The India Meteorological
Department predicted on Monday that the country would experience a normal monsoon
for the third successive year, with rainfall at 97% of the long period average (LPA). The monsoon is considered
normal if average rainfall is between 96% and 104% of the LPA. Anything less
than 90% of the LPA is considered a deficient monsoon.
However, a recent study,
conducted by Indian meteorologists, projects that about 50 years from now, the monsoon over the central Indian region is
expected to drastically reduce owing to a declining trend observed in the
number of Low Pressure Systems (LPS) that
usually bring rain to this area.
The region, according to the
study, will witness a 45% decline in the frequency of LPS activity, thereby
resulting in lesser rainfall in this heavily
rain-fed agrarian belt. This downward trend in rainfall is expected to be
realised during the decades spanning between 2065-2095, that the researchers
have defined as the end of the current century.
The collaborative study, by R S Ajayamohan
and a team of scientists from the Indian Institute of Tropical Meteorology
(IITM), IIT Delhi, New York University and University of California, which was
recently published in PNAS, also highlights a 10% increase in the instances of LPS forming over land, which will
eventually lead to extreme rainfall over the North Indian plains.
LPSes originate in the Bay of Bengal, and travel landwards in a
southeast-northwest direction crossing Odisha, Andhra Pradesh, Telangana,
Chhattisgarh, Jharkhand, Madhya Pradesh, Maharashtra and Uttar Pradesh. This
region is known as the core monsoon zone.
Speaking to The Indian Express,
Sabin T P, one of the authors and senior scientist from IITM, said, “One of the
main reasons for this decrease in rainfall, particularly during the monsoon,
could be the largescale decrease in the moist westerly winds travelling from
the Arabian Sea, called monsoon circulations, along India’s west coast onto the
mainland. In addition, these winds have been observed to have shifted
northwards from their normal track during their forward propagation.”
On the importance of studying the
core monsoon zone, Ravi Nanjundiah, director of IITM, said, “In order to have a
better understanding about the monsoon, this is a very crucial region as most
LPS pass by this region during the monsoon season, that is from June to
September. A new test-bed facility by the institution is being set up on the
outskirts of Bhopal, in order to study these key rain-bearing systems.”
According to R S Ajayamohan, global warming is getting more pronounced
with each passing year, when all previously known record temperatures have been
surpassed. Additionally, its effect even on the monsoon, especially over this
zone, is seen as inevitable.
He said, “With the rise in global temperature, the atmosphere would have a much
higher moisture holding capacity. But, at a certain juncture, this capacity
would collapse leading to extreme rainfall events, which are anyway found to be
increasing in recent years.”
Credit: Indian Express Explained
(http://indianexpress.com/article/explained/why-central-india-may-see-less-rainfall-over-the-next-50-years-5141618/)
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