南京雾-霾天气个例湍流运动特征的对比研究

Comparative study of turbulent characteristics between the fog day and haze day in Nanjing

  • 摘要: 利用超声风速仪、能见度仪等探测资料,采用Fortran、Matlab、Origin等软件处理数据并绘图分析,对比了南京郊区2013年12月4日一次霾过程、2013年12月7—9日一次雾过程和2013年12月3日一个晴天的湍流运动特征。结果表明,霾天和晴天平均水平风速、平均动能、湍流动能、湍流强度、摩擦速度、动量通量和热量通量都有明显的日变化,而这些参量在雾天没有明显的日变化,不同天气湍流参量大小有差异;霾、雾、晴天近中性层结下,u、v、w三个方向风速归一化标准差近似为常数,霾天分别为3.15、2.72、1.17,雾天分别为3.11、2.45、1.25,晴天分别为3.40、3.45、1.50;不稳定条件下霾、雾、晴天风速归一化标准差和湍流动能归一化标准差符合1/3幂次律,稳定条件下霾、雾、晴天无因次湍流动能均满足1/3幂次律;不稳定条件下霾、雾、晴天温度和湿度归一化标准差满足-1/3幂次律,稳定条件下霾、雾、晴天温度归一化标准差符合-2/3幂次律;雾天归一化u、v、w谱与Kansas谱吻合度比霾天和晴天高,霾天u、v、w谱峰值频率约为0.01 Hz,雾天u谱峰值频率约为0.004 Hz,v、w谱峰值频率约为0.1 Hz,晴天u、v、w谱峰值频率约为0.01 Hz。得出结论:雾天的边界层结构与霾天和晴天有所不同;不稳定条件下霾、雾、晴天风速、湍流动能、温度、湿度归一化标准差均符合莫宁-奥布霍夫相似理论;雾天归一化u、v、w谱比霾天和晴天更加符合莫宁-奥布霍夫局地各向同性理论,且霾天和晴天以机械湍流为主,雾天既有机械湍流也有热力湍流。

     

    Abstract: Using the softwares such as Fortran,Matlab and Origin to deal with the turbulence and visibility data and draw figures the comparison of turbulent characteristics anong a haze process on 4 December 2013, a fog process from 7 to 9 December 2013 and a sunny day on 3 December 2013. The results show that the average speed of wind, the average kinetic energy, turbulence kinetic energy, turbulence intensity, friction velocity, momentum transfer, and heat transfer on both the haze day and sunny day illustrate an evident diurnal variation, while there was no obvious diurnal variation on the fog day. There were also differences among the value of the turbulence parameters on haze day, fog day and sunny day. The normalized variance of the three-dimensional (3D) winds (u, v and w) in the near-neutral stratification was almost constant on the haze day, fog day and sunny day; the normalized variance of 3D winds on the haze day is 3.15, 2.72 and 1.17 respectively; on the fog day it is 3.11, 2.45 and 1.25, respectively; on the sunny day it is 3.40, 3.45 and 1.50, respectively. The haze day and fog day's normalized variance of 3D winds, normalized turbulence kinetic energy and the ratio of horizontal moisture momentum vs. vertical moisture momentum meet the 1/3 law with the stability parameter in the unstable condition. The haze day, fog day and sunny day's normalized turbulence kinetic energy meet the 1/3 law with the stability parameter in both stable and unstable conditions. The haze day, fog day and sunny day's normalized variance of temperature and moisture meet the -1/3 law with the stability parameter in the unstable condition, and the haze day, fog day and sunny day's normalized variance of temperature meet the -2/3 law with the stability parameter in the stable condition. The fog day's normalized spectra of 3D winds fit better with the Kansas spectra than the haze day's and sunny day's. The haze day's peak frequency of 3D winds is about 0.01 Hz, the fog day's peak frequency of the u spectra is about 0.004 Hz, the fog day's peak frequency of the v/w spectra is about 0.1 Hz, and the sunny day's peak frequency of 3D winds is about 0.01 Hz. The conclusions are as follows: the boundary layer structure on the fog day is different from that on either the haze day or sunny day.The normalized variance of the wind, turbulence kinetic energy, temperature and humidity on the fog day, haze day and sunny day all meet the Monin-Obukhov similarity theory in the unstable condition. The fog day's normalized spectra of 3D winds accords better with the Monin-Obukhov isotropic theory than the haze day's and sunny day's. The haze day and sunny day include mainly the mechanical turbulence, while the fog day includes both the mechanical turbulence and thermal turbulence.

     

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