INTRASEASONAL VARIABILITY OF KATABATIC WIND OVER EAST-ANTARCTICA AND PLANETARY FLOW REGIME IN THE SOUTHERN-HEMISPHERE

The Intraseasonal variation (30- to 50-day period) of katabatic wind has been found at Mizuho plateau, East Antarctica, as a predominant mode of the subseasonal time scale variability. The atmospheric circulation in the southern middle and polar latitudes associated with this fluctuation of katabatic wind has been deduced by using the NMC gridded 500-mbar zonal wind and geopotential height field. The axisymmetric circulation pattern to Antarctica is noticeable in the anomalous zonal wind and height field. That is, the strong (weak) katabatic wind phase corresponds to the shallower and broadened (deepened and narrowed) tropospheric circumpolar vortex with weaker (stronger) westerlies over the surrounding oceans. These results strongly suggest that the intraseasonal variation of katabatic wind regime over East Antarctica is part of the modulation of planetary flow regime and meridional circulation in the southern middle and high latitudes, i.e., part of the index cycle of the southern hemisphere.