Considering Calpuff Computational Domain

Posted by on Friday, March 15th, 2019 in Blog

Calpuff is a powerful tool for evaluating the potential dispersion of contaminants throughout a defined area. Developed originally to evaluate the dispersal of volcanic ash, it is also applicable to a wide range of other scenarios, including those that are too complex for evaluation by plume models such as AERMOD. Before you begin using Calpuff, it is a good idea to get a basic grasp of this program’s abilities, limitations, and potential. Here is a look at Calpuff’s computational domain, and how that domain might affect your use of this air quality modeling software. 

Calpuff utilizes the puff model of air quality modeling rather than the plume model. 

Plume or puff

One of Calpuff’s strengths is its use of the puff model of air quality modeling, as opposed to the plume model used by software likeAERMOD. The puff model evaluates the movement of air (and any relevant chemicals, pollutants, or particles) as puffs that move along three dimensions. Furthermore, the program is capable of breaking down a single puff into multiple puffs and evaluating the movement of each individual puff separately using the data provided by the user. 

One of the primary advantages of the puff model is its ability to evaluate non-steady-state air quality concerns. For example, complex terrain, shifting air flows, land flow patterns that are not uniform throughout the terrain, areas of stagnation, and more may affect the flow of the air under evaluation and therefore require the capabilities of a puff model. 

Calpuff, therefore, can be used to good effect in any scenario, whether steady state or non-steady-state, but possesses capabilities that make it most suitable for complex, changeable scenarios that cannot easily be handled by the steady state assumptions present in plume model. Since Calpuff is more complex than these other models, it is also best used for more complex air quality modeling challenges, where the extra work and data required to run the evaluation will be worth it. 

Calpuff utilizes a wide range of detailed information. 

Because Calpuff, and its puff model of air quality modeling, focus on non-steady-state concerns, the program requires and is capable of handling, a great deal of detailed information in its analyses. To this end, users of the program should expect to provide highly detailed data that describe the exact meteorological and topographical conditions of the area under consideration, as well as information regarding the actual particles involved in the air puffs. Data that will likely be required to accurately run Calpuff include the following: 

Smoke stacks
  • An updated input control file describing the parameters within which Calpuff should work. 
  • Topographical files describing the terrain over which the air movement occurs, including the height of the terrain. 
  • Meteorological data describing air currents, heights, weather conditions, and more
  • Particulate information, such as the size and composition of particles from emissions, pollutants, and chemicals
  • Wind field characterizations describing the existence and movement of wind across the terrain being studied
  • Existence of any coastal impacts 
  • Land use data, including information about things such as forest cover, power lines, buildings, and more.

You should also expect to divide the area under evaluation into a number of grids and zones in order to enable Calpuff to accurately analyze the area and conditions with which you are concerned. Providing accurate grids and sufficiently small grid and zone sizes can enhance the overall accuracy of the program. 

Calpuff requires careful handling when it comes to certain conditions. 

Calpuff, like any air quality modeling software, does have limitations that require awareness on the part of the user. Understanding these limitations and challenges can help you to make more accurate use of the software for your next project. Here are a few of the potential challenges of which you should be aware when handling Calpuff: 

Coastal Breeze
  • Coastal impacts: The effect of sea breezes and other coastal impacts can be difficult for Calpuff to evaluate. Currently, this capability is under development, and the software can handle certain scenarios involving coastal impacts, but understanding the software’s limitations here can help you achieve more accurate results for your project. 
  • Calm winds and areas of stagnation: Calpuff can handle periods of calm winds and stagnation by evaluating the puff as a stagnant puff during these times. However, extended periods of calm may be more difficult to evaluate with the software, and may be more suitable to evaluation with a plume model designed for steady-state concerns. 
  • Time zones and UTM zones: Calpuff will require that UTM zones and time zones to not overlap in its analyses. In addition, the program will require the breakdown of data into grids that are small enough to be evaluated individually, while being large enough to evaluate efficiently. Achieving this balance may require careful work on the part of the user. 

Calpuff can be a powerful tool for achieving accurate air dispersion modeling for non-steady-state situations. Thanks to its ability to evaluate non-steady-state air quality concerns, it provides businesses, scientists, and others with a way to handle circumstances that are frequently changing and otherwise hard to predict. However, as with any software, it has its own limitations and challenges that make it suitable for some applications and not for others. 

If you need help identifying the best air dispersion modeling software for your needs, do not hesitate to reach out to Providence-Oris. We offer a wide range of products for both plume modeling and puff modeling, and we can provide the consultation and guidance you need to find the right product for your circumstances. In addition, we offer a range oftrainingservices to help you understand and effectively use the software you select.