+ Earth-Sun Relationships Earth’s two principal motions: Rotation is the spinning of the earth on its axis, resulting in the daily cycle of day and night. Revolution is the movement of the Earth in an elliptical orbit around sun, producing one year. Its perihelion, the closest point to sun occurs on about January 3. The aphelion, which is the furthest point from sun occurs on about July 4.
+ Earth-Sun Relationships What causes the seasons? The gradual change in day length accounts for some of the differences in the seasons. A change in angle of the sun (altitude) also plays a significant role.
+ Earth-Sun RelationshipWhen the sun is directly overhead (at 90°) the solar rays are more concentrated and more intenseThe angle of the sun determines the path solar rays take as they pass through the atmosphere At 90° rays travel the shortest path to the surface At lesser angles the rays have farther to travel and more rays get dispersed
+ Earth-Sun Relationships Solstices: The summer solstice occurs on or about June 21 or 22. At that time, the sun’s rays are vertical on the Tropic of Cancer. (23 ½° north latitude) It also produces the longest day in the northern hemisphere. The winter solstice occurs on or about December 21 or 22. The sun’s rays are then vertical on the Tropic of Capricorn. (23 ½° south latitude) This results in the shortest day in the northern hemisphere.
+ Earth-Sun Relationships Equinoxes: Equinox means that day and night are equal. The autumnal (fall) equinox happens on or about September 21 or 22. The vernal (spring) equinox occurs on or about March 21 or 22. The sun’s rays are vertical on the equator. (0°) Earth isn’t tilted away or towards the sun
+ Energy, Temperature, and Heat Energy is the capacity to do work. 2 forms of energy: Kinetic energy describes an object in motion: the faster the motion, the greater the energy. Potential energy means that an object is capable of motion or work. Substances such as food, gasoline, or wood contain potential energy.
+ Energy, Temperature, and Heat Temperature: Temperature is a measure of the average kinetic energy of atoms or molecules in a substance. As temperature increases, energy is gained. Because the particles move faster As temperature decreases, energy is lost.
+ Energy, Temperature, and Heat Heat: Heat is the energy transferred in or out of object due to temperature differences. Energy absorbed but with no increase in temperature is called latent heat. Sensible heat is heat we can feel or measure with a thermometer.
+ Mechanisms of Heat Transfer Conduction: Conduction is the heat transferred through molecular and electron collisions from one molecule to another. Metals are good conductors Convection: Convection is the heat transferred via movement or circulation of a substance, primarily vertically Warm air rising creates thermal currents. Advection describes the primarily horizontal component of convective flow.
+ Mechanisms of Heat Transfer Solar radiation travels through space providing light and heat energy. Wavelength describes the length of the crest of one radio wave to the next. Visible light, often referred to as “white light,” actually describes the sensitivity of the human eye to a range of wavelengths. Infrared radiation cannot be seen by the human eye, but is detected as heat. Ultraviolet radiation, on the opposite side of the visible range, consists of wavelengths that may cause sunburns.
+ Mechanisms of Heat Transfer Laws of radiation: 1. All objects continually emit radiate energy of a range of wavelengths. 2. Hotter objects radiate more total energy per unit than colder ones. 3. Hotter objects radiate more short wave radiation than cooler ones. 4. Objects that are good absorbers of radiation are also good emitters.
+What Happens to IncomingSolar Radiation? Reflection: Lightbounces back from an object at the same angle and intensity. Scattering: Scatteringproduces a large number of weaker rays traveling in different directions. Backscattering: Scattering, both backwards and forwards, is known as backscattering.
+What Happens to IncomingSolar Radiation?Reflection and the Earth’s albedo: Albedo is the % of radiation reflected by an object. The albedo for Earth is about 30%. For the moon, the albedo is about 7%. Light objects have higher albedos and darker objects have lower albedos.
+What Happens to IncomingSolar Radiation?Diffused light: Diffused light is the result of dust particles and gas molecules scatter light in different directions. This diffusion results in clear days with a bright blue sky. A red sun on the horizon is the result of the great distance solar radiation must travel before it reaches your eyes.
+The Role of Gases in the Atmosphere The greenhouse effect: The greenhouse effect is a natural phenomenon and is a result of the Earth’s atmosphere trapping some outgoing radiation. Carbon dioxide and water vapor absorb longwave radiation, which heats the air. The greenhouse effect is NOT the same as global warming.
+ Earth’s Heat Budget Latitudinal heat balance: Balance of incoming and outgoing radiation applicable for whole earth is not maintained on latitudes. At 38°, incoming radiation and outgoing radiation are equal. Above 38°, the atmosphere loses more radiation. Below 38°, the atmosphere gains more radiation. This energy imbalance is what drives winds and ocean currents.