Rane, eAlad ot ’ . * i i ll te aed oe “a Cait h oga ccc al aetaathl ele cc coe carte cei at BhAMOR octlaateEEateOP 177 TABLE (5. Wind direction, ! Hour of day | | |__| degrees | (CST) | 1 300-350 | 08-11 | 300-350 | s | TastLatron Prepicrion TECHNIQUE mph : 47 ture, °F | °C/ 100 m A >2 | 0.05 | 0.10 | 0.12 0.15 | 0.20 | | 20-29 ' 4-7 | 20-29 No. Percentile values of SO, concentrations, ppm ‘Tempera- | Stability | Wind speed | Min. | . 10 | 2, 0 0.10 50 | 75 Max. 0.11 | 0.12 0.35 0.70! 300-350 08-11 08-11 4-7 4 | 10-18 10-19 >2 1.9-0.0 0.10 0.12 0.08 | 0,10 0.15 | 0.20 0.13 | 0.15 92 81 AL hy | 300-350 of cases 1.50 1.20 0.35 0.30 85 90 Season: December, January, February. (Data taken in 1966 and 1967.) Precipitation: No. TAMStation No, 4, a lowering of the mixing depth is probable because of pronounced subsidence. Any one of the above or similar phenomena markedly affects the pollution potential. The municipal meteorologist may issue forecasts such as a 24-hour air pollution index for the entire urban complex or the maximum levels for se- lected areas where special forecasts are warranted. With the availability of on-line computer facili- ties, some functions may be facilitated. For example, the hourly forecast may be entered into the computer and a printout received in proper format of the 50 per- centile values based on the Tabulation Prediction Scheme Tables stored on a dise or tape memory.It is possible for the computer to print out mapsof the area with plotted values of pollutants and weather variables. This 1s being done at the Argonne National Laboratory. The printout of maps with machine-drawn isopleths of variables has been accomplished by other meteorological organizations. Although the use of auto- matic machine-drawn maps appears to be a sophisti- cated operation, the availability of the computers and necessary software makes such maps quite feasible. The Tabulation Prediction Scheme is a new development in air pollution forecasting. There are a number of areas in which improvement is possible, but the improvements must be based on the individual needs. For example, the municipal meteorologist should conduct investigations to determine the conditions under which high values of pollutant concentrations occur, e.g., such as are found in the 90 to 100 percentile range. Case studies, especially of high pollution episodes, should be made. Theresults of these may well be applied to optimize the use of the Tabulation Prediction Scheme. Further, an investigation involving the persistence of high pollution levels should be made in each city desiring a high caliber pollution warning capability. The percentile value of the SQ, concentration at the beginning of the forecast period may be a good indicator of the probability of the con- centration values exceeding the 50 percentile value. ADVANTAGES AND DISADVANTAGES OF THE TABULATION PREDICTION SCHEME Some of the advantages are 1, It is easy to use and does not require on-line, real-time access to a computer. 2, It provides for rapid prediction of pollution concentration. 3. It provides the entire percentile distribution of pollutant concentrations to allow a forecaster to “fine tune” his predictions on the basis of synoptic situations. 4, It takes into account nonlinearities in the relationship between meteorological variables and pollution concentrations. 5. It is an effective method for analyzing and displaying air quality and relevant meteorological data. Disadvantages of the method are 1. It is necessary to use a large digital computer to construct the tables. 2. At least several years of historical data are necessary. 3. Changes in the emission sources degrade the tables, which must, therefore, be updated every one or two years. GENERAL APPLICABILITY OF THE TABULATION PREDICTION TECHNIQUE For general application, it appears that there is less work in applying the Tabulation Prediction Scheme