SCERP Project Number: AQ95-4
Principal Investigator: Jack Smith
University of Texas at El Paso
Summary
Wind and temperature profiles have been obtained hourly since October, 1993. There have been two extended periods, about ten months total duration, during which the equipment was not operational. All profile data were obtained from a radar located on the roof of the Engineering Building at UTEP. The data are permanently stored on 3.5" diskettes, each diskette contains 24 profiles for a particular day. In addition, the daily data has been read into a large data base.
It is the goal of this project to use the data base to develop monthly and seasonal averages and to use these averages as inputs to computer generated wind field models for the region. In addition the data can be used to validate wind field models which use other initialization schemes. A knowledge of wind fields coupled with the pollution source inventory should provide the information which could be used to formulate strategies to control the impact of air pollution in the airshed.
During the tenure of this project nine undergraduates and two graduate
students have received support while working on this project.
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 contains 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 is
recorded on disk and the data collection is continuous. Monthly and seasonal
profile averages and variances can be developed to show trends which may
exist in the upper level wind and temperature patterns. The profile data
obtained are compared with other independent wind and temperature measurements
in an effort to assure data quality.
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 southern 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 from the airshed 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 locating new industrial sites, for identifying areas of high pollution and health risks and for determining allowable emission levels will depend on computer generated results for a variety of scenarios involving polluting sources and atmospheric conditions, i.e., temperature, wind, rain. For the long term, the practical solution involves developing a wind field model for the complex terrain of this airshed which can predict the transport and diffusion of pollutants within and out of the airshed. In the absence of a computer model the complex terrain would require many observing sites to obtain the measurements necessary to map pollution transport. An extremely large volume of data would be generated making analysis very expensive. Alternately only one or two observing sites would be required to check a computer model's performance. However, for a given scenario to be computer analyzed or a computer model validated the upper air temperature and wind profiles must be known or have expected values and this information used as initial inputs to the computer model.
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 measured profiles.
The development of a prognostic model for the wind and temperature fields
in the region can be used with information on pollutant sources to determine
air quality conditions and trends.
Approach
A data base for the upper air temperature and wind profiles is being generated for the El Paso-Juarez 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 15o off vertical, one of the displaced beams is pointed toward the north and 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 30 minutes and placed in a file. See Appendix A.
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 the 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. See Appendix B.
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 versus altitude 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. See Appendix C for an example.
To help assure that the equipment is operating properly the profiles
obtained from the UT El Paso radar are compared with data obtained from
the National Weather Service balloons launched from, initially the El Paso
Airport and more recently, the Santa Teresa Airport. In addition several
tests have been conducted to compare the profiles obtained by the UTEP
radar with those obtained by a laser doppler velocimeter.
Status
The status of the project and related activities is detailed below. While data collection has been the main focus, a number of tasks were initiated in attempts to extend the profile data to both higher and lower altitudes. Not all of the tasks attempted had positive results. Some did not improve radar performance, some were too labor intensive to pursue on a large scale, but a few did result in improved performance. A filter was developed which reduced ground clutter and resulted in obtaining wind data to lower altitudes. A single wind insensitive antenna was also developed which can be pointed in each to the required three directions. This replaced the three antennas originally furnished with the system.
Personnel at other organizations who have contributed significantly
to the development and interpretation of the wind and temperature profiling
data at UTEP are:
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)
Bibliography
No referred publications have resulted from this project. The goal is
to develop a data base. To date we have accumulated 33 months of temperature
and wind profile data on several hundred 3.5" diskettes and have transferred
this information to a large data base on a SUN computer. The data base
will provide the information for synoptic studies.
| Shows the doppler derived radial wind speed from the antenna pointed toward the west. The spectra indicate radial winds of about 1 m/s at low altitudes increasing to about 3 m/s at 2000 meters altitude. No detectable signals were received from altitudes above 2000 meters. |
| Shows the intensity of the return signal, density of the contour lines, and the radial wind speed, *, versus altitude. A high density for the contours indicates strong signal returns and is an indication of data quality. |
| Shows the sampled radial velocities obtained from each antenna during a 30 minute sampling period. The SNR, signal to noise ratio, versus altitude is an indicator of data quality. Samples with SNR above 0 dB should be valid wind speeds. |
| These plots are derived from the averaged radial wind speeds obtained from the three antennas, the averages of the data shown in Figure A-3. The ordinate is altitude and left hand plot is the direction from which the wind is coming. North is 0 degrees and east 90 degrees. The right hand plot is the horizontal wind speed in meters per second at altitude. |
| This figure shows the wind profiles obtained for each hour and clearly indicates the profile variations with time. The wind direction is from the tail to the head of the wind vector. Typically there is a marked difference in the wind direction in going from low to high altitudes. Also under light wind conditions direction is not well defined. |
| The left hand plot shows sampled temperatures versus altitude. The sampled points are obtained over a 15 minute interval and are averaged to yield an estimate of the temperature for the hour. The right hand plot indicates the signal/noise ratio of the sampled signals and is an indication of data quality. |
| Illustrates the wind speeds measured for part of March 1997 at an altitude of 1000 m between 2:00 and 3:00 am. The average speed is about 7 m/s. |
| Illustrates the wind directions associated with the speeds of Figure C-1. The flow for the month was out of the southwest. |
| Is a hodograph illustrating both the windspeeds and directions for September 1994 at an altitude of 1510 m. between 2:00 and 3:00 am. For this period the winds are predominately out of the northeast. |
| Is a histogram showing the frequency particular windspeeds for the month of March 1997 over the entire altitude range. The same display could be used at one particular altitude. |
Please contact the principal investigator listed above for questions about this project.
Last updated 6/10/99