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Intro to the Atmosphere • The layers of gas that surround the other spheres of influence on our planet • Interacts frequently with - Hydrosphere- Clouds,Humidity,Rain Geosphere - Weathering,Wind Erosion,Dust Particles Exosphere- Blocks incoming Solar Radiation Biosphere- Us!, plants, animals How do we know about the atmosphere? • Measuring instruments - Thermometer- temperature - Barometer- pressure - Geiger Counter- radioactivity - Chromatograph- chemical composition • Space missions - satellites - aircraft • Theory - physics and chemistry Origins of Earth’s atmosphere • Early on- volcanic activity is responsible for atmospheric gases - rich in CO2, NO2, SO2,but no O2 - very different from today’s atmosphere! • planktonic life forms (phytoplankton) simple plants and bacteria changed the atmospheric composition over 2 billion years - increased the oxygen content in oceans, then air • Solar radiation also contributed - created other atoms by irradiating existing components - ozone layer Composition (modern) N 2 (nitrogen) = 78 % O 2 (oxygen ) = 21 % Ar (argon) = 0.93 % an inert gas CO 2 (Carbon Dioxide) = 0.0402% a greenhouse gas Aerosols, Water and other gasses = 0.03% • dust • and moisture particles small enough to stay up in the atmosphere, AND Gasses like CH4 (methane), SO2, and NO2 The structure of the atmosphere • divided based on • the temperature Ionosphere Composition is unchanging here Clouds form here Ozone Layer O3 Aurora Borealis & Australis Ionosphere & magnetosphere AURORA BOREALIS movies Factors associated with the atmosphere • Heat - different from temperature (avg. kinetic energy) - usually measured as the temperature of the air - F, C, K scales - a function of the kinetic energy (molecular motion). • Moisture - Measured as relative humidity - a function of temperature and availability - expressed as a percentage • Pressure - Measured in millibars, pascals, or inches Heat transfer One of the big things the atmosphere does! Conduction • contact between air and ground Convection • mixing due to temp related density changes Radiation- also known as radiative or electromagnetic energy • absorbed and emitted by all objects Conduction Heat transfer (2) • contact between hot & cool - transfers E from hot to cool • solids > liquids > gases - atmosphere poor at conduction Convection (& Advection) • "mixing" of hot & cold - Usually in currents - Con- is vertical; Ad- is horizontal or lateral Radiation • Sun is the source of most radiation - visible light = intermediate-wave radiation - infrared (heat)= Longwave radiation - X-rays, gamma rays, etc= very shortwave • Earth also gives off some radiation • Living things also give off radiation • Angle of approach and reflective properties are critical factors Air Pressure The "weight" of the air pressing down on the Earth's surface A simple barometer • measured by a Barometer - inches (or mm) of mercury rising up in a tube • adjusted according to height above avg. sea level - less air pressing down from above at higher altitudes • also takes into account motion of air - sinking vs rising Atmospheric Density 120 km • air is "thinner" aloft- less atoms of it • Pressure is lower aloft • Important for heat and pressure transfer 0 km Surface isobar map with fronts Moisture- the other main thing • dependent on temperature - warmer = hold more water vapor - colder = holds less water vapor • results from - evaporation of liquid water - cools surface and adds heat to air - sublimation - direct transformation from solid water (ice) to vapor • Acts as a trap for longwave radiation (heat) • Transports heat • Acts to transport water Interaction of Radiation,Pressure,Moisture at macro, or global, scale Weather patterns are dictated by moisture, pressure and temperature differences in various air masses • A hurricane (shown at right) is an extreme low pressure system that draws energy from warm water Interaction of Radiation,Pressure,Moisture at meso scale Sea Breeze- Interaction of Radiation,Pressure,Moisture at micro scale animation