Wave sources, energy propagation and conversion for anomalous Rossby wave activities along West Asian jet stream.

Characteristics of the wave sources，energy propagation and conversion for anomalous Rossby wave activities(RWA) along West Asian jet stream (WAJS) in summer are examined based on the NCEP/NCAR reanalysis dataset from 1958 to 2003 by using vorticity source equation, EliassenPalm (EP) flux, and wave energy equation with diabatic heating. As a result, the causes of RWA anomalies along WAJS are further comprehended from the atmospheric dynamic mechanism to improve understanding of mid-high latitude circulation anomalies. The results show that the negative vorticity source and the strong EP flux divergence over the Mediterranean Sea and the North Atlantic-Scandinavian Peninsula area act as the wave sources of RWA anomalies along WAJS. When the intensity and position of the wave sources are anomalous, the excited eastwardpropagation RWA along WAJS also behaviors anomalously. In strong (weak) years of RWA along WAJS, Rossby waves excited by the strong divergence of EP fluxes over the Iceland-Scandinavian Peninsula area (east to Scandinavian Peninsula) propagate eastward and southeastward. The eastward propagating waves strengthen (weaken) after turning southeastwards near the Ural Mountain and then entering into the Asian subtropical westerly jet stream(ASWJS) over the Caspian Sea -Aral Sea -Xinjiang, and the southeastward propagating waves strengthen (weaken) after directly entering into the ASWJS over the eastern Mediterranean-the Black Sea. Furthermore, the divergence of EP flux over the Mediterranean also strengthens (weakens) in the strong (weak) years, so they jointly bring about strong (weak) RWA along WAJS. Besides the perturbation available potential energy (PAPE) along WAJS(15°-60°E )produced by diabatic heating is far greater than the conversion from the kinetic energy of basic flow into perturbation kinetic energy and from the available potential energy of basic flow into PAPE. The RWA along WAJS looks stronger (weaker) than normal, when the PAPEs produced by diabatic heating over the Iran Plateau and west Asia obviously strengthen (weaken), therefore they are also the energy sources of RWA anomalies.