Effects of Synoptic Weather Systems Upon the Air Quality in an Asian Megacity

Author: Tanner P.A.   Law P-T.  

Publisher: Springer Publishing Company

ISSN: 0049-6979

Source: Water, Air, and Soil Pollution, Vol.136, Iss.1-4, 2002-05, pp. : 105-124

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

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Abstract

The Hong Kong Environmental Protection Department (HK EPD) monitoring data for SO_2, NO, NO_2and O_3 from 1995 and 1996 at three stations spanning the length of Hong Kong have been analyzed in the contexts of selected meteorological parameters, and the types of synoptic weather system. High level and episode days were defined according to two criteria. Higher pollutant gas concentrations were found for systems involving the transport of continental air masses to Hong Kong (cold front (type CF), north/northeast monsoon (type NE)), or when tropical cyclones approached (type AC) Hong Kong. Lower concentrations were observed when the cleaner maritime southerly (type S) airstreams were incident at Hong Kong. Most notably, tropical cyclones (type C) ventilated and diluted local pollution. Days with high levels of SO_2, NO and NO_2 were generally characterized by low windspeed and lower relative humidity conditions. By contrast, high concentrations of O_3 occurred both under low windspeed conditions (type AC) and under the advection of a continental air mass, generally at high windspeeds. The diurnal variation of O_3 levels is discussed: destruction is more important than production in determining local levels.

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