Source: NCERT Official Textbook
The spatial distribution of insolation is highest over subtropical deserts and decreases towards the poles. The chapter then details the mechanisms of atmospheric heating and cooling: conduction, convection, advection, and most importantly, terrestrial radiation—the long-wave radiation from the Earth that heats the atmosphere from below.
This leads to the concept of the Earth’s heat budget, a state of balance where 100 units of incoming solar energy are ultimately reflected or radiated back to space, preventing perpetual warming or cooling. The surplus heat in the tropics is redistributed towards the poles via atmospheric and oceanic circulations.
Finally, the chapter examines the factors controlling temperature distribution: latitude, altitude, distance from the sea, air masses, and ocean currents. It analyses global temperature patterns using isotherms, noting the pronounced effects of continentality and warm ocean currents like the Gulf Stream.
The phenomenon of temperature inversion, where temperature increases with height, is also explained, along with its effects like fog formation and frost protection in valleys.
When is the earth at its farthest point from the sun (aphelion)? (Pg. 1)
Why do slant sun rays (at higher latitudes) result in less net energy per unit area? (Pg. 2)
Over which areas is maximum insolation received? (Pg. 2)
What is the primary process by which the atmosphere is heated from below? (Pg. 2-3)
What is the term for the percentage of solar radiation reflected back by the Earth and its atmosphere? (Pg. 3)
Which of the following is NOT a factor controlling the temperature distribution of a place? (Pg. 4)
Why do places at higher altitudes generally have lower temperatures? (Pg. 4)
In January, why do isotherms bend northward over the North Atlantic Ocean? (Pg. 5)
What is a common consequence of a surface temperature inversion? (Pg. 7)
(Exercise) The sun is directly overhead at noon on 21st June at: (Pg. 7)
(Exercise) The atmosphere is mainly heated by the: (Pg. 7)
(Exercise) The main reason the earth experiences highest temperatures in the subtropics rather than at the equator is: (Pg. 8)
The energy received by the earth from the sun is termed ______. (Pg. 1) Page 67
The red colour of the rising/setting sun and blue sky are results of ______ of light. (Pg. 2) Page 68
The transfer of heat through direct contact between two bodies is called ______. (Pg. 2) Page 68
The process of vertical heating of the atmosphere through rising air currents is ______. (Pg. 2) Page 68
Out of 100 units of insolation, roughly ______ units are absorbed by the Earth’s surface. (Pg. 3) Page 69
The rate of decrease of temperature with increasing height is called the ______. (Pg. 4) Page 70
Lines joining places of equal temperature on a map are called ______. (Pg. 5) Page 71
The highest range of temperature (>60°C) is found over the ______ part of Eurasia. (Pg. 7) Page 73
In hilly areas, cold air flowing down slopes to collect in valleys is called air ______. (Pg. 7) Page 73
(Exercise) Pair the term ‘Albedo’ with its correct definition. (Pg. 8) Page 74
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