Chapter 2 Solar Energy To Earth and Seasons PDF

Chapter 2 Lecture Geosystems 9th Edition Chapter 2: Solar Energy to Earth and the...

Chapter 2 Lecture Geosystems 9th Edition Chapter 2: Solar Energy to Earth and the Seasons Ms. Hodgkinson [email protected] © 2015 Pearson Education, Inc.  Solar Energy to Earth and the Seasons Topics in this chapter: – The Solar System, Sun, and Earth – Solar Energy and the solar wind – Solar radiation and the electromagnetic spectrum – The seasons – Causes of seasonality © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  The Solar System, Sun and Earth Our solar system is located in the milky way galaxy, a flattened disk-shaped mass containing more than 400 billion stars. Our solar system is more than halfway out from the galactic centre in one of the milky way’s spiral arms – the Orion spur of the Sagittarius arm. The sun and the solar system are estimated at having formed more than 4.6 billion years ago. Video: Solar system 101 4:11 © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Dimensions and Distances In astronomy, what is the unit we use for distance? light-hour 60 light-minutes = 3600 light-seconds 6.706×108 miles light-day 24 light-hours = 86400 light-seconds 1.609×1010 miles light-week 7 light-days = 604800 light-seconds 1.127×1011 miles – light-year: distance that light travels in one year Light year is a unit of distance!!! – light speed: 300,000 km/s – 1 light-year (ly) = 9.5 trillion km © 2015 Pearson Education, Inc.  Dimensions and Distances Therefore, in light years the: – Milky Way Galaxy 100,000 light-years across – Our Solar System 11 light-hours across – Moon is 1.28 light-seconds away – Known universe that is observable from earth is approx. 12 billion light-years in all directions. – i.e. 9.5 trillion x 12 billion = a lot of zeros!!! Video: Mind blowing! Earth compared to the rest of the universe 3:33 © 2015 Pearson Education, Inc.  Our Solar System © 2015 Pearson Education, Inc.  Our Solar System © 2015 Pearson Education, Inc.  Our Solar System Earth's elliptical orbit and the plane of the ecliptic © 2015 Pearson Education, Inc.  Earth’s Orbit Earth’s orbit around the Sun is presently elliptical— a closed oval path. Plane of Earth’s orbit about the Sun is called the plane of the ecliptic. Average distance from Earth to the Sun is 150,000,000 km. Light reaches Earth from the Sun in 8 minutes and 20 seconds. – 152,083,000 km © 2015 Pearson Education, Inc.  Earth’s Orbit Perihelion—when the sun is closest to earth on January 3 – 147,255,000 km Aphelion—when the sun is farthest from earth on July 4 – 152,083,000 km © 2015 Pearson Education, Inc.  What is Solar Energy? Energy is the capacity of a physical system to do work. The unit is Joule (J). Solar energy is radiant energy (i.e., radiant light and heat) from the Sun. Solar energy is generated by the nuclear fusion reaction process in which pairs of hydrogen nuclei are joined, form helium, and emit a large amount of energy. © 2015 Pearson Education, Inc.  Sunspots Sunspots are caused by magnetic storms on the Sun. They are more than 12 times Earth’s diameter. Their temperatures are less than the temperatures of their surroundings. Sunspots have an activity cycle of 11 years. © 2015 Pearson Education, Inc.  Sunspots Solar eruption or Coronal Mass Ejection (CME) Video: Solar Wind’s effect on Earth © 2015 Pearson Education, Inc.  Sunspots © 2015 Pearson Education, Inc.  Sunspots and Solar Wind Sunspots can produce the solar wind. Solar winds are clouds of electrically charged particles, and takes about 3 days to reach Earth. The magnetosphere deflects (shields) the solar wind toward both of Earth’s poles and only a small portion of it enters the atmosphere and produces the auroras. © 2015 Pearson Education, Inc.  Sunspots and Solar Wind Solar wind: (stream of energetic material) travels more slowly than light at 50 million kms a day. Most of the solar wind does not reach the earth’s surface, therefore research on it is done in space. Auroras: folded sheets of green, yellow, blue and red light that undulate across skies of latitudes higher than 65° latitude. © 2015 Pearson Education, Inc.  Auroras The Aurora Borealis is located in the Northern Hemisphere The Aurora Australis is located in the Southern Hemisphere Video Aurora Borealis Explained 5:01 © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Solar Radiation Solar radiation occupies a portion of the electromagnetic spectrum of radiant energy. The electromagnetic spectrum is the range of wavelengths or frequencies over which electromagnetic radiation extends. © 2015 Pearson Education, Inc.  Solar Radiation This radiant energy travels at the speed of light to Earth. – Light reaches Earth from the Sun in about 8 minutes and 20 seconds. The total spectrum of this radiant energy is made up of different wavelengths. Video: Electromagnetic Spectrum 5:19 © 2015 Pearson Education, Inc.  The Electromagnetic Spectrum of Radiant Energy High frequency is associated with small wavelengths and high energy. Solar radiation consists of three parts: 1. Gamma rays, X-rays, UV (8%) 2. Visible light (47%) 3. Infrared (45%) © 2015 Pearson Education, Inc.  The Electromagnetic Spectrum of Radiant Energy © 2015 Pearson Education, Inc.  Solar and Terrestrial Energy Distribution by Wavelength High energy/ frequency (or shortwave radiation) is associated with high temperature. Low energy/frequency (or longwave radiation) is associated with low temperature. Low temp High temp  © 2015 Pearson Education, Inc.  Earth’s Energy Budget Earth receives shortwave radiation (high T °) from the sun in the form of UV, visible light and shortwave infrared waves. The Earth emits/reradiates longwave radiation (lower T°) in the form of thermal infrared energy back into space © 2015 Pearson Education, Inc.  Insolation Solar radiation that reaches a horizontal plane at Earth is called insolation, i.e., incoming solar radiation. Insolation at the top of the atmosphere is expressed as the solar constant the value of the solar constant as it travels to the surface of the earth is reduced by half or more by: reflection, scattering and absorption of short-wave radiation. © 2015 Pearson Education, Inc.  Insolation © 2015 Pearson Education, Inc.  Distribution of Insolation The thermopause (480 km above Earth’s surface) is the outer boundary of Earth’s energy system. Earth only receives one of two-billionths of Sun’s total energy output. Tropics receive more concentrated insolation due to Earth’s curvature. Tropics receive more than 2.5 times of what poles receive. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Insolation Receipts and Earth’s Curved Surface Subsolar point is the location where insolation is perpendicular to the surface. © 2015 Pearson Education, Inc. Figure 2.9  Insolation Receipts and Earth’s Curved Surface © 2015 Pearson Education, Inc. Figure 2.9  Insolation Receipts and Earth’s Curved Surface Subsolar point moves between 23.5° north (tropic of cancer) and 23.5° south (tropic of Capricorn). This changes the angle of insolation at each point on the surface throughout the year. All places away from the sub-solar point receive energy at more obtuse, angles less than 90°, more diffuse energy. © 2015 Pearson Education, Inc. Figure 2.9 © 2015 Pearson Education, Inc. Figure 2.9  The Seasons - Causes Seasons result from: – the sun’s altitude above the horizon – it’s declination, (see image below) – the day length. Video: Bill Nye explains seasons 4:45 © 2015 Pearson Education, Inc.  The Seasons - Causes The variations in these are caused by various physical factors: 1. Earth’s revolution around the sun 2. Earth’s rotation around it’s axis 3. Tilt of the earth’s axis 4. Axial parallelism 5. Sphericity © 2015 Pearson Education, Inc.  Reasons for Seasons - Revolution Revolution Earth revolves around the Sun Voyage takes one year Earth’s speed is 107,280 km/h This results in seasons Southern hemisphere summer November to January Northern hemisphere summer June to August The hemisphere experiencing summer is tilted towards the sun Video: Rotation and revolution of Earth 3:39 https://youtu.be/cDed5eXmngE © 2015 Pearson Education, Inc.  Revolution and Rotation © 2015 Pearson Education, Inc. © 2012 Pearson Education, Inc. Figure 2.13  Reasons for Seasons – Tilt of the axis Tilt of Earth’s axis Axis is tilted 23.5°from the perpendicular to the plane of the ecliptic. The result is that a particular hemisphere is tilted towards the sun and the other away from the sun at particular season. In mid-autumn and mid-spring the axial tilt is equal for both hemispheres (Equinox) Video: Mechanism of the Seasons 5:59 © 2015 Pearson Education, Inc.  Reasons for Seasons Plane of the ecliptic is the plane of the earth’s orbit. So, if you were to draw a line from the sun, the plane on which the rays would impact directly all year round would be the plane of the ecliptic, it is not the same as the equator. Or 66.5 degree angle from the plane itself. © 2015 Pearson Education, Inc.  Axial Tilt and Parallelism © 2015 Pearson Education, Inc.  Reasons for Seasons – axial parallelism and Sphericity Axial parallelism Axis maintains alignment during orbit around the Sun (tilt does not change) North pole points toward the North Star (Polaris) Sphericity Earth’s shape is known as a geoid (equatorial bulge and polar flattening). This increases the insolation at the equator and decreases it at the poles. © 2015 Pearson Education, Inc.  Plane of the ecliptic and the subsolar point © 2015 Pearson Education, Inc.  Reasons for Seasons - Rotation Rotation Earth rotates on its axis once every 24 hours Rotational velocity at equator is 1674 km/h Results in day and night Day will be longer in the hemisphere tilted towards the sun, increasing temperatures. Difference between day and night length with seasons increases from the equator to towards the poles This increases summer and decreases winter temperatures © 2015 Pearson Education, Inc.  Reasons for Seasons Revolution: one hemisphere is tilted towards the sun while the other is tilted away from the sun during summer or winter. Autumn and spring: zone (circle) of illumination lines up with the lines of longitude meaning that everywhere on the earth’s surface experiences 12 hours of daylight and 12 hours of night*. Equinoxes. And intercepts the equator at exactly 90°C. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Midnight Sun Video: Midnight sun © 2015 Pearson Education, Inc.  Annual March of the Seasons In its orbit, Earth is at perihelion (its closest position to the Sun) during our Southern Hemisphere summer (January 3). It is at aphelion (its farthest position from the Sun) during the Northern Hemisphere summer (July 4). © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  The Four Seasons © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Annual March of the Seasons © 2015 Pearson Education, Inc. © 2012 Pearson Education, Inc. Figure 2.15  Annual March of the Seasons Summer solstice Southern Hemisphere – December 21 or 22 Subsolar point above the Tropic of Capricorn Longest day and shortest night in the SH Autumn equinox Southern Hemisphere – March 20 or 21 Subsolar point above the Equator All places on Earth have equal day and night © 2015 Pearson Education, Inc.  Annual March of the Seasons Winter solstice Southern Hemisphere – June 20 or 21 Subsolar point above the Tropic of Cancer Longest night and shortest day in the SH Spring (vernal) equinox Southern Hemisphere – September 22 or 23 Subsolar point above the Equator All places on Earth have equal day and night © 2015 Pearson Education, Inc.  Winter and Summer Solstice © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  End of Chapter 2 Online class test due Monday by 17:00 on Chapter 2. Remember to use these slides and videos together with your textbook © 2015 Pearson Education, Inc.  Summary of Chapter 2 Our Solar System is located on a remote, trailing edge of the Milky Way Galaxy, a flattened, disk-shaped mass estimated to contain up to 400 billion stars. In its orbit, Earth is at perihelion (its closest position to the Sun) during our Southern Hemisphere summer (January 3). It is at aphelion (its farthest position from the Sun) during our Northern Hemisphere summer (July 4). Sunspots are caused by magnetic storms on the Sun. Solar winds are clouds of electrically charged particles, and takes about 3 days to reach Earth. Solar radiation occupies a portion of the electromagnetic spectrum of radiant energy. Solar radiation that reaches a horizontal plane at Earth is called insolation. Five reasons of seasons: 1) revolution, 2) rotation, 3) tilt of Earth’s axis, 4) axial parallelism, and 5) sphericity. © 2015 Pearson Education, Inc.