| In this paper, the measured precipitation date, objective analysis data and WRF numerical simulation fine data were used, statistical analysis of the torrential rain days in Jianghuai region along the past five years, classified the rainstorm background situation type. Focus analysis on the a westerly trough and tropical cyclones configuration type rainstorm. Study the two typical process in Jianghuai region in2011, westerly trough and tropical cyclones in the "0625" Storm were in close proximity, and in the "0718" rainstorm they were relatively far away. Analysis the baroclinic nature of the temperature and pressure field, background flow fields baroclinic component, as well as the wet power baroclinic characteristics in the heavy rain area of the critical system. Due to the strong baroclinity on the slot area between the tropical cyclone and westerly trough, can easily induce and sustain the development of the small and medium-scale systems, therefore, analysis of the rainstorm characteristics of the small and medium-scale systems before the westerly trough combining the cloud images, radar data and encryption station information.Focused on the two typical rainstorm process in the development of positive slope pressure structural characteristics and the transformation mechanism. And quantitative comparison rainstorm process positive baroclinic characteristics of the same and different, understanding of the influence of the two westerly trough and tropical cyclones configuration positive baroclinic characteristics and positive baroclinic component conversion accompanied to the heavy rain.The results show that, the barotropic component of the flow field can be reflected the layer flow field characteristics and critical systems (westerly trough and tropical cyclones) in the two progress. In the in the "0625" close configuration system, big value of the baroclinic component of low-level in tropical storms and high-level in westerly trough become the the baroclinic component’s source, the small value of the baroclinic component in Tropical Storm high-level and westerly trough low-level is the baroclinic component exchange, and the baroclinic component of the flow fields account for a significant dominance. In the "0718" rainstorm, the positive pressure component of the flow field dominate.In terms of the characteristics of barotropic and baroclinic flow fields, under the conditions of key synoptical systems at short range in the case of0625", baroclinic kinetic energy prevails and increases with time and barotropic kinetic energy fore-and-aft the duration of rainfall; while in the case of "0718" with the configuration of key synoptical systems at remote range, barotropic and baroclinic kinetic energy match closely fore-and-aft the duration of rainfall.In terms of the characteristics of kinetic energy conversion terms, Cl (KS, KM) play an important role in the conversion process, followed by C2(KS, KM) entry. The total energy conversion terms in both cases show conversion of baroclinic kinetic energy to barotropic energy.After dividing the moisture convergence flux into the barotropic and baroclinic parts, it’s found that the baroclinic parts behave more stronger than the barotropic parts. In the case of "0625", there exist mesoscale convergence centers of moisture convergence flux near Nanjing. For case "0718", the baroclinic parts of moisture convergence flux are weaker due to the stronger barotropic charasteristics in this case. During different stages of rainfall, there is no big changes in barotropic parts of moisture convergence flux while the baroclinic parts of moisture convergence flux increase gradually.In terms of wet potential vorticity, The rainstorm areas locates in the unstable aeras where MPV1negtative center and MPV2positive center exist simultaneously at the vertical section for the "0625" case and at the isobaric surface for the "0718" case. Both barotropic and baroclinic parts of the wet potential vorticity fit together, which benefit the development of the heavy rain and full of certain indicating significance for predicting the rainfall aeras.For two cases of heavy rain, the convergence field of Q-vector divergence at mid and low levels basically mach with the accumulated precipitation and the rainbelt moving trend. The distribution of convergence centers of Q-vector divergence appears in accordance with the feature of vertical motion alternate with lifting and falling centers, which trigger the existence of the secondary circulation... |
PDF Full Text Request