Page 128 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

92 part I The Energy–atmosphere System
Earth’s biosphere pulses with flows of solar energy concludes with a look at the energy environment in our
that cascade through the atmosphere and sustain
our lives. Earth’s shifting seasonal rhythms, de- scribed in Chapter 2, are driven by the concentrations of solar energy on Earth’s surface, which vary with latitude throughout the year. Although solar energy sustains life, it can also be harmful without the protection of Earth’s atmosphere, as we saw in Chapter 3. Solar energy is the engine for functioning systems on Earth—it drives wind and ocean currents and heats Earth’s surface, driving moisture into the atmosphere where it forms clouds and precipitation. These energy and moisture exchanges between Earth’s surface and its atmosphere are essential elements of weather and climate, discussed in later chapters.
Photographs of Earth taken from space reveal some of the effects of solar energy (see the NASA Blue Mar- ble Earth image in Figure 1.30, and the images on the inside front cover). Visible on these images are clouds above the Atlantic Ocean off the coast of Florida and over the Amazon rainforest, swirling weather pat- terns above the Pacific Ocean, and clear skies above the southwestern United States. These patterns result from regional differences in solar energy receipts and the processes driven by insolation on Earth.
In this chapter: We follow solar energy through the troposphere to Earth’s surface, looking at processes that affect insolation pathways. We discuss the balance be- tween solar radiation inputs and outputs from Earth—the energy balance in the atmosphere—and apply the “green- house” concept to Earth. We also examine surface energy and daily radiation patterns, analyzing the transfer of net radiation that maintains Earth’s energy balance. Focus Study 4.1 discusses applications for solar energy, a re- newable energy resource of great potential. The chapter
cities, where the air shimmers as summer heat radiates skyward over traffic and pavement.
Energy-Balance Essentials
In Chapter 2, we introduced the concept of Earth’s energy budget, the overall balance between shortwave solar ra- diation to Earth and shortwave and longwave radiation to space (please review Figure 2.7). A budget in terms of energy is a balance sheet of energy income and expendi- ture. For Earth, energy income is insolation, and energy expenditure is radiation to space, with an overall balance maintained between the two.
Transmission refers to the uninterrupted passage of shortwave and longwave energy through either the atmosphere or water. Our Earth–atmosphere energy budget comprises shortwave radiation inputs (ultravio- let light, visible light, and near-infrared wavelengths) and longwave radiation outputs (thermal infrared wavelengths) that pass through the atmosphere by transmission. Since solar energy is unevenly distrib- uted by latitude and fluctuates seasonally, the energy budget is not the same at every location on Earth’s sur- face, even though the overall energy system remains in steady-state equilibrium (see a simplified diagram in Figure 4.1 and discussion ahead; the more detailed en- ergy balance is in Geosystems in Action, Figure GIA 4, on pages 100 and 101).
Energy and Heat
For the purpose of studying Earth’s energy budget, energy can be defined as the capacity to do work, or move matter. (Matter is mass that assumes a physical
◀Figure 4.1 Simplified view of the Earth–atmosphere energy system. Energy gained and lost by Earth’s sur- face and atmosphere includes incoming and reflected shortwave radiation, energy absorbed at Earth’s surface, and outgoing longwave radia- tion. Refer back to this diagram as you read about energy pathways and principles in the atmosphere. a more complete illustration of the Earth– atmosphere energy balance
Reflection to space
Sun
Shortwave radiation
Energy gained and lost by the atmosphere
Direct radiation
Energy gained and lost by Earth’s surface
To space
Longwave radiation
is in Figure Gia 4.
Diffuse radiation
Animation
Global Warming, Climate Change
Animation
Earth–Atmosphere Energy Balance