Diagnostic analysis for interaction of upper and lower level jet streams during two heavy rainfall events in the summer

The energetics of the interaction between the tropospheric upper and lower level jet streaks during the development of summer severe convective storms developed in Beijing on 21 July 2012 and in Jiangsu on 12 July 2010 were analyzed using ERA-Interim six-hourly data and energy equations. It revealed that eddy kinetic energy (EKE) generation associated with the upper jet stream was mainly determined by the baroclinic processes and the convergence of ageostrophic geopotential fluxes, while in the lower level jet the latter plays an important role in the EKE generation. The descending motion induced by upper level jet streaks transported the EKE downward from upper level jet to low level to enhance lower level jet streak by vertical ageostrophic geopotential fluxes when the eddy geopotential was negative in middle and lower troposphere, which provides favorable conditions for the development of the summer storm. The transport of energy from upper to lower level by direct (indirect) circulation was significantly different during the two heavy rain events.