They also help confine it to the subcontinent. The north-western parts of India—Punjab and Ganga plains—are invaded by shallow cyclonic disturbances moving from west to east and having their origin in the Mediterranean Sea. This change of the upper tropospheric circulation above northern India from westerly jet to easterly flow coincides with a reversal of the vertical temperature and pressure gradients between 600 and 300 millibars. Above the heated land, the air below 1,500 metres 5,000 feet becomes unstable, but it is held down by the overriding easterly flow. This creates low pressure on the landmass, while high pressure is created over the seas during daytime, but is reversed during the night time.
The monsoon winds encounter various atmospheric conditions on their way and hence are pulsating in nature, and not steady. Although the annual average precipitation in India is 98 cm, it may show a deficit of 20 cm as in 1899 and a surplus of 30 cm as in 1907. This concept explains the basically Indian sub-continental phenomenon in terms of differential seasonal heating of land and sea which induces low and high pressure centres in successive seasons. Effects of monsoon rainfall in India: a Indian agriculture is largely dependent upon the water from the monsoon rains. As a result, the summer monsoon winds bring in a huge amount of moisture and cause heavy rainfall, especially in Bangladesh and the neighboring States of India.
Classical Theory or Thermal Concept of Indian Monsoons: According to this theory, the differential heating of land and sea at the time when the sun makes an apparent northward movement is the main cause of the Indian monsoonal regime. The north-eastern part of the country receives the maximum rainfall of this season. These cyclones contribute to the bulk of the rainfall of the Coromandel Coast. A result, warm moist air expands and rises rapidly. Alternating wet and dry season: - this manifests in the annual cycles of floods and droughts. These conditions continue from October till mid-December and are known as the retreating monsoons or the north-east monsoons.
The overall pattern of the advance follows a , but local episodes may differ considerably. As such, the shift of the jet is sudden and abrupt, causing the bursting of southwest monsoon rains onto the Indian plains. As these winds blow from land to sea, most parts of the country experience a dry season. There are three Mediterranean sea that affects the depth of Indian Ocean: the Persian Gulf which is the smallest constituting an average depth of 25 m 82 ft and a maximum depth of 90 m 295 ft ; the red sea with an average depth of 490 m 1607. Most of India thus begins a sunny, dry, and dusty season.
The Indian landscape, its flora and fauna, etc. These storm clouds are usually 5 km wide and 8 km high. This rainfall benefits the rabi crops. Late, low or excessive rains have a negative impact upon crops. And also inter-seasonal and inter-annual variations.
This rainfall is locally known as mahawat. The single most dominant element of the climate of Bangladesh is the rainfall. A recent assessment of the monsoonal changes indicate that the land warming has increased during 2002-2014, possibly reviving the strength of the monsoon circulation and rainfall. The fifth condition develops during the summer due to the movement of the westerly jet streams to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian Peninsula. These monsoon winds reach the southern states of India by October, and are responsible for a second round of rainfall. The opposite shift is also possible, with midlatitude upper air flowing along the south face of the Himalayas and bringing drought to the northern districts. These upper level easterly jets create an air flow on the southern side of the Tibetan plateau reaching down to low levels over northernmost India.
It has two major basin groups which are draining to the Mozambique to the west and into the Indian ocean in the east. Western , , and Arabia remain dry probably because of the divergence in this jet and thus become the new source of surface heat. The landmass in the north-west India gets intensely heated during summer causing a very low pressure area there. As we all know India falls in the monsoon climatic region. . The monsoon of South Asia is among several geographically distributed.
What causes the Indian monsoon? In the case of the monsoon, the cause is primarily , due to the presence of highlands in the path of the winds. This is because the monsoon picks up additional moisture from the Bay of Bengal as it heads towards the Himalayan range. The El-Nino Southern Oscillations in monsoonal variability. In certain years, there is a reversal in the pressure conditions. The of coastal districts in the Indian region rises above 70 percent, and some rain occurs. As a result, windward side gets heavy rain while the leeward side gets scanty rain.
The centres of action, air masses involved, and the mechanism of precipitation of the Indian monsoon are altogether different from other monsoon systems. This causes the winds to blow over the Indian subcontinent toward the in a northeasterly direction, causing the northeast monsoon. These cyclones usually cross the eastern coasts of India and cause heavy and widespread rain. Various weather systems say troughs bring in moisture and thermal instability. Sometimes, despite average annual rainfall, the daily distribution or geographic distribution of the rain is substantially skewed. While less rain is usually received overall in September, the rain that does come can often be torrential. Most of the festivals in India are related to agricultural cycle.