The diurnal temperature range is largest
Answer: C
Dry cloudless air neither traps outgoing radiation at night nor blocks incoming sunlight by day. Water vapour and cloud both damp the range considerably. Deserts show the greatest daily swings. Clear dry air neither traps nor blocks.
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Consider the following statements about the diurnal temperature range.
1. Cloud cover reduces the range at both ends.
2. Humidity reduces the range through the greenhouse effect of water vapour.
3. The range is largest over the ocean.
Answer: D
The first two are correct. The third is quite wrong, since the great heat capacity of water keeps the ocean surface temperature almost constant through the day. Cloud works at both ends of the day. Water has an enormous heat capacity.
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A temperature inversion is a layer in which temperature
Answer: A
Correct answer: increases with height
An inversion is a layer in which the normal decrease with height is inverted, so warm air lies above cold. Because the cold air below is denser, the layer is very stable and resists vertical motion - which is what makes inversions matter far beyond their thermal profile, as the next item shows.
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Assertion (A): Air pollution episodes are often associated with a temperature inversion.
Reason (R): The inversion is a stable layer that prevents pollutants from mixing upwards.
Answer: B
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives the mechanism. Under an inversion the air beneath is trapped: convection cannot lift pollutants through the warmer layer above, so emissions accumulate in a shallow depth instead of dispersing through the troposphere. The classic severe episodes - London in 1952, Los Angeles, the Po valley in winter - all occurred under persistent inversions.
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Match each type of inversion with how it forms.
List I
A. Radiation inversion
B. Subsidence inversion
C. Frontal inversion
D. Valley inversion
List II
1. warm air riding over colder air at a front
2. surface cooling on a clear calm night
3. cold dense air draining downhill at night
4. sinking air warming by compression aloft
Answer: C
Correct answer: A-2, B-4, C-1, D-3
Four routes to the same profile. A radiation inversion forms when the ground loses heat on a clear calm night and chills the air touching it. A subsidence inversion forms aloft where sinking air in a high-pressure system warms by compression. A frontal inversion occurs where warm air rides over colder air at a front. And a valley inversion forms when cold dense air drains downhill and pools in the bottom.
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All of the following increase the annual temperature range EXCEPT
Answer: D
Correct answer: a maritime windward coast
A windward coast has the ocean upwind, so its air arrives already moderated by water - that is precisely what reduces the annual range. The other three all widen it: distance from the ocean removes the moderating influence, high latitude increases the seasonal swing in insolation, and clear skies allow strong heating in summer and strong radiative loss in winter.
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Three of the following moderate temperature extremes. Which is the odd one out?
Answer: A
A dry interior does the opposite and produces the largest extremes of any climate type. The other three all damp the swings in one way or another. Dry interiors show the widest extremes. Water in any form damps the swing.
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A station at sea level has a mean of 25 degrees. Using the average lapse rate, what mean would you expect 2 kilometres above it?
Answer: B
Correct answer: 12 degrees
\[ 25 - (2 \times 6.5) = 25 - 13 = 12\ \mathrm{degrees}. \] The two-kilometre climb is what makes tropical highlands habitable: a station at 2,000 metres in the tropics has the mean temperature of a temperate lowland while keeping the small annual range of its latitude, which is why cities such as Nairobi, Bogota and Addis Ababa sit where they do.
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The urban heat island is the tendency for cities to be
Answer: C
Correct answer: warmer than the countryside at night
The heat island is strongest after dark and under calm clear conditions. Concrete and asphalt store the day’s heat and release it slowly, buildings restrict the sky the surface can radiate to, there is little vegetation to cool by evaporation, and heating, traffic and air conditioning add heat directly. The daytime difference is usually much smaller.
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Assertion (A): The urban heat island is strongest on calm clear nights.
Reason (R): Wind mixes the urban air with rural air and cloud reduces the radiative cooling that the city resists.
Answer: D
Both are true and the reason gives both mechanisms, and this dependence on weather is one reason the effect varies so much from night to night. Wind and cloud both weaken the island. Calm clear nights show it at its strongest.
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