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21/10/2010 The Global Heat Budget
reflected by clouds and dust, water vapour and other gases in the atmosphere Solar Insolation 100% 26% 19% absorbed by clouds and dust, water vapour and other gases in the atmosphere 55% reflected by surface 4% absorbed by surface 51%
Solar Insolation 100% solar insolation 26% reflected by atmosphere TOTAL ALBEDO = 26 + 4 = 30% 19% absorbed by atmosphere ALBEDO = REFLECTIVENESS 55% reaches surface TOTAL ABSORPTION = 19 + 51 = 70% 4% reflected by surface 51% absorbed by surface
Tasks: • Copy figure 2.2 into your jotter. • Answer all of question 3 on page 32
Energy Receipt and Latitude Need to be able to: • Describe variations in the amount of solar energy reaching the earth’s surface by latitude. • Explain which areas of the world (by latitude) receive more solar energy and the reasons why.
Exam Question - 2002 With the aid of an annotated diagram of the earth, describe and explain the latitudinal variation of the Earth’s energy balance? Use Figure 2.3 on page 7 to help What is this question asking? • DESCRIBE the variation in solar energy at different latitudes – notably the tropics and polar regions • EXPLAIN why this variation occurs – i.e. why does what you are saying to the first part of the question actually happen
Energy Receipt and Latitude Tasks: • Make a neat copy of diagram 2.4 and label it. • Study figure 2.3 describe the areas of energy surplus and deficit. • Using page 6 give 3 reasons why there is a net gain of energy in the low tropics. • Find 3 reasons why the poles are an area of energy deficit.
ENERGY SURPLUS and DEFICIT • The Earth's atmosphere is put into motion because of the differential heating of the Earth’s surface by solar insolation. • The Poles receive less heat than the Tropics because: • Insolation has to pass through more of the Earth’s atmosphere • The angle of incidence of insolation • Higher levels of surface albedo.
3 2 1 IT IS VERY IMPORTANT TO PRACTICE / LEARN A VERSION OF THIS DIAGRAM Insolation has to pass through more of the Earth’s atmosphere 1 The angle of incidence of insolation - energy is spread out over a larger area because the sun’s rays strike the surface at a lower angle. 2 3 Higher levels of surface albedo - the ice-cap reflects more solar insolation