【作者】 董林；

【导师】 端义宏； 王式功；

【作者基本信息】 兰州大学 ， 气象学， 2008， 硕士

【摘要】 热带气旋(tropical cyclone,TC)的路径和强度是热带气旋研究领域的两个重要方面。但是相对于TC路径方面的研究而言,强度及其变化方面的研究工作进展还比较缓慢。本文运用统计分析和数值模拟两种方法,对经过台湾岛的热带气旋进行研究,旨在寻找TC受台湾地形影响后其强度变化的规律。在统计分析部分,本文用中国气象局整编的1949—2006年共58年的《台风年鉴》和《热带气旋年鉴》资料,将资料线性插值到1小时,挑选出经过台湾岛的热带气旋,用统计分析的方法,揭示TC经过台湾岛时的强度变化特征。结果表明:TC从东侧登陆台湾岛其强度的减弱程度为西侧登陆的2倍以上;TC登陆时的路径方向与台湾中央山脉长轴的交角越接近垂直,其过岛后强度减弱程度就越小,在岛逗留的时间也越短;TC登陆台湾岛东侧时其强度的减弱程度与TC登陆前其自身的强度呈正相关。而对登陆台湾岛西侧的TC则没有明显的统计规律;TC从台湾西侧登陆时不但出现强度不变或者增强的几率更大,而且增加的强度也更多。经过台湾岛的TC频数并没有显著的年际变化,但其经过台湾岛时强度减弱的程度却有下降的趋势。另外,为了考察统计资料的信度,本文对西北太平洋3个主要预报中心(CMA,RSMC Tokyo和JTWC)的资料进行检验,对比1977—2006年经过台湾岛的TC,分别对其频数、强度分布、强度变化以及通过台湾岛所用时间进行对比分析,结果表明:西北太平洋3家预报中心经过台湾岛的TC资料无显著差异,资料有很好的相关性。在数值模拟部分,本文选取“0709”号超强台风“圣帕”为研究对象,利用MM5和WRF两个模式相结合的方法,对其经过台湾岛的过程进行模拟。结果表明:加入适当强度的人造涡旋可以有效地改善初始场的质量,模拟TC在路径、极值强度和强度变化上更加接近实况。在地形敏感性试验中,我们将台湾岛地形高度分成不同情况来研究地形高度对TC经过台湾岛强度变化的影响。模拟结果显示当把台湾地形高度削平为1m、设置为原始地形高度的1/2、原始地形高度、比原始地形高度升高1倍四种情况时,若以原始地形的影响为100%计算,则气旋登陆该岛时其强度的减弱程度分别达48%、61%、100%和161%。不难看出,有无台湾岛地形显得至关重要,且其影响程度随台湾岛地形高度的增加呈现出近于线性变化的关系。气旋强度的减弱也是在接近台湾岛时开始的,先于登陆时间2～6个小时左右;而且台湾地形的高度越高,所经气旋出现减弱的时间也越早,TC非对称性的程度也越高。更多还原

【Abstract】 Track and intensity change are two important aspects in studying tropical cyclone (TC).However,compared to the abundant research on TC track research,the research on TC intensity change is much more challenging and therefore results in slower progress. The main aim of this thesis is to find some properties on intensity change of TCs that passed Taiwan by carrying out both statistical analysis and numerical simulations.Here are the primary contributions of the work:First,a statistical analysis is performed and the analytical results reveal a couple of characteristics on the intensity change of TCs passed Taiwan.In our analysis,the TC data of 58 years(1949-2006) from Typhoon yearbook and tropical cyclone yearbook compiled by China Meteorological Administration(CMA) is used.The data of each typhoon are linearly interpolated to one hour per record and only TCs that passed Taiwan are selected for analysis.Several conclusions can be drawn from the statistical results.First of all,the degree of intensity decrement of TCs landing from east side is twice more than that of TCs from west side.Second,the more perpendicular for the angle between the moving direction of landing TC and long axis of Taiwan central mountain,the smaller degree of intensity reduction and less duration on the island.Third,there is a positive correlation between the intensity decrement and initial intensity for the TCs landing from east side whereas no such correlation exists for TCs from west side.Fourth,the probability that the intensity remains the same or increases is higher for TCs landing from west side than TCs from east side.Fifth,although no pronounced annual variation of TC number is seen, there is a trend of decreasing intensity reduction for TCs passing Taiwan.Furthermore,to examine the difference of typhoon data from three primary forecast centers in north-west Pacific Ocean(CMA,RSMC Tokyo and JTWC),a statistical comparison on frequency,intensity change and duration is made with selected TCs that passed Taiwan during 1977-2006.The comparison results show that there is no pronounced discrepancy in the frequency and there is a good correlation in intensity change and duration among data from three forecast centers. Second,a series of numerical simulations are conducted to examine the intensity change of super typhoon sepat(code number 0709) during its passing in Taiwan using a combination of ARW-WRF model and MM5 model.In the control experiments,a complete Taiwan terrain is used and a NCAR-AFWA bogussing scheme is applied.It is shown in the results that adding a bogussing TC with proper intensity not only improves the initial data quality but also makes the simulation data more accordant with the real-time data in terms of track,extremum and intensity change.In the terrain-sensitive experiments,four schemes of Taiwan terrain elevation are designed to examine the effect of terrain elevation on TC intensity change.In details,the elevation is set to 1 meter in one scheme and to 50%,100%,200%of that used in the control experiment in others.It is shown in the experimental results that the intensity decrements are respectively 48%, 61%,100%and 161%of that in the control experiment.This reveals an approximately linear relationship between intensity decrement and terrain elevation.It is also found that TC intensity starts to decrease 2-6 hours before landing.Moreover,the higher is the terrain elevation,the earlier the intensity begins to decrease and the more asymmetric the TC is.更多还原