Climate — Important Questions

1st June

Step 1: The southwest monsoon follows a fixed pattern of arrival across India. Step 2: It sets in over the Kerala coast by 1st June — this is considered the official onset of the southwest monsoon in India. Step 3: From Kerala, it reaches Mumbai and Kolkata by 10–13 June. Step 4: It spreads all over the subcontinent by 15th July. Step 5: 1st May is too early, 15th June is the time it reaches other parts, and 1st July is approximately when it reaches the northwestern parts.

Loo

Step 1: During summer, the northern plains of India experience extremely high temperatures. Step 2: Hot, dry, and oppressing winds blow during the daytime over the northern and northwestern India, especially between Punjab and Bihar. Step 3: These winds are called 'Loo'. They are most intense between Delhi and Patna. Step 4: Mango Showers are pre-monsoon showers in Kerala that help ripen mangoes. Step 5: Nor Westers (Kalbaisakhi) are thunderstorms in Bengal and Assam — not hot dry winds of the north.

25°N

Step 1: The ITCZ is the zone where northeast and southeast trade winds converge near the equator. Step 2: Its position shifts with the apparent movement of the sun — northward in summer and southward in winter. Step 3: In summer, as the sun moves towards the Tropic of Cancer, the ITCZ shifts northward to about 25°N over India and Pakistan. Step 4: This northward shift creates low pressure over northwestern India and attracts the southwest monsoon winds. Step 5: 0°, 10°N, and 15°N are positions of the ITCZ during other times or seasons — not during Indian summer.

Arabian Sea Current

Step 1: The southwest monsoon has two main branches — the Arabian Sea Current and the Bay of Bengal Current. Step 2: The Arabian Sea Current originates in the Arabian Sea and reaches the western coast of India. Step 3: One sub-current of the Arabian Sea Current strikes the Western Ghats and causes heavy rainfall (above 250 cm) on the western slopes and the West Coastal Plain. Step 4: After crossing the Western Ghats, it enters the rain-shadow area and causes little rainfall there. Step 5: The Bay of Bengal Current mainly affects northeastern India and the Ganga plains — not the Western Ghats d