.0604 Landing Tropical Cyclone "bilis" Diagnostic Analysis

This paper studies on the structure and process of development in a long time to maintain and evolution of the 4th tropical cyclone "Bilis" in 2006 after landing, the mesoscale convective systems and the structural characteristics of the development mechanism of "Bilis" internal circulation. First of all, through the conventional observational data and NCEP1o*1o further analysis of information obtained "Bilis" evolution and large-scale background analysis. Use NCEP data to research the low-frequency oscillations of the South China Sea monsoon and the impact of "Bilis" circulation. Use Tbb images, encryption observation, NCEP re-analysis information on analysis of the "Bilis" structure and maintain mechanism; Analysis on the three-dimensional structure of MCS and the development mechanisms of MCS in the "Bilis" internal circulation .Introduction of the first chapter, mainly on research of the tropical cyclone, including the structure and intensity variation, landing and maintaining mechanism, and effects of water vapor of tropical cyclone; precipitation characteristics of tropical cyclone, the interaction of low -Mid latitude circulation, the impact of terrain, mesoscale system and typhoons storms. The study introduces the mesoscale system within typhoon: the definition and characteristics of mesoscale convective clouds, the diagnostic analysis of mesoscale convective systems in typhoon, several factors of the mesoscale convective systems within typhoon circulation. Progress of typhoons storms studies in the dynamics and numerical. The progress of Hurricane in and abroad,the low-frequency oscillations of the South China Sea summer monsoon in the last.The second chapter introduces the features of the 0604th tropical storm "Bilis": a strange tropical cyclones, it shows the unique performance in intensity variation, "eccentric" structure, low pressure moving and maintaining after landing, distribution of wind ring, and the heavy precipitation form of the interaction with monsoon cloud sea, and some other aspects. Diagnostic analysis shows that, "Bilis" is come about and development in an advantaged situation of large-scale field and weather scale conditions: west move of the subtropical high, the outbreak of monsoon surge, the strong of mainland high-pressure, a stable structure of two troughs with a ridge in high latitudes.Chapter III use NCEP data, satellite data on the research of "Bilis" structure and its development, mechanisms to maintain in the long period of time, the mesoscale convective systems structure of "Bilis" internal circulation and its mechanisms of development. "Bilis" maintains tropical cyclone weather systems characteristic of the warm core vortex structure, in the low pressure, the warm moist in the lower troposphere rise as cyclone-convergence, divergence until the high-altitude, resulting in the strong development of the convective clouds within a tropical cyclone and rainstorm occurred. Adequate supply of water vapor, and the instability of the local stratification and the accumulation of the convective available potential energy produces the favorable conditions for the heavy rain's occurrence. Heavy rainfall occurred in inland areas is due to the interaction between three, the monsoon surge, the typhoon circulation and terrain, and constantly arouse a mesoscale convective systems. "Bilis" played an important role in the organization to its external remnants of spiral cloud band and monsoon cloud surge, not only played on the convective clouds gather, but also strengthened the increased movement and conducive to the heavy rainfall occurred , at the same time , Latent heat of condensation released by the decompression is conducive to the maintenance of its own. The terrain forced up and "Bilis" organization ascending motion of its own trigger the region's instability energy has long been stored. In addition, the secondary circulation caused by dry intrusion between the northerly winds in the west of "Bilis" circulation and southerly winds of the south monsoon surge also promote the development and maintenance of the troposphere .Chapter IV through the water vapor characteristics analysis of the "Bilis", and found that the outbreak of the South China Sea monsoon is the main reason for the maintenance in a long time. Use of power spectrum and band-pass filtering method to analysis the low-frequency oscillations in the South China Sea, found that quasi-week oscillation and quasi-two weeks oscillation play a major role to the South China Sea Monsoon during "Bilis" maintained. Analysis of the characteristics of low-frequency spread vibration, found that the meridional wind affected the South China Sea region has a clear westward spread in the quasi-week and quasi-two weeks , and the meridional wind in low-latitude areas has the spread trend from the south to the north. The spread source of the Quasi-week is in the southwest of subtropical high, the Philippines area, probably because of strong convection in this regions, the trigger mechanism is formed then lead to a quasi-week oscillation. Its westward spread can affect the cross-equatorial flow, thereby affecting the southwest monsoon.The main study of Chapter V use WRF to simulation development of the "Bilis" after landing. The model simulate the path,intensity variation and the movement of rain bands of the "Bilis" well after landing, especially simulated the evolution of MCS process. And a terrain sensitive experiments is done, if there is no "trumpet" terrain, the heavy rainfall in inland will move south to the middle of Guangdong.