Geography 1 (41100). Prof. Dean . Wint., Jan 4, 2012 . Read Chp 3 . Pg 54-73 1 Chapter 3 Introduction to the Atmosphere I. Introduction a. The Earth’s Atmosphere is what allows life to exist. i. It supplies oxygen. ii. It supplies carbon dioxide needed by plants. iii. It allows for insulates the Earth’s surface against extreme temperatures. iv. It protects the Earth from ultraviolet radiation. v. It allows the planet to maintain liquid water. II. Size of the Earth’s Atmosphere a. It can be thought of as a vast ocean of air that uniformly surrounds Earth. b. It can move independent of the Earth but is held by gravity because it is composed of materials that have weight. c. Extends out to 10,000 Kilometers (6,000 miles), but it begins to thin at higher elevations, therefore its most concentrated area is as very low elevation. More than 50% of its total mass is below 6 km. III. Composition of the Atmosphere a. Permanent Gases (do not significantly impact the weather) i. Nitrogen (78% of total) & Oxygen (21% of total) are the most abundant gases, the last major gas is Argon (1%) 1. Nitrogen is made by the decay and burning of organic matter, volcanic eruptions, and the chemical breakdown of certain rocks. 2. “Oxygen is produced by vegetation and is removed by a variety of organic and inorganic process.” b. Variable Gases (significantly impact the weather) i. Water Vapor 1. Is considered a variable gas because it has a range of concentration of 4% over tropical areas, to less than 1% over deserts and Polar Regions. Geography 1 (41100). Prof. Dean . Wint., Jan 4, 2012 . Read Chp 3 . Pg 54-73 2 2. W.V. does not include clouds, those are visible liquid, not vapor which is invisible. Although W.V. is the source of generation for clouds. 3. Significantly impacts the weather by helping to thermoregulate the Earth. ii. Carbon Dioxide 1. Is able to absorb infrared radiation and as a result warm up the lower atmosphere. 2. It’s concentration in the atmosphere has steadily increased by 0.0002% due to the burning of fossil fuels and with its increase is expected to have significant effects on global climate change. iii. Ozone 1. Is composed of three oxygen atoms. 2. Absorbs ultraviolet solar radiation. c. Particulates (Aerosols) i. Are non-gaseous particles that exist in the atmosphere. 1. Includes liquid water, ice, volcanic ash, smoke, emissions, etc. 2. Help to make clouds, rain snow, sleet, etc. 3. Most common around areas that create them, such as above cities. ii. Affect the weather in two ways. 1. Works to form clouds by being hygroscopic (meaning they absorb water) 2. They either absorb or reflect sunlight. IV. Vertical Structure of the Atmosphere a. In order of the most atmospheric thermal layers from the surface up into the atmosphere is: i. Troposphere: Goes from Earths surface up to 10-15 km and is where most weather occurs as air is overturned. ii. Stratosphere: mostly stagnant air. iii. Mesosphere: middle of the atmosphere. iv. Thermosphere: where “heat” rests. v. Exosphere start of transition into interplanetary space. Geography 1 (41100). Prof. Dean . Wint., Jan 4, 2012 . Read Chp 3 . Pg 54-73 3 b. Temperature Patterns in the Atmosphere i. Changes with altitude. ii. Temperature does not steadily decrease as you move up into the atmosphere. It moves in a zig-zag pattern. c. Air Pressure i. Analogous to the “weight” of the air. ii. Decreases with height at non-constant rate. iii. Low-level air is compressed by air above, so surface pressure is higher closer to the Earth. iv. 90% of atmosphere is in the lowest 16km (10 miles). d. Composition i. Homosphere-lowest 80km and is where we find a uniform mixture of atmospheric gases. ii. Heterosphere-above homosphere and gases tend to become layered according to their weights. iii. Ozone layer- between 15 and 48 km; ozonosphere is not entirely composed of ozone, it is just where it is found in greatest concentration. iv. Ionsophere-between 60 and 400 km; source of auroras aid aids long distance communication because of electrically charged molecules and atoms. e. Human-Induced Atmosphere Change i. Mainly seen as the introduction of impurities into the atmosphere at rapid pace. ii. Received international attention in recent years. iii. Example is the reduction of ozone by CFCs, which were present in aerosols, refrigerants and other cooling devices. f. Depletion of Ozone Layer i. The Ozone Layer is a thin layer of molecules, each made up of three Oxygen atoms, which are found in the stratosphere and absorb most of the potentially dangerous ultraviolet radiation from the sun. ii. Chemistry of ozone depletion. 1. Since the 1970s the Ozone layer has been depleted, primarily by the release of chlorofluorocarbons (CFCs), Geography 1 (41100). Prof. Dean . Wint., Jan 4, 2012 . Read Chp 3 . Pg 54-73 4 which in themselves are not harmful but when they reach the ozonosphere and are influenced by UV radiation, a chlorine atom is released which begins to degrade Ozone molecules. Furthermore, each chlorine atom can destroy as many as 100,000 ozone molecules. iii. The “Hole” in the Ozone layer. 1. All areas of the ozone are thinning but some areas, over the Antarctic and the Arctic are totally disappearing or are gone. 2. Ozone depletion is severely impacting polar regions because of a set of unique weather developments called a polar vortex which accelerates ozone depletion. iv. The Montreal Protocol was a world meeting to discuss issues with the Ozone layer and banning of CFCs. g. Human-Induced Atmospheric Change i. While pollutants have always been in the atmosphere (from things such as volcanoes, wildfires, etc.), humans have greatly magnified the amount of harmful pollutants within the atmosphere. ii. Primary versus secondary pollutants iii. Primary pollutants 1. Particulates 2. Carbon monoxide 3. Nitrogen compounds 4. Sulfur compounds iv. Secondary pollutants: are when a gas will react to ultraviolet radiation from sunlight to produce a secondary pollutant. 1. Photochemical smog 2. Ozone v. Consequences of Anthropogenic Air Pollution. 1. All affect human lung function. 2. Some produce acid rain. 3. Some specifically damage plant life. Geography 1 (41100). Prof. Dean . Wint., Jan 4, 2012 . Read Chp 3 . Pg 54-73 5 V. Weather and Climate a. Weather- short-term atmospheric conditions for a specific area. b. Meteorology is the study of weather. c. Climate- aggregate long-term weather conditions. d. Climatology e. Weather versus climate i. Weather and climate both have a direct affect on the type of life that can develop in an area. ii. Our goal of studying atmosphere is to understand the climate of given areas it is helpful to also understand the more dynamic actions of weather. f. Elements (how we perceive weather and climate) and the Controls (what causes changes in weather and climate). i. Elements: Temperature, pressure, wind and moisture content ii. Controls: Latitude, distribution of land and water, general circulation of the atmosphere, general circulation of the oceans, altitude, topographic barriers and storms. g. Seattle, WA, and Fargo, ND, have vastly different climates because of the different controls of weather, specifically its proximity to water. h. Maritime climates typically much more humid than continental climates. i. General circulation of the atmosphere i. Semipermanent wind pattern on Earth j. General circulation of the oceans i. Oceanic broad-scale semi-permanent motions that also assist, to a lesser degree than the atmosphere, in thermoregulation. k. Altitude i. Four controls of weather and climate affected by altitude and generally decrease upward in the troposphere. l. Topographic barriers i. Can drastically alter climate due to orographic change in wind patterns. m. Storms i. Control weather and climate through atmospheric modification. Geography 1 (41100). Prof. Dean . Wint., Jan 4, 2012 . Read Chp 3 . Pg 54-73 6 1. Some storms prominent enough to affect climate VI. Coriolis effect a. Rotation of Earth modifies/defects the path of forward motion of freely moving objects (ball, bullet, airplane, or even a person walking) over great distances. i. If a rocket were fired from the North Pole directly downward towards New York City, the rocket would have to be adjusted for the Nothern Hemispheres rotation from the West for it to properly reach its target. b. Discovered by Gaspard Coriolis c. Causes a rightward turn to motion in the Northern Hemisphere. d. Causes a leftward turn in the Southern Hemisphere. e. Deflection greatest at the poles; zero at the equator. f. Deflection increases in proportion to the speed of the object, faster objects are affected more. g. Has no influence on speed only direction. h. It affects both wind and ocean currents.