The TexAQS-2000 field program was conducted in and around Houston, Texas, from mid-August to mid-September 2000. A comparison of profiler and surface-based observations shows that systematic wind shear patterns develop during the nighttime hours in addition to the expected decoupling of near-surface and free tropospheric winds. These wind patterns are related to the land/sea breeze cycle, which is nearly resonant with the inertial frequency at the latitude of Houston. On a typical day, nighttime wind directions vary by as much as 90 degrees per kilometer of altitude, resulting in transport patterns undiscernable from surface observations. Implications for data assimilation and modeling of chemical transport are discussed.