Extended Abstract (16K)1.5
Observations of localized thunderstorm outflow in an urban area
Arthur L. Doggett IV, Texas Tech University, Lubbock, TX; and M. Conder, T. E. Gill, C. B. Chang, R. E. Peterson, and J. Schroeder
The Texas Tech University (TTU) Wind Science and Engineering group has an established national program for research, modeling, and training related to threats from wind-borne hazards. The release of chemical/biological (CB) agents or other toxic materials in an urban area, whether from an industrial accident or terrorist act, represents a real threat to large populations. A central issue for emergency planning, warning, and mitigation purposes is to understand how CB agents are physically transported in the urban boundary layer. As part of this program, mesoscale numerical models (MM5 and RAMS) and field observations will be used to simulate the transport and dispersion of CB agents in the boundary layer at resolutions approaching the urban scale.
As a test of the TTU mobile data collection platforms, an urban scale data collection project was undertaken on 24-25 June 2001. The goal of this project was to determine the scale of features that could be detected with these platforms and to produce a database for the testing of analysis techniques. Four mobile mesonet (MM) units were deployed in separated, predefined routes in and around the city of Lubbock, TX. The MM systems are rack mounted to standard automobiles and can be used to collect data while the vehicle is in motion. In the current configuration, MM data is collected every three seconds and stored on a laptop in the vehicle so that the data may be viewed in real time. To supplement the MM data, two portable three-meter towers were deployed on the periphery of the data collection domain and data from several fixed mesonet sites surrounding the city of Lubbock were utilized.
From approximately 21 UTC 24 June 2001 to 00 UTC 25 June 2001, conditions over Lubbock remained relatively quiescent. Just before 00 UTC 25 June, a strong thunderstorm began to develop directly over the city of Lubbock. The slow-moving thunderstorm produced heavy rains and strong winds before it dissipated. The storm did not affect the entire urban domain, however, as it moved to the north and west of the city over time. As a result, a well-defined cool outflow pool was left behind that persisted throughout the remainder of the data collection process. The cool pool was most evident in the northern and western portions of the city, while the environment to the east and south of the city quickly returned to ambient conditions. Sampling of the urban-scale properties of both the undisturbed and rain-cooled conditions continued until approximately 07 UTC 25 June.
The goal of this data collection project was to evaluate the capabilities of TTU mobile facilities for collecting data in an urban environment. The fortuitous occurrence of a strong but short-lived thunderstorm within part of the data domain facilitated the effort. The use of MM and portable fixed towers provided detailed information about variations in surface conditions across the city of Lubbock. Further fieldwork needs to be competed to examine how less dramatic variations are observed.
Session 1, Urban effects on weather
Monday, 20 May 2002, 9:00 AM-10:29 AM
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