Chapter Nine Notes - Chapter 9 The Atmosphere in Motion I...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 9: The Atmosphere in Motion I) Air pressure: mass of air above a given level A) Always decreases with increasing height 1) Most of our atmosphere is crowded close to the earth’s surface 2) causes air pressure to decrease with height, rapidly at first then more slowly at higher altitudes B) Atmospheric model: column of air extending well up into the atmosphere 1) Inside the column dots represent air molecules 2) Assumes that: a) air molecules are not corded close to the surface b) Air density remains constant from the surface up to the top of the column c) Width of the column does not change with height 3) Two air molecules are located at the same elevation and have identical surface air pressures a) Same number of molecules in each column b) Surface air pressure remains the same but the first column cools and the second warms i) Column 1: cools, molecules move more slowly and crowd closer together, more dense air,  column shrinks ii) Column 2: warms, air becomes less dense, column rises C) Warm air a lot is associated with high atmospheric pressure and cold air aloft is associated with low  atmospheric pressure D) Horizontal difference in temperature creates a horizontal difference in pressure.   1) Pressure difference makes a pressure gradient force. 2) Air moves from higher pressure toward lower pressure a) Air begins to accumulate over the lower pressure which causes the air pressure to rise b) Air above higher pressure moves away so the pressure drops E) Any cyclic change in surface pressure brought on by daily temperature changes is concealed by the  pressure changes created by the warming of the upper atmosphere F) Daily pressure changes: 1) In tropics: a)  Max pressures occur around 10am and 10pm b) Minimum near 4:00am and 4:00pm 2) Largest pressure difference occurs near the equator 3) Due to absorption of solar energy by ozone in the upper atmosphere and by water vapor in lower  atmosphere 4) Warming and cooling of the air creates density oscillations (thermal tides) that show up as small  pressure changes near the earth’s surface II) Pressure Measurements A) Barometers: instruments that detect and measure pressure changes 1) Mercury barometer: long glass tube open at one end and closed at the other a) Removing air from the tube and covering the open end then immersing in mercury b) Removing the cover the mercury rises up the tube c) Column of mercury balances the weight of air above the dish 2) Aneroid barometer: most common home barometer a) Small flexible, metal box called an aneroid cell b) Before cell is tightly sealed air is partially removed so that small changes in eternal pressure cause 
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern