The origins of this simulation involved the desire to convert a standard introductory meteorology lecture course into one where constructivism was the main instructional model and students were expected to take a more active role in their own learning-all without reduction of class size. The course goals were expanded to include learning how to learn science as well as learning science content. One of the major tools used to accomplish this was the use of World Wide Web server software that manages Internet class activities. ClassNet, Van Gorp and Boysen (1997), was developed to accomplish this task (http://classnet.cc.iastate.edu/). This tool allowed every student to be an active participant in learning activities with easy access to course materials, enhanced communication with the instructor and other students, rapid feedback concerning assignment and exam scores, and ready access to their private records of course performance.

Course materials have been designed for introductory science courses at the secondary and college level. They are intended to be supplemental to the course, allowing the instructor to decide which materials to use and which to omit. Experience with these materials has shown that their effect, especially the effect of the simulations, is gradual and sufficient time must be allowed to observe a difference in student behavior and attitude. At Iowa State University students often find the simulations to be uncomfortable at first because they use them before they hear the corresponding lectures, but this approach is deliberate and is intended to create questions in students' minds so they will come to class seeking answers.

It is recommended that part of class time be allotted to the use of Small Group Activities. These allow students the opportunity to break away from the passive mode utilized in most large-scale classes and become more active learners. These activities have been well received by students. They often end up sitting in about the same place in the auditorium for every class meeting and usually look forward to interacting with the people who sit near them week after week. Various collaborative activities are used to draw each student into the construction of hypotheses for explaining observed scientific phenomena or processes. Lectures are then used to provide explanations when students have explored, tested and questioned various factors that relate to central course concepts.

Materials development for the new learning environment did not rely on traditional instructional development models. The new materials could not be designed to simply teach the course content when the goal was to encourage the learner to explore, conjecture and test ideas. The chosen solution was to develop problem-based simulations that pose scenarios and provide tools with which learners can explore, and that accurately reflect the results of specific learner's actions. The materials have served to set the stage for further learning by revealing misconceptions, raising questions, activating relevant existing knowledge, and alerting the learner to the structure and utility of the material to be learned.

MountainSim (Figure 1) models the adiabatic process of a rising and falling air mass. An animated air mass, whose temperature and vapor pressure are displayed numerically and graphically, passes over a mountain. The student's goal is either to cause precipitation at a given altitude or to produce a specified temperature increase when the air mass descends. To reach these goals, the student must set the initial temperature and vapor pressure values for the air mass. When set in motion, the simulation animates the air movement and any precipitation that occurs. Two graphs are also displayed. One graph plots temperature and vapor pressure for the air mass and the other shows temperature and altitude. A notebook (use the View Log button) that records all trials is also provided.

Figure 1. MountainSim

A deep understanding of the simulation involves the ability to cause precipitation at a specified altitude, predict and produce temperature changes, and interpret and use the graphical representations. Students who make use of the notebook are usually the most successful.

The use of MountainSim supports two major goals. It provides a semi-controlled opportunity for students to exercise skills in scientific reasoning and problem solving, and it serves as a foundation for understanding adiabatic phenomena. For these goals to be met the instructor must take care in assigning the simulation and must follow the simulation experience with discussion of problem solving strategies.

MountainSim is intended for use before rather than after any lecture on related topics. Experience has shown, however, that the simulation should be previewed in class prior to asking the students to use it. The operational features of the simulation should be demonstrated and the graphs and dials explained. The permanent line on the vapor pressure vs. temperature graph should be identified as the vapor saturation curve. However, students should not be told how to solve the problems.

It is recommended that students be advised to play with the simulation and then to complete the assigned tasks. They should be strongly encouraged to make and test predictions as well as to try and explain the events they observe. The following Problem Solving Strategy (or one similar to it) is recommended.

Simulation experience:

1. Explore the simulation, identifying the inputs, outputs and goals.

2. Estimate and note the expected outcomes.

3. Develop a plan to test these expectations.

4. Collect sufficient data and record results.

5. Analyze and summarize the data.

6. Compare and contrast the results with the expected results.

7. Question the reasonableness of the results and seek explanations for them.

8. Rethink the process, identifying additional data that needs to be collected and important questions that need to be resolved.

A general approach to help students learn to think as scientists think is to have them respond to questions similar to the following:

What general patterns can you see in your observations?

What might explain what you observed?

What did you observe that you didn't expect?

What factors are there that you can't explain?

The student responses can be used to generate discussion in class.

Introduction: A leaf as a marker (Figure 1) traces a wind blowing from left to right across the mountain. The initial conditions of the atmosphere at the base of the mountain on the left side are represented by the leaf placement on the vapor pressure/temperature graph. Use the slider controls to manipulate the initial conditions and run the simulation to answer the associated questions. Be patient, the simulation may take a while to load. You should see a picture of a mountain and two graphs. If you are having trouble viewing the simulation, you may need to click on the "Start Wind" button, or try another computer that is Java enabled.

Humidity emphasis questions:

1) Start with a vapor pressure of 10mb. Enter a temperature (between 0 C and 40 C) that will cause a cloud to form.

2) Start with a vapor pressure of 10mb. Enter a temperature (between 0 C and 40 C) that will not cause a cloud to form.

3) Given an initial air temperature of 28 C, enter an initial dew point temperature (between 0 C and 40 C) which will cause a cloud to form below 500m.

4) Given an initial air temperature of 28 C, enter an initial dew point temperature (between 0 C and 40 C) which will cause a cloud to form above 1000m.

5) Given an initial air temperature of 28 C, enter an initial dew point temperature (between -10 C and 40 C) which will cause no cloud to form.

6) Given an initial air temperature of 20 C, enter an initial water vapor pressure (between 0 mb and 24 mb) which will cause instantaneous cloud formation.

7) Given an initial air temperature of 20 C, enter an initial water vapor pressure (between 0 mb and 24 mb) which will cause cloud formation above 1000m.

8) Given an initial air temperature of 20 C, enter an initial water vapor pressure (between 0 mb and 24 mb) which will cause no cloud formation.

Adiabatic process emphasis questions:

A. Run the simulation for the default case (Temperature=25; Water Vapor Pressure=7; Dewpoint Temperature=2) and use this as a reference for future observations.

B. Next experiment with various initial positions of the leaf on the vapor pressure/temperature graph in order to achieve a desired 5-5.5 degree Celsius difference between the initial and final temperature.

1) What would be a good strategy for finding the initial leaf position that caused the desired change?

2) How does the leaf path on the vapor pressure/temperature graph for the reference case compare with the path where the 5-5.5 degree Celsius temperature difference occurs? What do you think is happening?

3) How does the path on the altitude/temperature graph for the reference case compare with the path where the 5-5.5 degree C temperature difference occurs? Suggest a reason for the differences.

4) Watch both graphs simultaneously during conditions when a cloud forms. What relationship between the two curves do you observe?

5) In this simulation, rain falls each time a cloud appears. Often there are clouds present, but no rain. Hypothesize if a cloud formed but no rain fell, would you see the same temperature difference between the windward and leeward sides of the mountain? Why or why not?

During an in-class activity you may be asked to share what you noticed that is curious about these graphical representations.

Following students' use of the simulation, the strategies for completing the tasks and the conclusions that were reached can be shared. A small group activity is a good method to encourage students to share and justify their observations. Some or all the following conclusions should result from group discussions:

1. The temperature of the air mass decreases as the air rises.

2. If the temperature decreases to a point on the vapor saturation curve, precipitation occurs.

3. Only if precipitation occurs is the final temperature of the air mass higher than the initial temperature.

4. The temperature vs. vapor pressure plot does not cross the vapor saturation curve.

5. For a given initial temperature, higher vapor pressures produce precipitation at lower altitudes.

6. The temperature of the air passing over the mountain changes at different rates depending on the occurrence of precipitation.

Group observations can lead to questions of why these phenomena occur and set the stage for the subsequent lecture. The following thought questions may also be used to promote deeper thinking about the processes occurring in the simulation.

1. If the simulation forms a cloud at a vapor pressure of 10 mb and a given initial temperature, what change must be made in the initial temperature to prevent the formation of a cloud at 10 mb of pressure? Why does this temperature change prevent the cloud from forming?

2. If the simulation forms a cloud at an air temperature of 20 C. and a given initial vapor pressure, what change must be made to the initial vapor pressure to MountainSim with humidity emphasis to prevent a cloud from forming at a temperature of 20 C.? Why does this vapor pressure change prevent the formation of a cloud?

3. What causes condensation? What changes in initial temperature and/or pressure would cause a cloud to form? Give at least two answers.

4. Under what meteorological conditions would the temperature of an air mass decrease?

5. Under what meteorological conditions would the vapor pressure of an air mass increase?

MountainSim with advection emphasis:

1. Two air masses pass over identical mountains. In one air mass precipitation occurs at the base of the mountain and continues to the top. For the other air mass no precipitation occurs. If the initial temperatures of the two air masses are the same, will their temperatures still be the same at the mountain peaks? Explain your answer.

2. What about the temperatures of the two air masses when they descend to the bases of the mountains on the leeward side? Will they be higher, lower or the same as their initial temperatures?

MountainSim with adiabatic processes emphasis:

1. Why does air cool when it rises but warm when it descends?

2. Why are there no clouds on the side of the mountain where the air descends?

3. What causes the temperature change from one side of the mountain to the other?