Problem Solving Environments for Airshed Models

Supported by NSF CAREER grant ATM-9985025   
The PSE Airshed program provides a much needed front end to the CIT Airshed Program. The CIT Airshed Program is a Fortran program written to simulate aerosol and gas photochemical transport. The domain, or area of simulation, is the South Coast Basin of California. The simulation period is during August 27,28 and 29 of 1987. The CIT Airshed Program is a three dimensional comprehensive model with 47 gas species and 19 aerosol species resolved into 8 size bins.

The PSE Airshed program is a tool to modify the CIT Airshed Program. The PSE Airshed program is written in MS Visual Basic 5 and requires MS Windows 95, 98, NT and 325 MBytes of hard disk on a Pentium (higher) with at least 32 MByte of Ram. The PSE Airshed program is self-sustaining under Windows.

The fundamental purpose of the PSE Airshed Program is to facilitate researchers and instructors the use of the CIT Airshed Program. With PSE the user is able to view and modify inputs to the model with ease. PSE provides answers to common questions such as, "If Long Beach emits twice as much NO2, who will suffer and how much"?  This is one of many questions that the PSE can answer with ease.


After all modifications are made by scaling and such, the user saves the file and executes the CIT Airshed program from the File menu. After the program finished execution (18 minutes for gas phase and 1 day for aerosol on PII 233), the user can view the output form a simple contour program. The Figure above shows such a contour of ozone resulting from the CIT Airshed Program. The user can view all the input fields of CIT Airshed Program and  bserved data also.

The user can view time series plot also. A time series plot is a plot of values at a particular location varied through time. The above figure shows the  bserved ozone concentration for Anaheim on Aug 27 1987.
An interesting feature of the PSE Airshed program is the newly developed sensitivity model. The sensitivity model analyzes behavoir of species in a  column of air. The sensivity model can answer in detail questions like, "On a column of air, what is most important to ozone formation." Not only does the model tells what is most important, it tells how much.  The figure above shows a sample of the output of a simulation where the species are under chemical reactions, aerosol dynamics, depositions, vertical transport and emissions for 30 minutes.  It seems that the most important contribution to ozone is how much ozone was there initially,  then by temperature, by ultra violet radiation, and how much NO2 was there initially, etc. Note that ozone concentration after 30 minutes depends on how much ozone was there initially by the sensivity of 0.202.  This means, if the initial ozone concentration was increased by 1ppb then  the resulting change in ozone after 30 minutes is only 0.202!

Intrinsic to the PSE Airshed is the contour plotting program to make the PSE self sustaining. However, if the user chooses to utilize Matlab for movies and professional contours, the user has that option. The postprocessing of the output to CIT Airshed processed by Matlab is done through the interface shown in the above figure.
The PSE Airshed can be a powerful tool for research and learning. The user friendly interface provides a easy approach to answer important questions. If you have any questions about the PSE Airshed contact Donald Dabdub,