CC.10 Modeling
ESSENTIAL TO KNOW
- The Earth can be considered a system in which things that can range from the planet to atoms interact with each other according to physical laws.
- To understand environmental processes, we must create a conceptual or mathematical model of the system (or parts of the system) that describes the components of the system and their interactions. The parts are often called “cells,” “boxes,” or “compartments.”
- There are many types of interaction. Examples are heat transfer between ocean and atmosphere, and the effect of changes in food supply on the population of an animal species.
- Conceptualized models must be parameterized and tested. Parameterization includes applying data to each model cell and developing equations to describe the flow of the modeled parameter between each adjacent pair of cells. Testing consists of running the model to see how it fits measured data. Parameters are adjusted between tests until the model fits the data set.
- Models must be validated by being applied to a data set that was not used in testing the model. This is often difficult to do for models for which the environmental data sets are sparse.
- Sensitivity analysis is performed by changing model inputs or assumptions and observing the changes in output. This type of analysis can help identify the parameters or processes that most affect the system’s behavior and, thus, are the most important for field studies or monitoring.
- To facilitate model creation, interactions are often assumed to be linear. Interactions are linear if one component of a system varies in direct proportion to a change in the other. However, most, if not all, natural systems include many nonlinear interactions.
- The nonlinear nature of natural systems limits the degree to which models can be used to make accurate predictions of future changes in the modeled system. Models of systems that are nonlinear in nature can be used only to predict a range of likely future conditions, and these predictions become more uncertain with increasing time into the future.