Geography
Insolation
Insolation refers to the amount of solar radiation received on a given surface area within a specific time period. It is influenced by factors such as the angle of the sun, duration of daylight, and atmospheric conditions. Insolation plays a crucial role in shaping climate patterns, driving processes like evaporation, and influencing temperature variations on Earth's surface.
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10 Key excerpts on "Insolation"
eBook - PDF- Alan H. Strahler(Author)
- 2013(Publication Date)
- Wiley(Publisher)
A portion of the intercepted radiation is reflected back to space, while the remainder is absorbed. The absorbed radiation is then ultimately emitted as longwave radiation to outer space. Insolation refers to the flow rate of incoming solar radiation. It is high when the Sun is high in the sky. 64 Chapter 2 The Earth’s Global Energy Balance the Sun is directly overhead, and it decreases when the Sun is low in the sky, since the same amount of solar energy is spread out over a greater area of ground sur- face (Figure 2.7). The Sun’s Noon Angle and the Length of Day Imagine yourself, through this animation, watching the Earth from a point far out in space, where it is easy to see how both the Sun ’s angle at noon and the length of day vary with the seasons and latitude for any point on Earth. DAILY Insolation THROUGH THE YEAR Daily Insolation at a location is the average Insolation rate taken over a 24-hour day. Daily Insolation depends on two factors: (1) the angles at which the Sun’s rays strike the surface during that day, and (2) how long the location is exposed to the rays. In Chapter 1 we saw that both of these factors are controlled by lati- tude and the time of year. At midlatitude locations in summer, for example, days are long and the Sun rises to a position high in the sky, heating the surface more intensely. 2.7 Solar intensity and Sun angle The intensity of the solar beam depends on the angle between the beam and the surface. 1 unit of surface area One unit of light is concentrated over one unit of surface area. 90° 1.4 units of surface area One unit of light is dispersed over 1.4 units of surface area. 45° 2 units of surface area One unit of light is dispersed over 2 units of surface area. 30° VERTICAL RAYS Sunlight, represented by the flashlight, is most intense when the beam is vertical. RAYS AT 45° ANGLE When the beam strikes the surface at an angle of 45°, it covers a larger surface, and so is less intense.
eBook - PDF- Timothy Foresman, Alan H. Strahler(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
90° 1 unit of surface area One unit of light is concentrated over one unit of surface area. T he amount of solar radiation that reaches spe- cific locations on the Earth changes over the course of a day, as well as over the course of a year, and it varies by latitude. These differ- ences have a profound impact on regional climates around the globe. Daily Insolation Incoming solar radiation is known as Insolation. It is measured in units of watts per square meter (W/m 2 ). At any given location, the average Insolation over a 24-hour day depends on two factors: (1) the angle of sunlight and (2) day length. Insolation is measured at the top of the atmosphere, so it is unaffected by clouds and weather. Angle of sunlight You saw in Chapter 1 that the angle of sunlight changes over the course of a day as the Earth rotates on its axis. Near noon, the Sun at its zenith is high above the horizon, whereas early in the morning and late in the evening, the Sun is low in the sky, just above the horizon. Insolation is greatest when the Sun is directly over- head, and it decreases when the Sun is low in the sky, be- cause the same amount of solar energy is spread out over a greater area of ground surface (Figure 2.4). Because the surface of the Earth is curved, however, the noon Sun is directly overhead at only one point on the globe at any given moment. This point is called the sub- solar point, and it receives the Sun’s strongest rays. We call the latitude of the subsolar point the Sun’s declina- tion. We’ll say more later about how the Sun’s declination travels between the tropics of Cancer and Capricorn over the course of a year. 42 CHAPTER 2 The Earth’s Global Energy Balance Day length The second factor that determines daily inso- lation is the amount of time that a given location is exposed to the Sun’s rays. The Sun’s rays always divide the Earth into two hemispheres—one that is bathed in light and one that is shrouded in darkness.
eBook - PDF- James Petersen, Dorothy Sack, Robert Gabler, , James Petersen, James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
This period lasts for 6 months at the North Pole but is as short as one day at locations directly on the Arctic Circle. The equinoxes are the days when sunrise and sunset occur at the North and South Poles. Similarly, there is a south tropical zone, a south midlatitude zone, and a south polar zone, or Antarctic zone, all separated by the Tropic of Capricorn and the Antarctic Circle in the Southern Hemisphere. These areas receive their Insolation at opposite times of the year from the northern zones. Despite various Insolation patterns received in these lati- tudinal zones, we can make some generalizations. For exam- ple, annual Insolation tends to decrease from lower latitudes to higher latitudes (Lambert’s law together with Beer’s law). The closer a place is to the poles, the greater its seasonal variation in Insolation. Factors such as elevation and humid- ity also affect the solar radiation received at a location, even on cloudless days. Although latitude remains an important factor, global patterns of annual Insolation do not follow lati- tudinal zones exactly. Annual variations in Insolation world- wide are shown in ● Figure 3.26. Here you can see the sunniest and least sunny places in terms of average annual receipt of solar energy at ground level, and you can see that factors other than latitude also affect Insolation. This United Nations map uses NASA satellite data to illustrate the geo- graphic distribution of the potential for using solar power as an energy resource. The amount of Insolation received by the Earth system is important in understanding atmospheric and oceanic dynamics and the geographic distributions of climate, soils, and vegeta- tion. Climatic elements—such as temperature, precipitation, and wind—are controlled in part by the solar energy a location receives. People depend on certain levels of solar radiation for physical comfort, and plant life is especially sensitive to the availability and seasonality of sunlight.
eBook - PDF- Alan F. Arbogast(Author)
- 2017(Publication Date)
- Wiley(Publisher)
As you will see in later chapters, convection is a very important mechanism of heat transfer on Earth and is associated with atmospheric circulation and precipitation. Flow of Solar Radiation in the Atmosphere With the mechanisms of heat transfer in mind, it is time to explore the various ways that solar radiation interacts with Earth. As you work your way through this discussion, refer to Figure 4.16, which illustrates the flow of solar radiation on the planet. Of all the incoming radiation that reaches Earth, about 25% flows uninterrupted to the surface as direct radiation. However, this amount can vary greatly depending on local geo- graphic variables such as cloud cover or density of atmospheric dust. Figure 4.17 shows, for example, the impact that cloud cover can have on direct solar radiation. The remaining 75% of incoming Insolation is either absorbed or otherwise redirected in the atmosphere (see Figure 4.16). Absorption takes place when variable gases and particulates in the atmosphere interrupt the flow of solar radia- tion by absorbing specific wavelengths. For example, almost all UV wavelengths (those less than 0.3 μm or micrometer in length) are absorbed by oxygen and ozone. Similarly, radiation at the 1.3 μm and 1.9 μm wavelengths is absorbed very strongly by water vapor and CO 2 . Overall, approximately 24% of incoming solar radiation is absorbed, with 18% absorbed by atmospheric water vapor and dust, 3% by ozone, and 3% by clouds. Remember, this absorption of solar radiation is important because it helps to moderate temperature in the atmosphere. Insolation Amount of solar radiation measured in watts per square meter (W/m 2 ) that strikes a surface perpendicular to the Sun’s incoming rays. Radiation Energy that is transmitted in the form of rays or waves. Conduction The transfer of heat energy from one substance to another by direct physical contact.
eBook - PDFMeteorology and Energy Security
Simulations, Projections, and Management
- Paul S. Samuel(Author)
- 2016(Publication Date)
- Apple Academic Press(Publisher)
With an increased stake in the invest-ment and return, site selection and assessments of long-term sustainability for solar power plants become increasingly important. One of the factors that affect the long-term planning for solar energy is the local climatol-ogy. Long hours of sunshine at a location are essential for a viable solar power plant. The available solar energy at a given site is quantified by the downward solar (shortwave) radiation at the surface. At a given latitude and day of the year, this quantity is affected by atmospheric water vapor Trends in Downward Solar Radiation at the Surface over North America from Climate Model Projec-tions and Implications for Solar Energy. © Saenz GA and Huang H-P. Advances in Meteorology 2015 http://dx.doi.org/10.1155/2015/483679. Licensed under Creative Commons Attribution 3.0 Unported License, http://creativecommons.org/licenses/by/3.0/. 146 Meteorology and Energy Security and trace gases, the amount of aerosols in the atmosphere, and, most impor-tantly, cloud cover (e.g., Li et al. [1]). Considering those factors, climatolog-ical maps of downward solar radiation have been widely produced for solar energy applications (e.g., National Renewable Energy Laboratory, http:// www.nrel.gov/gis/solar.html, Maxwell et al. [2], and George and Maxwell [3]). Since climate is constantly changing due to anthropogenic and natural processes, the estimates of solar power potential based on present-day cli-matology are not guaranteed to be true in the future. In this study, we will analyze the projection of the changes in the downward solar radiation in the 21st century over North America using a set of climate model simulations driven by anthropogenic greenhouse-gas (GHG) forcing from the Climate Model Intercomparison Project—Phase 3 (CMIP3) archive (Meehl et al. [4]). The global climate models have relatively coarse horizontal resolutions but are capable of producing the first-order features of atmospheric general circulation.
eBook - PDF- Bruce Anderson, Alan H. Strahler(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
High, thin clouds absorb upwelling longwave radiation, enhancing the greenhouse effect and warming the Earth. ▲ Oceans Oceans play a key role in the climate system. Ocean currents carry warm water poleward and cool water equatorward, moving heat around the globe. Ocean waters evaporate, carrying latent heat upward into the atmosphere. When the water vapor condenses, the latent heat is released at a different location. ▲ Solar power Shortwave radiation from the Sun is the power source that heats the Earth. ▲ GLOBAL ENERGY FLOWS Energy exchanges between oceans, lands, and atmosphere control the Earth’s climate system. Visualizing Earth’s climate—the greenhouse effect and global energy flows Figure 3.24 1 Electromagnetic Radiation 1. All objects give off electromagnetic ra- diation. Hotter objects emit greater amounts of electromagnetic radiation. They also emit radiation at shorter wavelengths than cooler objects. 2. The radiation from the Sun is called shortwave radiation, while the radia- tion from objects on the Earth and in the atmosphere is called longwave radiation. 3. On a global scale, the amount of short- wave radiation absorbed by the Earth system exactly balances the amount of longwave radiation the Earth emits back to space. 2 Geographic Variations in Energy Flow 1. Insolation is the rate of solar radiation flow at a location at a given time. It varies with the angle of the incoming sunlight as well as the length of time the sunlight hits a particular location. 2. At a given location and during a given time of year, there can be an imbalance between the amount of absorbed short- wave radiation and emitted longwave radiation. The difference between the two is called the net radiation. On aver- age, at latitudes below 40 degrees, an- nual net radiation is positive, while it is negative at higher latitudes. 3. Latent heat is taken up or released when substances change between solid, liquid, and gas states.
- A.K. Oppenheim(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
This is mostly due to the fact that it markedly changes the reflectivity, or albedo, of the surface, whether it be snow cover or glaciers on land or floating sea ice. The land itself must, of course, play a part in the heat balance of the system, and this is where mankind has undoubtedly already taken a hand in altering the climate due to his changes of the characteristics of the land. One has only to fly over almost any inhabited part of the earth to witness the man-made transforma-tions, and where forests have been cleared, deserts irrigated, or lakes created, the amount of solar radiation retained and the water vapor added to the atmosphere is not the same as before. We do not yet know how to quantify the effects of these alterations, but they are surely significant. Finally, we should probably not ignore the sun as a factor in determining the climate. While the total flux of radiation from the sun has been essentially con-stant for as long as it has been measured (so far as we can tell), there are frequent short-term increases in the shortwave solar radiation (ultraviolet and X-radiation) and in the outward flow of protons. These produce dramatic effects in the upper atmosphere, such as magnetic storms, auroral displays, and radio blackouts, but the corresponding effects in the lower atmosphere are so subtle as to defy any clear description at this time. Thus, while we cannot ignore the possible influence of short-term changes in solar activity on the weather and long-term changes on the climate, we will resist the temptation to pursue such a speculative subject very far in this brief review. 3. Observing the radiation budget of the System Having shown how the behavior of the climate system depends on the energy inputs and outputs that make it run, an obvious next question is: how can we use satellites to measure them?
eBook - PDFPractical Handbook of Photovoltaics
Fundamentals and Applications
- Augustin McEvoy, Tom Markvart, Luis Castaner, T. Markvart, L. Castaner(Authors)
- 2003(Publication Date)
- Elsevier Science(Publisher)
usually well-defined periods in tropical regions. There is always a considerable amount of cloud during the wet seasons. There is also often quite a lot of cloud in the drier seasons too. The daily pattern of irradiation is often dominated by convective clouds. The clouds build up as the surface temperatures increase. These clouds frequently obstruct the sun and some produce large amounts of rainfall. This rainfall is often associated with 22 Practical Handbook of Photovoltaics: Fundamentals and Applications violent thunderstorms. The normal pattern of Insolation is therefore an oscillating mix of periods of bright sunshine intermingled with periods of heavy obstruction of the solar beam. The diffuse radiation frequently dominates throughout the year. The variations in the amount and type of cloud cover associated with the different seasons is the main factor influencing the monthly mean global solar radiation available at different times of the year. The patterns of radiation experienced reflect the impacts of the general circulation of the earth’s atmosphere in tropical regions. Surface warming by the sun induces a global atmospheric circulation pattern of ascending air above the equatorial zone. Air from both the northern hemisphere and the southern hemisphere flows horizontally in at the bottom at low levels to drive this vast vertical circulation system in the equatorial zone. This air ascends in massive convection cells that move upwards, cooling and shedding moisture as they ascend. Vertical clouds that may grow to considerable heights in the atmosphere often form producing heavy rain. The air that has ascended, loosing much of its initial moisture on the way up through rainfall, then flows away from the equatorial region towards higher latitudes, moving horizontally at relatively high levels close to the stratosphere. This circulating air eventually descends heated adiabatically by recompression to reach the surface of the land, warm and dry.
eBook - ePub- Benoit Beckers(Author)
- 2013(Publication Date)
- Wiley-ISTE(Publisher)
Chapter 5Worldwide Aspects of Solar Radiation Impact 1
Any thermal state can be modeled as a system subjected to cyclic flows of mass and energy. The Earth is a sphere that is almost smooth, slightly flattened at the poles, and which rotates around the Sun on a slightly elliptical path. This is the largest thermal system that we have to deal with, the one that determines all the other systems such as territory, city, building, machinery, plant, or animal.5.1. Global energy budget at the Earth level
The distance between the Earth and the Sun is about 150 million km (1 AU: astronomical unit) and the radius of the Earth is approximately 6,370 km. The Earth rotates in just less than 24 h (1 day) on it axis, and around the Sun in the ecliptic plane, with a period of about 365.25 days. The axis of the first rotation (which defines the two poles) is tilted 23.5° relative to the normal to the ecliptic plane. This obliquity determines the peculiar tropical latitudes (23.5° with respect to the equator) and the polar circles (23.5° with respect to the poles, and thus 66.5° from the equator).The surface of the Sun behaves approximately like a blackbody with a temperature of 5,780 K. By Stefan–Boltzmann law, we deduce that a unit area located at the distance of 1 AU, set perpendicular to the sunrays, intercepts a power of 1,367 Wm−2 . The emitted spectrum has its maximum at 500 nm (wavelength of yellow perceived by the human eye) and is divided almost equally in visible light and near infrared (λ < 4μ ), with a small amount of ultraviolet.The solar constant (1,367 Wm−2 ) is equivalent to the average irradiance that can be captured in the vicinity of the Earth. It varies from about 6.9% during the year due to the elliptical shape of the Earth’s orbit (1,412 Wm−2 in early January to 1,321 Wm−2
eBook - PDF- Elisha B. Babatunde(Author)
- 2012(Publication Date)
- IntechOpen(Publisher)
When we speak of solar radiation, we mean the electromagnetic radiation of the Sun. The energy distribution of electromagnetic radiation over different wavelength is called Spectrum. The electromagnetic spectrum is divided into different spectral ranges (Figure 1.2). Fig. 1.2. Spectral ranges of electromagnetic radiation Solar Radiation Models and Information for Renewable Energy Applications 113 Solar radiation as it passes through the atmosphere undergoes absorption and scattering by various constituents of the atmosphere. The amount of solar radiation finally reaching the surface of earth depends quite significantly on the concentration of airborne particulate matter gaseous pollutants and water (vapour, liquid or solid) in the sky, which can further attenuate the solar energy and change the diffuse and direct radiation ratio (Figure 1.3). Fig. 1.3. Radiation balance of the atmosphere The global solar radiation can be divided into two components: (1) diffuse solar radiation, which results from scattering caused by gases in the Earth’s atmosphere, dispersed water droplets and particulates; and (2) direct solar radiation, which have not been scattered. Global solar radiation is the algebraic sum of the two components. Values of global and diffuse radiations are essential for research and engineering applications. Global solar radiation is of economic importance as renewable energy alternatives. More recently global solar radiation has being studied due to its importance in providing energy for Earth’s climatic system. The successful design and effective utilization of solar energy systems and devices for application in various facets of human needs, such as power and water supply for industrial, agricultural, domestic uses and photovoltaic cell largely depend on the availability of information on solar radiation characteristic of the location in which the system and devices are to be situated. This solar radiation information is also required in
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