In recent, the India Meteorological Department (IMD) announced that India will likely have a normal monsoon, with a chance of ‘above normal’ rain in August and September,
The IMD issues a two-stage forecast: the first in April, followed by a more detailed one in the last week of May, which will also illustrate how the monsoon will spread over the country.
The IMD’s confidence stems largely from global weather models pointing to negligible chances of El Nino, a warming of the central equatorial Pacific that’s associated with the drying up of monsoon rain.
India: Monsoon type of Climate:
The climate of India is described as the ‘monsoon’ type. In Asia, this type of climate is found mainly in the south and the southeast.
Out of a total of 4 seasonal divisions of India, monsoon occupy 2 divisions:
The southwest monsoon season – Rainfall received from the southwest monsoons is seasonal in character, which occurs between June and September.
The retreating monsoon season – The months of October and November are known for retreating monsoons.
To what extent has the monsoon covered the country?
- The monsoon has covered the whole of south as well as eastern India.
- By July 15 the monsoon should have ideally covered its last outpost in western Rajasthan, but this is unlikely given the delay in the monsoon’s advent.
- In the week ahead, it’s expected to make further inroads into central India and most of Gujarat and Uttar Pradesh.
- However, the geographic spread obscures the quantity of rain. Only two of India’s 36 meteorological subdivisions have posted normal rainfall and 27 of them are grappling with deficient rainfall.
- By June 30, a low-pressure pulse is expected to form over the Bay of Bengal and give a significant push to the monsoon.
Indian monsoon phenomenon:
- Monsoons are seasonal winds which reverse their direction with the change of season.
- They flow from sea to land during the summer and from land to sea during
- Countries like India, Indonesia, Bangladesh, Myanmar etc. receive most of the annual rainfall during south-west monsoon season whereas South East China, Japan etc., during north-east rainfall season.
- During the summers of northern hemisphere, North India receives high insolation and generates low pressure.
- This low pressure attracts winds from all direction. Heating of Tibetan plateau also plays role here.
- During the same time, Inter-Tropical convergence zone also shifts to the north and as a result trade winds starts blowing towards India carrying moisture with them.
- The shift in the position of the ITCZ is also related to the phenomenon of the withdrawal of the westerly jet stream from its position over the north Indian plain, south of the Himalayas.
- The easterly jet stream sets in along 15°N latitude only after the western jet stream has withdrawn itself from the region.
- This easterly jet stream is held responsible for the burst of the monsoon in India.
Does the monsoon have a bearing on India’s water crisis?
- India’s water crisis, according to experts, is due to over-extraction of groundwater resources and not enough storage of rain water and surface water.
- The Central Water Commission, in its recommendation of how reservoirs should store and release water assumes that reservoirs will be empty on June 1 and gradually refill over the course of the monsoon, and be available for the non-monsoon months.
- Given that June contributes only 17cm or about 20% of the monsoon rainfall and is known to progress in spurts, farmers have already delayed sowing and relying on crop varieties that grow relatively quickly.
- Moreover, several farmers plant intensely water-guzzling crops that aren’t suited to their climate or prevalent water table.
- While a July rainfall can temporarily alleviate parched ground, it can’t solve the graver crisis of depleting groundwater and insufficiently charged aquifers.
Indian Ocean Dipole impact the southwest monsoon:
IOD is the difference between the temperature of eastern (Bay of Bengal) and the western Indian Ocean (Arabian Sea).
This temperature difference results into pressure difference which results in flowing of winds between eastern and western parts of Indian Ocean.
IOD develops in the equatorial region of Indian Ocean from April to May peaking in October.
- Although El Nino Southern Oscillation (ENSO)was statistically effective in explaining several past droughts in India, in the recent decades the ENSO-Monsoon relationship seemed to weaken in the Indian subcontinent.
- For e.g. the 1997, strong ENSO failed to cause drought in India.
- It was later discovered that just like ENSO was an event in the Pacific Ocean, a similar seesaw ocean-atmosphere system in the Indian Ocean was also at play which was IOD.
- However, there is no established correlation between Indian summer monsoon rainfall and IOD.
- But studies have shown that a positive IOD year sees more than normal rainfall over central India.
- It was demonstrated that a positive IOD index often negated the effect of ENSO, resulting in increased Monsoon rains in several ENSO years like the 1983, 1994 and 1997.
- Further, it was shown that the two poles of the IOD – the eastern pole (around Indonesia) and the western pole (off the African coast) were independently and cumulatively affecting the quantity of rains for the Monsoon in the Indian subcontinent.
- The indicated connection is between below-normal SST in the eastern Indian Ocean and above-normal rain over central India, and vice versa.
- A negative IOD, on the other hands, complements El NINO leading to severe drought.
- At the same time, Positive IOD results in more cyclones than usual in Arabian Sea.
- Negative IOD results in stronger than usual cyclogenesis (Formation of Tropical Cyclones) in Bay of Bengal. Cyclogenesis in Arabian Sea is suppressed during this time.
- But there is some anomaly in the phenomenon of IOD and Monsoon.
Although there are wide variations in weather patterns across India, the monsoon brings some unifying influences on India. The Indian landscape, its flora and fauna, etc. are highly influenced by the monsoon.
The entire agricultural calendar in India is governed by the monsoon. Due to these reasons, monsoon is often a great unifying factor in India.
The population of India is increasing and to provide food security to the population, a large part of the monsoon water which is currently unutilized should be held at suitable locations for irrigation and power generation purposes.
India needs to invest more resources in better prediction of Monsoon forecast in order to achieve reliability and sustainability.