fronts, Warm fronts, and Occluded fronts are the four different types of weather fronts.
Stationary Front
When two contrasting air masses converge and form a boundary without intermixing of winds is a stationary front. Both the wind parcel fails to push each other and remains stationary. The wind flow is parallel to the front but in opposite direction. Such fronts are temporary fronts and are mostly short-lived.
Weather along a Stationary Front
It produces Cumulonimbus Clouds. Frontal precipitation results from warm air overrunning along a front like this. Cyclones moving along a still front can produce substantial flooding along the front by dumping large volumes of precipitation.
Read More: Types of Clouds
Warm Front
When a warm air mass moves towards a cold air mass, the contact zone is a warm front. As the warm air ascends the slope it condenses and causes precipitation. The warm front has a gentle slope of 1 km of rise for every 100 or 200 km of distance.
1. Weather along a Warm Front
In contrast to a cold front, the temperature and wind direction changes are gradual as the warm air flows up the slope, causing condensation and precipitation. These fronts bring about light to moderate precipitation across a wide area and for several hours. A rise in temperature, a drop in pressure, and a shift in the weather signal the passing of a warm front.
2. Clouds along a Warm Front
The hierarchy of clouds as we approach is cirrus, stratus, and nimbus. There are no cumulonimbus clouds due to the mild gradient. The sun and moon are surrounded by cirrostratus clouds that are in front of the warm front.
Read More: Pressure Belts
Cold Front
It is a front in which the cold air is moving towards the warm air zone. As the cold air mass is dense, it remains on the ground. The cold air mass forcibly uplifts the warm and less dense air mass. The front is associated with a narrow band of clouds and precipitation. The cold front has a steeper slope than the warm front. It has a slope of 1 km of rise for a 50 or 100 km of distance.
1. Weather along a Cold Front
- The narrow zone of cloudiness and precipitation that runs along such a front determines the weather.
- Storms with high winds are possible. Thunderstorms are frequent in the warm sector during the summer.
- Tornadoes can occur in warm places, such as the United States.
- Cause whether to change more abruptly. Within the first hour, temperatures might drop by more than 15 degrees.
2. Cloud Formation along a Cold Front
Increased wind activity in the warm sector and the arrival of cirrus clouds, followed by lower, thicker altocumulus and cirrus clouds, signal the approach of a cold front.
Heavy downpours are brought on by cumulonimbus and black nimbus clouds at the front. A cold front quickly dissipates, but the weather it causes is severe.
Read More: Atmospheric Circulation
Occluded Front
An occluded front is formed when a cold front overtakes a warm front. As the cold front moves faster than the warm front, the warm sector is reduced in size. Eventually, the warm air is completely displaced. Ultimately, the cold and warm fronts merge into one to form a long, backwards swinging front. This is called an occluded front. The weather conditions in the occluded front are more variable with erratic rainfall.
1. Weather along an Occluded Front
A complex combination of a cold front and warm front weather exists along an occluded front. West Europe frequently experiences such fronts. the structure Occluded fronts emerge during the development of mid-latitude cyclones, often known as temperate or extratropical cyclones.
2. Clouds along an Occluded Front
At both the cold front and the warm front, a mixture of clouds formed. On the opposing side of the occlusion are cold front clouds and warm front clouds.
Read More: List of Major Local Winds
Front Climatic Significance
The weather changes when a front passes through a region. Weather conditions like rain, thunderstorms, strong winds, and tornadoes are brought on by the phenomenon. A cold front may bring about violent thunderstorms. There can be low-stratus clouds at a warm front. After the front has passed, the skies often clear.
Other frontogeneses only change the temperature; nevertheless, some front forms can initiate the biggest storms on Earth. Off the coast of Africa, in the tropical Atlantic Ocean, a front known as tropical wave forms. If the conditions are right, these can also intensify into hurricanes or tropical storms.
They travel across the surface of the Earth over several days, and powerful winds like Jet Streams are frequently used to direct their motion. Mountains and other land features can alter the convergence’s route.
Read More: Types of Winds
Fronts UPSC
The interface or transition zone between two air masses with varying densities and temperatures; intermittent weather flare-ups along this zone, including sporadic thunderstorms and electrical activity, were compared by the Norwegian meteorologists who gave it its name during World War I to the fighting along the front lines in Europe. Frontal zones frequently include low barometric pressure (a pressure trough), notable changes in wind direction and relative humidity, as well as a great deal of cloud cover and precipitation.
In this article, we have addressed a number of topics that are crucial for the UPSC test, including the definition of the front, different types of fronts, stationary fronts, cold fronts, warm fronts, occluded fronts, and prerequisites for frontogenesis.
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