Presentation on theme: "the ground, and the air above is warmed by conduction, convection, and"— Presentation transcript:
1the ground, and the air above is warmed by conduction, convection, and Air in the lower atmosphere is heated from the ground upward. Sunlight warmsthe ground, and the air above is warmed by conduction, convection, andinfrared radiation.Air in the lower atmosphere is heated from the ground upward. Sunlight warms the ground,and the air above is warmed by conduction, convection, and infrared radiation. Further warming occurs during condensationas latent heat is given up to the air inside the cloud.Further warming occurs during condensation as latent heat is given up to the air inside the cloud.
2Energy Balance in radiative terms. Earth’s surface receives 147 units ofradiant energy from sun and atmosphere,while it radiates away 117 units, producinga surplus of 30 units.The atmosphere receives 130 units ofradiant energy, from sun (19 units) andthe earth (111 units), while it loses 160units, producing a deficit of 30 units.The balance is the warming of the atm. through conduction, convection and latent heat.
3Particles and AuroraSolar wind or plasma is charge traveling through space from sun to Earth.Solar wind interacts with Earth’s magnetic field and creates aurorasAurora borealis (northern lights)Aurora australis (southern lights)
4A magnetic field surrounds the earth just as it does a bar magnet. It protects the Earth from the solar wind.FIGURE 2.19 A magnetic field surrounds the earth just as it doesa bar magnet.
5shape known as the magnetosphere. The stream of charged particles from the sun (solar win) distorts the earth’s magnetic field into a teardropshape known as the magnetosphere.FIGURE 2.20 The stream of charged particles from the sun—called the solar wind—distorts the earth’s magnetic field into a teardropshape known as the magnetosphere.
6The aurora borealis is a phenomenon that forms as energetic particles from the sun interact with the earth’s atmosphere.FIGURE 2.22 The aurora borealis is a phenomenon that forms asenergetic particles from the sun interact with the earth’s atmosphere.
7Seasonal and Daily temperatures Chapter 3Seasonal and Daily temperatures
8Why the Earth has seasons Earth revolves in elliptical path around sun every 365 days.Earth rotates counterclockwise or eastward every 24 hours.Earth closest to Sun (147 million km = 3668 Earth’s circumference at Equator) in January, farthest from Sun (152 million km = 3793 (3% increase) Earth’s circumference at Equator) in July.Distance not the only factor impacting seasons.
9Elliptical pathFIGURE 3.1 The elliptical path (highly exaggerated) of the earthabout the sun brings the earth slightly closer to the sun in January thanin July.100%103%
10Our seasons are regulated by the amount of solar energy received at the earth’s surface.ACTIVE FIGURE 3.2 Sunlight thatstrikes a surface at an angle is spread over alarger area than sunlight that strikes the surfacedirectly. Oblique sun rays deliver less energy(are less intense) to a surface than directsun rays. Visit the Meterology Resource Centerto view this and other active figures atacademic.cengage.com/loginSunlight that strikes a surface at an angle is spread over a larger area than sunlight that strikes the surface directly.Oblique sun rays deliver less energyto a surface than direct sun rays.
11Why the Earth has seasons The amount of energy that reaches the Earths surface is influenced by the distance from the Sun, the solar angle, and the length of daylight.When the Earth tilts toward the sun in summer, higher solar angles and longer days equate to high temperatures.
12As the earth revolves about the sun, it is tilted on its axis by an angle. The earth’s axis always points to the same area in space (as viewed from a distant star).Astronomical 1st dayof summer in NHAstronomical 1st dayof winter in NHTropic of CancerTropic of CapricornACTIVE FIGURE 3.3 As the earth revolves about the sun, it is tilted on its axis by an angle of 231⁄2ｰ. The earth’saxis always points to the same area in space (as viewed from a distant star). Thus, in June, when the NorthernHemisphere is tipped toward the sun, more direct sunlight and long hours of daylight cause warmer weather than inDecember, when the Northern Hemisphere is tipped away from the sun. (Diagram, of course, is not to scale.) Visit theMeterology Resource Center to view this and other active figures at academic.cengage.com/loginAstronomical 1st dayof spring in NH2. The second important factor determining how warm the earth’s surface becomes is the length of time the sun shines each day. June (NH tilted towards sun) vs. December (NH tilted away from the sun).
13The relative amount of radiant energy received at the top of the earth’s atmosphere and at the earth’s surface on June 21 — the summer solstice.FIGURE 3.5 The relative amount of radiant energy receivedat the top of the earth’s atmosphere and at the earth’s surface onJune 21 — the summer solstice.Incomingsolarradiation
14reaches the earth’s surface farther south. During the NHsummer, sunlightthat reaches theearth’s surface infar northernlatitudes haspassedthrough a thickerlayer of absorbing,scattering, andreflectingatmospherethan sunlight thatreaches the earth’s surface farther south.FIGURE 3.6 During the Northern Hemisphere summer, sunlightthat reaches the earth’s surface in far northern latitudes has passedthrough a thicker layer of absorbing, scattering, and reflecting atmospherethan sunlight that reaches the earth’s surface farther south. Sunlightis lost through both the thickness of the pure atmosphere and byimpurities in the atmosphere. As the sun’s rays become more oblique,these effects become more pronounced.
15How the sun would appear in the sky to an observer at various latitudes during the June solstice (June 21), the December solstice (December 21), and the equinox(March 20 and September 22).JuneJuneJuneEquinoxEquinoxEquinoxDecJuneEquinoxEquinoxDecEquinoxJuneDecDecFigure 2.24: The apparent path of the sun across the sky as observed at different latitudes on the June solstice (June 21), the December solstice (December 21), and the equinox (March 20 and September 22).JuneFig. 3-8, p. 63
16Equinox Equinox TABLE 3.1 Length of Time from Sunrise to Sunset for Various Latitudes on Different Dates in the Northern Hemisphere
17Why the Earth has seasons First day of winterDecember 21 is the astronomical first day of winter, sun passes over the Tropic of Capricorn; not based on temperature.Seasons in the Southern Hemisphere (SH)Opposite timing of Northern Hemisphere (NH)Closer (about 3%) to sun in January (summer!); energy at top of the atmosphere is 7% greater in January than July. Does that make summers in SH warmer than NH? No, due to:Greater amount of water absorbing heat summer is not as hot in SH, and winters are not as cold in SH.Shorter season (see Fig. 3.9)
18Local seasonal temperature variations In the middle latitudes of the NH, objects facing south will receive more sunlight during a year than those facing north. This fact becomes more apparent in hilly or mountainous country Southern exposure: warmer, drier locations facing south. Implications for:Vegetation: south side mostly deciduous, north side mostly coniferous.Viniculture: southern slopesSki slopes: northern slopesLandscaping: plants that like sun over the south sideArchitecture: homes designed for reducing heating and cooling costs.
19In areas where small temperature changes can cause major changes in soil moisture, sparse vegetation on the southfacing slopes will often contrast with lush vegetation on the northfacing slopes.FIGURE 3.10 In areas where small temperature changes cancause major changes in soil moisture, sparse vegetation on the southfacingslopes will often contrast with lush vegetation on the northfacingslopes.
20Local temperature variations Environmental Issues: Solar HeatingIn order to collect enough energy from solar power to heat a house, the roof should be perpendicular to the winter sun.For the mid-latitudes the roof slant should be 45°- 50°
21Daily temperature variations Each day like a tiny season with a cycle of heating and coolingDaytime heatingAir poor conductor so initial heating only effects air next to groundAs energy builds convection begins and heats higher portions of the atmosphereAfter atmosphere heats from convection high temperature 3-5PM; lag in temperatureSurprisingly, noontime is not usually the warmest part of the day. Even though incoming solar radiation decreases after noon, it still exceeds the outgoing heat energy from the surface for a time. Afternoon cloudiness will change the time of maximum temperature for the day.
22On a sunny, calm day, the air near the surface can be substantially warmer than the air a meter or so above the surface.On a night, calm day, the air near the surface can be substantially colder than the air a meter or so above the surface.FIGURE 3.11 On a sunny, calm day, the air near the surface canbe substantially warmer than the air a meter or so above the surface.
23develops better on the calm night. Vertical temperature profiles just above the ground on a windy night and on a calm night. Notice that the radiation inversiondevelops better on the calm night.Vertical temperature profiles above an asphalt surface for a windy and a calm summer afternoon.FIGURE 3.12 Vertical temperature profiles above an asphaltsurface for a windy and a calm summer afternoon.