Chapter 1 Overview of the Earths 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 Earths Atmosphere Composition 99% of the atmosphere is within 30km of the Earths surface N 2 78% and O 2 21% The percentages represent a constant amount of gas but cycles of destruction and production are constantly maintaining this amount. Overview of the Earths 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 Earths Atmosphere Special Topic: A Breath of Fresh Air 1 breath of air = molecules stars in the universe Overview of the Earths Atmosphere The Early Atmosphere The Earths first atmosphere was composed mostly of hydrogen and helium. The atmosphere evolved due to outgassing of CO 2 and H 2 O from the cooling center of the Earth causing rain and eventually lakes and oceans. Lakes and oceans acted as a sink, absorbing CO 2 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 Earths surface the pressure of the atmosphere is 14.7 lbs/in 2. Standard sea level pressure is mb = hPa = 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 planets 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 Satellites 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