Models in Environmental Regulatory Decision Making (2007) / Chapter Skim
Currently Skimming:
3 Model Development
3 Model Development
Pages 83-103
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 83... ...
Model development involves the definition of model objectives, conceptualization of the problem, translation into a computational model, and model testing, revision, and application. Although almost all model development follows these general steps, models designed for regulatory purposes are subject to constraints in addition to those for models developed strictly for research.
|
From page 84... ...
Box 1-1 in Chapter 1 contains a brief history of EPA's effort to model tropospheric ozone. ALTERNATIVE MODEL DEVELOPMENT PATHWAYS Some regulatory models arise from those developed as general research tools.
|
From page 85... ...
Documentation occurs at each step of the process, as do certain aspects of evaluation. Chapter 4 describes in detail the evaluation process that occurs throughout the model's life cycle, compressing the model lifecycle further into 4 steps (problem identification, conceptual
|
From page 86... ...
and antitampering program benefits. • In-use emissions-factor estimates for nonexhaust emissions adjusted for real-world fuel volatility as • measured by Reid vapor pressure (RVP)
|
From page 87... ...
programs patterned after California regulations. • Revised speed corrections used to model emissions factors over range of traffic speeds.
|
From page 88... ...
model development, computational model development, model use) to make the evaluation process more tractable to the reader.
|
From page 89... ...
State variables represented Level of process detail necessary Scientific foundations Computational Model Development Algorithms Mathematical/computational methods Inputs Hardware platforms and software infrastructure User interface Calibration/parameter determination Documentation Model Testing and Revision Theoretical corroboration Model components verification Corroboration (independent data) Sensitivity analysis Uncertainty analysis Robustness determination Comparison to evaluation criteria set during formulation Model Use Analysis of Scenarios Predictions evaluation Regulations assessment Policy analysis and evaluation framework, allowing alternative policy initiatives to be analyzed, perhaps by varying basic model assumptions.
|
From page 90... ...
MODEL DEVELOPMENT PHASES Definition of Model Purpose The first step involves defining the major purpose or purposes for which the model is developed. As discussed in Chapter 4, this occurs at the problem identification stage when decision makers, model developers, and other analysts must consider regulatory needs and whether
|
From page 91... ...
(2005) describe examples of how integrated measurements and modeling have advanced risk assessment modeling by providing more insight on how intake of chemicals by humans relates to tissue dose and metabolism.
|
From page 92... ...
This initial stage sets the direction for the conceptual model and the computational model development. The sidebar from Alice in Wonderland illustrates this message.
|
From page 93... ...
• Summarize available knowledge needed for regulatory decisions. Insight from Alice's Adventures in Wonderland by Lewis Carroll Alice speaking to the Cheshire cat: "Would you tell me, please, which way I ought to go from here?
|
From page 94... ...
• Who will be the major model users and what constraints does that imply for model application once developed? What is the level of expertise of the proposed users?
|
From page 95... ...
Dealing with the issue of how to obtain the required inputs before developing the computational model and before building bridges with the measurement communities can make a substantial difference in the success of the modeling effort. All the above questions apply to both pre- and post-regulatory models.
|
From page 96... ...
Figure 3-2 provides an example of a conceptual model for assessing eutrophication. This conceptual model can be viewed as a map summarizing the structure of a model, the inputs, the state variables and outputs, and possibly the domain of applicability.
|
From page 97... ...
There are distinct trade-offs in model development that should be addressed at the time of the conceptual model formulation. No one model can do everything.
|
From page 98... ...
• Methods for analysis of model results, including graphic outputs and the capability to conduct sensitivity and uncertainty analysis.
|
From page 99... ...
Thus, there are limitations to the degree that CMAQ can be adapted. Another example is the MOBILE model (Table 3-1)
|
From page 100... ...
described how EPA's new mobile-source emissions model, known as the MOVES model, will address this and other issues raised by the NRC. Additional considerations probably will arise for pre- and postregulatory models.
|
From page 101... ...
CMAQ allows its user to choose among three gas-phase chemistry mechanisms, depending on the specifics of the problem being modeled. The modular approach to CMAQ allows the level of complexity in the application to be aligned with the needs of the regulatory decisions.
|
From page 102... ...
Measurements are also a critical tool for corroborating model results. Once developed, models can drive priorities for measurements that ultimately get used in modifying existing models or in developing new ones.
|
From page 103... ...
Recommendations Models used in the regulatory process should be no more complicated than is necessary to inform regulatory decisions. In the process of evaluating whether a model is suitable for its given application, there should be a critical evaluation of whether the model has been made unreasonably complicated.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.