The monsoons of Southern Asia which includes India, Pakistan, and Bangladesh are described as ‘ideal monsoons’. Burma and Indo-China situated in the east of the Indian subcontinent have also the monsoonal circulation, but no detailed study has been made about their circulation patterns.
Moreover, in the absence of a physical barrier like the Himalaya-Tibet system to their north, the above mentioned countries cannot be separated effectively from the wind systems prevailing in Eastern Asia.
Burma, Malaysia and Indo- China are more or less affected by the monsoonal circulation of the Indian sub-continent and Eastern Asia. However, the Indian monsoon has been discussed separately in detail. Monsoons of South and East Asia Compared
The monsoons of South Asia differ in many respects, as stated below, from those of Eastern Asia:
(1) The land mass of Eastern Asia lies in the temperate zone, whereas South Asian land mass is confined within the tropics. Therefore the different geographical locations of these regions lead to climatic differences therein.
(2) The Himalayas and other mountain systems to the north and east of the Indian subcontinent protect India, Pakistan, and Bangladesh from the cold and dry winds blowing out from the Central Asian High pressure centre during winter.
But in the absence of such east-west mountain systems the countries of Eastern Asia such as China and Japan are open to cold air invasion from the east Siberian anticyclone.
(3) Winter monsoon in Eastern Asia is stronger and more vigorous than the summer monsoon. Besides, the prevailing wind direction is more constant in winter than in summer. On the contrary, in case of the Indian sub-continent the summer monsoons are stronger than winter monsoons.
The summer monsoons are characterized by a higher degree of constancy in the prevailing wind direction than the winter monsoons.
The difference in the vigour of East Asian monsoons is caused due to the fact that Siberian high pressure centre in winter is more powerful than the low pressure centre during summer. On the other hand, the summer time low pressure centre over the Indian sub-continent is far more vigorous than the winter high pressure system.
(4) There is a marked variation in the geographical locations of the centers of action affecting the South and East Asian monsoons. The focus of East Asian monsoons lies over the central part of Asia, whereas the Indian monsoons are controlled by the high and low pressure centers developed over north-western region of the sub-continent.
(5) The burst of monsoon over India is associated with turbulent weather, whereas the advent of East Asian monsoon is characterized by mild weather disturbances. However, there are certain characteristic features that are common to both the East Asian and the South Asian monsoons.
When the monsoons are fully established over the respective regions, the weather is not so turbulent. But the advent or the retreat of monsoons is always marked by violent weather. It is a common experience that while the monsoons are retreating, various types of atmospheric disturbances are produced.
Some of these initially mild disturbances grow into more violent hurricanes or typhoons and play havoc especially in the coastal regions. They also cause a great damage to life and property.
The most interesting feature of monsoonal precipitation is that when the monsoons are at their peak, most of the precipitation occurs from numerous shallow depressions, technically the monsoon depressions that have their origin in the convergence zone of different air masses.