逾量旋转动能在区分我国龙卷与非龙卷中气旋中的应用

多普勒天气雷达中气旋算法是为探测直径在1.8～9.2km(1～5nmi)的中气旋而设计的。绝大多数强龙卷都属于发生在中气旋内部的超级单体龙卷,但并不是所有的中气旋都能发展成龙卷。文中引入中气旋核的逾量旋转动能(ERKE)概念,结合中气旋算法和速度产品,分析了龙卷和非龙卷中气旋个例维持期间ERKE值的演变特征,并计算了一些超级单体风暴个例的中气旋初始的ERKE及其权重高度值。结果表明,与非龙卷中气旋相比,龙卷中气旋中ERKE的值普遍较大且其权重高度较低;超级单体风暴的初始中气旋ERKE值及其权重高度可以有效地区分中、低对流层中的龙卷和非龙卷中气旋,并可作为龙卷中气旋识别的定量指标。同时在我国平均中气旋气候特征的基础上,还绘制了ERKE图解,可从中气旋旋转速度和旋转半径快速查得对应ERKE值的大小。

Application of Excess Rotation Kinetic Energy in Distinguishing the Tornadic and Non-Tornadic Mesocyclones in China

Doppler radar mesocyclone algorithm is designed to detect mesocyclones with diameters from 1.8 to 9.2 km(1～5 n mi).Majority strong tornadoes occur in mesocyclone with supercell,but not all of the mesocyclones can develop into tornadoes.In this paper,the concept of the Excess Rotational Kinetic Energy(ERKE) of a mesocyclone core is introduced.Combining with mesocyclone algorithm and radial velocity products,the temporal variation features of ERKE and weighted height are analyzed in some tornadic and non-tornadic mesocyclone lifetime,and the initial ERKE value and weighted height of other cases are also calculated.The results show that the ERKE are generally larger and the weighted heights are relatively lower in tornadic mesocyclone,comparing with non-tornadic mesocyclone.Furthermore,the tornadic and non-tornadic mesocyclones in the low-and mid-troposphere layers can be distinguished by the initial ERKE value of mesocyclone with supercell storm effectively,which can be used as the quantificational identification indicator of tornadic mesocyclone.Finally,the ERKE diagram is given on the basis of the climatological mature mesocyclone in China.From the diagram,ERKE value can be quickly gained via the values of rotational speed and the mesocyclone radius.