Chapter 1: The Earth’s Atmosphere What is Meteorology? Weather vs. climate Earth’s atmosphere overview What is Meteorology? • First defined by Aristotle in Meteorologica • Meteors used to be everything that fell from the sky • Now, meteorology is the study of the atmosphere and its phenomena Weather and Climate • What is weather? • What is climate? What Is Weather? • Weather is the condition of the atmosphere at any given time • The temperature is 86°F • The sky was cloudy this morning • Remember in 1983 when it poured at the baseball game? Elements of Weather Air temperature Air pressure Humidity Clouds Precipitation Visibility Wind • Certain weather elements, like clouds, visibility and wind, are of particular interest to pilots. What Is Climate? • The study of weather over a long period of time • The average temperature for today is 86°F • San Francisco is usually cloudy in August • It usually rains during 15 baseball games a year Climate Average weather Extremes “What usually happens” Weather and Climate in Our Lives Wind chill, cold weather Fig. 1-16, p. 19 Weather and Climate in Our Lives Crop damage from cold weather, freeze Weather and Climate in Our Lives Hot weather, drought, heat stroke Weather and Climate in Our Lives Hot weather, drought, heat stroke Weather and Climate in Our Lives Severe thunderstorms, tornadoes, flooding Weather and Climate in Our Lives Severe thunderstorms, tornadoes, flooding Overview of the Earth’s Atmosphere Credit: NASA Composition of the Atmosphere • Two category of gases Permanent • • Output balanced by input Variable • Output and input not always balanced in time and place Table 1-1, p. 3 Source and Removal of Nitrogen (N ) 2 Abundant because mainly inert Removed by soil bacteria, ocean plankton Source is from decaying plants and animals, volcanoes Source and Removal of Oxygen (O ) 2 Removed when plant and animals decay Removed in chemical processes when oxygen combines with other stuff Removed during breathing Source is from plants during photosynthesis (CO2 + water = sugar and oxygen) Source and Removal of Water Vapor (H O vapor) 2 Very, very important Varies greatly in place and time Only substance in lower atmosphere as gas, liquid, and solid Removed when precipitation falls to surface Source is from evaporation, sea wind Source and Removal of Carbon Dioxide (CO ) 2 Occupies small portion of atmosphere Removed during photosynthesis. CO2 is stored in roots and branches Removed by the oceans (massive storage - 50 times atmospheric content) Source is burning of fossil fuels (stored CO2), deforestation, vegetation decay, exhalation, volcanoes Past measurements come from ice cores Fig. 1-4, p. 5 Two-faced Ozone (O ) 3 Largest concentration in the stratosphere (above 10 km) Forms when oxygen atoms combine with oxygen molecules Good in upper atmosphere, absorbs ultraviolet radiation Bad near the surface, irritates eyes and throats. Main ingredient of photochemical smog Other Stuff in the Atmosphere Aerosols • • • Ash from volcanoes Salt from wind blown saltwater Dust from wind (dust devils) Pollutants • Nitrogen dioxide, carbon monoxide, hydrocarbons, sulfur dioxide A Changing Atmosphere The earliest atmosphere • • Most likely made of of hydrogen and helium So light they escaped to space Subsequent atmosphere • • Volcanoes put gas, outgassing, (water vapor, CO2, and some Nitrogen) into environment Water vapor produced rain for thousands of years, CO2 into oceans, Nitrogen abundant A Changing Atmosphere • Oxygen increased due to the development of plants How Is the Atmosphere Structured? What is above our heads? Vertical temperature profile Where does the weather happen? Air Pressure and Air Density Air density (weight per volume) • Air pressure (force per area) • • Gravity holds molecules to surface (most dense near surface) Always decreases with height Air pressure changes with changing air density Sea-level pressure • Atmospheric standards (14.7 lbs per square inch=1013.25 mb=29.92 inch Hg) Fig. 1-7, p. 8 Fig. 1-8, p. 9 Layers of the Atmosphere Temperature vertical profile more complicated Troposphere Temperature generally decreases with height Cools due to sun heating surface Temperature increasing with height is called an inversion Contains all weather we know Great vertical movement Stratosphere Is characterized by increasing air temperature Height of tropopause varies in height Ultraviolet light is absorbed in the stratosphere, warming the layer Very limited vertical development Mesosphere Temperature decreases rapidly once again Air very thin Thermosphere Air temperature warms once again due to absorption of the sun by O2 Just a small amount of absorption leads to warming The Ionosphere Electrified regions of the atmosphere D, E, and F regions D region is efficient at absorbing AM radio waves, thus these waves don’t travel very far But, at night, the D region dissipates, allowing for AM waves to bounce off the E and F regions Fig. 1-11, p. 13 A Satellite’s View of the Weather Geostationary satellites • Atmospheric observation from satellites was an important technological development in meteorology. Other important developments include computers, internet, and Doppler radar. Storms of All Sizes Mid-latitude cyclonic storms – storms that occur outside the tropics Hurricanes and tropical storms – very powerful storms that feed off of warm water Thunderstorms – very common during Spring Tornadoes – spawned from “Supercell Thunderstorms” A Look at a Weather Map Wind speed and direction Cyclones and anticyclones Fronts • Wind direction is defined in the opposite way as ocean currents: a southerly current means water is moving towards the south. Fig. 1-13, p. 17 A Satellite’s View of the Weather Current view • Satellite view