Application of satellite data in a regional model to improve long-term ozone simulations

To investigate an alternative technique of providing background and transboundary transport inputs for ozone (O₃) simulations on a regional scale, the EPA’s Community Multi-scale Air Quality (CMAQ) model was integrated with high spectral resolution data from the Tropospheric Emission Spectrometer (TES) aboard the NASA’s Aura satellite. This study presents a comprehensive model evaluation of O₃ for the entire year of 2009 over the contiguous United States with a focus on the State of Texas using both ozonesonde and ground measurements. While improving model performance in the upper atmosphere, CMAQ’s initial and boundary conditions (IC/BC) derived from the original TES data do not improve model performance in the troposphere because the satellite data exaggerated concentration of tropospheric O₃. With a 10-ppb deduction of O₃ concentration from TES, the IC/BC derived from the adjusted TES improves model performance from ground level through the upper atmosphere. The mean bias of daily maximum 8-h average concentration of O₃ (MDA8) from the ground monitored in Texas decreased from 7 ppb to 4 ppb. Model results also show small influences of O₃ from the upper troposphere on the concentrations at the ground level. With a complete exclusion of stratospheric layers, changes of annual mean MDA8 of O₃ concentrations at ground-level were smaller than 1.1 % in Dallas and Houston. In addition, limitations of satellite data are discussed and recommendations are provided regarding the future application of satellite data in regional O₃ simulations.