1.
INTRODUCTION
Both education and research in atmospheric science are hampered by the fact that the atmosphere and terrain cannot be brought physically into the classroom or research lab to study and manipulate. Advanced atmospheric simulation models are customarily utilized only by weather forecasters and the research community. Research done by MESO, Inc. and Saint Louis University addressed the possibility of utilizing advanced atmospheric simulation models to create an inquiry-based educational software system called the Virtual Atmospheric Laboratory (VALÔ). The primary objective of the project was to explore the feasibility of developing an easy-to-use interactive experimentation tool that allows students at various educational levels to explore and learn about the atmosphere and the related solar, terrestrial and oceanographic interactions. A secondary, but important, objective was to demonstrate the feasibility of utilizing a low-cost desktop computer to run the experiments---ultimately making this educational tool accessible to every student. A major component of this project was to develop a university-level prototype. This paper will focus on the description and evaluation of the university-level prototype.
2. ATMOSPHERIC MODEL
DESCRIPTION
The simulation model used in the VAL is based on a deterministic numerical atmospheric mesoscale model developed and maintained by MESO, Inc. called the Mesoscale Atmospheric Simulation System (MASS) (Manobianco et al. 1996). The model was adapted for this experimentation. Details of MASS and its configuration capabilities can be found on the web at www.meso.com.
3.
DESCRIPTION OF THE VAL
MESO designed and built a working prototype that can be used to experiment on both real (historical) and idealized cases. The VAL was installed on the Saint Louis University UNIX-based computer laboratory workstation network in the meteorology department.
The prototype VAL software system required the seamless merging of: (1) a
sophisticated physics-based atmospheric mesoscale 3-D model (MASS version
5.11); (2) databases of the basic properties of the earth's surface, e.g.,
terrain elevation, land/water distribution, land use, soil texture, and density
of vegetation; (3) graphical user interfaces which allow the user to easily
control complex computer programs; (4) an idealized data ingestor (5) a model
experimentation module; (6) an experiment visualization module; and (7) hypertext
instructional databases for the user to pursue threads of knowledge through the
use of words and phrases.
A series of HTML pages were developed that activate appropriate common gateway interface (CGI) scripts. On the HTML page, users first select the type of experiment they would like to run. The student then selected and set the meteorological parameters from a menu-based list of 18 parameters and configuration options, e.g., start time and date, land water distribution, and shape of the coastline. An example of the user interface for the configuration phase is shown in Figure 1.
Through the interface, the user is able to choose initialization data from a real (historical) case or one of several idealized atmospheric profiles. This data is then used to form the initial state of the base atmospheric sounding. The base soundings used are tropical, mid-latitude summer, mid-latitude winter, subarctic summer and subarctic winter (McLatchey et al. 1972). The base sounding can then be modified in several ways. The low-level temperature may be adjusted by an arbitrary amount. The adjustment is applied at ground level and the temperature profile is automatically modified in the lowest 150 mb to blend into the base sounding. The water vapor mixing ratio can be modified to preserve the relative moisture lapse rate of the original sounding. A weak (2.5 K per vertical model level) or strong (5 K) temperature inversion may be added to the base sounding at 900 mb.
There are several methods for the user to add cloud cover to the initial state. For example, a single model layer of cloud cover may be added at either 2 km or 13 km above the ground. The cloud layer may be thin (liquid water path of 10 g m‑2) or thick (200 g m‑2). The relative humidity may be specified (overriding the relative humidity in the idealized base states) in three layers of the atmosphere (below 800 mb, between 800 and 450 mb, and above 450 mb). Similarly, the wind direction and speed may be specified in these same three layers.
Once the configuration is complete, the student submits the entries and a quality check of the input is performed. The student is then given the opportunity to either accept or reenter the input data. If the student is satisfied that everything is within realistic ranges, the execution phase of the experiment is initiated. It typically took about 40 minutes for an 18-hour simulation to be completed on a 300 MHz SUN Ultra workstation. This same configuration can now be run on a 400 MHz PC in approximately the same time.
In the prototype VAL, the students were able to view the output, using the visualization software GEMPAK, by choosing from a pre-selected set of fields through the web interface. The fields included many traditional meteorological displays, e.g., mean sea-level pressure, wind vectors, and relative humidity, as well as a few advanced diagnostic parameters, e.g., frontogenetical forcing and advection of equivalent potential temperature.
Figure 1. A excerpt of the user interface display for the configuration phase of the VAL.
4. DESCRIPTION OF THE EXPERIMENTS
There are many ways in which the VAL could be used in the university setting. The syllabi of the undergraduate-level Synoptic Meteorology II and Dynamic Meteorology II courses at Saint Louis University were evaluated to determine which topics would lend themselves naturally to use of the VAL. A sample of the topics that were considered as appropriate for the VAL were:
(1) Development of a direct thermal circulation during frontogenesis;
(2) Development of a direct thermal circulation in lake/sea breezes;
(3) Cyclogenesis and baroclinic instability;
(4) Geostrophic adjustment (forced direct and indirect circulations related to upper‑level jet streaks);
(5) Low‑level jet development related to changes in the planetary boundary layer;
(6) Lake‑effect precipitation; and
(7) Studying the effects of increased soil moisture or deforestation.
It was decided to focus on two fundamental concepts: (1) direct thermal circulations, and (2) dynamically forced direct and indirect thermal circulations. These topics were selected because they both demonstrate important and theoretically well-understood concepts in meteorology. It was important to start with concepts that are well-defined so the VAL could be evaluated for both its accuracy and its educational utility. The direct thermal circulation is the most fundamental and intuitive of atmospheric motions, with the motion being caused by the warmer air rising and cooler air sinking. The other basic circulation type is a dynamically forced circulation, which results in either a direct (indirect) thermal circulation in the entrance (exit) region of an upper-level jet streak. The indirect circulation forces the cooler air to rise and the warmer air to sink. The indirect thermal circulation is very important to many meteorological situations, such as synoptic-scale cyclogenesis, but it is not intuitive to the beginning student and can be a challenge to teach.
The sea breeze direct thermal circulation and forced direct and indirect thermal circulations in the vicinity of upper‑level jet (ULJ) streaks were chosen as the meteorological situations to demonstrate the two selected concepts. The sea breeze experiments demonstrate how unequal heating generates a direct thermal circulation. The geostrophic adjustment experiments demonstrate that divergence and convergence in the entrance and exit regions of an ULJ streak help create direct and indirect thermal circulations. Due to time constraints of the project, the undergraduate students focused on the sea-breeze experiments, while the forced direct and indirect thermal circulations were reviewed by graduate students and instructors.
In these two experiments the educational objectives were to have students (1) understand what parameters play critical roles in developing the vertical circulation, (2) see the time scale of the circulations and the effect on the sensible weather, (3) visualize the depth, strength, and lateral extent of the vertical circulations and their change with time as the Coriolis effect takes hold, (4) test the sensitivity of the circulations to small changes in key variables and compare the idealized case with a real sea breeze case. An important added benefit of this exercise was that the students also became familiar with how to set up and run a numerical model, albeit some of the details of the model would remain "hidden".
An important point to stress is that the VAL experiments were integrated into a course, i.e., they were performed only after lectures were given describing both the MASS model and the physics of the specific phenomena investigated. It is envisioned that all the phenomena studied using the VAL would follow classroom instruction. Then the VAL would be used to experiment on the complex nonlinear interactions involving the specific phenomena.
It was commented by several evaluators that it would seem more appropriate to evaluate a "basic" concept such as a cold front that is more widely taught and understood. This misconception highlights the value of the VAL. Many of the concepts in meteorology, such as the cold front, are based on necessarily oversimplified conceptual models of very complex phenomena that are really the product of many interactions at numerous scales. The VAL can certainly be used to investigate and help reveal the true nature of complex phenomena, However, it was felt that it is essential to begin with a system that operates at one meteorological scale in order be able to understand how the VAL was working.
5. EVALUATION OF THE EXPERIMENTS
There were two parts to evaluating the experimental results. First, did the experiments reinforce the concept being taught and second, did the experiments provide any new insights that could not be illustrated or determined with traditional teaching methods? The answer to both questions is yes.
For example, the basic structure and evolution of the direct thermal circulation was clearly depicted in each experiment. A more classic picture emerged in the control case, but in each case the sea breeze circulation was evident. This helped to reinforce to the students how a direct thermal circulation forms and evolves.
The experiments clearly highlighted some aspects of the sea breeze formation and strength that are not intuitively obvious. The students found that the strength and structure of the sea breeze is not influenced greatly by the exact temperature of the water so long as a minimal thermal contrast of at least 5 ° C developed between the land and the water. Greater thermal contrast has little influence. This intuitively did not seem "right" to the students. However, upon their reexamining theory in a more rigorous manner it was revealed to the students this indeed should be the case. When one examines theory closely it is found that as long as enough thermal contrast exists to create a sea breeze it is the temperature of the warmer (land) surface that is critical to the structure and evolution of the sea breeze. Even a degree or two can make significant differences. However, the exact temperature of the colder (water) surface has little impact on the sea breeze. The reason for this is that it is the warmer air that is acted upon and lifted by the colder air, so the temperature (thermal stability) of the warmer air is very critical to how the direct thermal circulation evolves and what type of weather results. The colder air is not lifted, so its thermal stability has little impact. This actually led to a reinforcement of the larger principle that applies to all lifting mechanisms, that the stability of the lifted air mass is much more important than the stability of the air mass doing the lifting.
The impact of wind direction, wind shear and thermal stability were also investigated. Wind direction of the synoptic-scale wind field was found to have the most significant impact on the sea breeze. Even at a wind speed of 5 knots the change in direction from east to west caused significant changes to the structure and evolution of the sea breeze. In the case where the ocean is positioned on the eastern half of the domain and land positioned on the west, an easterly wind produced similar results to the control case while the west wind case produced a significantly deeper but narrower circulation that is more conducive to upright convection.
Idealized experiments examining geostrophic adjustment of a jet streak were also performed. The hypothesis tested was the influence of curvature on the classic four‑cell vertical motion pattern traditionally taught and used as a forecasting guide. The control case involved a straight jet streak that produced the classic vertical motion pattern. However, the experiment with a cyclonically-curved jet streak produced a very different pattern. Areas of upward motion propagated through quadrants of the jet streak that classic theory predicts on downward motion should occur. This demonstrated the possibility of gaining additional insight into the real nature of specific atmospheric phenomena.
Several real cases of the sea breeze and jet streak were also examined by techniques that could be easily employed in VAL by the researchers and presented at a VAL evaluation workshop which included grade 5-12 science teachers, technical educators, university educators and students. To aid in the selection of effective real sea-breeze cases, researchers were contacted at the Kennedy Space Center's Applied Meteorology Unit involved with sea breeze modeling research. Suggestions, data and analysis from cases were provided to MESO. Several details became apparent when examining the real cases: (1) results of the real cases were substantially more complicated than the ideal cases; (2) ideal cases were much better to use to teach and reinforce basic meteorological concepts; and (3) after examining several ideal cases, the real cases were easier to interpret.
6. EVALUATION OF THE VAL
The general opinion of the educators and students was the VAL performed well at Saint Louis University. The input interfaces allowed the students to set up and run the model quite easily. This part of the VAL was judged by both students and instructors to be a complete success. The only significant limitation within the prototype VAL was in evaluation of the model output and results. The analysis and display capabilities will need the most enhancements.
The major technical issue involved in the mesoscale modeling part of the VAL was that the synthetic initial conditions created by the VAL did not have time-dependent lateral boundary conditions (LBCs) for the model to use. Currently the VAL is capable of generating initial states with a wide range of surface characteristics and vertical atmospheric structure. However, the lack of time-dependent LBCs would be a significant limitation when investigating phenomena such as fronts and baroclinic waves that require initial states with meteorologically realistic horizontal variations. The lack of time-dependent LBCs allowed artificial gradients to develop near the lateral boundaries of the grid.
Meteorologically, the VAL performed very well producing very realistic results. For example, the model results allowed the students to see aspects of the sea breeze development not easily understood. The students were able to see how the temperature and pressure gradient strengthened while the sea breeze developed. The vertical circulation was also clearly evident when viewing cross‑sections of ageostrophic winds on potential temperature surfaces. Clearly the analysis of certain parameters (such as potential temperature) and certain perspectives (such as cross sections) demonstrated that the VAL could provide insight into the real nature of atmospheric phenomena that would otherwise be impossible. This was made clear during the VAL workshop when many experienced teachers and professors came away saying that they learned unique aspects of the sea breeze that they had not understood before. For example, the relative importance of the land‑water temperature contrast as compared to the synoptic-scale wind direction was not clearly understood by the students until running the VAL experiments.
7. SUMMARY AND CONCLUSIONS
Overall, the prototype performance of the VAL met the educational objectives. The VAL interfaces worked well for setting up and running the experiments. Improving the appearance of the output is clearly critical. Features need to be added to the visualization capability of the VAL to allow a more thorough analysis of the output so students can look for the characteristics of the phenomena being examined.
Another critical lesson learned during the evaluation is the instructor needs to spend time working with the VAL in order to "spin‑up" before using it in the classroom setting. With this experience they can help the students choose the most useful parameters and time periods to see the development of the phenomena being investigated. In the author's opinion, the use of the VAL experiments are most effective as a teaching tool only after a careful in-class treatment of the physical processes being examined. Thus, the VAL is used as a tool to rein-force and visualize concepts introduced in the lectures and during map discussions.
The research on the prospects of hosting the VAL on a PC demonstrated that the primary challenge is to operate in a MS Windows environment, which will require further development.
It was exciting to affirm that a real potential exists to utilize advanced atmospheric simulation models in the classroom. MESO is currently exploring avenues for interested parties to collaborate in the further development of the VAL.
8. ACKNOWLEDGMENTS
The authors wish to thank the educators and instructors from the university community, the National Weather Service, and the U.S. Air Force for evaluating the prototype VAL. A special thanks goes to the many Atmospheric Education Resource Agent (AERA) teachers for their suggestions and assistance. This work was supported by the National Science Foundation SBIR program (DMI-9760520).
REFERENCES
Manobianco, J, J.W. Zack, G.E. Taylor, 1996:
Workstation-based real-time mesoscale modeling designed for weather support to
operations at the Kennedy Space Center and Cape Canaveral Air Station. Bull. Amer. Meteor. Soc., 77,
653-672.
McLatchey, R. A., R. W. Fenn, J. E. A. Selby, F. E. Volz, and J. S. Garing, 1972: Optical Properties of the Atmosphere, Environ. Res. Paper 411, Air Force Cambridge Research Lab, Bedford, MA.