Study on Subtropical High Activity over the Western Pacific and QBO in the Stratosphere
Li Chongyin and Long Zhenxia (LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100080)
Based on the data analyses, the quasi-biennial oscillation feature of subtropical high over the western Pacific is studied. This oscillation is very clear in both relative intensity and the ridge-latitude location of subtropical high. The analyses still show that the vertical shear of zonal wind in the lower stratosphere is related to subtropical high activity over the western Pacific, easterly (westerly) shear corresponds to stronger (weaker) subtropical high and the ridge locating to north (south) side. The ascending (sinking) motion in the upper troposphere over the equator caused by the easterly (westerly) shear in lower stratosphere will rise (weaken) the Hadley cell, and this is a possible important mechanism in relation to the influence of QBO on the subtropical high activity over the western Pacific. The simulations in IAP-GCM are also completed in this study and the results are similar with that in the observation data analyses.