SCERP Project Number: AQ94-3.1 and AQ-OF-2
Principal Investigator: Jack Smith
University of Texas at El Paso
Goal: The goal of the work is to develop a data base containing information on the temperature and wind profiles at the upper altitude levels in the El Paso-Juarez area. The data base will contain hourly information on the wind profiles to 2500 meters above ground level and temperature profiles to eight hundred meters above ground level. Data for each 24 hour period will be recorded on disk and the data collection will be continuous. Monthly and seasonal profile averages and variances will be developed to establish any trends which may exist in the upper level wind and temperature patterns. These data will be correlated with other air quality measurements.
Rationale: The implementation of the North American Free Trade agreement between Canada, Mexico and the U.S. will 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 the 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 location of new industrial sites, for determining allowable emission levels and identifying least detrimental sites 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 identify high risk areas and to estimate air quality, the transport and diffusion of pollutants within and 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 pollutant transport. 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.
Approach: A data base for the upper air temperature and wind profiles is being generated for the El Paso-Juárez airshed by continuous remote sampling of these parameters. The measurements are being made through the use of a doppler radar and an acoustic sounder. The equipment is installed on the roof of the Engineering Complex at UT El Paso. This location is a quarter mile from the border and about a half mile north of downtown El Paso.
Wind speeds are measured with the pulsed doppler radar. The radar has three pointing directions, one vertical and the other two 15û 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. For each hour the altitude wind profile data is averaged over a period of 15 minutes and placed in a file.
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 radar return is analyzed to obtain a temperature versus altitude profile.
The radar and acoustic units are computer controlled and 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 are downloaded daily to 3.5" diskettes according to operator instructions.
The daily information is placed in a large data file on a SUN computer. Through the use of this data base specific times and altitudes can be selected to provide information on the monthly and seasonal trends of the temperature, wind, speed and direction at a particular time of day and altitude.
To help assure that the equipment is operating properly information obtained from the UT El Paso radar is compared with information obtained from the daily weather balloon launches from the El Paso Airport. In addition several tests have been conducted to compare the results from the UTEP radar with those obtained from a laser doppler velocimeter.
Status: The radar and acoustic systems were operating continuously until January 1996 when the radar antennas were damaged during a severe windstorm. Hourly averages of windspeed, wind direction and temperature versus altitude were being saved on 3.5" diskettes. Each saved diskette contains 24 hours of wind profiles to 800 meters with 50 meter resolution, wind profiles to 2500 meters with 75 meter resolution and temperature profiles to 800 meters with 50 meter resolution.
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 obtained at about the same time.
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 and chemical sensors was being obtained from TNRCC in an attempt to correlate anomalous ground sensor reading with wind and temperature conditions. Currently we are not receiving this information, but the information flow will be resumed.
A field study was conducted which compared the wind profiles to 600 meter altitude obtained by the UTEP system with those obtained by a laser doppler velocimeter. The profiles compared fairly well considering the laser system tracks the motion of airborne particles to determine wind speed while the UTEP system tracks turbulent air cells.
The data from all the 3.5" diskettes are being copied to a file in a SUN computer and algorithms are being developed to extract particular information in the desired format.
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 altitudes, 100 meters to 500 meters. Above 500 meters our results compare well with those obtained from other independent measurements. A ground clutter filter was developed and installed in the wind profiling software. Both laboratory and field tests confirmed that the filter affected a marked improvement in the performance of the radar at the lower altitudes.
A comparison of radar the performance during the summer as compared to late fall shows a marked difference. Profiles to higher altitudes are obtained during the summer. Currently the data are being studied to determine if this condition is related to climatology or to the presence and strength of temperature inversions. If the latter is true then the radar data would also contain information on the altitude integrated pollution content of the atmosphere. Algorithms could then be developed to determine pollutant levels as well as wind and temperature profiles.
The damage sustained by the radar antennas during the January wind storm was extensive. The repair required complete rebuilding of one of the antennas and some repair to the other two. Upon completion of the repairs the manufacturer of the doppler radar (Radian Corporation) was contracted to check the radar to determine if it met the operating specifications. It was tested by Radian engineers and it operated properly. The radar profiler was put back into service on Jun 12, 1996.
Practical Use: Data from the UTEP radar was used in a major field study of the air migration patterns in the El Paso-Juarez region conducted in September, 1994. Data from lidars, sodars, towers, balloon borne instruments, doppler radars and laser doppler velocimeters located at various sites in the valley were used in the study.
Data from the UTEP radar were used to evaluate the capability of a lidar, developed by Los Alamos National Laboratory, to measure wind fields.
Wind and temperature profile data for a period of one year were supplied to the Climatology Department at Arizona State University. These data can be used to supplement the surface data used in their studies of the El Paso region.
Upper atmospheric conditions should be correlated with PM10 and other surface chemical sensors to determine air quality and the transport of pollutants from industrial sources.
Based on expected air migration patterns planners could designate the most appropriate locations for new industrial development to minimize the effects of pollutants due to industrial processes as well as traffic associated with new sites.
Potential Users:
El Paso-Juárez airshed modelers.
Texas Natural Resources Conservation Commission
El Paso County Health Department
Industrial Planning
Other Personnel:
Personnel at other organizations who have contributed significantly
to the development and interpretation of the wind and temperature profiling
data at UTEP are:
Sandra Brazel (Arizona State University)
Pete Brietenbock (Texas Natural Resources Conservation Commission)
John Hines (Atmospheric Sciences Laboratory, White Sands Missile Range)
Bruce Kennedy (Physical Sciences Lab., New Mexico State University)
Greg Moran (Physical Sciences Lab., New Mexico State University)
The FY93 SCERP-supported phase of this project: AQ93-3
The FY94 SCERP-supported phases of this project: AQ94-3.1/
AQ94-OF-2
The FY95 SCERP-supported phase of this project: AQ95-4
Last updated 7/1/99