Please enable JavaScript.
Coggle requires JavaScript to display documents.
Ch 4: Climate (Elements of weather (Temperature, Pressure, Wind direction…
Ch 4: Climate
-
Factors
a. Location and Relief
Latitude: north of TOC => sub-tropical and temperate zone, south of TOC => tropical zone
Himalaya: protect from the cold northern winds, trap the monsoon winds
Land/Water Distribution: differential heating of land and sea => different air pressure zones in different seasons => reversal in the direction of monsoon winds
-
Altitude: temperature decreases with height.due to thin air, places in the mountains are cooler that on the plains.
-
b. Air Pressure and Wind
-
Upper air circulation caused by factors controlling global weather and the inflow of different air masses and jet streams.
Inflow of western disturbances during winter season and tropical depressions during SW monsoon period, creating favourable to rain condition
Mechanism of weather
Winter season
Surface pressure and winds (lower level of atmosphere) - high pressure centre to the north of Himalayas during winter => dry continental air mass come in contact with trade winds over NW India.
Jet Stream and Upper Air Circulation - (lower troposphere) - independent from above - north of Himalayas parallel to the Tibetan Highlands => Bifurcated into north of Tibetan highlands and south of Himalayas at 25 deg N.
Western Cyclonic Disturbance and Tropical Cyclones - western disturbances originates over Mediterranean Sea and brought to India by jet stream - increase in the prevailing night temperature : indicator. Tropical cyclones originate over BoB and IO => TN, AP and Odisha coast.
Summer Season
Surface pressure and winds - complete reversal of wind circulation both at lower and upper levels, ITCZ shifts northwards (monsoon trough), SW monsoon with moist air
-
Easterly Jet Stream and Tropical Cyclones - easterly jet stream steers the tropical depressions into India -
Features of Monsoon
Onset
SW monsoon => continuation of SE trades deflected towards the Indian subcontinent after crossing the Equator, easterly jet stream => responsible for the burst of monsoon in India
-
Break in Monsoon
-
reasons
In Northern India, if rain-bearing storms are not frequent along ITCZ
-
-
ENSO
Phases
El-Nino (Child Christ)
-
Mechanism
-
Trade winds are weak => no push for warm current which slowly moves towards central and eastern side of Pacific
-
Ocean temperature near Australia is cold hence no rain (drought) while Peruvian coast receives heavy rainfall(flood)
-
-
-
-
-
Rainfall
Winter
In NW India, due to western disturbances => Punjab, Haryana, Delhi, Western UP. => beneficial for Rabi crops
-
Central India and northern of Peninsula, Arunachal Pradesh and Assam also gets rainfall
torrential rainfall over TN coast, southern AP, SE Karnataka and SE Kerala
-
SW Monsoon
Arabian Sea Branch
a. Obstructed by Western Ghats => heavy rain falls to windward side of Sahyadris and Western Coastal Plain. => little rainfall to the east of Western Ghats (rain shadow)
b. coast north of Mumbai => Moving along Narmada and Tapi river valleys => rainfall in central India => mingle with the Bay of Bengal branch
c. Saurashtra Peninsula and Kachchh=> passes over Rajasthan and along Aravalis => joing BoB branch in Punjab and Haryana
Bay of Bengal Branch
-
-
b. moves up the Brahmaputra valley in the north and NE. Mawsynram located on the crest of Khasi => highest rainfall
-
-
Retreat
marked by clear skies and rise in temperature, land is still moist => high temperature and humidity "October Heat"
