Key for Homework 5

 

  1. Fill in the blanks in this paragraph: "The ITCZ is a region of __RISING_____________ (sinking or rising?) motion in the atmosphere. It is characterized by __FREQUENT_____________ (frequent or infrequent?) thunderstorms, and is typically found ___NEAR_______________ (far from or near?) the equator, typically in the __SUMMER_____________ (summer or winter?) hemisphere. At the ___TROPOPAUSE__________ (surface or tropopause?), outflow from the ITCZ flows poleward, and is deflected by __THE_CORIOLIS_FORCE_____ (friction, the pressure gradient force, or the coriolis force?) into the __SUBTROPICAL_JET_____________ (polar jet or subtropical jet?). At these latitudes, air __SINKS_________ (rises or sinks?) into the subtropical __HIGH___________ (high or low?) pressure belts, which are regions of great __DESERTS_____ (deserts or rain forests?). These motions of the atmosphere constitute the _HADLEY________ (Hadley, Ferrell or Polar) Cell."

     

  2. Fill in the blanks in this paragraph: "The polar regions are characterized by ___HIGH_____ (high or low?) pressure. At the surface, winds flow from the polar latitudes and ___CONVERGE_______ (converge or diverge?) with winds flowing poleward from the subtropical highs at the polar front, which is a region of ___RISING_____ (rising or sinking?) motion. According to the Thermal Wind Relationship, directly above the polar front we should find the __POLAR_____ (subtropical or polar?) jet stream. This jet stream is found just below the ___TROPOPAUSE____ (stratopause, tropopause or mesopause?) and occurs because of differences in thickness on the poleward and equatorward sides of the polar front. Equatorward of the polar front, thicknesses are __LARGE______ (small or large?), whereas poleward of the polar front, thicknesses are _SMALL____ (small or large?). Aloft, these differences in thickness result in _LARGE______ (small or large?) pressure gradient forces. Since this jet stream _IS_ (is or is not?) geostrophic, the winds in the jet stream blow _PARALLEL_TO_____________________ (parallel to or across) contours, with colder temperatures to the _LEFT___ (right or left?) of the flow in the Northern Hemisphere."

     

  3. What are "trade winds"? (Tell me where you find them on earth, at what level you find them, what direction these winds are blowing, etc.)

    Trade winds are winds near the surface that blow from east to west at tropical latitudes.

     

  4. What are the winds like in the "horse latitudes"? Where are the "horse latitudes"?

    Winds are weak in the horse latitudes, which are centered near 30°N and 30°S.

     

  5. If the rotation of the earth reversed, which way would the subtropical jet stream flow? Why?

    If the rotation of the earth reversed, the Coriolis Force would deflect motions to the LEFT in the Northern Hemisphere, rather than to the RIGHT. Therefore, upper-level outflow from the ITCZ would be deflected to the LEFT and create a jet stream that flowed from east to west (that is, the opposite of the direction it flows in the real world). (NOTE: This was a particularly difficult question and therefore will be graded very leniently!)

     

  6. Follow these instructions (or just go directly to this web page):
    • Go to the textbook's website at http://info.brookscole.com/ackerman. (You will need to be using Internet Explorer--not Firefox or any other browser--for this to work.)
    • Click on the link that reads "Student Book Companion Site" (the link is red and on the right side of the window).
    • On the dropdown menu for "Select a chapter", pick Chapter 7--"Global Scale Winds".
    • Along the left side of the wind, click on "Applets".
    • Finally, click on "Making a Jet Stream".

    Once you have loaded the applet, use it to answer the following questions about the Thermal Wind Relationship:

    1. As you change the temperature gradient what happens to the maximum wind speed?

      The stronger the temperature gradient, the stronger the maximum winds are.

    2. What does this simple model predict about the global winds if the temperature was uniform across the globe?

      If the global temperatures were uniform, the thermal wind relationship tells us that there would be no jet streams.

    3. About how high up are the strongest winds in the Midlatitude Jet Stream?

      About 10 kilometers, or approximately the height of the tropopause.

    4. At about what latitude would you find the Midlatitude Jet Stream?

      About 45°N in the Northern Hemisphere.

     

  7. In a cold air mass, the 500mb surface is ______________ (closer to or farther from?) the ground than it is in a warm air mass? Why?

    CLOSER. The thickness of the 1000mb-500mb layer will be less for cold air than it is for warm air. Since the 1000mb surface will be near the ground regardless of the temperature of the air, in cold air the 500mb surface is relatively close to the ground.

  8. Explain the requirements for a geographic region to serve as a "source region" for an air mass?

    To be a source region, an area must be (1) extensive, (2) uniform, and (3) have generally weak winds.

     

  9. Why is there no such thing as a mA air mass?

    On Earth, there is no viable source region for maritime arctic (mA) air masses. Such a source region would need to be very cold yet moist, but any place on Earth that is very cold will not have open water.