Observation and modeling of the evolution of Texas power plant plumes

• Main Authors: W. Zhou, D. S. Cohan, R. W. Pinder, J. A. Neuman, J. S. Holloway, J. Peischl, T. B. Ryerson, J. B. Nowak, F. Flocke, W. G. Zheng
• Format: Article
• Language: English
• Published: Copernicus Publications 2012-01-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/12/455/2012/acp-12-455-2012.pdf
• ISSN: 1680-7316; 1680-7324

During the second Texas Air Quality Study 2006 (TexAQS II), a full range of pollutants was measured by aircraft in eastern Texas during successive transects of power plant plumes (PPPs). A regional photochemical model is applied to simulate the physical and chemical evolution of the plumes. The observations reveal that SO<sub>2</sub> and NO<sub>y</sub> were rapidly removed from PPPs on a cloudy day but not on the cloud-free days, indicating efficient aqueous processing of these compounds in clouds. The model reasonably represents observed NO<sub>x</sub> oxidation and PAN formation in the plumes, but fails to capture the rapid loss of SO<sub>2</sub> (0.37 h<sup>−1</sup>) and NO<sub>y</sub> (0.24 h<sup>−1</sup>) in some plumes on the cloudy day. Adjustments to the cloud liquid water content (QC) and the default metal concentrations in the cloud module could explain some of the SO<sub>2</sub> loss. However, NO<sub>y</sub> in the model was insensitive to QC. These findings highlight cloud processing as a major challenge to atmospheric models. Model-based estimates of ozone production efficiency (OPE) in PPPs are 20–50 % lower than observation-based estimates for the cloudy day.