SCERP Project Number: AQ93-3
Principal Investigator: Jack Smith
The University of Texas at El Paso
Rationale: The implementation of the North American Free Trade agreement between Canada, Mexico and the U.S. may exacerbate the air quality problems along the border. The expected increase in manufacturing activity in Mexico will result in increased population in the border area along with the attendant problems.
Maintaining air quality will require the development of strategies for controlling the spread of air pollution and minimizing its impact on the airshed. Pollution levels depend on the rate, amount, size and location of material injected into the air as well as cleansing processes. Dominant factors in pollution removal are upper air temperature and wind profiles. The development of effective control strategies depends upon knowledge of both the contaminating and cleansing processes.
The development of plans for the desired location of industrial sites, for determining allowable emission levels and least detrimental locations will depend on computer generated results for a variety of scenarios involving polluting sources and atmospheric conditions, i.e., temperature, wind, rain. For the computer models to estimate air quality, the transport and diffusion of pollutants out of the airshed must be known. For a given scenario the upper air temperature and wind profiles must be known or have expected values and be supplied as inputs to the computer models.
To accommodate this need the wind and temperature profile data obtained from the radar will be used to develop expected monthly and seasonal conditions for the region. The expected conditions can be used by airshed modelers to predict upper level winds. In addition, their predictions can be validated by comparison with the profiles obtained by the UTEP radar.
Continued long term measurements will allow the correlation of wind and temperature profile information with other air quality trends.
The data will be saved in a most general form as the features of importance and their use will vary dependent on the study under consideration.
Approach: A database for upper air temperature and wind profiles is being generated for the El Paso-Juarez airshed through continuous remote sampling of the parameters mentioned above. The measurements are made using a pulsed doppler radar and a radio acoustic sounder. The equipment is installed on the roof of the Engineering Complex at UT El Paso and has been collecting data for thirteen months.
Wind speeds are measured with the pulsed doppler radar. The radar has three pointing directions, one vertical and the other two 15deg. off vertical, one of the displaced beams is pointed toward the north and the other pointed toward the east. The doppler frequency shifts observed in the radar signal returns scattered by the atmospheric turbulent eddies in each pointing direction are proportional to the radial velocity of the winds. The width of the radar pulse determines the depth of the altitude cell probed. The time delay associated with the pulse return determines the altitude of the cell being observed. As the return signals are very weak pulse averaging is employed to determine the doppler shifts. Measuring the three radial wind speeds at each altitude cell allows calculation of the associated horizontal wind speed and direction. The altitude wind profile can be data averaged over periods as short as 15 minutes and placed in a disk file. The file can be downloaded daily and the information made available.
Temperature profiles are measured using a combination of a vertically transmitted variable frequency acoustic wave and vertically transmitted radar pulses. The acoustic wave covers a selected range of frequencies and produces pressure waves which travel at temperature dependent velocities. The frequency of dominant signal scattered back from an altitude cell contains a temperature dependent doppler shift. The frequency spectrum of the pulsed radar return is analyzed to obtain a temperature versus altitude profile.
The radar and acoustic units are computer controlled and can obtain and process data continuously. Computer programs control the operation of the radar and acoustic hardware, analyze the return doppler shifted signals to yield wind speed, wind direction and temperature and save these data to disk files which can be downloaded daily, according to operator instructions.
Status: The status of the project and the items being addressed or already accomplished are described below.
The radar and acoustic systems are operating continuously and hourly averages of wind speed, wind direction and temperature versus altitude, are being saved on computer disks.
Access to data from the National Weather Service balloon launches at the El Paso Airport has been established and hard copies are saved. The lower altitude temperature and wind profile data are being compared with the UTEP measurements.
Access to the National Weather Service general forecasts has been established. Hard copies of these data are saved and will be correlated with the UTEP data.
Data from the ground sensors, PM10, carbon monoxide etc. are being obtained from TNRCC. We will attempt to correlate anomalous ground sensor reading with wind and temperature conditions during the event.
We have participated in two field tests:
(a) UTEP data were compared with data obtained from a demonstration of a lidar capability to measure wind fields in April, 1994. The lidar was developed by Los Alamos National Laboratory.Algorithms are being developed to format atmospheric data from various sources, balloons, ground sensors, etc. for correlation studies, and for symptotic presentation.
(b) A border air quality study was conducted during September 1994. UTEP participated in the effort which involved measuring the air migration patterns in the El Paso-Juarez region. Data from lidars, sodars, towers, doppler radars and laser doppler velocimeters at various locations in the valley were used in the study.
Graphical hard copy of daily wind profile and temperature data can be produced.
The UTEP doppler radar is located in an area which produces considerable ground clutter. This clutter may be affecting the accuracy and resolution of the observed wind profiles at the lower altitude, 100 meters to 500 meters. Above 500 meters our results compare well with those obtained from other independent measurements. We are currently reorienting the antennas and modifying the clutter screens around the antennas in an attempt to minimize the clutter.
Potential Users:
Personnel at other organizations who have contributed significantly to the development of the wind and temperature profiling effort at UTEP are:
Last updated 7/1/99