Evaluation of some urban surface layer characteristics during JU2003 using two instrumented 30-m towers

The Joint Urban 2003 Study was conducted in Oklahoma City during July 2003. As part of that study, two 30-m towers were each equipped with four 3-D sonic anemometers and four fan-aspirated PRT temperature sensors at heights of approximately 8 m, 14 m, 23 m and 28 m AGL, and placed in two locations in the city. One site was about 2 km northeast of the central business district (CBD) on a grassy area surrounded mostly by grassy fields and a few buildings, and was operational for 32 days; the other site was about 0.8 km northwest of the CBD on a grassy area in the middle of a paved region surrounded by many buildings and streets, and was operational for 18 days. Winds were generally from the south during the study, so both towers were more or less downwind of the city. Data were collected continuously, and wind and turbulence variables were calculated for each tower’s levels using a half-hour average. Wind speed, wind direction, momentum flux, heat flux, the components of turbulent kinetic energy, friction velocity, and roughness lengths were analyzed to evaluate urban daytime and nighttime changes and/or differences at each site. Additionally, data were compared between each tower to evaluate and examine the representativeness of both the heights of the instruments and the locations of each tower.