Mechanism of Weather

-

Winter Season

Surface Pressure and Winds
  • Influenced by the distribution of pressure in Central and Western Asia. (Western Disturbance).
  • High pressure in north of Himalayas, rise to the flow of air at the low level from the north towards the Indian subcontinent.
  • Contact with trade winds over northwestern India.
  • Position of this contact zone is not stable. May shift its position as far east as the middle Ganga valley.
  • Result, whole of the northwestern and northern India up to the middle Ganga valley comes under the influence of dry northwestern winds.
Jet Stream and Upper Air Circulation
  • About 3 km above the surface of the earth, a different pattern of air circulation is observed.
  • Variations in the atmospheric pressure closer to the surface of the earth have no role to play in the making of upper air circulation
  • All of Western and Central Asia remains under the influence of westerly winds along altitude of 9-13 km from west to east.
  • Winds blow across, latitude north of the Himalayas roughly parallel to the Tibetan highlands – Jet Streams.
  • Tibetan highlands act as a barrier, jet stream bifurcated. One of its branches blows to the north of the Tibetan highlands, while the southern branch blows in an eastward direction, south of the Himalayas (Influence of winter season).
Western Cyclonic Disturbance and Tropical Cyclones

  • Jet streams blow south of the Himalayas, all through the year except in summer. western cyclonic disturbances experienced in the north and north-western parts of the country originate over the Mediterranean Sea bought India by the westerly jet stream. Influence the weather of the north and north-western regions of India.
  • Tropical cyclones originate over the Bay of Bengal and the Indian ocean. Hit the Tamil Nadu, Andhra Pradesh and Odisha coast.
  • Part of the easterly flow, disturbances affect the coastal regions of the country.
Summer Season
Surface Pressure and Winds
  • Middle of July, low pressure belt nearer the surface (ITCZ), shifts Northwards, roughly parallel to the Himalayas between 20° N and 25° N.
  • Westerly jet stream withdraws.
  • ITCZ being a zone of low pressure, attracts inflow of winds from different directions.
  • maritime tropical airmass (mT) from the southern hemisphere, after crossing the equator, rushes to the low pressure area in the general southwesterly direction.
Jet Streams and Upper Air Circulation
  • Easterly jet stream flows over the southern part of the Peninsula in June.
  • Easterlies normally do not extend to the north of 30°N latitude in the upper atmosphere.
Easterly Jet Stream and Tropical Cyclones
  • Steers the tropical depressions into India.
  • Determining the rainfall pattern during the southwest monsoon period.
  • Air moves, high-pressure area over the southern Indian Ocean, in a south-easterly direction, crosses the equator, and turns right towards the low-pressure areas over the Indian subcontinent. Southwest Monsoon winds. 
Jet stream:Westerly winds in the troposphere. Most constant are the mid-latitude and the sub-tropical jet stream.
ITCZ: located at the equator where trade winds converge. In July, 20°N-25°N latitudes (over the Gangetic plain) – Monsoon trough.
Southwest monsoon - Trade winds of the southern hemisphere cross the equator between 40° and 60°E longitudes and start blowing from southwest to northeast due to the Coriolis force.
Northeast monsoon - ITCZ moves southward, and so the reversal of winds from northeast to south and southwest, takes place.
Month of January
  • Subtropical westerly jet stream moves north of the Himalayas. Tropical easterly jet Stream blows over peninsular India
Month of June


Comments

Post a Comment

Popular posts from this blog

Indian Painting - Pre History

-
Image
    History and Evolution of Painting in India - An Overview India has a long tradition of artistic excellence and painting is one of the major mediums that has been used to express it. There is several evidence suggesting that painting flourished in India since ancient times. Archaeologists have found wall paintings in parts of India, which suggest that even the early historic man in India was engaged in activities of art and leisure The history of painting can be traced through the ancient and medieval period where the books were illustrated with paintings Then came the miniature style that dominated the Mughal and Rajput courts. With the coming of the Europeans, the art of painting and engraving took a western turn. Modern painters experimented with styles, colours and designs. Many Indian painters have gained worldwide recognition and are winning prizes and accolades for their vision. Principles of Painting The history of paintings can be known from primitive rock paintings of Bhim
Read more

Classification of Indian Paintings

-
Image
    Classification of Indian Paintings Indian Paintings have been broadly classified into two. Mural Paintings Miniature Paintings Mural Paintings The work on the walls or a solid structure are referred to as Murals. These have existed in India since ancient times and can be dated between 10th century BC and 10th century AD. The evidence of such paintings can be found at several locations in India. The beauty and the exquisiteness of mural paintings can be seen in places like Ajanta, Armamalai Cave, Ravan Chhaya Rock Shelter, Bagh Caves, Sittanavasal Caves and Kailash Temple in Ellora. Most of the mural paintings are either in natural caves or in rock cut chambers. The paintings follow a theme, the most common being Hindu, Buddhist and Jain. Mural paintings were also made to adorn any mundane premise. For e.g. Ancient theatre room in Jogimara Caves. Ajanta Cave Paintings One of the oldest surviving murals of Indian sub-continent, Ajanta caves were carved between 2nd century BC to 5th c
Read more

Folk Paintings

-
    Madhubani Paintings Traditionally done by the women of villages around Madhubani town (Bihar). It is also called Mithila Paintings. The paintings have a common theme and are usually drawn from religious motifs of the Hindus, including Krishna, Rama, Durga, Lakshmi and Shiva. The paintings are also made depicting auspicious occasions like birth, marriage and festivals. Flowers, trees, animals, etc. are used to fill any gaps in the painting. Traditionally, these were painted on walls using rice paste and vegetable colours on a base of cow dung and mud. With time, the base changed to handmade paper, clothes and canvas. Since there was no shading, the paintings are two-dimensional. Some of the common features of these paintings include double line border, bold use of colours, ornate floral patterns and exaggerated facial features. Since the art has remained confined to a specific geographical area, it has been given GI (geographical indication) status. Pattachitra Painting A traditiona
Read more