鄱阳湖地区复杂地表条件下一次强降水过程的近地面边界层特征

使用鄱阳湖北部70 m气象塔湍流和梯度观测数据,分析了2011年6月6日夜间一次暴雨过程中近地面边界层特征.结果表明,此次过程是在高空低槽和西南急流的天气背景下,受鄱阳湖复杂地表影响产生的局地性强降水.强降水发生前受东南暖平流影响,近地面边界层中水汽累积,不稳定性增加；强降水过程中,近地层感热、潜热通量迅速增加,同时,近地面层湍流动量通量下传和水平输送增加,鄱阳湖的水汽输送加强降水强度.另外,强降水过程中,近地面湍流动能迅速增大并达到最大值,而平均动能的增大发生在强降水结束后,表明地表作用明显,近地面边界层的湍流场为暴雨提供动力条件.尺度分析表明,强降水前,中尺度动量通量占主要地位,降水过程中湍流动量通量显著加强.

Characteristics of surface layer during a heavy rainfall process over the complex surface of Poyang Lake

The gradient and turbulent data observed by 70 m meteorological tower at the north part of Poyang Lake are employed to analyze the characteristics of surface layer of a heavy rain process on 6 June 2011.It is found that,under the weather background of upper trough and southwest jet,the heavy rain process is obviously affected by the complex surface of Poyang Lake.Before the precipitation happens,affected by the warm southeast advection,the water vapor and instability increase.During the heavy rainfall process,the sensible and latent heat fluxes,and the horizontal and vertical turbulent momentum fluxes increase rapidly,and the water vapor transport from Poyang Lake surface strengthens the rainfall.In addition,the turbulent kinetic energy increases rapidly and reaches a peak during the heavy rainfall,while the mean kinetic energy reaches a peak after the heavy rainfall process,showing that the local surface provides a dynamic effect on the heavy rainfall process.Dimensional analysis shows that the mesoscale momentum flux is larger than the turbulent momentum flux before the heavy rainfall,however,during the heavy rainfall process,the turbulent flux increases obviously.