2Weather vs. climateWeather: The state of the atmosphere at a given time (hour to hour or day to day)Climate: A description of aggregate weather conditions, based on observations that take place in a region over a period of years
3Basic elements of weather & climate Air temperatureHumidityType and amount of cloudinessType and amount of precipitationAir pressureThe speed and direction of the wind
4Composition of the Atmosphere Nitrogen: 78%Oxygen: 21%Other gases 1%
5Carbon dioxide Formula: CO2 Absorbs heat energy radiated by earth Influences heating of the atmosphere
6Water vapor Formula: H2O Varies from 0-4% composition Source of all clouds and precipitationAbsorbs or release heat energy (latent heat)
7Ozone Formula: O3 Ozone is concentrated in the stratosphere Ozone absorbs harmful ultraviolet radiation from the sunOzone is being slowly depleted from the atmosphere due to use of chlorofluorocarbons (CFC’s)
8Structure of the Atmosphere Four layers of the atmosphereTropospheretropopauseStratospherestratopauseMesopheremesopauseThermosphere
10Structure of the Atmosphere (cont.) 50% of our atmosphere lies below an altitude of 3.5 miles above the Earth’s surface
11Troposphere The bottom layer of the atmosphere Virtually all life exists in this layerThis layer is responsible for all our weatherTemperature of troposphere decreases with increasing altitude (3.5oF per 1000 ft.)Outer boundary is called the tropopause
12Stratosphere This layer lies beyond the tropopause Temperature remains constant to height of 13 miles, then the temperature will gradually increaseOzone is concentrated in this layerOuter layer is called the stratopause
13MesosphereTemperature decreases gradually with increasing height until one reaches the mesopauseAt that point temperature reaches around-90oC (-130oF)
14Thermosphere Layer extends beyond the mesopause Temperature rise rapidly and are very high (>1000oC or 1800oF)
15Earth-Sun relationships Virtually all the energy that drives the earth’s weather comes from the sunSolar energy is not evenly distributed over the earth’s surface. Amount of energy depends on latitude and seasonWind and currents are due to unequal heating of the earth
16Earth’s motions Two principal motions: 1) rotation: Spinning of the earth about its axis2) revolution: movement of the earth about the sun.
17When the Earth orbits the Sun, the Earth tilts 23 1/2 degrees from the perpendicular This is called the inclination of the axis
18The greater the angle of the sun, the more concentrated to the Earth’s surface. The sun’s angle is highest in summer, and lowest in the winter
19Seasons Seasons are based on two contributing factors: a) length of daylightb) angle of the sun
20During the summer solstice (June 21), the Northern Hemisphere is leaning 23 ½ degrees towards the sunDuring the winter solstice (December 21), the Northern Hemisphere is leaning 23 ½ degrees away from the sun
21During the autumnal and spring equinoxes (September 22 & March 21), the Earth is tilted 0o from the sun.
22Facts about the summer solstice Occurs June 21 or 22Vertical rays of the sun are striking the Tropic of Cancer (23 ½ north latitude)Northern Hemisphere are experiencing the greatest length of daylightLocations north of the Tropic of Cancer are experiencing the highest noon Sun angles
23The farther you are north of the equator, the longer the period of daylight, until the Arctic Circle is reached, where the daylight lasts for 24 hoursThe opposite occurs during the winter solstice
24Heat & Heat transferHeat: Form of energy that moves from a warmer body to a cooler bodyIf two objects of unequal temperature are in contact with each other, heat will travel from the warmer body to the cooler body.The temperature of the warmer will decrease, temperature of the cooler body will increase
25Mechanisms of Heat Transfer ConductionConvectionradiation
26ConductionTransfer of heat through matter by molecular activity (direct contact)Transfer occurs by collisions from one molecule to anotherConduction of heat varies from one material to anotherMetals are the best heat conductors
27ConvectionTransfer of heat by mass movement or circulation within a substanceConvection primarily takes place in fluidsThis is the type of heat transfer that primarily occurs in the atmosphere
28Radiation Transfer of energy through a vacuum or space Solar energy reaches our planet by way of radiation
29Forms of Radiation Visible Infrared Ultraviolet X-rays Microwaves radiowaves
30Radiation (cont.)All these radiations constitutes a collection of radiations called an electromagnetic spectrumEach of these radiations have a characteristic wavelengthWavelength: Distance from one crest to the next
31Visible radiation Radiation which can be seen by our eyes. Visible radiation can be broken down into its seven colors (what are the colors?)
32Infrared radiationRadiation is longer in wavelength than visible lightLies above the red region of the visible spectrumResponsible for heat radiation
33Ultraviolet radiation Shorter wavelength than visible radiationLies below the violet region of the visible spectrumPrimary source of radiation from the sun. Responsible for sunburn
34Basic Laws of Radiation All objects give off radiation, regardless of temperatureHotter objects give off more radiation than colder objectsThe hotter the radiating body, the shorter the wavelength of maximum energyObjects that are good absorbers are also good emitters as well
35Fate of incoming solar radiation When radiation strikes an object, three possible outcomes can occur:1) Radiation can be absorbed by the object2) Radiation can be transmitted (go through) the object3) Radiation can be reflected (bounced off) an object
37Solar radiation and our Earth About 50% of the solar energy reaching the atmosphere is absorbed by the Earth’s surfaceAbout 30% is reflected back into space by the atmosphere, clouds, and other reflective surfacesAbout 20% is absorbed by clouds and the atmosphere’s gases
38ReflectionAbout 30% of the solar energy reaching the outer atmosphere is reflected back to the spaceThis fraction of total radiation that is reflected is called albedo
39ScatteringOccurs when a beam of light produces a larger number of weaker raysThe weaker rays travel in all directionsScattering of light accounts for the blueness of our sky
40Absorption Gases are selective absorbers Nitrogen is a poor absorber of solar radiationOxygen removes most of the shorter wavelength ultraviolet radiation and ozone absorbs most of the ultraviolet rays from the stratosphere
41Factors affecting albedo Amount of cloud coverSun’s anglePresence of particulate matterNature of the Earth’s surface
42The greenhouse effectThis is the increase in the temperature of a planet’s atmosphere caused when infrared-absorbing gases are introduced into the atmosphere
43Greenhouse gases Carbon dioxide Water vapor Without the greenhouse effect, life on our planet will not exist
44Temperature controlsA factor that causes temperature to vary from place to place and from time to time
45Why Temperatures VaryFactors other than latitude that exert a strong influence on temperature include heating of land and water, altitude, geographic position, cloud cover, and ocean currents.
46Temperature Controls Land and Water Land heats more rapidly and to higher temperatures than water. Land also cools more rapidly and to lower temperatures than water.
53Cloud Cover and AlbedoAlbedo is the fraction of total radiation that is reflected by any surface.Many clouds have a high albedo and therefore reflect back to space a significant portion of the sunlight that strikes them.
54AlbedoThe fraction of radiation that is reflected by the earth’s surfaceAlbedo of the Earth, as a whole is 30%Albedo varies on Earth from place to place and from time to time
5550% of the solar energy that strikes the Earth’s surface is absorbed Most of this radiation is radiated skywardThe radiation that the Earth gives off has longer wavelengths than solar radiation
56World Distribution of Temperature Isotherms are lines on a weather map that connect points where the temperature is the same.Isotherms generally trend east and west and show a decrease in temperatures from the tropics toward the poles.