HR: 0800h
AN: A51B-0348    [Abstracts]
TI: Observations of the Nocturnal Boundary Layer and Morning Transitional Periods in Houston, Texas during the TexAQS II Campaign
AU: * Day, B M
EM: bmday@uh.edu
AF: University of Houston, 4800 Calhoun Rd., Houston, TX 77204-5007, United States
AU: Clements, C B
EM: clements@met.sjsu.edu
AF: San Jose State University, One Washington Square, San Jose, CA 95192, United States
AU: Rappenglueck, B
EM: brappenglueck@uh.edu
AF: University of Houston, 4800 Calhoun Rd., Houston, TX 77204-5007, United States
AB: High-temporal resolution tethersonde profiles taken during the TexAQS II field campaign in Houston were used to study the overnight development and progression of the nocturnal boundary layer (NBL) and the evolution of the convective boundary layer after sunrise. The measurements were made at the University of Houston campus, located approximately 4 km southeast of the downtown Houston central business district, and consisted of vertical profiles of potential temperature, water vapor mixing ratio, wind speed, wind direction, and ozone concentration. Profile heights averaged 250 m AGL with a few reaching 400 m AGL. Profiles were taken at approximately 30 min intervals throughout 4 nights during Intensive Observational Periods (IOPs), including both the evening and morning transitional periods. Tethersonde experiments also were performed during several additional morning break-up periods during the campaign. Preliminary results from the overnight experiments of Sept 7-8 and Sept 14-15, 2006 showed different NBL evolutions. Sept 7-8 exhibited a stronger and deeper inversion compared with Sept 14-15 when the inversion was weak with a fairly constant height throughout the night. The Sept 7-8 profiles showed elevated bluff-like structures in the virtual potential temperature profiles between 0300-0400 CDT, indicating neutral stability within the 40-90 m AGL level. And, just before sunrise a neutral layer with constant potential temperature developed between the surface and 75 m AGL reflecting horizontal cold air advection. Further analyses will be presented for other vertical profiles taken during the campaign, including the additional overnight profiles as well as the profiles taken during the morning transition to the convective boundary layer.
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 3307 Boundary layer processes
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting