ATMS 120 1st Edition Exam 1 Study Guide Lectures 1 10 indicates takeaway important note Lecture 1 January 23 Air pressure decreases rapidly with height The primary gases in Earth s atmosphere Water vapor Nitrogen 78 most abundant Methane Ozone Carbon Dioxide Oxygen 21 Argon The rest of these gases add up for the other 1 of Earth s atmosphere Greenhouse gases are not transparent to the sun s energy They efficiently absorb this energy and warm the atmosphere Ozone carbon dioxide methane water vapor Without greenhouse gases our planet would be at 0 C Temperature a measure of the average speed of all the molecules in a substance solid liquid or gas The higher the temperature the faster the air molecules move The faster the molecules move the more space they will need to move around Warming the air will cause it to expand Cooling the air will cause it to contract This is why warm air is less dense than cold air Lecture 2 January 28 Uneven surface heating drives atmospheric circulations This is caused by The angle of the sun s rays and length of daylight hours are not constant This is what causes seasons The earth is covered with many different surface types that absorb energy differently Mother nature constantly tries to get to equilibrium The tilt of the earth dominates seasons it s not about the distance between the sun and earth Summer Solstice June 21st The sun s rays are direct on the Tropic of Cancer 23 5 N Most daylight hours Autumnal Equinox September 21st The sun s rays are direct on the equator 12 hours of daylight and 12 hours of night Winter Solstice December 21st The sun s rays are direct on the Tropic of Capricorn 23 5 S Least daylight hours Vernal Equinox March 21st The sun s rays are direct on the equator 12 hours of daylight and 12 hours of night The greater the latitude the greater the yearly variation in temperature The proximity to large bodies of water can also affect temperature variation Land heats and cools 5x faster than water Example San Francisco and Champaign Urbana IL are at very similar latitudes but San Fran has a lower variation in yearly temperature because it is located on the west coast and our weather generally comes from the west The Pacific Ocean takes longer to change temperatures and this affects cities immediately east of it keeping them relatively constant The layers of the atmosphere starting at the lowest level Troposphere where we live and where all the world s weather occurs Stratosphere Mesosphere Thermosphere The troposphere and stratosphere are separated by the tropopause or lid Lecture 3 January 30 Pressure the force per unit applied by air Equivalent to the weight of the air in a column over an area such as a square inch Measured in millibars mb An average high pressure can measure up to 1045 mb in Champaign Urbana An average low pressure can measure as low as 980 mb in Champaign Urbana Low pressure causes bad weather Higher pressure is associated with nicer weather Pressure is measured by barometers Barometers use liquid mercury in a dish with a vacuumlike effect The average atmospheric pressure read by a barometer is 29 92 inches As atmospheric pressure increases it pushes on the mercury in the dish driving the mercury in the glass tube past 29 92 inches The thickness of the atmosphere changes based on the temperature Pilots need to adjust their flying altitude based on the temperature of the region in which they are flying in to balance out the pressure There is a very close relationship between wind and pressure Air moves because of horizontal pressure differences Air always moves from higher pressure to lower pressure Lecture 4 February 4 Water is the only element that naturally exists in all three phases solid liquid and gas In the gas phase it is called water vapor In the liquid phase it exists as clouds and raindrops In the solid phase it exists as ice snow ice pellets soft hail graupel and hail You cannot see water vapor Water vapor and steam are not the same thing To change water phases energy in the form of heat is necessary Going from solid liquid gas heat is required energy is supplied to the system Going from gas liquid solid heat is released The energy required to boil a gallon of water is equivalent to 5 sticks of dynamite So the energy released in a phase change of water example Hurricane Katrina s clouds is enormous Total air pressure is the sum of the pressures from individual gases On earth the primary contributors to the dry air pressure are oxygen nitrogen and argon Since water vapor is a highly variable gas in space and time it can contribute a significant amount to the total air pressure Vapor pressure the force per unit area ONLY by the water vapor molecules The combination of dry air and moist air equal total vapor pressure Hot air has the ability to retain more water than cold air When water condenses a lot of energy is released Vapor pressure cannot be measured directly Vapor pressure is calculated based on the dewpoint temperature Saturation vapor pressure the vapor pressure when the atmosphere can no longer hold any more water vapor without condensing out as a liquid When the saturation vapor pressure equals vapor pressure meaning the amount of water in the atmosphere matches the amount that it can hold the relative humidity is 100 and the air is saturated When the saturation vapor pressure is greater than the vapor pressure the relative humidity is less than 100 and the air is not saturated Air has a finite holding capacity for water vapor that depends on temperature Lecture 5 February 6 Dewpoint temperature the temperature to which the air must be cooled for condensation to begin form clouds dew frost and fog When temperature is close to dewpoint temperature humid air When temperature is far from dewpoint temperature dry air Relative humidity a measure of the actual amount of moisture in the air relative to its maximum capacity Relative humidity vapor pressure saturation vapor pressure x 100 If the air is heated up relative humidity drops If the air is cooled down relative humidity rises If water vapor is added relative humidity rises When relative humidity is high evaporation rate is low It is easier to saturate cold air because it doesn t have the ability to contain lots of water vapor Isodrosotherm line of constant dewpoint temperature 5 F increment The primary instrument to measure air data is called a Rawinsonde weather balloon Universal Coordinated Time UTC is the international standard for time