Ozone plume transport patterns across mountain barriers in California and Colorado

Gaps or channels in mountain ranges are often regarded as favored transport corridors for pollutants, aerosol, moisture, or other quantities. During field measurement experiments in the Colorado Front Range and several California mountain ranges, NOAA/ESRL's airborne ozone lidar performed surveillance flight patterns over 3 summers to map out the ozone plumes from major source regions, such as Denver and Los Angeles. These flights were aimed at studying the transport patterns in to and through mountain barriers in the regions. Cases have been identified when gaps or passes formed the primary transport corridors. But more often ozone plumes followed the direction of the prevalent ridgetop-level winds and passed directly across the mountain barrier, eschewing the gaps and passes. Analyses of both types transport will be presented, highlighting the differences in winds and stability profiles associated with each transport pattern.