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Comprehensive field observations of fog were conducted during the winters of 2006-2009 at the Nanjing University of Information Science & Technology, in order to study macro-and micro-physical structures and physical-chemical processes of dense fogs in northern Nanjing. The fog boundary-layer structures of different types and their corresponding characteristics are presented in Part I of these twin papers. In this second part, microphysical characteristics and droplet spectrum distributions of different types of fogs, microphysical relationships (among fog droplet concentration, liquid water content, and mean diameter), and microphysics of atmospheric aerosols during haze/fog events are discussed. The results show that there are large differences in microphysical parameters among four types of haze/fog. Many interesting phenomena, including fog burst reinforcement, fog droplet spectrum broadening, fog bimodal or multi-modal drop-size distributions, and critical triggering maxD value of fog coagulation growth, were captured during the 4-year field study.

Comprehensive fog field observations were conducted during the winters of 2006-2009 at the Nanjing University of Information Science and Technology to study the macro and micro-physical structures and the physical-chemical processes of dense fogs in the area. The observations included features of the fog boundary layer, characteristics of fog water, the particle spectrum, the chemical composition of atmospheric aerosols, radiation and heat components, turbulence, meteorological elements (air temperature, pressure, wind speed, wind direction), and environmental monitoring. The fogs observed were divided into four types: radiation fog, advection-radiation fog, advection fog, and precipitation fog, according to the mechanisms and primary factors of the fog processes. Fog boundary-layer structures of different types and their corresponding characteristics were then studied. Fog boundary-layer features, temperature structures, wind fields, and fog maintenance are discussed. The results show that radiation fog had remarkable diurnal variation and formed mostly at sunset or midnight, and lifted after sunrise or at noon, and that advection-radiation fog and advection fog were of very long duration. Extremely dense fogs occurred only in radiation-related cases. Inversion in radiation fog was short-lived, disappearing 1 or 2 hours after sunrise or at noon, faster than that in advectionradiation fog. When wind direction reversed from easterly to westerly or from southerly to northerly, the fog became an extremely dense fog. Low-level jet at times impeded fog development, whereas at other times it encouraged fog continuance. The deep inversion was merely an essential condition for a thick fog layer; sufficient vapor supply was advantageous to the formation and maintenance of a deep fog layer.

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