Solar
Energy,
Seasons And
the
Atmosphere

Solar Energy, Seasons and the Atmosphere The Solar System, Sun, and Earth Solar Energy: From Sun to Earth The Seasons Atmospheric Composi;on, Temperature, and Func;on • Variable Atmospheric Components • • • • Earth’s Orbit » Average distance from Earth to the Sun is 150,000,000 km (93,000,000 mi) • Perihelion – closest at January 3 – 147,255,000 km (91,500,000 mi) • Aphelion – farthest at July 4 – 152,083,000 km (94,500,000 mi) • Earth is 8 minutes 20 seconds from the Sun • Plane of Earth’s orbit is the plane of the eclip;c Solar Energy: From Sun to Earth • Solar Wind • ElectromagneNc Spectrum of Radiant Energy • Incoming Energy at the Top of the Atmosphere – Solar constant – Uneven distribuNon of insolaNon – Global net radiaNon 1 The ElectromagneNc Spectrum • Sun radiates shortwave energy • Shorter wavelengths have higher energy • Earth radiates longwave energy INSOLATION: SOLAR RADIATION INTERCEPTED BY THE EARTH REACHES EARTH AT A HORIZONTAL PLANE DIFFERENCES IN THE ANGLE OF SOLAR RAYS AT EACH LATITUDE RESULT IN AN UNEVEN DISTRIBUTION OF INSOLATION AND HEATING DistribuNon of InsolaNon • Tropics receive more concentrated insolaNon due to the Earth’s curvature • Tropics receive 2.5x more than poles 2 The Seasons • Seasonality • Reasons for Seasons – RevoluNon – RotaNon – Tilt of Earth’s axis – Axial parallelism • Annual March of the Seasons – Seasonal observaNons Seasonality • Seasonal changes – Sun’s alNtude – angle above horizon – DeclinaNon – locaNon of the subsolar point – Daylength Factors That Influence Seasonal Change • • • • RevoluNon RotaNon Tilt of Earth’s axis Axial parallelism 3 RevoluNon • Earth revolves around the Sun • Voyage takes one year • Earth’s speed is 107,280 kmph (66,660 mph) RotaNon • Earth rotates on its axis once every 24 hours • RotaNonal velocity at equator is 1675 kmph (1041 mph) Reasons for Seasons • Tilt of Earth’s axis – Axis is Nlted 23.5° from plane of eclipNc • Axial parallelism – Axis maintains alignment during orbit around the Sun – North pole points toward the North Star (Polaris) • Sphericity 4 Annual March of the Seasons • Winter solsNce – December 21 or 22 – Subsolar point Tropic of Capricorn • Spring equinox – March 20 or 21 – Subsolar point Equator • Summer solsNce – June 20 or 21 – Subsolar point Tropic of Cancer • Fall equinox – September 22 or 23 – Subsolar point Equator THE SOLSTICES DENOTE THE EXTREMES OF DAYLENGTH DECEMBER 12 AND JUNE 21 ARE TERMED THE SOLSTICES -THE SPECIFIC POINTS IN TIME AT WHICH THE SUN’S DECLINATION IS AT: ITS FARTHEST POINT NORTH - THE TROPIC OF CANCER - 23.5*N OR . . . ITS FARTHEST POINT SOUTH - THE TROPIC OF CAPRICORN AT 23.5*S WINTER SOLSTICE: DECEMBER 21: NORTH POLE IS EXCLUDED FROM SUNLIGHT AND SOUTH POLE IS IN TOTAL DAYLIGHT THE SUBSOLAR POINT IS 23.5*S THE NORTHERN HEMISPHERE IS TILTED AWAY FROM THE DIRECT RAYS OF THE SUN -LOWER ANGLE AND MORE DIFFUSE PATTERN OF INSOLATION 5 SUMMER SOLSTICE JUNE 21: SOUTH POLE IS EXCLUDED FROM SUNLIGHT AND NORTH POLE IS IN TOTAL DAYLIGHT THE SUBSOLAR POINT SHIFTS TO 23.5*N THE SOUTHERN HEMISPHERE IS TILTED AWAY FROM THE DIRECT RAYS OF THE SUN VERNAL EQUINOX: MARCH 21 OR 22: WHEN THE SUN’S DECLINATION CROSSES THE EQUATORIAL PARALLEL AND ALL PLACES ON EARTH EXPERIENCE DAYS AND NIGHTS OF EQUAL LENGTH THE SUN RISES AT THE NORTH POLE AND SETS AT THE SOUTH POLE AUTUMNAL EQUINOX: SEPTEMBER 22 OR 23: THE SUN’S DECLINATION CROSSES THE EQUATORIAL PARALLEL AND ALL PLACES ON EARTH EXPERIENCE DAYS AND NIGHTS OF EQUAL LENGTH THE SUN RISES AT THE SOUTH POLE AND SETS AT THE NORTH POLE 6 Atmospheric ComposiNon, Temperature, and FuncNon • • • • Atmospheric Profile Atmospheric ComposiNon Criterion Atmospheric Temperature Criterion Atmospheric FuncNon Criterion Atmospheric Profile • Atmosphere extends to 32,000 km (20,000 mi) from surface • Exosphere begins at 480 km (300 mi) • Three criteria to examine atmosphere – ComposiNon – Temperature – FuncNon Atmospheric ComposiNon • Heterosphere – outer atmosphere – 80 km (50 mi) outwards – Layers of gases sorted by gravity • Homosphere – inner atmosphere – Surface to 80 km (50 mi) – Gases evenly blended 7 Atmospheric Temperature • Thermosphere – Roughly same as heterosphere – 80 km (50 mi) outwards • Mesosphere – 50 to 80 km (30 to 50 mi) • Stratosphere – 18 to 50 km (11 to 31 mi) Atmospheric Temperature • Troposphere – Surface to 18 km (11 mi) – 90% of mass of atmosphere – Normal lapse rate – average cooling at rate of 6.4 C°/km (3.5 F°/1000 f) – Environmental lapse rate – actual local lapse rate Atmospheric FuncNon • Ionosphere – Absorbs cosmic rays, gamma rays, X‐rays, some UV rays • Ozonosphere – Part of stratosphere – Ozone (O3) absorbs UV energy and converts it to heat energy – Chlorine from CFCs destroys O3 8 Variable Atmospheric Components • • • • Natural Sources Natural Factors That Affect Air PolluNon Anthropogenic PolluNon Benefits of the Clean Air Act Natural Factors That Affect Air PolluNon • Winds • Local and regional landscapes • Temperature inversion Anthropogenic PolluNon • • • • Carbon monoxide Photochemical smog Industrial smog and sulfur oxides ParNculates 9