The Study Of Multi-scale Energy Interactions During A Meiyu Front Rainstorm

This paper mainly discussed the multi-scale energy interaction during Meiyu front rainstorm.The kinetic energy equations and potential energy equations of large scale,meso-a scale and meso-? scale were derived from motion equations and thermodynamic equations in the z coordinate system using the anelastic approximation by dividing the basic physical quantity into three scales for the purpose to analyze the multi-scale energy interactions.Various energy conversions were presented in the energy equations.The kinetic energy equations mainly included kinetic energy transportation or conversion,the work of horizontal pressure gradient force,vertical perturbation pressure gradient force,buoyancy,Coriolis force and friction.The potential energy equations mainly included potential energy transportation or conversion,and the effects of buoyancy and diabetic heating.Among them,the effect of buoyancy was substantially the energy conversion term between the potential energy and kinetic energy,and thus was the most critical energy conversion term in the process of rainstorm development.The fusion data of observations collected at automatic stations in China and CMORPH(Climate Prediction Center Morphing technique for the production of global precipitation estimates)hourly precipitation at 0.1° resolution were used to identify a typical Meiyu front rainstorm,the time for the 08:00 on June 30th to 21:00 on July 1st 2016.The intense of the rainstorm was maximum and its scope was the most concentrated.So this paper chose this process in the heavy rainfall process as the research object.The WRF model was used to simulate the precipitation process.The simulation data is filtered by Barnes filtering.The energy equations were applied to analyze the filtered data for the purpose to quantitatively analyze the effects of interactions between multi-scale energy on the rainstorm intensity.The results were as follows.The simulated precipitation and its intensity were consistent with observations,which indicated that the simulation can be used in the following research.Besides,these derived energy equations can be applied to the rainstorm.The interactions between energy on the three scales involved a variety of cross scale energy interactions.During the entire rainstorm process,the baroclinic energy conversions across various scales included the energy conversions not only from available potential energy to kinetic energy,but also from kinetic energy to available potential energy.However,the baroclinic energy conversions between these scales were always unidirectional,and the value was large,that is,the strength of kinetic energy was maintained mainly by the energy transformation from the available potential energy to the kinetic energy.The baroclinic energy conversions influenced the rainstorm intensity.And the baroclinic energy conversions of large scale were stronger than others in the upper and middle troposphere,while the baroclinic energy conversions of meso scale were stronger than others in the lower troposphere,especially the meso-? scale.Meso-? scale disturbance may be the key system that influences the intensity of rainstorm.The magnitude of wind shear affected energy conversions between different scales of kinetic energy.The magnitude of temperature or potential temperature gradient affected energy conversions between the available potential energies at various scales.The energy conversions between the available potential energy and kinetic energy were mainly related to distributions of vertical velocity and temperature of each scale.The rising of warm air and the sinking of cold air were the main processes of the conversions from available potential energy to kinetic energy at various scales.