| Based on the TRMM satellite 3B42 rainfall estimates during 2001-2009, the axisymmetric and asymmetric rainfall structures in tropical cyclones (TCs) making landfall over China were analyzed. The relationships between the axisymmetric and asymmetric rainfall and TC intensity were discussed. Using NCEP reanalysis data, the effects of environmental vertical wind shear (VWS), TC motion (both direction and speed), and land-sea contrast on the landfalling TCs rainfall over China were investigated, and further to explore the characteristics differences of TCs making landfall in different regions of China, thus to reveal the relationship between VWS, TC intensity, TC motion, and land-sea contrast and asymmetric rainfall distribution of the landfalling TCs, and relation physical process. Besides, the numerical models of MM5 and WRF were utilized to study the terrain and underlying surface of water-body effects on landfalling TC rainfall by TC case studies. In addition, binary TCs of a TC over sea and a landfalling TC as a special environment, this thesis has discussed the binary TCs process effects on the landfalling TCs. The main conclusions were shown as below.While the TC intensity affected the axisymmetric rainfall in landfalling TCs, the intensity change of TCs also had important influences. TCs of higher intensity had higher peak axisymmetric rain rate, with higher amplitude of the axisymmetric rainfall component relative to the total rainfall and lower amplitude of wavenumber-1,2,3,4 rainfall components relative to the total rainfall; and vice versa. According to the rate of intensity change, the landfalling TCs were categorized into five groups:rapid decay (RD), slow decay (SD), unchanged, slow intensification (SI), and rapid intensification (RI). TCs of RD (RI) had the lowest (highest) peak azimuthally-averaged rain rate and the largest (smallest) averaged radius where the peak azimuthal-mean rain rate occurred. In addition, the axisymmetric rainfall characterics had differences in TCs making landfall in the different regions of China, which were connected with the different intensities of the TCs.For the asymmetric rainfall of TCs, different intensity TCs had different contribution of the asymmetric rainfall to the total TC rainfall. But for weak or strong TCs, the maximum asymmetric rainfall was always located down-shear to down-shear-left, which indicated that the TC intensity had no obvious effects on the asymmetric raindfall distribution of the landfalling TCs. So, what is the main factor to control the landfalling TCs asymmetric rainfall distribution? The analysis results showed that the TC motion (both direction and speed) had no obvious effects on the asymmetric rainfall. But the environmental VWS mainly controlled the wavenumber-1 rainfall asymmetries of landfalling TCs of China. The results reveal that in landfalling TCs, the wavenumber-one rainfall asymmetry shows the downshear to downshear-left maximum in VWS, which is consistent with previous studies for TCs over the open oceans. The rainfall asymmetries in TCs that made landfall in Hainan (HN), Guangdong (GD), Fujian (FJ), Zhejiang (ZJ) Provinces of Mainland China and Taiwan (TW) were also analyzed. A cyclonic rotation from South China to East China in the location of the rainfall maximum has been identified.However, further analysis showed that the location of asymmetric rainfall maximum in landfalling TCs was generally offshore and downshear to downshear-left, when the VWS was large. When the VWS turned weak (less than 5 ms-1), the location of the asymmetric rainfall maximum in the outer-core region could change from downshear and offshore to upshear and onshore prior to and after landfall. Particularly at the time of landfall, the rainfall maxima both in the inner-and outer-core regions were located onshore and upshear, indicating that coastline could have significant effects on the rainfall asymmetry during landfall when the environmental VWS was weak.The impact of terrains on the precipitation of landfalling typhoon Talim (2005) over mainland China is investigated using numerical studies, to compare the different impacts between coastal and inland terrains. It is found that the coastal terrains would increase the rainfall intensity, while the inland terrains could cause rainfall enhancement with mid-latitude environmental system effects. This has further concluded that the large-scale environment had main influences on the TC rainfall when the environment effects were strong. It further analyzed the Hangzhou Bay effects on the landfalling tropical depression rainfall process ("0185’" heavy rain). By using numerical sensitivity tests, it analyzed the TC of Danas effects on the heavy rainfall process of landfalling TC of Fitow in the binary TCs environment. The preliminary results show that "Danas" had important effects on the asymmetric rainfall associated with the landfalling TC "Fitow"... |
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