Observation and modeling of the evolution of Texas power plant plumes

摘要

During the second Texas Air Quality Study 2006 (TexAQS II), a full range ofpollutants was measured by aircraft in eastern Texas during successivetransects of power plant plumes (PPPs). A regional photochemical model isapplied to simulate the physical and chemical evolution of the plumes. Theobservations reveal that SO₂ and NO_y were rapidly removed fromPPPs on a cloudy day but not on the cloud-free days, indicating efficientaqueous processing of these compounds in clouds. The model reasonablyrepresents observed NO_x oxidation and PAN formation in the plumes, butfails to capture the rapid loss of SO₂ (0.37 h?1) andNO_y (0.24 h?1) in some plumes on the cloudy day. Adjustments to thecloud liquid water content (QC) and the default metal concentrations in thecloud module could explain some of the SO₂ loss. However, NO_y inthe model was insensitive to QC. These findings highlight cloud processingas a major challenge to atmospheric models. Model-based estimates of ozoneproduction efficiency (OPE) in PPPs are 20–50 % lower thanobservation-based estimates for the cloudy day.