Monsoon

🎯 How This Word Works in UPSC Writing

A seasonal reversal of wind direction bringing marked wet and dry seasons. Two explanations are examined side by side. The older thermal concept treats the monsoon as a giant land and sea breeze driven by the differential heating of the subcontinent and the surrounding ocean. The modern dynamic explanation adds the seasonal migration of the Inter-Tropical Convergence Zone, the Tibetan Plateau acting as an elevated heat source, the withdrawal of the subtropical westerly jet from south of the Himalayas and the appearance of the tropical easterly jet, and the Somali jet feeding moisture across the Arabian Sea. Year to year variation is governed largely by the El Nino Southern Oscillation, which typically suppresses rainfall, and by the Indian Ocean Dipole, whose positive phase can offset it. IMD calls a season normal at 96 to 104 per cent of the Long Period Average, revised to 87 cm on 1971-2020 data from the earlier 88 cm.