一次冷锋过境过程的中尺度通量观测

OBSERVATION OF MESOSCALE FLUX OF A COLD FRONT PASSAGE

根据Taylor假定 ,通过对铁塔定点观测冷锋过境湍流资料的谱分析 ,分离出其中尺度过程 ,从而计算出其中尺度通量 .计算结果的分析表明 ,在强背景风场条件下 ,湍流动量输送占据绝对优势 ;当背景风较弱时 ,中尺度动量通量不能被忽视 ,它甚至强于湍流动量通量 .而中尺度感热通量的强弱受多种因素的制约 .总的说来 ,冷锋后的中尺度感热通量大大强于湍流感热通量 .对于湍流通量参数化计算的理论分析表明 ,在较长的时间尺度进行湍流通量参数化时 ,有必要考虑因中尺度扰动而产生的修正 .合理的通量计算参数化方案需要全面包含湍流通量。

In this paper, the mesoscale process of a cold front passage was studied by using spectral analysis of turbulent data obtained from a tower. The mesoscale fluxes were estimated according to the Taylor hypothesis. The results showed that turbulent momentum flux was much higher than that for high background wind, implying the mesoscale flux could not be ignored when the background wind was low. The mesoscale sensible heat flux is influenced by many facts. Generally, the mesoscale sensible heat flux was higher than the turbulent sensible heat flux after the cold front. The analysis of the turbulent flux parameterization shows that it is necessary to include the modification of the mesoscale disturbance when using parameterization method on long time scale. Reasonable parameterization method for flux calculation should include the turbulent flux, the measoscale flux and the mesoscale modification on the turbulent flux. [