Wintertime extreme precipitation event over southern Chinaand its typical circulation features

This study objectively defined an extremeprecipitation event （EPE） over southern China and inves-tigated the associated typical circulation pattern on theintraseasonal time scale. The occurrence of the EPEresulted from the joint operations of anomalous circula-tions over the subtropics and mid-high latitudes. During theEPE, simultaneous enhancements of the trough over theBay of Bengal （BBT） and the Western Pacific subtropicalhigh （WPSH） facilitated thetions over southern China,abundant water vapor condi-whereas the weakened EastAsian major trough （EAT） led to a moderate cold airinvasion to that region, producing a persistent convergencezone over southern China. Wave train pattern in NorthAtlantic and Europe may be viewed as precursory signalsfor the EPE over southern China, and it contributed to theRossby wave propagation in association with the EPE.These wave packets propagated toward East Asia mainlyalong the North African-Asian subtropical westerly jetwaveguide. Low-frequency disturbances along this wave-guide contributed to the enhancement of the BBT andWPSH and the weakening of the EAT, constitutingfavorable circulation conditions for the EPE.     

纳米莫来石的制备及其机理研究

以正硅酸乙酯(TEOS)、结晶氯化铝(A lC l3.6H2O)为主要原料制备纳米莫来石前驱体溶胶,然后采用超临界流体干燥处理(SCDF)技术制备了A l2O3-S iO2体系纳米超细粉体,经1 100℃热处理后全部转化为针状纳米莫来石。借助透射电子显微镜(TEM)、X-射线衍射仪(XRD)、X-射线光电子能谱仪(XPS)和物理吸附仪等仪器对纳米莫来石进行了表征,并对其机理进行了探讨。