Insights Into Houston Air Quality From Rawinsonde and Ozonesonde Data

Since the summer of 2004, over 250 rawinsondes and 150 ozonesondes have been launched from the campuses of Rice University and the University of Houston, each about 3 miles from downtown Houston. These sounding launches have been sponsored by NASA, the Shell Center for Sustainability of Rice University, and the Texas Commissions for Environmental Quality as part of a large effort to understand Houston's ozone problem. Data from these soundings have provided valuable insight into the seasonal and diurnal variations of the vertical ozone distribution and their relationship to changes in atmospheric conditions. Preliminary analyses revealed a strong connection between the possibility of an ozone episode and atmospheric conditions described by soundings in the early morning. It is found that, in addition to relatively weak wind speed, directional shear in the lower atmosphere is necessary for the development of ozone episodes. A strong surface-based morning inversion favors high ozone concentration later that day, while a relatively deep, near neutral residual layer above the inversion layer tend to reduce the probability for an ozone episode. Multiple rawinsonde and ozonesonde soundings on forecasted episode days further revealed how boundary layer development and local circulation affect ozone concentration in Houston.