The impact of the vortex in the easterlies over the tropical upper troposphere on the subtropical anticyclone over Western Pacific

【摘要】：By employing the NCEP/NCAR reanalysis data sets(1000~10hPa, 2.5o×2.5o), the impact of the vortex in the easterlies(shorten as EV)over the tropical upper troposphere along the east-west direction movement of the subtropical anticyclone over the Western Pacific Ocean(shorten as WPSA) on June 19~25 2003 is analyzed in this paper. It is shown that the EV can extend from mid-troposphere to the height of 50 hPa, the maximum locating at 200 hPa. The vertical thermal distribution appears to be the characteristics of "warmer in the upper layer and colder in the lower layer". The WPSA retreats eastward abnormally when the EV and the vortex in the westerlies(shorten as WV) encounter around the same longitude while they move from the opposite directions. It can be also showed that the effect of the vorticity trend extends from the troposphere to the height of 50 hPa level, the most prominence level locates at 200 hPa by the diagnostic analyses of the vertical vorticity equation. The WPSA appears to abnormally retreat eastward while the negative/positive vorticity change becomes stronger near the east/west side of the EV and the vorticity tendency positive areas both in the EV and in the WV link as one belt along 130°E during the process of the EV and the WV moving forward face to face. In the vorticity equation, the positive contribution causing from the hotizontal advection term is the maximum, and the minimum is caused from the Beta effect. It is also found that the increases of the horizontal vorticity advection and Beta effect, as well as the "barotropic development" resultinfg from the superposition in–phase of the south wind and the north wind in the easterlies and the westerlies near 130°E are in agreement with the WPSA retreat.