zt aa yet baia kn ete gt a .aek : ne lef ee a ee een : we baa tt ge ‘ - bt Eaet aed eel od teok le i. de ad bl: 130 METEOROLOGICAL STUDIES CHICAGO AIR POLLUTION SYSTEM MODEL EXPERIMENTAL STUDIES J.f. Carson The city of Chicago's Department of Air Pollution Control and the Argonne National Laboratory’s Meteorology Group have joined forces to obtain certain meteorological measure- ments needed for a proper understanding of diffusion rates over the city; these data are not available from other sources, such as the U. S. Weather Bureau. Fifteen flights, using both helicopters and light planes, have been made to measure the vertical and horizontal variations of temperature, humidity, and sulfur dioxide. Temperature sensors are being placed 1200 feet above street level on the TV support towers on the roof of the John Hancock Building. These data will result in continuous measure of the stability of the atmosphere over thecity. Preliminary results using the sulfur hexafluoride (SFe) tracer technique are discussed. The data show that background levels of this gas, at least near Argonne, are alarminglyhigh. INTRODUCTION Argonne National Laboratory, with the cooperation of the Chicago Department of Air Poilution Control (DAPC) and the support of the Department of Health, Education, and Welfare��s National Air Pollu- tion Control Administration (NAPCA), is developing a numerical model to predict air pollution levels (specifically, sulfur dioxide concentrations) from forecast meteorological and stack emission data. If a numerical model can be formulated which accurately forecasts SOs levels, it will then be possible to design air pollution abatement strategies which are effective with the least amount of cost and disruption to industry. Complete information on the Argonne diffusion model can be found in the progress reports issued to date."-+) CHICAGO URBAN METEOROLOGICAL EXPERIMENTS In order to predict SOs concentrations in an urban area accurately, it is necessary to know how the atmosphere transports and dilutes effluents ejected into it. That is, we must know howthe diffusive capacity of the atmosphere over Chicago varies in time and a better understanding of urban flow patterns and how the city itself affects the structure of the atmosphere. The four experimental programs in which Argonne is involved are: (1) helicopter sounding program, (2) instrumentation of tall buildings in the eity, (8) tracer studies, and (4) fuel switch tests. In an earlier report of this series, the projected experimental programs were discussed in considerable detail. This paper will spell out the progress that has been made to imple- ment and improve these projects. AIRCRAFT SOUNDING PROGRAMS Approximately fifteen flights have been made by DAPC and Argonne personnel to measure vertical sulfur dioxide and temperature profiles in and near Chicago. Both helicopters and light airplanes have been used. The primary objective of this sounding program is to evaluate atmospheric and diffusion conditions (such as the horizontal and temporal variations of the urban lapse rate; the height, base, and thickness of inver- sions; the depth and extent of penetration of lake breeze circulation; and the altitudes of maximum 5Qz concentration) for a number of typical weather situa- tions. Argonne’s role in this program is to design the flight program and to analyze the resultant data in- ventory. The accomplishments during the fiscal year are discussed in the next article. INSTRUMENTATION OF TALL BUILDINGS The helicopter is an ideal sensor platform for ob- taining data over large areas rapidly and at moderate cost. Unfortunately, neither helicopters nor radiosonde balloons permit continuous observations to be made at heights well above the surface. very accurately, estimated from standard meteorolog- The Chicago Department of Air Pollution Control has obtained permission to locate one aspirated temperature sensor on each of the two television towers on the roof of the John Hancock Building m Chicago. These sensors will be about 365 meters (1200 feet) Four experimental programs to obtain additional meteorological measurements in Chicago and to measure dispersion rates over the uneven terrain of the city have been initiated. These projects are giving about 45 meters (150 feet) above street level on the nearby Chicago Water Tower. DAPC will shortly begin discussions with the operator of one or two inter- space and from one meteorological regime to another. The diffusion parameters can be indirectly, but not ical data, such as wind speed and cloud cover. above ground level and about 30 meters above the roof of the structure. Another sensor will be located