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Abstract
We investigated the distribution and transport of ozone in the Colorado Front Range area by deploying NOAA’s airborne ozone lidar on a Twin Otter aircraft and flying several missions in each of the past three summers (2006 – 2008). The aircraft typically flew at altitudes of 3 to 5 km above sea level and the downward-looking lidar provided profiles of ozone and aerosol backscatter at high spatial and temporal resolution from just below the aircraft to the ground. In 2008, the airborne lidar measurements were complemented by a ground-based Doppler lidar, a small network of radar wind profilers, and a surface meteorological station on the Continental Divide west of Denver in order to better characterize transport patterns. In addition, we used the FLEXPART Lagrangian particle dispersion model coupled with high-resolution Weather Research and Forecasting (WRF) model runs to forecast pollutant transport and guide flight planning efforts.
For the majority of flights, we observed that polluted air from the Denver metro area was transported by easterly winds towards and into the adjacent mountains. The highest ozone levels were typically found over the western suburbs of the Denver metro area and along the eastern slope of the mountains. If the mixed layer was deep enough the ozone plume was pushed further west across the Continental Divide. Otherwise, pollutants were often vented into the free troposphere and transported back east over the Denver area by predominantly westerly winds above the boundary layer.
We will present results from several flights that will illustrate the complexity of the transport patterns and resulting pollutant distribution in the Colorado Front Range area. Another focus of the presentation will be the comparison of the transport model forecasts with lidar and wind profiler measurements for a number of cases.