Ozone columns below 147 hPa are derived over the United States from September 2004 to August 2005 from the differences between clear-sky Aura OMI columns and coincident MLS columns. The mean difference from coincident ozonesonde measurements at four USA sites is 0.3 DU with an rms difference of 10.1 DU and a correlation coefficient of 0.67. Semimonthly patterns of the columns over the USA for the summer of 2005 have been produced. The observed columns, as well as Regional Air Quality Forecast (RAQAST) model columns, show high values over the southeastern USA and its surrounding oceans. Changes of these columns exceeding 6 DU in many places were observed between June 17--30 and July 1--16 and the changes reversed in the following two-week period. Comparisons against calculations from the RAQAST model, as well as correlations with geopotential height changes at 147 hPa, indicate that these changes were primarily related to dynamics.