Competitive Exams: Indian Geography Weather

Weather conditions

Cold Weather Season Southerly branch of the jet stream occupies its position south of the Himalayas, which is accompanied with the restoration of light northeast trade winds (monsoons) to the surface, withdrawal of the inter tropical convergence zone, formation of anti cyclonic cell over north western India and dry weather prevailing, over most of the areas in the country

Temperature conditions: General increase of temperature from North to South, Isotherms run almost parallel to the latitudes (in January the 21° C isotherm runs through the middle of the country connecting Tapti estuary to the Mahanadi delta) in the east. West India Punjab, Haryana West U. P and Northern Rajasthan Less than 15° C.

In South India the isotherm, tend to bend southward and run parallel to the coast. The western coast is warmer than the eastern one by about LT C. This season is characterized by the inflow of depression from the west and the North West. These low pressure systems originate in West Asia near the Mediterranean Sea and are known as Western Disturbances. Their average frequency is four to five depressions per month and highly intensified Between December and February (Rainfall due to these disturbances is highly helpful for RABI crops). Fine weather, clear skies, low humidity, absence of rainfall, low temperature and a large diurnal variation in it are the usual features of the winter season.

  • North East parts of India also get some rainfall during this season.

  • A low pressure area occupies the northern parts of the Bay of Bengal during October, which moves southward and get deflecting towards, the coromandal coast thereby producing rains on this coast. The presence of inter tropical convergence and the easterly depression are responsible for these rains. Hot and Dry Weather is characterized by low pressure system high temperature, unstable pressure and wind circulation.

  • The dust storms of Punjab and Haryana, the Loos of UP, the Norwesters (Kalbaisakhis) of W. Bengal and cyclonic depressions of the eastern coast produce a stormy and turbulent weather.

  • The rains caused by thunderstorm in Karnataka are called ‘Cherry Blossoms’ These are beneficial for coffee plantation. Elsewhere in South India they are known as ‘Mango Showers’

  • Dry and dusty westerly winds flow in the northern western parts of the country which make the outdoor life difficult are known as Loo. The Wet Season: The southern branch of the western jet is withdrawn from south of the Himalaya thereby leading to the formation of a dynamic depression over the surface thermal low. The ITC shifts northwards allowing equatorial westerlies to in the subcontinent.

  • Indian subcontinent receives bulk of its rainfall (around 80%) from the southwest

  • The Arabian Sea current causes rainfall all along the Western Coast, Western Ghats, Gujarat, Maharashtra, parts of M. P and Rajasthan.

  • While crossing the Sahyadris (Western Ghats), the monsoonal current produce heavy rainfall on the windward and scanty rainfall on the leeward side thereby producing a rain shadow area. The rainfall is also erratic on the leeward side, which results in frequent drought in Maharashtra and Karnataka

  • The Tamil Nadu coast goes dry in this season.

  • The Arabian Sea branch meets the Bay of Bengal branch over ChhotaNagpur Plateau producing copious rainfall.

  • Absence of moutain barrier in Kutch, parallel position of the Aravalli, effect of the hot and dry air results in failure of Arabian Sea branch to produce adequate rainfall. The Bay of Bengal branch, obstructed by the eastern hill is deflected westward towards the Ganga Plain. Entrapped in the valleys of Meghalaya, the current produces very heavy rainfall [Cherapunji (1087cm) and Mawsynram (1141 cm) ]

  • The weather is also affected by a number of cyclonic depressions entering the country through the Bay of Bengal and the Arabian Sea. About 20 to 25 such depressions develop during monsoon period.

  • With the exception of J & K and Parts of Tamil Nadu, most of the country receives heavy rainfall.

Season of Retreating Monsoon

  • South West begins to retreat from the second or third week of September.

  • Unlike the Sudden burst, the retreat is highly gradual.

  • The southerly branch of the jet stream returns to its winter position by October and this is accompanied by the restoration of light North East trade winds to the surface.

  • Cloudiness and moisture are low except in the southern parts of the Peninsula.

  • It is this retreating monsoon which brings rain to the Tamil Nadu coast as North East Monsoon.