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

 Page 1


 
AIRMASS 
When the air remains over a homogenous area for a sufficiently longer time, 
it acquires the characteristics of the area.   
The homogenous regions can be the vast ocean surface or vast plains.  
SOURCE REGIONS 
The homogenous surfaces, over which air masses form, are called the source 
regions. 
 
CONDITIONS FOR THE FORMATION OF AIR MASSES 
 
Source region should be extensive with gentle, divergent air 
circulation . 
 
The main source regions are the high pressure belts in the sub 
tropics (giving rise to tropical air masses) and around the poles 
(the source for polar air masses). 
 
There are no major source regions in the mid-latitudes as these 
regions are dominated by cyclonic and other disturbances. 
 
NOTE: 
• Maritime air masses contain high humidity and produce a 
large amount of precipitation. 
• Continental air masses are dry and produce less amount of 
precipitation 
 
 
 
 
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AIRMASS 
When the air remains over a homogenous area for a sufficiently longer time, 
it acquires the characteristics of the area.   
The homogenous regions can be the vast ocean surface or vast plains.  
SOURCE REGIONS 
The homogenous surfaces, over which air masses form, are called the source 
regions. 
 
CONDITIONS FOR THE FORMATION OF AIR MASSES 
 
Source region should be extensive with gentle, divergent air 
circulation . 
 
The main source regions are the high pressure belts in the sub 
tropics (giving rise to tropical air masses) and around the poles 
(the source for polar air masses). 
 
There are no major source regions in the mid-latitudes as these 
regions are dominated by cyclonic and other disturbances. 
 
NOTE: 
• Maritime air masses contain high humidity and produce a 
large amount of precipitation. 
• Continental air masses are dry and produce less amount of 
precipitation 
 
 
 
 
 
COLD AIR MASS 
Cold source regions  
Polar air masses 
 
Arctic Ocean – cold and moist 
Northern Canada – cold and dry 
 
WARM AIR MASS 
Warm source regions  
Tropical air masses 
Sahara Desert – warm and dry 
Tropical Oceans – warm and moist 
 
 
CLASSIFICATION OF AIR MASSES 
Broadly, the air masses are classified into polar and tropical air masses. 
Both the polar and the continental air masses can be either of maritime or 
continental types. 
Page 3


 
AIRMASS 
When the air remains over a homogenous area for a sufficiently longer time, 
it acquires the characteristics of the area.   
The homogenous regions can be the vast ocean surface or vast plains.  
SOURCE REGIONS 
The homogenous surfaces, over which air masses form, are called the source 
regions. 
 
CONDITIONS FOR THE FORMATION OF AIR MASSES 
 
Source region should be extensive with gentle, divergent air 
circulation . 
 
The main source regions are the high pressure belts in the sub 
tropics (giving rise to tropical air masses) and around the poles 
(the source for polar air masses). 
 
There are no major source regions in the mid-latitudes as these 
regions are dominated by cyclonic and other disturbances. 
 
NOTE: 
• Maritime air masses contain high humidity and produce a 
large amount of precipitation. 
• Continental air masses are dry and produce less amount of 
precipitation 
 
 
 
 
 
COLD AIR MASS 
Cold source regions  
Polar air masses 
 
Arctic Ocean – cold and moist 
Northern Canada – cold and dry 
 
WARM AIR MASS 
Warm source regions  
Tropical air masses 
Sahara Desert – warm and dry 
Tropical Oceans – warm and moist 
 
 
CLASSIFICATION OF AIR MASSES 
Broadly, the air masses are classified into polar and tropical air masses. 
Both the polar and the continental air masses can be either of maritime or 
continental types. 
 
 
AIR MASSES BASED ON SOURCE REGIONS 
 
There are five major source regions. These are: 
(i) Warm tropical and subtropical oceans;  
(ii)  The subtropical hot deserts;  
(iii)  The relatively cold high latitude oceans; 
(iv)  The very cold snow covered continents in high latitudes; 
(v)   Permanently ice covered continents in the Arctic and Antarctica.  
 
 
Accordingly, following types of airmasses are recognised:  
(i) Maritime tropical (mT);  
(ii)  Continental tropical (cT); 
(iii)   Maritime polar (mP);  
(iv)  Continental polar (cP); 
(v)   Continental arctic (cA). 
 
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AIRMASS 
When the air remains over a homogenous area for a sufficiently longer time, 
it acquires the characteristics of the area.   
The homogenous regions can be the vast ocean surface or vast plains.  
SOURCE REGIONS 
The homogenous surfaces, over which air masses form, are called the source 
regions. 
 
CONDITIONS FOR THE FORMATION OF AIR MASSES 
 
Source region should be extensive with gentle, divergent air 
circulation . 
 
The main source regions are the high pressure belts in the sub 
tropics (giving rise to tropical air masses) and around the poles 
(the source for polar air masses). 
 
There are no major source regions in the mid-latitudes as these 
regions are dominated by cyclonic and other disturbances. 
 
NOTE: 
• Maritime air masses contain high humidity and produce a 
large amount of precipitation. 
• Continental air masses are dry and produce less amount of 
precipitation 
 
 
 
 
 
COLD AIR MASS 
Cold source regions  
Polar air masses 
 
Arctic Ocean – cold and moist 
Northern Canada – cold and dry 
 
WARM AIR MASS 
Warm source regions  
Tropical air masses 
Sahara Desert – warm and dry 
Tropical Oceans – warm and moist 
 
 
CLASSIFICATION OF AIR MASSES 
Broadly, the air masses are classified into polar and tropical air masses. 
Both the polar and the continental air masses can be either of maritime or 
continental types. 
 
 
AIR MASSES BASED ON SOURCE REGIONS 
 
There are five major source regions. These are: 
(i) Warm tropical and subtropical oceans;  
(ii)  The subtropical hot deserts;  
(iii)  The relatively cold high latitude oceans; 
(iv)  The very cold snow covered continents in high latitudes; 
(v)   Permanently ice covered continents in the Arctic and Antarctica.  
 
 
Accordingly, following types of airmasses are recognised:  
(i) Maritime tropical (mT);  
(ii)  Continental tropical (cT); 
(iii)   Maritime polar (mP);  
(iv)  Continental polar (cP); 
(v)   Continental arctic (cA). 
 
 
 
INFLUENCE OF AIR MASSES ON WORLD WEATHER 
? Convectional Lifting: Vertical distribution temperature . 
? Atmospheric moisture from oceans to continents and cause 
precipitation over landmasses. 
? Orographic lifting : When air masses lifted up over mountains 
they can also change the weather conditions this way known as 
orographic lifting. 
? Transport latent heat. 
? Most of the migratory atmospheric disturbances such as 
cyclones and storms originate at the contact zone between 
different air masses. 
 
 
CHARACTERISTICS OF AIR MASS 
It must be large. A typical air mass is more than 1600 kilometres across and 
several kilometres deep. 
At any given altitude in the air mass, its physical characteristics primarily 
temperature, humidity, and stability are relatively homogeneous. 
It must be distinct from the surrounding air, and when it moves, it must 
retain its original characteristics and not be torn apart by differences in 
airflow.