Eddy kinetic energy study of the snowstorm over Southern China in January 2008

The energetics of the third stage of a snowstorm over China was analyzed using ECWMF data. The analysis of the energy budget for the Middle East trough and the western Pacific trough that developed toward China on 25–28 January 2008 showed the advection of the geopotential by the ageostrophic wind to be both a crucial source and the primary sink of the eddy kinetic energy centers associated with the troughs. The magnitudes of the energy conversion terms, interaction kinetic energy conversion and baroclinic conversion, were too small to explain the development of the energy centers and the jet streaks. The energy centers gained energy at their entrance regions via the convergence of the ageostrophic geopotential fluxes, and then lost energy at their exit regions by the same fluxes. At the entrance regions, the fluxes converged, increasing the geopotential gradient, which generated a stronger geostrophic wind and higher kinetic energy, resulting in an ascending motion in this area. When the troughs moved to China, the ascending motion caused by the convergence of the fluxes at entrance region intensified the snowstorms over central and southern China.