Study on Microphysical Characteristics of Winter Fog in Nanjing Area, China

A comprehensive observation of fog was carried out at Pancheng in Nanjing area, China from Nov. 30 to Dec. 27, 2006. This paper focuses on microphysical data of a prolonged severe fog measured by a high-speed droplet spectrometer (FM-100, Droplet measurement technologies). Results suggest that the roles of liquid water content and number concentration play in the reduction of visibility are not equal according to the fitting result by an emendatory formula. Average spectrum and instantaneous spectra are all fitted with gamma distributions. It is found that the fitting average spectrum is a hyper exponential distribution. For instantaneous spectra, the temporal evolution of intercept parameter (N₀) is in phase with, while the evolutions of shape parameter (mu) and slope parameter (lambda) are out of phase with appearance times of discontinuous spectrum per min.