Fronts - Notes | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
FRONTS  
When two different air masses meet, the boundary zone between them is 
called a front. The process of formation of the fronts is known as 
frontogenesis.  
Fronts are the typical features of midlatitudes weather (temperate region – 
30° – 65° N and S). They are uncommon (unusual) in tropical and polar 
regions. 
The two air masses don’t merge readily due to the effect of the converging 
atmospheric circulation, relatively low diffusion coefficient and a low 
thermal conductivity. 
 
FRONT FORMATION 
The process of formation of a front is known as Frontogenesis and 
dissipation of a front is known as Frontolysis . 
Frontogenesis involves convergence of two distinct air masses.  
Frontolysis involves overriding of one of the air mass by another. 
NOTE: 
Mid-latitude cyclones or temperate cyclones or extra-tropical cyclones 
occur due to frontogenesis. 
 
TYPES OF FRONTS: 
There are four types of fronts: (a) Cold; (b) Warm; (c) Stationary; (d) 
Occluded  
 
 
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FRONTS  
When two different air masses meet, the boundary zone between them is 
called a front. The process of formation of the fronts is known as 
frontogenesis.  
Fronts are the typical features of midlatitudes weather (temperate region – 
30° – 65° N and S). They are uncommon (unusual) in tropical and polar 
regions. 
The two air masses don’t merge readily due to the effect of the converging 
atmospheric circulation, relatively low diffusion coefficient and a low 
thermal conductivity. 
 
FRONT FORMATION 
The process of formation of a front is known as Frontogenesis and 
dissipation of a front is known as Frontolysis . 
Frontogenesis involves convergence of two distinct air masses.  
Frontolysis involves overriding of one of the air mass by another. 
NOTE: 
Mid-latitude cyclones or temperate cyclones or extra-tropical cyclones 
occur due to frontogenesis. 
 
TYPES OF FRONTS: 
There are four types of fronts: (a) Cold; (b) Warm; (c) Stationary; (d) 
Occluded  
 
 
 
 
STATIONARY FRONT 
     
When the front remains stationary, it is called a stationary front.  
Initially, the front is stationary. 
When the surface position of a front does not change (when two air masses 
are unable to push against each other; a draw), a stationary front is 
formed. 
Cumulonimbus clouds . 
Overrunning of warm air along such a front causes frontal precipitation. 
COLD FRONT 
  
When the cold air moves towards the warm air mass, its contact zone is 
called the cold front .  
Frontolysis begin when the warm air mass is completely uplifted by the 
cold air mass. 
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FRONTS  
When two different air masses meet, the boundary zone between them is 
called a front. The process of formation of the fronts is known as 
frontogenesis.  
Fronts are the typical features of midlatitudes weather (temperate region – 
30° – 65° N and S). They are uncommon (unusual) in tropical and polar 
regions. 
The two air masses don’t merge readily due to the effect of the converging 
atmospheric circulation, relatively low diffusion coefficient and a low 
thermal conductivity. 
 
FRONT FORMATION 
The process of formation of a front is known as Frontogenesis and 
dissipation of a front is known as Frontolysis . 
Frontogenesis involves convergence of two distinct air masses.  
Frontolysis involves overriding of one of the air mass by another. 
NOTE: 
Mid-latitude cyclones or temperate cyclones or extra-tropical cyclones 
occur due to frontogenesis. 
 
TYPES OF FRONTS: 
There are four types of fronts: (a) Cold; (b) Warm; (c) Stationary; (d) 
Occluded  
 
 
 
 
STATIONARY FRONT 
     
When the front remains stationary, it is called a stationary front.  
Initially, the front is stationary. 
When the surface position of a front does not change (when two air masses 
are unable to push against each other; a draw), a stationary front is 
formed. 
Cumulonimbus clouds . 
Overrunning of warm air along such a front causes frontal precipitation. 
COLD FRONT 
  
When the cold air moves towards the warm air mass, its contact zone is 
called the cold front .  
Frontolysis begin when the warm air mass is completely uplifted by the 
cold air mass. 
 
Temperatures can drop more than 15 degrees within the first hour. 
Vertically developed clouds, such as cumulonimbus clouds, are common, 
with considerable turbulence and showery precipitation. 
WARM FRONT 
  
When warm air mass moves towards the cold air mass, the contact zone is 
a warm front. 
Frontolysis (front dissipation) begin when the warm air mass makes way 
for cold air mass on the ground, i.e. when the warm air mass completely 
sits over the cold air mass. 
Such fronts cause moderate to gentle precipitation over a large area, over 
several hours. 
The passage of warm front is marked by rise in temperature, pressure and 
change in weather. 
Because the frontal uplift is very gradual, clouds form slowly and 
turbulence is limited. High-flying cirrus clouds may signal the 
approaching front many hours before it arrives. As the front comes closer, 
the clouds become lower, thicker, and more extensive, typically developing 
into altocumulus or altostratus. Precipitation usually occurs broadly 
OCCLUDED FRONT 
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FRONTS  
When two different air masses meet, the boundary zone between them is 
called a front. The process of formation of the fronts is known as 
frontogenesis.  
Fronts are the typical features of midlatitudes weather (temperate region – 
30° – 65° N and S). They are uncommon (unusual) in tropical and polar 
regions. 
The two air masses don’t merge readily due to the effect of the converging 
atmospheric circulation, relatively low diffusion coefficient and a low 
thermal conductivity. 
 
FRONT FORMATION 
The process of formation of a front is known as Frontogenesis and 
dissipation of a front is known as Frontolysis . 
Frontogenesis involves convergence of two distinct air masses.  
Frontolysis involves overriding of one of the air mass by another. 
NOTE: 
Mid-latitude cyclones or temperate cyclones or extra-tropical cyclones 
occur due to frontogenesis. 
 
TYPES OF FRONTS: 
There are four types of fronts: (a) Cold; (b) Warm; (c) Stationary; (d) 
Occluded  
 
 
 
 
STATIONARY FRONT 
     
When the front remains stationary, it is called a stationary front.  
Initially, the front is stationary. 
When the surface position of a front does not change (when two air masses 
are unable to push against each other; a draw), a stationary front is 
formed. 
Cumulonimbus clouds . 
Overrunning of warm air along such a front causes frontal precipitation. 
COLD FRONT 
  
When the cold air moves towards the warm air mass, its contact zone is 
called the cold front .  
Frontolysis begin when the warm air mass is completely uplifted by the 
cold air mass. 
 
Temperatures can drop more than 15 degrees within the first hour. 
Vertically developed clouds, such as cumulonimbus clouds, are common, 
with considerable turbulence and showery precipitation. 
WARM FRONT 
  
When warm air mass moves towards the cold air mass, the contact zone is 
a warm front. 
Frontolysis (front dissipation) begin when the warm air mass makes way 
for cold air mass on the ground, i.e. when the warm air mass completely 
sits over the cold air mass. 
Such fronts cause moderate to gentle precipitation over a large area, over 
several hours. 
The passage of warm front is marked by rise in temperature, pressure and 
change in weather. 
Because the frontal uplift is very gradual, clouds form slowly and 
turbulence is limited. High-flying cirrus clouds may signal the 
approaching front many hours before it arrives. As the front comes closer, 
the clouds become lower, thicker, and more extensive, typically developing 
into altocumulus or altostratus. Precipitation usually occurs broadly 
OCCLUDED FRONT 
 
  
If an air mass is fully lifted above the land surface, it is called the occluded 
front.  
Frontolysis begin when warm sector diminishes and the cold air mass 
completely undertakes the warm sector on ground. 
Weather along an occluded front is complex—a mixture of cold front type 
and warm front type weather.  A combination of clouds formed at cold 
front and warm front.