Chapter 1 The Earth and Its Atmosphere
Overview of the Earth’s Atmosphere • The atmosphere is a delicate life giving blanket of air surrounding the Earth. • Without the atmosphere the Earth would not have lakes or oceans. • Radiant energy from the sun energizes the atmosphere driving day to day weather.
Overview of the Earth’s Atmosphere • Composition • 99% of the atmosphere is within 30km of the Earth’s surface • N2 78% and O2 21% • The percentages represent a constant amount of gas but cycles of destruction and production are constantly maintaining this amount.
Overview of the Earth’s Atmosphere • Composition • Water a variable gas following the hydrologic cycle. • Carbon dioxide has risen in recent years and is an important greenhouse gas. • Other greenhouse gases exist beyond carbon dioxide.
Overview of the Earth’s Atmosphere • Special Topic: A Breath of Fresh Air • 1 breath of air = 1022 molecules • 1022 stars in the universe
Overview of the Earth’s Atmosphere • The Early Atmosphere • The Earth’s first atmosphere was composed mostly of hydrogen and helium. • The atmosphere evolved due to outgassing of CO2 and H2O from the cooling center of the Earth causing rain and eventually lakes and oceans. • Lakes and oceans acted as a sink, absorbing CO2 from atmosphere. • Plants evolved producing oxygen to form our current atmosphere several 100 million ybp.
Vertical Structure of the Atmosphere • Air Pressure and Air Density • Weight = mass x gravity • Density = mass/volume • Pressure = force/area • At the Earth’s surface the pressure of the atmosphere is 14.7 lbs/in2 . • Standard sea level pressure is1013.25 mb = 1013.25 hPa = 29.92 in Hg • Atmospheric pressure decreases with an increase in height.
Vertical Structure of the Atmosphere • Layers of the Atmosphere • Lapse rate = change in temperature with a change in height • Isothermal environment = no change in temperature with height • Inversion layer = change in the sign of the lapse rate
Vertical Structure of the Atmosphere • Layers of the Atmosphere • Troposphere: decrease in temperature, day to day weather, tropopause • Stratosphere: increase in temperature, ozone, stratopause • Mesosphere: decrease in temperature, mesopause • Thermosphere: increase in temperature, suns strongest radiation
Vertical Structure of the Atmosphere • Special Topic: The Atmospheres of Other Planets • Each planet’s atmosphere is unique in terms of temperature and composition.
Vertical Structure of the Atmosphere • Observation: Radiosonde • Weather balloon • Instrument and transmitter • Air temperature, humidity, pressure
Vertical Structure of the Atmosphere • The Ionosphere • Not a true layer but an electrified region • Ions = molecule with an additional or minus an electron • Exists at the top of the atmosphere in the thermosphere • F,E,D layer • Sun light creates layers, D disappears at night and less interference with AM radio transmissions.
Weather and Climate • Weather: short term air temperature, air pressure, humidity, clouds, precipitation, visibility, and wind • Climate: long term patterns and average weather; not just magnitude but also frequency
Weather & Climate • Meteorology • Study of the atmosphere and its phenomena • Aristotle 340 B.C. Meterologica, meteoros: high in air • 1843 telegraph • 1920s air masses • 1940s upper air • 1950s radar and computers • 1960s satellite
Weather & Climate • Satellite’s View • Geostationary satellite • Meridians measure longitude (W-E) • Parallels measure latitude (N-S) • Weather maps: pressure cells, fronts, surface stations
Weather & Climate • Weather and Climate in Our Lives • Two general reasons for studying how weather and climate impacts our lives: economic efficiency and public safety. • Clothing • Crops • Utilities • Extreme cold and heat • Tornados and hurricanes
Weather & Climate • Special Topic: Meteorologist • Any person with a college degree in meteorology or atmospheric science; not just the TV weather person • Half of 9000 meteorologists employed by the US National Weather Service • Researchers and operational meteorologists