Relative humidity of the air is measured by which of the following instruments?

The correct answer is C, the eye. The eye of a tropical cyclone is the roughly circular column of calm, descending air at its centre, usually a few tens of kilometres across, where the pressure is lowest, the winds are light and the sky is often nearly clear. Around it stands the eye wall, a ring of tall cumulonimbus clouds carrying the strongest winds and the heaviest rain, so the passage of a cyclone over a place gives violent weather, then an interval of calm, then violent weather again from the opposite direction. Option A is wrong because base is not a term used for any part of a cyclone. Option B is wrong because focal point belongs to optics and to earthquake studies, not to meteorology. Option D is wrong because trigger point is not a recognised term in the structure of a storm.

The correct answer is B, Tauktae. Tauktae formed in the Arabian Sea in May 2021, intensified into an extremely severe cyclonic storm, moved north along the Konkan coast and made landfall in Gujarat, which is why it is remembered as an Arabian Sea system of the western coast. Option A is wrong because Vardah struck the Tamil Nadu coast near Chennai in December 2016 and came from the Bay of Bengal. Option C is wrong because Titli hit Odisha and Andhra Pradesh in October 2018, again a Bay of Bengal storm of the eastern coast. Option D is wrong because Hudhud crossed the coast at Visakhapatnam in October 2014. Note the useful contrast: the Bay of Bengal produces far more cyclones than the Arabian Sea, so an Arabian Sea landfall such as Tauktae is the one examiners pick out.

The correct answer is B. The local names of the tropical cyclone are a standing favourite: baguio belongs to the Philippines, hurricane to the United States and the wider Atlantic and Caribbean region, typhoon to China and the north-western Pacific, and willy-willy to Australia. That gives A with 3, B with 4, C with 2 and D with 1, which is option B. Option A is wrong because it pairs typhoons with Australia and willy-willies with China, reversing the last two. Option C is wrong because it begins by sending baguio to China. Option D is wrong because it pairs hurricanes with Australia and willy-willies with the United States. Add two more names to the list while revising: the storm is simply called a cyclone in the Indian Ocean and taifu in Japan.

The correct answer is B, Julia. Julia was a storm of the Atlantic basin and never approached India, so it cannot belong to a list of Indian landfalls. Option A is wrong because Yaas crossed the Odisha coast near Balasore in May 2021, only days after Tauktae struck the opposite coast. Option C is wrong because Tauktae formed in the Arabian Sea in May 2021 and made landfall in Gujarat. Option D is wrong because Gulab crossed the north Andhra Pradesh coast in September 2021 and its remnant later re-formed in the Arabian Sea as Shaheen. The point of the question is that the names of the north Indian Ocean storms come from a panel of countries of the region, so a name from the Atlantic list, where the storms are named separately, is the odd one out.

The correct answer is B, relative humidity. Relative humidity compares the water vapour actually present in the air with the maximum amount the air could hold at that temperature, so it is a ratio and is stated as a percentage; air at a hundred per cent relative humidity is saturated. Option A is wrong because absolute humidity is the actual weight of vapour in a given volume of air and is stated in grams per cubic metre. Option C is wrong because specific humidity is the weight of vapour in a unit weight of air, stated in grams per kilogram, and it is preferred in weather work because it does not change as the air expands or contracts. Option D is wrong because the dew point is a temperature, stated in degrees. Note also that heating air lowers its relative humidity even when no vapour has been added or removed.