Daily Static Quiz Prelims Practice 2027
Option (a) is correct — IMD declares Kerala onset when at least 60% of 14 designated stations report ≥2.5 mm rainfall on two consecutive days after May 10, the 925 hPa wind field shifts to westerly/southwesterly at 15–20 knots, and OLR falls below 200 W/m², indicating deep convection; option (a) best captures this multi-parameter approach. Option (b) is wrong — the rainfall threshold applies to 60% of 14 designated stations, not "any station in Kerala." Option (c) is wrong — ITCZ positioning and Bay of Bengal lows are contextual, not formal IMD onset criteria, and coastal Karnataka isn't part of the Kerala declaration. Option (d) is wrong — the single-station Thiruvananthapuram threshold and cloud cover percentage are fabricated, not actual IMD parameters.
- A positive IOD is characterised by warmer than normal sea surface temperatures in the western Indian Ocean and cooler than normal temperatures in the eastern Indian Ocean near Sumatra.
- A positive IOD is statistically associated with above-normal rainfall during the Indian summer monsoon season.
- A negative IOD reinforces the suppressing effect of El Niño on the Indian monsoon, and their co-occurrence typically produces severe drought conditions.
- The IOD index is measured as the difference in sea surface temperature anomaly between the western pole (50°E–70°E, 10°S–10°N) and the eastern pole (90°E–110°E, 10°S–0°N).
All four statements are correct. A positive IOD has warmer western and cooler eastern Indian Ocean SSTs, enhancing moisture flux toward India, and is statistically linked to above-normal monsoon rainfall — the strong 2019 IOD partly offset a weaker monsoon. A negative IOD reinforces El Niño's suppressive effect, with combined El Niño plus negative IOD years (like 1997) among India's severest droughts. The IOD index (Dipole Mode Index) is precisely the SST anomaly difference between the defined western pole (50°E–70°E, 10°S–10°N) and eastern pole (90°E–110°E, 10°S–0°N).
Option (c) is correct — a monsoon break occurs when the monsoon trough shifts northward to the Himalayan foothills, intensifying rainfall along that belt and northeastern India while central India, the Indo-Gangetic Plain, and the peninsula experience dry spells. Option (a) is wrong — a southward trough shift is associated with active spells, not breaks; the mechanism is reversed. Option (b) correctly identifies the northward shift but wrongly claims plains rainfall intensifies, contradicting the defining dry-plains feature of a break. Option (d) is wrong — western disturbances are winter-season Mediterranean phenomena unrelated to monsoon breaks, which are internal oscillations linked to the MJO and the trough's own variability.
- The northeast monsoon originates as dry continental winds blowing from the land over the Bay of Bengal, picking up moisture before depositing rainfall along the Coromandel Coast.
- Tamil Nadu receives the bulk of its annual rainfall during the northeast monsoon (October–December), unlike most other Indian states.
- The northeast monsoon is associated with the formation of tropical cyclones in the Bay of Bengal, which cause significant damage along India's eastern coast.
- Cherrapunji and Mawsynram receive their heaviest rainfall during the northeast monsoon due to orographic lifting by the Khasi Hills.
Statements 1, 2 and 3 are correct. The northeast monsoon begins as dry continental winds that cross the Bay of Bengal, gather moisture, and deposit rainfall along the Coromandel Coast — the reverse pathway of the southwest monsoon. Tamil Nadu is the key exception in India's monsoon geography, drawing roughly 48–60% of its annual rainfall from this October–December season. The post-monsoon Bay of Bengal, at peak warmth, is India's most active cyclone season on the eastern coast (e.g., Cyclone Ockhi 2017, Cyclone Gaja 2018). Statement 4 is incorrect — Cherrapunji and Mawsynram receive their extraordinary rainfall during the Southwest Monsoon, when Bay of Bengal moisture is funnelled into the Khasi Hills, not during the northeast monsoon.
Reason (R): The moisture-laden Arabian Sea winds rise sharply along the windward western slopes, cool adiabatically and precipitate heavily; the descending air on the leeward eastern side warms and dries, creating a pronounced rain shadow over the Deccan Plateau.
Both A and R are correct, and R explains A. Mahabaleshwar (western slopes, ~6,000 mm annually) contrasts sharply with Pune (~730 mm) just 100 km east, one of India's starkest orographic rainfall gradients. This is textbook relief rainfall: forced ascent on the windward side causes adiabatic cooling past the dew point, releasing heavy precipitation, while descent on the leeward side causes adiabatic warming (föhn effect), sharply lowering humidity — the exact physical mechanism producing the asymmetry described in A.
