DataStreme Activity 6B:

RISING AND SINKING AIR

Do Now:

  1. Print this file.
  2. Print the Wednesday Image 1 File.
  3. Print (when available) the Thursday, 19 October 2000, Daily Summary File.

To Do Activity:

  1. Read Chapter 6 in STUDY GUIDE, Part A: Narrative.
  2. Go to STUDY GUIDE, Part B: Applications. Start Activity 6B.
  3. Return here (Wednesday Activity B File) when told to do so.

Go To STUDY GUIDE - Activity 6B Now


WELCOME BACK: Procedure continued from STUDY GUIDE.

  1. Rising and sinking air motions occurring in the atmosphere may be produced by several situations. Rising motion can be caused by approaching fronts, convergence of winds blowing into a surface low pressure center which forces air aloft, localized daytime solar heating, or orographic flow over rising terrain. Conversely, sinking motion can occur with divergence of air in Highs or by air flow down descending elevations. Image 1 is the Stüve diagram of the sounding from Tallahassee, Florida (TLH) for 0000Z 18 OCT 2000. The high pressure system that has dominated the weather of the eastern US for over a week provided generally clear skies in Tallahassee where several days of solar heating produced vertical motions that have mixed the lower atmosphere.

    The winds at various atmospheric levels inferred from the radiosonde's drift during its ascent are plotted along the right side of the graph at altitudes represented by tic marks on the vertical axis. The direction for each wind barb follows the surface station model where north is to the top of the page. The surface wind is from the [(northwest) (southeast)] at 1 to 2 knots. This light wind and clear sky situation favored radiational cooling of the surface.

  2. The heavy curve to the right on the Stüve diagram is the temperature profile while the heavy curve to the left is the dewpoint profile. Radiational cooling of the air immediately above the ground can be seen in the temperature profile as [(a temperature inversion) (an isothermal layer)]. Also, the temperature profile from about 820 mb up to 800 mb is [(a temperature inversion) (an isothermal layer)].

  3. Under clear afternoon skies solar heating of the ground forced near-surface air to warm, expand, and rise. The surface air would have begun rising as a(n) [(unsaturated or "dry") (saturated)] air parcel. This rising air would therefore [(warm) (cool)] adiabatically. The air temperatures observed in this rising air are shown by the temperature profile from about 1000 mb to about 820 mb. Note that this line is parallel to the solid adiabatic lapse rate line on the Stüve. This path indicates the air was cooling at the [(dry) (saturated)] adiabatic lapse rate.

  4. The air temperature at the 950 mb level is about [(22) (20) (18)] °C . The air temperature at 850 mb is about [(20) (18) (13)] °C. Thus, the temperature change of the air in rising from the 950 mb to 850 mb is about ________ C°.

    From the altitude values along the left side of the Stüve diagram at the pressure levels, 950 mb occurs at ________ m and 850 mb occurs at ________ m. Therefore the distance between 950 and 850 mb is ________ m. Thus this temperature change per altitude is approximately equal to the [(dry) (saturated)] adiabatic lapse rate of 10 Celsius degrees per thousand meters.

  5. For comparison, we can look at air in the middle troposphere above the surface influences producing vertical motions. As you recall from Activity 6A, the presence of clouds is indicated on a Stüve diagram when the temperature and the dewpoint at a designated level differ by several degrees or less. Compare the temperatures and dewpoints of the air from 700 mb to 600 mb. This air is [(saturated) (unsaturated)]. The temperature at 700 mb is about [(10) (8) (0)] °C while the temperature of the air at 600 mb is about [(10) (1.5) (-5)] °C. The temperature change of the air from the 700 mb to 600 mb is about ________ C°.

    From the altitude values on the Stüve diagram, 700 mb occurs at ________ m and 600 mb occurs at ________ m. Therefore the distance between 700 and 600 mb is ________ m. This actual lapse rate of the air is about 5 Celsius degrees per 1000 m.

  6. The temperature and dewpoint are within several degrees of each other at about [(420 mb) (360 mb) (both of these levels)].Consequently, the air at these levels can be assumed to be [(saturated) (unsaturated)], indicating that clouds [(are) (are not)] probably present. If clouds were present, considering the temperatures at those altitudes, the clouds would probably contain [(water droplets only) (ice particles perhaps mixed with supercooled water droplets)]. This type of cloud would be a [(cumulus) (cirrus)] cloud. (Clouds at these levels are not formed by the near-surface lifting processes mentioned at the beginning of this activity.)

DataStreme Activity 6A (Clouds, Temperature, and Air Pressure) investigated the relationships between air temperature and air pressure changes. The Stüve diagram used in this activity graphically displays these relationships with sets of lines drawn to represent temperature changes which occur when saturated or unsaturated air undergoes vertical motion. The radiosonde sounding for Tallahassee which you have just examined shows that air in the open atmosphere actually behaves according to these relationships!

You might have your students print out the text data of rawinsonde observations and plot them on a blank Stüve diagram (available on the DataStreme homepage) when Highs, Lows, and fronts pass nearby. Then compare your cloud and sky conditions with the temperature profiles you have plotted.


Faxing Instructions:

After completing this week's applications, fax the following pages to your LIT mentor by Monday, 23 Oct. 2000:

  1. Chapter 6 Progress Response Form from the Part B: Applications binder, Week 6, or the DataStreme Homepage Progress Response Form,
  2. 6A and 6B Activity Response Form

You may wish to trace the temperature processes of Activity 6B on the Stüve (STUDY GUIDE, Part B: Applications, page 6B-2) and fax it to your mentor for review along with those pages above if you have questions.


Return to DataStreme Homepage

URL: datastreme/learn/b_act.html
©Copyright, 2000, American Meteorological Society