Image of local energy anomaly during a heavy rainfall event

A clear and interesting image of local total energy anomaly(EA) is depicted for a heavy rainfall event in this study.Before the convection development, it exhibits a positive local EA, implying local total energy(TE) experiences heaping up to prepare for the future system development. As the convection grows, it transforms into an opposite spatial modality with negative EA dominant, which means that the local TE is consumed to feed the convection growth in the middle and lower levels. The local total EA has consistent variation regular in intensity with severe weather system evolution. By utilizing the local TE budget equation in variable density fluid, the flux divergence of energy and its components are investigated, which could account for the local TE variation better. To relax the restriction and complexity introduced by identifying sporadic and alternative positive/negative signals of EA, the method taking the absolute-value operator on energy flux divergence is used to further simplify analyses. The derived characteristic signal of absolute EA is clearer and cleaner than before.Thus, the EA could be illustrated based on the active degree of energy supply/consumption in a generalized sense whatever positive or negative anomaly should be it, which could be used easily to identify and even predict the system development for operational application. Note that, although two sets of methodologies are used to define EA herein, they play absolutely different roles in nature throughout the whole context. For example, the taking-perturbation method provides a diagnostic tool to portray a preliminary sketch and to give sufficient necessity of this research, while tendency equation of local TE illuminates more predictive sense and accounts for future local EA related to following system evolution. Therefore, the latter could be a more effective tool to routine usage.     

台风“彩虹”(2015)高分辨率数值模拟及涡旋Rossby波特征分析

采用中尺度数值预报模式对2015年22号台风"彩虹"进行高分辨率的数值模拟,成功地模拟出台风"彩虹"的移动路径、强度和降水分布,尤其是在台风登陆前后,模拟结果与实况比较接近.以此为基础,利用模式输出资料,分析台风的动力、热力精细结构和台风雨带的宏观特征.眼墙处具有低层径向入流、高层径向出流的动力配置.在眼墙附近,同时存在切向风速高值区、垂直上升区、正温度距平区,并随高度向外侧倾斜,雷达回波较强,对流系统比较深厚.次级雨带、主雨带和远距离雨带的雷达回波相对较弱,对流系统垂直厚度略小.再利用尺度分离方法,得到涡旋Rossby波的扰动场资料,进一步分析涡旋Rossby波的特征.1波、2波同时朝切向和径向传播,1波的振幅明显大于2波.研究结果表明,1波、2波正涡度扰动对应强雷达回波,存在强对流活动.降水区上空的垂直涡度扰动呈上正下负的配置,与水平散度扰动的垂直配置相似时,会加强低层辐合和高层辐散,有很强的垂直上升运动,有利于对流系统发展,降水增强.1波、2波扰动的动力配置影响了对流系统的发展,并对降水强度和分布有一定的诊断作用.     

Water Vapour Potential Vorticity and Its Applications in Tropical Cyclones

A new tracer is presented to diagnose tropical cyclones （TCs） and their correspondent rainfall. It is defined as water vapour potential vorticity （WPV） by replacing potential temperature with specific humidity in the potential vorticity （PV）. The WPV is compared with PV and moist potential vorticity （MPV） in diagnosing three tropical cyclone cases occurred in North-West Pacific during 10 July to 21 July 2005 （Haitang）, 30 July to 9 August 2005 （Matsa） and 25 September to 3 October 2005 （Longwang） separately. The results show that in tracing the track of TCs, WPV is not nicer than PV but better than MPV. While diagnosing TCs＇ onshore rainfall, WPV is better than MPV in all the three cases. Moreover, the advection of WPV is a good indication of TC rainfall after its landing.     

从流场分解角度改进Q矢量分析方法及其在暴雨动力识别中的应用

依据水平风场分解思路,运用调和-余弦算法,准确分解有限区域Q矢量.根据已有的关于Q矢量散度和新发展的Q矢量涡度与天气系统对应关系的研究,运用分解得到的Q矢量旋转分量场和辐散分量场,改进传统Q矢量分析方法中单纯依靠Q矢量水平散度场进行的诊断分析.通过对一次暴雨个例的比较研究表明,在雨带形势和暴雨中心位置的动力识别方面,改进的Q关键词： 矢量分析 调和-余弦算法 暴雨 动力识别