城市粗糙子层内湍流特性研究——以合肥一站点为例

Research on Turbulence Characteristics in Urban Rough Sublayer-Taking a Site in Hefei as an Example

城市边界层粗糙子层内的平均场和湍流场特征通常利用局地相似理论来描述,但在很多场合仍然适用于Monin-Obukhov相似性理论。在合肥城区开展气象观测,获取粗糙子层内两不同高度的风速温度数据,分析Monin-Obukhov相似性理论与局地相似性理论的差异,同时分析风速、温度的归一化标准差与局地稳定度的关系随高度的变化。结果表明,两高度上的摩擦速度u_(*)相差超过13%,特征温度T_(*)相差小于2%。风速、温度归一化标准差与稳定度之间的关系可以采用平坦下垫面近地层得到的拟合关系式,只是具有不同的拟合系数,且两个高度的拟合系数不同。这说明本实验地点符合一般粗糙子层的特征,与平坦均匀下垫面近地面层有较大的差别。

In the rough sublayer of the urban boundary layer,the local similarity theory is usually used to describe the characteristics of the average field and the turbulence field.However,Monin-Obukhov similarity theory is still used in many occasions.By acquiring the wind speed and temperature data at two different heights in a rough sublayer of Hefei city,China,the difference between the Monin-Obukhov similarity theory and the local similarity theory is analyzed.At the same time,the universal function of the normalized standard deviation of wind speed and temperature with the local atmospheric stability varying with height is also focused.The statistical results show that the friction speed u_(*) at two heights differs by more than 13%,and the characteristic temperature T_(*) differs by less than 2%.It is also shown that the universal function of wind speed and temperature of the local atmospheric stability in surface layer of the flat underlying surface can be adopted here,however,the fitting coefficients are not the same as those in surface layer of the flat underlying surface and different at two height.It shows that the location of this experiment has the characteristics of a general rough sublayer,which is quite different from the flat and uniform underlying surface near the ground layer.