Relationships of coastal nocturnal boundary layer winds and turbulence to Houston ozone concentrations during TexAQS 2006

Abstract

Measurements made with a ship‐based Doppler wind lidar during the summertime 2006 Texas Air Quality Study are used to study the relationship between lower‐tropospheric vertical structure and winds and ozone (O3) concentrations in Houston, Texas, under two different flow regimes. We observed that strong southerly flow regimes, dominated by the subtropical anticyclone (Bermuda high) off the Atlantic coast of the United States, resulted in strong (i.e., high wind speed) onshore nocturnal low‐level jets (LLJ) and low O3 and oxidant Ox (where Ox = O3 + NO2) concentrations at night and the following afternoon. In contrast, periods dominated by northerly or easterly flow resulted in relatively weak (low wind speed), but still onshore, nocturnal LLJs associated with higher concurrent and next‐day concentrations of O3 and Ox. We present lidar data from 24 h example periods for each of these conditions and demonstrate how each type of flow regime is related to in situ ship‐based ozone measurements. We expanded the study to include all days during the study when the ship was near Houston, to demonstrate how the strength of the meridional winds aloft show a better relationship to concurrent ship‐measured Ox concentrations than the winds near the surface do. We found a strong relationship between a parameterization of the observed nocturnal jets, which reflect the synoptic conditions, to peak hourly O3 measured the next day at the ship and averaged throughout the Houston/Galveston/Brazoria continuous ambient monitoring stations monitoring network, indicating potential applications for planning air quality.