Lecture9 - EAS 1600 Introduction to Environmental Sciences...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
EAS 1600 Introduction to Environmental Sciences Class 9 - Circulation of the Atmosphere In this class we discuss the general circulation of the atmosphere and its role in redistributing the energy that was unevenly deposited on the Earth by the absorption of solar energy. It is sometimes said that the atmosphere is one massive heat engine driven by solar radiation and that weather is simply the manifestation of the heat engine’s work. Today we find out why ... But first a few definitions: General circulation: The long-term average winds (directions and speed) in the atmosphere as a function of location. By long- term,we usually mean on decadal time scales. Climate: The long-term average state of the atmosphere. Weather: The instantaneous state of the atmosphere and its short-term variability. Sensible heat: The energy contained in molecules as a result of their random kinetic energy (or motion). In other words the energy you can feel as heat. Thermal conduction: The transfer of sensible heat through materials or gases that are in contact as a result of the collision of hot molecules with cool molecules. Note no transfer of mass is required. Thermal convection and advection: The transfer of sensible heat by the movement (or exchange) of mass. Convection usually refers to vertical movement and advection to horizontal movement. Our motivation: Recall: The energy budget of solar and planetary radiation is in balance in total, but not as a function of latitude.
Image of page 1

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

View Full Document Right Arrow Icon
The imbalance requires energy flow from tropics to poles… One possible way for the atmosphere to accomplish this is through its General Circulation. If winds carry warm air pole-ward and cool air to the tropics (on average), there will be a net flow of energy (as sensible heat) like that illustrated above. Let’s see how... Air, like all bodies, are subject to the Laws of Motion. Things at rest will tend to remain at rest. To move an object at rest or change the speed or direction of an object, a force must be applied. F = ma So the movement of air requires a force. In general there are two forces available: 1. Gravity 2. Pressure (Remember! This is actually a force per unit area.) If the sum of the gravitational and pressure forces are not in balance there will be a net force and the air will move . The movement of air is wind . Winds averaged over long-time scales is part of the General Circulation. Horizontal Motion is caused by pressure forces alone. Since gravity acts in the vertical motion, it can not influence horizontal movement For pressure to move air, it must supply a net force, and ... Pressure provides a net force if there is a change in pressure over some distance – we call this the pressure gradient force. Air tends to moves from regions of high pressure to regions of low pressure.
Image of page 2
Image of page 3
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