Use of Ozone Monitoring Instrument (OMI) Ozone Profiles in Air Quality Assessment Studies

Newly available satellite observations of tropospheric trace gases provide a wealth of information that can potentially reduce some of the persistent uncertainties in the air quality assessment studies. Satellite measurements can also help in evaluating the performance of the models used in these studies. Numerical air quality models are the preferred tools used for air quality forecast and in regulatory air quality assessment practices. Improving the performance of these models through the utilization of satellite observations is particularly beneficial.

In this study, we have utilized the observations of tropospheric ozone profiles by Ozone Monitoring Instrument (OMI) on board NASA Aura satellite to provide the initial state of the atmosphere, as well as the lateral boundary conditions for the U.S. EPA’s Community Multiscale Air Quality (CMAQ) Modeling System. Model simulations span over August 2006 and cover the continental United States. This period coincides with INTEX Ozonesonde Network Study 2006 (IONS-06) campaign and offers a unique comprehensive set of ozonesonde measurements for evaluating OMI ozone vertical profiles, as well as model predictions in the free troposphere. Model predictions were also evaluated against measurements from EPA’s surface monitors, as well as detailed surface and aircraft measurements from second Texas Air Quality Study (TexAQSII).

OMI ozone profiles showed a good agreement with the ozonesonde measurements. The model results indicated a significant improvement in the predictions of tropospheric ozone when satellite data is utilized. The use of satellite observation for specifying lateral boundary conditions could considerably improve the ozone predictions in the upper troposphere where a significant vertical gradient in ozone concentration exists. This indicates that in this region horizontal transport is the dominant factor in determining ozone concentrations and the correct specification of the lateral boundary condition can also correct some of the error caused by improper top boundary condition.