Weather and climate Weather Weather is over a short period of time Constantly changing Climate Climate is over a long period of time Generalized composite of weather Weather and climate Elements of weather and climate Temperature Humidity Cloudiness Precipitation Air Pressure Winds speed and direction Composition of the atmosphere Air is a mixture of gases Major components of clean dry air Nitrogen N 78 Oxygen O2 21 Argon and other gases Carbon dioxide CO2 0 036 absorbs heat energy from Earth Proportional volume of gases that compose dry air Figure 16 3 Composition of the atmosphere Variable components of air Water vapor Aerosols Ozone Dust and aerosols Atmospheric pressure variation with altitude Figure 16 5 Structure of the atmosphere Atmospheric layers based on temperature Troposphere Stratosphere Mesosphere Thermosphere Thermal structure of the atmosphere Figure 16 7 Weather Balloon Earth Sun relations Earth motions Rotates on its axis Revolves around the Sun Seasons Result of constant axial tilt Changing Sun angle Changing length of daylight Earth Sun relations Special days Solstice Sun s vertical rays are located at the Tropic 23 latitude June 21 22 December 21 22 Equinox Sun s vertical rays located at the Equator 0o latitude March 21 22 September 21 22 Relationship of sun angle to the path of solar radiation Figure 16 11 Animation of Earth s orbit Earth Sun Relations Earth Sun relationships Figure 16 12 Characteristics of the solstices and equinoxes Figure 16 13 Atmospheric heating Heat is always transferred from warmer to cooler objects Mechanisms of heat transfer Conduction Convection Radiation electromagnetic radiation Mechanisms of heat transfer Figure 16 16 The electromagnetic spectrum Figure 16 17 Atmospheric heating Incoming solar radiation Atmosphere is largely transparent to incoming solar radiation About 50 absorbed at Earth s surface Atmospheric effects Reflection albedo percent reflected Scattering Absorption Most visible radiation reaches the surface Average distribution of incoming solar radiation Figure 16 19 Atmospheric heating Earth re radiates energy at the longer wavelengths infra red heat Longer wavelength terrestrial radiation is absorbed by Carbon dioxide and Water vapor in the atmosphere Lower atmosphere is heated from Earth s surface Heating of the atmosphere is termed the greenhouse effect The heating of the atmosphere Figure 16 21 Temperature measurement Daily maximum and minimum Other measurements calculated from these Daily mean temperature Daily range Monthly mean Annual mean Annual temperature range Mean monthly temperatures for two locations in Canada Figure 16 24 Mean monthly temperatures for Eureka California and New York City Figure 16 26 Controls of temperature Receipt of solar radiation is the most important control Other important controls Differential heating of land and water Altitude Geographic position Cloud cover Albedo Clouds reduce the daily temperature range Figure 16 28 World mean sea level temperatures in January Figure 16 29 World mean sea level temperatures in July Figure 16 30
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