By Maxwell Pereira
‘mon-soon’ this year is ‘mon-late’…
screamed a headline the other day, describing what’s foremost
on the minds of most people ‘midst this blistering season
of heat in Delhi and most other parts of north India around this
time. As the heat wave sweeps across the land with its mercy-less
broom, everyone is waiting in anticipation for the rains to come
and cool down the climes, to relieve all from the furnacy climate
that makes life a living hell, miserable and scorching.
escape the rigours of the blistering summer, a minimissal few
who can afford head to hill-stations or lands across the seas
or mountains. While those who cannot, just suffer and wilt away
even while hoping for the desert-ly loo bearing dusty winds to
change to moisture laden rain bearing ones, for relief and succour
to fauna, flora and the human stock alike.
actual fact, the much awaited ‘monsoon’ hardly touches
Delhi and surrounding parts of north India – unlike it does
most of south India or north-eastern India that experience its
real impact. For some of us who grew up in the South, monsoon
meant the rains and the rainy season, there being only three seasons
in a year – the summer, rainy and the winter, to contend
so, the very term ‘monsoon’ owes its origin, we are
told, to the Arabic mausin or mausem which means season (…or
the season of winds) - most often applied to the seasonal reversals
of the wind direction along the shores of the Indian Ocean, and
especially in the Arabian Sea, that blow from the southwest during
one half of the year and from the northeast during the other.
the legendary Greek sailor Hippalus was credited to have been
the first to use the monsoon to speed across the Indian Ocean,
and so the ancient name for the monsoon was also called Hippalus.
But perhaps he was simply the first Greek to master the monsoon,
since Yemeni sailors were known to be trading with India long
before his time.
monsoon seasonal change is characterized by a variety of physical
mechanisms which produce strong seasonal winds, a wet summer and
a dry winter. All monsoons share three basic physical mechanisms:
differential heating between the land and oceans; Coriolis forces
due to the rotation of the Earth; and the role of water which
stores and releases energy as it changes from liquid to vapour
and back. The combined effect of these three mechanisms produces
the monsoon's characteristic reversals of high winds and precipitation.
have described two key ingredients needed to make a monsoon –
a hot land mass and a cooler ocean. Monsoons occur when land heats
up and cools down quicker than water. In summer, the land reaches
a higher temperature than the ocean, making the air over it to
rise – thereby causing an area of low pressure to make winds
from areas of high pressure to blow over areas of low pressure.
The constant moisture laden wind thus blowing from the ocean causes
rainfall when it rises up and gets cooled. Conversely, in winter
since the land cools down quickly, the ocean is warmer. Air then
rises, causing a low over the ocean. The wind then blows back
out over the ocean. Since the temperature difference between the
ocean and land is less than in summer, this wind is not as constant.
this basic principle, the land mass of the Indian sub-continent
absorbs heat faster from the sun than the surrounding Indian Ocean
does. Consequently as the air rises, a cooler, moistier, and heavier
air from over the ocean replaces it. This damp, cool layer over
India is estimated to be up to three miles thick. As the cool
air arrives, the winds also shift. During dry season, the winds
blow offshore, from land to sea. Then, as the monsoon begins,
the winds blow onshore, from sea to land. In the case of the Indian
Ocean Monsoon the first and third mechanisms produce more intense
effects than in any other place in the world.
do occur in other parts of the world too, like in Australia and
in the southwest portions of the United States. As monsoons have
gradually been understood better, the term has now been broadened
to include almost all phenomena associated with the annual weather
cycle within the tropical and subtropical continents of Asia,
Australia and Africa, and the adjacent seas, and to indicate climatic
systems anywhere in which the moisture increases dramatically
in the warm season. The Asian monsoon, which affects the Indian
subcontinent and southeast part of the Asia, is the most noted
of the monsoons.
more popular south-western summer monsoons occur from June to
September. Intense low pressure developed over central Asia, makes
the jet stream of south-eastern winds to blow over this area,
passing over south-east Asia, which experiences large amounts
of rainfall in this period. Meanwhile, the south-west monsoon
is drawn towards the Himalayas, creating winds blowing rain clouds
towards India, which receive up to 400 or more inches of rain
in some areas.
north-eastern winter monsoons take place from December to early
March – when temperatures over central Asia are lower, creating
a zone of high pressure there. The resultant jet stream directing
north-easterly winds to blow across south Asia create dry air
streams that produce clear skies over India from the months of
November to May. Meanwhile, a low pressure system develops over
northern Australia and winds are directed towards Australia. During
the NE winter monsoon, apart from north-eastern India, south-east
Asia and Australia too receive large amounts of rainfall.
words: Copy Right © Maxwell Pereira: 3725 Sec-23, Gurgaon-122002.
You can interact with the author at http://
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