L 0 E -v. V5. <0 Vg·Vg>0 B项 v>0 <0 dh II Schematic 500-mb geopotential field showing regions positive and negative advections of relative and planetary vorticitySchematic 500-mb geopotential field showing regions positive and negative advections of relative and planetary vorticity 0 0 − > − ⋅∇ ζ < dy df v V g g g 0 0 − < − ⋅∇ ζ > dy df v V g g g B 项