HR: 0800h
AN: A11B-0867    [Abstracts]
TI: Photochemical Mechanism Computational Speed Improvements Using Asynchronous Time Stepping
AU: * Lee, J H
EM: atmlee@ucdavis.edu
AF: Jung H. Lee, Atmospheric Science Graduate Group, Department of Land, Air, and Water Resources, University of California, Davis, CA 95616 United States
AU: Zhang, K M
EM: maxzhang@ucdavis.edu
AF: Ke Max Zhang, Department of Mechanical and Aeronautical Engineering, University of California, Davis, CA 95616 United States
AU: Tonse, S
EM: tonse@lbl.gov
AF: Shaheen Tonse, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 United States
AU: Harley, R A
EM: harley@ce.berkeley.edu
AF: Robert A. Harley, Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 United States
AU: Wexler, A S
EM: aswexler@ucdavis.edu
AF: Anthony S. Wexler, Departments of Mechanical and Aeronautical Engineering, Civil and Environmental Engineering, and Land, Air, and Water Resources, University of California, Davis, CA 95616 United States
AB: The system of atmospheric gas phase photochemical reactions is stiff because the range of time scales for each reacting species spans several orders of magnitude. Asynchronous Time Stepping (ATS) has proven to be accurate and computationally efficient for solving large systems of stiff ODEs in molecular dynamics and nonlinear solid mechanics. In this work, we apply ATS to photochemical reactions used to simulate urban and regional air pollution events. ATS is tested and evaluated in terms of accuracy as well as speed on 1500 test cases representative of air quality in the San Joaquin Valley of California. The cases were chosen so that 500 represent daytime conditions, 500 represent nighttime and 500 represent sunset/sundown transitions. Data sets generated by ATS and more commonly used solvers such as Gear (i.e. DLSODE and DVODE) and Hybrid are compared in terms of speed and accuracy on the SAPRC-99 chemical mechanism. ATS is at least four times faster than the Gear and Hybrid solvers in terms of speed. Accuracy-efficiency tests are performed on the data sets obtained by all the solvers using performance measurements such as a relative root mean square error. Gear solvers provide the most accurate solutions. ATS is less accurate than Gear although faster, more accurate and better at conserving mass than Hybrid.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005