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Fuzzy logic approach for description of meteorological impacts on urban air pollution species: A Hong Kong case study
PAPER WITHDRAWN
Oleg M. Pokrovsky, Main Geophysical Observatory, St.Petersburg, Russia; and R. H. V. Kwok and C. N. Ng
The aim of the present paper is to develop an alternative approach to conventional dynamic and photochemical models for operational short-term forecasting of urban air pollutants. It is well known that there are some practical difficulties which prevent necessary progress in the development of these models as a forecasting tools. A fuzzy logic based method has been developed here to study the impact of meteorological factors on the evolution of air pollutant levels and to describe them quantitatively. The developed model bases on simulation of diurnal cycles of principal meteorological variables (wind speed and direction, solar irradiance, and air temperature) and the corresponding diurnal patterns of various air pollutants (O3, NO2, NO, NOy). Hourly air quality data from eight ambient and one roadside stations in Hong Kong are used to demonstrate the practical usefulness of the present methodology. As Hong Kong is located at the South China coast, its air quality is influenced by both continental and maritime air mass, depending on the season of the year. It is revealed that there is clear relationship between wind speed and wind direction. In winter the relationship is fairly strong under the easterly and south-easterly winds, but rather weak under the westerly and south-westerly. In summer, easterly and westerly winds dominate, but in most cases strong wind are of easterly. . In winter at most sites the easterly winds are often accompanied by cloudy sky, and lower level of solar radiation and air temperature. On the contrary, the weak westerly wind involves clear sky and high air temperature conditions. The solar irradiance and air temperature evolve in good mutual agreement. At most sites high NO2 concentrations are likely to occur under south-easterly winds, and an increase of the NO and NOy concentrations are more probable after the influence of easterly winds, but these values are less sensitive to wind speed and duration. Latter is due to main emission sources occurred at Hong Kong city. But NO and NOy values are less sensitive to wind speed and duration. Photochemistry factors are also studied in this approach. Under clear sky conditions at some sites there appears linkages between low or high ozone and NO2, NO and NOy values, and vice versa. However, under cloudy conditions the pollutant concentrations seem to be more dependent on wind fuzzy set. There is also some modulation between air temperature and nitrogen dioxide concentrations: i.e. low temperature - low NO2. Analysis of spatial patterns allow us to find out the NOx and NOy extreme events, their locations and meteorological conditions for previous days at sites. Results of our fuzzy set analysis confirm that the role of photochemistry in the local ozone balance depends strongly on NOx concentrations. At the similar wind conditions the ozone concentration depends on solar radiation amounts : the less cloudiness the more of the ozone concentrations. However, ozone production rate also depends on amount of NOx transported by south- easterly and easterly winds. As a result we expect to get an independent tool for estimation e of ozone photochemistry production rate from observational data.
Session 1, Fuzzy Set Applications
Monday, 10 January 2000, 9:00 AM-11:00 AM
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