The Comparison Of Turbulence Characteristics Between Haze-day And Fog-day In Nanjing

We compare turbulent characteristics during a sunny day on December 3, a haze process on December 4, and a fog process on December 7-9 of 2013. We analyzed the development process, temperature distribution and humidity distribution in the boundary layer on the fog day, the haze day and the sunny day. Then, we studied the evolution characteristics, statistical characteristics and spectrum distribution characteristics of turbulence parameters. Lastly, we analyzed the effect of turbulence on micro-physical parameters on the haze day and the fog day. The results are as follows. The average wind speed, the average kinetic energy, the average turbulence kinetic energy, turbulence intensity, friction velocity, momentum transfer, and heat transfer on both haze day and sunny day had evident diurnal variation, while there was no obvious diurnal variation on the fog day. There were differences in the values of turbulence parameters on the haze day, the fog day and the sunny day. The normalized variance of three-dimensional (3D) winds in the near-neutral stratification was almost constant on the haze day, the fog day and the sunny day. The normalized variances of 3D winds on the haze day was 3.15,2.72 and 1.17 in x, y and z directions, respectively; on the fog day, these values were 3.11,2.45 and 1.25, respectively; on the sunny day, they were 3.40,3.45 and 1.50, respectively. The normalized variances of 3D winds on the haze day and fog day, and the normalized turbulence kinetic energy adjusted to the 1/3 law with the stability parameter in the unstable condition. The normalized turbulence kinetic energy on the haze day, the fog day and the sunny day adjusted to the 1/3 law with stability parameter in both stable and unstable conditions. The normalized variances of temperature and moisture on the haze day, the fog day and the sunny day adjusted to the-1/3 law with the stability parameter in the unstable condition. The normalized variance of temperature on the haze day, the fog day and the sunny day adjusted to the -2/3 law with the stability parameter in the stable condition.The normalized spectra of 3D winds on the fog day fit better with Kansas spectra than those on the haze day and sunny day. The peak frequency of 3D winds on the haze day was about 0.01 Hz, the peak frequency of u spectra on the fog day was about 0.004 Hz, the peak frequencies of v and w spectra on the fog day were about 0.1Hz, the peak frequency of 3D winds on the sunny day was about 0.01 Hz. The normalized spectra of 3D winds on the fog day agreed better with the M-O isotropic theory than those on the haze day and sunny day. There was mainly mechanical turbulence on the haze day and sunny day, while there were both mechanical turbulence and thermal turbulence on the fog day.The stronger the fog developed, the bigger the fluctuation of number concentration and liquid water content were, and the smaller the fluctuation intensity was. Number concentration of fog droplet increased with turbulence intensity. On the haze day, the fluctuation of radius increased with radius, and the fluctuation of number concentration increased with number concentration. Radius and fluctuation strength of radius decreased with turbulence intensity, fluctuation of radius decreased with longitudinal turbulence intensity, fluctuation intensity of radius increased with transverse and vertical turbulence intensity and then decreased with longitudinal and vertical turbulence intensity. Number concentration and fluctuation of number concentration increased with 3D direction of turbulence intensity.