Abstract
To explicitly describe the energy exchange between meso and synoptic-scale motions, a diagnostic scheme of kinetic energy has been developed. By using a horizontal filtering technique, meteorological variables are separated into synoptic and mesoscale components. A set of budget equations are derived for the kinetic energy K̂ of synoptic scale motion V̂, the kinetic energy K′ of mesoscale motion V′, and the scalar product V̂·V′.
The scheme is applied to diagnose a severe rainstorm case over northern China during summer. The results show that the scale interactions between wind and height fields produce V̂·V′, which transfers kinetic energy to K̂ and K′. The term V̂·V′ thus acts as a medium in scale interactions conveying the energy between meso- and synoptic-scale motions and the potential energy source residing in the mass field.
