The light scattering and absorption coefficients of aerosol particles at low relative humidity had been measured continuously at Cape D'Aguilar, a remote area at the south-eastern tip of Hong Kong, from September 1997 to April 1999. Higher reading was recorded in winter (November-February) than in summer (May-August). The second winter (November 1998-February 1999) registered higher reading than the first winter (November 1997-February 1998). Forty-four episodes were identified when sudden increase in scattering coefficients or absorption coefficients lasted for two or more consecutive hours and exceeded three standard deviations of the monthly mean.