Geography Quiz: Insolation, Heat Budget and Temperature

The word is a contraction of incoming solar radiation, and it means the short-wave energy from the sun that reaches the earth, measured in India by the India Meteorological Department in units of energy per unit area per unit time.

Of every hundred units of insolation arriving at the top of the atmosphere, about thirty-five are turned back before they can heat the ground, twenty-seven from the tops of clouds, two from snow and ice covered surfaces and the remainder scattered by the atmosphere; this reflected share is the albedo…

This is the normal lapse rate, the average fall of temperature with height in the troposphere, and it is the reason a hill station is cool while the plain at the same latitude is hot.

The orbit of the earth is an ellipse, so the distance from the sun changes through the year; the earth is closest at perihelion about the third of January and farthest at aphelion about the fourth of July, which is option D and the usual distractor in this question.

Advection is the sideways or horizontal transfer of heat by moving air, and in the middle latitudes most of the day to day variation in temperature comes from it; the hot loo that blows over north India in summer and the cold wave that follows a north-westerly wind in winter…

An inversion needs the ground to lose heat quickly and the air above to stay undisturbed: a long night gives time for terrestrial radiation to escape, a clear sky lets it escape, dry air absorbs little of it, and calm conditions keep the cold air lying in place, so the…

Insolation measured at the top of the atmosphere is greatest over the equator, but what reaches the ground depends on cloud as well as on the angle of the rays, and the subtropical deserts lie under the descending limb of the Hadley circulation, where the sky is clear for most…

An isotherm joins places of equal temperature, and on a world map the isotherms run roughly east to west, parallel to the latitudes, bending sharply where a continent meets an ocean because land and water heat at different rates.

In convection the heated matter itself moves and carries its energy with it: air near a warm surface expands, becomes lighter, rises as a current and is replaced by cooler air sinking in its place, and the same happens in a pan of boiling water.

High clouds such as cirrus are thin and made of ice crystals; they let most of the sunlight pass through but absorb the outgoing infrared radiation from the surface, so their net effect is to warm.

Evaporation is the escape of molecules from a liquid surface into the air, and it slows as the air above fills with vapour; when the humidity falls the air can hold more vapour, so the rate of evaporation rises.