Impact of Assimilated Boundary Conditions on WRF-NMM/CMAQ Air Quality Predictions Researchers at NESDIS, NCEP and the NWS used global ozone analyses from the 2006 Real-time Air Quality Modeling System (RAQMS) OMI/TES chemical analysis to investigate the influence of time-dependent boundary conditions on operational air quality forecast system (WRF-NMM/CMAQ) ozone predictions. Chemical boundary conditions from 3 global models including RAQMS (Figure 1) , MOZART, and GFS (O3 above 10km only) were evaluated relative to the operational fixed boundary conditions. Comparisons with IONS ozonesonde (Figure 2) and EPA AIRNow surface ozone measurements (Table 1) showed systematic improvements in linear slopes and correlation coefficients relative to fixed boundary conditions. However, inclusion of time-dependent BCs tended to increase mean biases in the predicted surface ozone mixing ratios. Analyzed Eastern Pacific CO Analyzed Eastern Pacific O3 Figure 1: July 21-Aug 05, 2006 mean RAQMS O3 and CO analysis at 130oW. Windspeed (black contours) and potential temperatures (white dashed contours) are also shown. Table 1: Aug 1-5, 2006 WRF-NMM/CMAQ EPA AIRNow surface network comparisons for Fixed, RAQMS, MOZART, and GFS BCs. Figure 2: Aug 1-5, 2006 WRF-NMM/CMAQ ozonesonde comparisons for Fixed, RAQMS, MOZART, and GFS BCs.