Chapter 3: SEASONS
- Seasons in India are
of four broad categories:
[ hot weather season] March to May
[ cold weather season] December to February
[ southwest monsoon season ] June to September
[ season of retreating monsoon] October – November
is the day to day or hour to hour condition of the
atmosphere. The average weather conditions of a place
for a longer period are known as climate. Climate of a place is dependent on its distance from the
sea, altitude, location and relief.
Weather and Conditions
The northern part of
India falls in the sub tropical and temperate zone
and the southern part lies in the tropical zone. The
southern region has smaller annual and diurnal temperature
range but the northern region has higher range.
People living on the
coast have an equable temperature throughout the year due
to moderation by sea but people living in the
interiors experience extreme weather.
In places that are
colder, the air becomes heavy. The cold heavy air sinks
and creates a high pressure. High pressure area is
associated with a clear sunny sky.
of the sun to the southern hemisphere. The northern region
becomes colder and high pressure conditions develop on the
north of the Himalayas.
flows from this region to the Indian subcontinent south of
winds blew from central India to the Indian subcontinent
as dry air mass. They also come in contact with the
northwestern trade winds.
upper level of troposphere 9-13 km from the surface the
jet stream blows from west to east in the area north of
the Himalayas, at the Tibetan plateau the jet stream gets
bifurcated. The northern arm blows eastward parallel to
the Tibetan plateau and the southern arm goes to the south
of the Himalayas.
arm is responsible for Indian winters.
Fig 1: Indian winter
India is divided into five types:
2: Vegetation map of India
occur in areas with heavy rainfall. They are so dense
that sunlight doesn’t reach the ground. Many species of
trees are found here that shed their leaves at different
points of the year. As a result they always appear green
and hence are called evergreen. E.g. Mahogany, ebony,
Tropical forest is
well stratified. Layers closer to the ground are covered
with shrubs and creepers, followed by short structured
trees and tall structured trees.
these trees are found in a large area in India. The shed
their leaves at a particular time of the year. E.g. Sal,
Teak, Neem, Peepal and Shisham.
they are found on the dry land where precipitation is
scanty. Hence their leaves are modified into spines.
at height of 1500-2500m trees are of conical shape.
These are coniferous trees which are Chir, Pine and
This is of two types
southern Montane and northern montane forests.
these can survive salty water. India has 7% of the
mangroves plantation of the world. 0.14% of its area has
mangroves. Sunderban mangroves are the only ones in the
world where tiger population is found. Mangroves act as
a barrier to landward winds during cyclones and protect
the coastal regions.
Mangroves in the
eastern region of India are more luxuriant and diverse
due to the presence of nutrient rich deltas of the
The east and
northeast margins of continents are covered by temperate
evergreen and temperate deciduous trees. The west and
southwest margins of continents are covered with
Fig 3: Altitude wise vegetation
In Himachal Pradesh
and Arunachal Pradesh, Himalayan yew trees are found that
are used to obtain Taxol
– a chemical that cures cancers. Quinine – to
cure malaria is from cinchona tree, drug for leukemia from
vinca rosea. Aspirin – tropical willow tree.
mountainous regions, the decreasing temperature with
increasing altitude leads to corresponding change in the
natural vegetation. In this ranges all types of vegetation
occur from tropical to tundra. Wet temperate forests are
seen between 1000 – 2000 m. between 1500 – 3000 m
coniferous forests of temperate types are seen. Above
3600m alpine grasslands are seen. Himalayan ranges are an
example of this.
Tropical regions occupy one fourth of the total area of
the world but have 75% of the total world population.
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