E矢量
defined by Hoskins et al,1983,
The Shape, propagation and mean-flow interaction of large-scale weather systems
In pressure coordinates:
在三维准地转近似条件下，是EP通量的近似扩展，发现该公式对于纬向平均时，最后两个分量与Eliassen-Palm通量的分量相同。
The E vector can be referred to as an extended Eliassen-Palm flux, whose convergence (divergence) suggests a possible increase (decrease) of wave activity density. The direction of E vector approximately indicates the group velocity (velocity of energy propagation) of Rossby waves relative to the mean flow. It is also an effective tool diagnosing the eddy feedback onto the mean flow. The westerly wind slows down when E vectors converge. The westerly wind slows down when E vectors converge.
从北半球250 hPa的低频以及高频瞬变涡旋的结果看，低频涡旋的E矢量居然向西传。