High concentrations of atmospheric gases and aerosols can reduce, visibility, increase the production of tropospheric ozone, as well as increase the risks of public health hazards. In order to study and predict the occurrences of these high atmospheric concentrations, it is essential that model simulations and measurements be assessed to provide the highest possible level of accuracy. Atmospheric composition, aerosol optical depth, and air particle trajectories were examined during recent air quality experiments that occurred over Mexico City and Houston, Texas. Ozone and nitrogen dioxide levels were investigated using model simulations and in situ, and satellite measurements. Additionally, a MATLAB algorithm was created to locate coincident sample grids between model simulations, and satellite and airborne data sources to analyze measurements and simulations of aerosol optical depth. Furthermore, air parcel trajectories determined from two algorithms were also examined. Utilizing the Sulfur Transport Eulerian Model (STEM) simulations from the University of Iowa, ozonesonde data from balloons deployed in Houston, Texas, and measurements from the Tropospheric Emission Spectrometer (TES) aboard NASA's Aura satellite, ozone and nitrogen dioxide levels were compared. Tropospheric ozone concentration correlations were found between STEM and ozonesondes in Houston, Texas and percentage error rates were found between TES and ozonesondes. The values of ozone concentrations were also compared to the EPA regulations for ozone levels in both study regions. The airborne High Spectral Resolution Lidar (HSRL) developed by the NASA Langley Research Center (LaRC) was utilized during the Intercontinental Chemical Transport Experiment-B (INTEX-B) campaign to fly aboard the NASA King Air B200 over Mexico City in March 2006 to retrieve aerosol distributions and optical properties. Aerosol optical depth values derived from HSRL measurements of aerosol extinction profiles were used to evaluate aerosol optical depth derived from Terra's MODerate Resolution Imaging Spectroradiometer (MODIS). Significant correlations between the HSRL and MODIS aerosol optical depths. WRF-Chem simulations of aerosol optical depth were also compared to aerosol optical depth derived from both HSRL and MODIS to help examine the ability of WRF-Chem o forecast aerosol parameters. Air parcel trajectories produced by simulations from Florida State University and the HYbrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT) were also examined in part to examine the impact of assimilation of airborne data during INTEX-B on trajectory computations.