Based on the theory of information entropy concerning nonlinear errors,the growth rules for the nonlinear errors of the Lorenz system and its predictable components are studied.The results show that the impact of the uncertainties,both in the initial error and in the system itself,needs to be considered in a quantitative estimation of the system predictability.The nonlinear error growth is related to the magnitude of the initial error,and to the spatial distribution of the initial error vectors.Even if these initial errors have the same magnitude but different directions,there are also differences in the nonlinear error growth.The predictability of nonlinear error growth is related to the error component,but not related to the ratio of these components.The component with the highest/lowest rate of contribution does not necessarily have the greatest/least predictability.The different components have different predictabilities,and in different time periods,the different predictable components also have different predictabilities.
利用ECMWF的逐日再分析资料,通过环流分析和物理量诊断方法,揭示2015年12月9日广东暴雨的产生机理。结果表明:来自东欧高纬度的干冷空气南下对暴雨的发生起了重要作用;干冷空气流经青藏高原时发生绕流,南支气流绕过青藏高原并在孟加拉湾反气旋环流的挟卷作用下经南支槽抵达华南,形成了干冷空气的主要通道。暴雨发生前,暖湿气流主要来自西太平洋,暴雨发生期间,偏东气流转为偏南气流,使南海成为9日暴雨的主要水汽源地。冷暖空气的汇合使暴雨区上空等θse线陡峭,沿等θse面有强烈的上升运动,但上升运动区不存在深厚的位势不稳定。冷空气的南下激发了暴雨区700 h Pa的锋生,其中水平变形项和水平辐合项对锋生有正贡献。锋生激发了正的次级环流,环流中心也位于700 h Pa,这有利于气流的抬升,故锋生及次级环流是暴雨区上升运动发展的重要机制。
