What are environmental models?

Environment models seek to re-create what occurs during some event in nature. It is much easier and practical to create computer models to run certain experiments than it is to go out and do the same experiment again and again. Computer models take equations which were usually formulated through testing under natural conditions, and put them into computer programs where they can be run quickly and easily. A model can then output the results of doing these equations into a form which can be output to a screen for the user to view.

What is the basic structure of the model?

Models have three basic parts, starting with the science, moving towards a mathematical representation of that science, and ending in the solution of the mathematics on a computer. The process is actually more like a circle: the answer that comes out of the computer is used to refine the science, which leads to a new set of mathematics, which leads to a new computer program. One of the tasks we face in computer modeling is deciding when we think the answer is "right".

The parts of all the modeling process are:

1. Application: This is the subject that the model is going to address. It determines what is going to be important to the model -- for example, we wouldn't want to include information on how quickly ammonia is converted to atmospheric Nitrogen in a model about how much water runoff there is after a storm. In other words, the application say: This is what we will model. Now how will we do it?
2. Algorithm: How will we get the answer to the question posed above? Here is where we determine which equations are important and where they should be put in the computer program.
3. Architecture: The architecture determines how the model will be used. What kind of computer will run the program, and what kind of programs will use the information? Will the program be downloaded and loaded onto the permanent storage space of a computer, or will it be run over the Internet? Will it run only on Unix workstations, or also on Macintoshes or other PC's?