影响台湾岛海域的西太平洋台风特征分析

选取台湾岛附近海域(20~27°N,117~125°E)为计算区域,对1949~1999年发生在该海域的西太平洋台风的路径分类、月际变化、年际变化、周期特征、移速和强度等要素进行了气候统计学分析,得出7~9月是台风发生的关键月份,台风发生频次的年际变化表现为下降的趋势,且1995~1999年近5年时间台风频次一直稳定维持在较低水平。用Mann-Kendall方法做突变分析和t检验,没有明显的突变年。利用小波分解技术,计算得出影响台湾岛海域的西太平洋台风年发生频次具有4~6年和13~14年左右的周期。西北行路径西太平洋台风是登陆台湾岛和进一步登陆我国大陆的主要台风,西行路径台风51年来没有登陆我国大陆的记录,转向行路径台风强度最大,平均移速最快。     

西北太平洋热带气旋强度变化的若干特征

使用NOAA海表温度资料、ECMWF再分析资料和JTWC台风最佳路径数据,对1984—2013年30年西北太平洋热带区域（100 °E~180 °,0~60 °N）内热带气旋（TC）的强度变化特征及其与环境风垂直切变（VWS）、海表温度（SST）、最大风速半径（RMW）的关系作了统计分析,尤其关注TC强度突变。结果表明:（1）在研究区域内,TC样本中35.2%强度稳定,52.8%强度变化缓慢,仅12.0%强度突变,约92.7%的迅速加强TC样本发生在其台风及以上强度等级;（2）2000年以来,TC强度稳定样本减少,强度迅速变化样本增多。5月和9—10月是TC强度突变的高频期;（3）超过12 m/s的环境VWS下TC迅速加强较少,且只有台风及以上强度TC才能在大于12 m/s的VWS下迅速加强;（4）TC加强和迅速加强主要在28.5~30.0 ℃的SST洋面上发生,在较低SST下仍迅速加强的TC强度等级较高;（5）TC样本的RMW多小于100 km,其中强度突变TC RMW峰值区在20~40 km;（6）加强TC的RMW的24 h变化一般减小,减弱TC的RMW则增大;其中强度突变TC尤其明显,超强台风发生迅速加强时,RMW减小的比率达84.6%,但仍有15.4%比率的RMW增大。      

不对称环流对台风强度变化的影响

利用卫星云图和NCEP再分析风场资料对0207号台风HALONG云系和风场变化特征进行了分析.结果表明,台风云系不对称的结构,台风西侧高空急流向台风中心的移动和辐散是台风迅速减弱的主要原因.为了了解不对称台风环流对台风强度的影响,还对比分析了0417号台风AERE、0216号台风SINLAKU在中国沿海减弱和重新加强的环流特征.在低层流入台风中心南侧的西风分量大,在高层流入台风中心西侧的北风分量小,有利于台风的加强.台风南、北两侧的东西向风场垂直切变梯度差异不利于台风加强.东西向风场垂直切变对台风强度的影响比南北向风场更重要.     

A NUMERICAL STUDY OF THE INFLUENCE OF SEA SURFACE TEMPERATURES WITH DIFFERENT TEMPORAL RESOLUTIONS ON TYPHOON DUJUAN OVER THE SOUTH CHINA SEA

Daily and weekly sea surface temperature data of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager and Advanced Microwave Scanning Radiometer-Earth Observing System sensors are used as forcing of the underlying sea surface in the mesoscale numerical model to simulate Typhoon Dujuan that moved across the South China Sea in 2003. The numerical results show that different SSTs near the typhoon center result in differences in the atmospheric wind field, indicating that the model has a fast and obvious response to SSTs. Different SST influences the intensity and track of Dujuan to some degree and has significant impacts on its precipitation and latent heat flux near the eye. The SST influence on Dujuan is mainly fulfilled by changing the latent heat flux between the ocean surface and the atmosphere above.     

Air-sea Interaction of Typhoon Sinlaku （2002） Simulated by the Canadian MC2 Model

Three experiments for the simulation of typhoon Sinlaku (2002) over the western North Pacific are performed in this study by using the Canadian Mesoscale Compressible Community (MC2) atmospheric model. The objective of these simulations is to investigate the air-sea interaction during extreme weather conditions, and to determine the sensitivity of the typhoon evolution to the sea surface temperature (SST)cooling induced by the typhoon. It is shown from the three experiments that the surface heat fluxes have a substantial influence on the slow-moving cyclone over its lifetime. When the SST in the East China coastal ocean becomes 1℃ cooler in the simulation, less latent heat and sensible heat fluxes from the underlying ocean to the cyclone tend to reduce the typhoon intensity. The cyclone is weakened by 7 hPa at the time of its peak intensity. The SST cooling also has impacts on the vertical structure of the typhoon by weakening the warm core and drying the eye wall. With a finer horizontal resolution of (1/6)°×(1/6)°, the model produces higher surface wind, and therefore more surface heat fluxes are emitted from the ocean surface to the cyclone, in the finer-resolution MC2 grid compared with the relatively lower resolution of 0.25°×0.25°MC2 grid.     

海洋垂直混合对中尺度海气浪耦合模式预报效果的敏感性试验

为了比较两个不同的海洋垂直混合参数化方案在中尺度海气浪耦合模式数值预报中的效果,采用军队T₇₉₉全球预报系统和西北太平洋海洋预报系统的预报场资料驱动区域中尺度海气浪耦合模式,针对西北太平洋在2014年9月7—10日和17—20日的大气和海洋要素场进行数值回报试验,并将同期台风观测资料、NCEP再分析资料以及NOAA海表面温度数据各自与模式结果进行比较。结果表明,在无台风天气下使用GLS-ε方案对大气要素的预报效果更好,而MY2.5方案在台风天气影响下表现更好,同时其在连续8天的预报中无溢出现象,较GLS-ε方案稳定性更好;台风影响区域的海表面温度对MY2.5方案更敏感;台风天气过程中,MY2.5方案引起的海洋上层温度混合更强烈。      

一次变性台风再增强过程的敏感性试验

采用位涡反演技术与数值模拟相结合的方法,通过初值敏感性试验和物理量场的诊断分析,对台风变性后再度增强的影响因子和物理机制进行了深入的分析和研究。结果表明:台风低压由变性减弱转为发展增强主要是由于台风低压环流与西风带斜压锋区之间的相互作用所造成的,随着高空冷涡低槽的加深南下和台风低压的继续北上,两个系统之间的距离逐渐减小,西风带高空槽与台风低压之间相互作用的正反馈机制逐步成为台风变性后强烈加深发展的主要原因。     

台风“彩虹”(1522)近海急剧加强的特征分析

采用多种大气和海洋资料对1522号台风"彩虹"近海急剧加强的特征进行了诊断分析。结果表明大气环流形势的变化、海洋环境的维持和台风内部结构的变化都有利于台风的近海加强。具体表现为:高层南亚高压西部型转东部型和中层西太平洋副热带高压加强西伸引起的环流形势的变化,使得台风区域高层辐散增强,中低层气旋性环流增强,低层台风东侧的水汽通量增强;低层北方弱冷空气侵入台风外围区域促进辐合抬升,环境风切变的减弱及弱切变的维持有利于台风加强,这些都是有利于台风增强的环流和动力条件。台风路径海域高海表温度和海洋暖涡的存在对台风急剧增强起了重要作用。此外,由于环流变化引起的潜热加热增大,导致了双中心位涡柱的形成和高层暖心的增加,台风内部结构的变化也有利于台风的进一步加强。     

台风低压发展的数值模拟研究——凝结加热廓线的影响

本文用一个同时考虑Ekman抽吸和积云动量输送作用的二维轴对称原始方程模式,就对流凝结加热廓线对台风低压发展的影响进行了数值模拟研究。试验结果表明,对流层中下部有较强加热时,模式台风低压的低压环流发展较快;对流层上部有较强加热时,系统结构更类似于实际台风。在台风低压发展过程中,对流凝结加热廓线也会改变,最强加热可能由对流层中下部向中上层发展和传播,从而,台风低压发展既快、系统结构又类似于实际台风。这样一种过程可能正是热带低压发展为台风的一般过程。      

海洋和大气状态异常对西北太平洋台风活动的影响

本文分析了33年(1951—1983年)逐月平均的赤道东太平洋海温距平(SSTA)、热带西北太平洋500hPa高度距平和西北太平洋台风频数距平资料,指出:赤道东太平洋热力状况的异常对西北太平洋台风活动有明显影响。进一步对于1982—1983年的厄尼诺过程进行诊断分析,认为,SSTA异常可以通过经圈环流改变中、低纬环流的相互作用,以此来制约西北太平洋台风活动,即:当赤道东太平洋出现暖水时,北半球的哈得来环流加强,导致中纬度上空西风带加强、斜压扰动向南发展,结果,北半球副热带高压滞留在较低纬度、热带盛行东风气流,形成了不利于西北太平洋台风发生、发展的大尺度环流条件。     

INVERSION OF TEMPERATURE FROM AMSU-A AND ITS APPLICATION ON WARM-CORE OF TROPICAL DEPRESSION OVER THE SOUTH CHINA SEA

The linear regression and horizontally stepwise correction are conducted on the observational data from AMSU-A L1 B of NOAA polar orbit satellite to invert a 40-layers(from 1,000 h Pa to 0.1 h Pa) dataset of atmospheric temperature with a horizontal resolution of 0.5°×0.5° after the correction of satellite antenna pattern and limb adjustment. Case study shows that the inversion data of temperature can reveal the detail structure of warm core in tropical cyclone. We choose two categories of tropical depressions(TDs) over the South China Sea, including the non-developing TDs and developing TDs. Both of them are developed downward from the middle and upper level to the lower level. Comparison between the evolutions of warm core in the two categories of TDs indicates that the warm core is developed downward from the middle and upper troposphere to the sea surface in all the downward-developing TDs. The difference is that in the group of further developing TDs, the warm core in the upper troposphere is intensified suddenly when it is extending to the sea surface. The warm core in the upper and lower troposphere is strengthened in a meantime. But the similar feature is not observed in the non-developing TDs. Then it may be helpful to judge the TD development by monitoring the change in its warm-core structure.     

散射计和下投式探空仪资料对台风模拟的影响

为了评估同化QuikSCAT海平面气压场资料和Dropsonde资料对台风"Bilis"和"Kat-rina"模拟的影响,通过WRF-3DVAR变分同化系统将QuikSCAT海平面气压场资料和Dropsonde资料同化到WRF模式中,并以未同化任何资料和同化了QuikSCAT海平面气压场以及同化了Drop-sonde资料的数据为初始场,应用WRF模式进行模拟预报,并对得到的初始分析场和模拟预报得到的结果与台风实况报文进行了对比,得到的结论是:对台风初始时刻海平面气压场分布、初始台风中心定位、台风初始暖心结构的改善、台风路径、海平面最低气压场、海面最大风速和雷达回波的模拟方面,同化QuikSCAT海平面气压场的效果比同化Dropsonde资料明显,其中二者对海平面最低气压场的改进效果比海面最大风速的要好。但是两种资料的同化对初始相对湿度和台风强度细节变化方面都没有产生明显改善作用。同化QuikSCAT海平面气压场试验虽然仅仅同化了单层海平面气压场,但是在三维变分同化系统的动力约束作用下,也可以影响到中高层的各个要素场。     

珠海市台风及其次生风暴潮特征分析与评估

基于1961—2018年广东省珠海市气象观测资料以及珠海三灶站1964—2018年逐日潮位数据,分别对珠海市台风及风暴潮进行特征分析和频率计算。通过构建台风数据集,计算得到影响珠海的可能最强台风的中心气压、移动速度、最大风速半径以及可能移动路径,并模拟该台风引起的珠海三灶站的最高潮位和极值增水,最后通过1713号台风“天鸽”和1822号台风“山竹”对模拟结果进行了验证,验证结果与计算方案下强台风级别在台山登陆引起的计算结果一致。      

THE IMPACT OF MID-LATITUDE CIRCULATION OVER THE TIBETAN PLATEAU ON THE TRACK OF TYPHOON OVER THE NORTHWEST PACIFIC

There is a close relationship between variation of middle latitude synoptic system over theTibetan Plateau and movement of typhoon over the Northwest Pacific.This paper tries to discussthe mechanism of it through the numerical simulation and dynamic diagnosis.25-year statistical results during the period from 1970 to 1995 indicate that the relationshipbetween middle latitude circulation over the Plateau and the track of typhoon over the NorthwestPacific are as follows.When longwave trough in 500 hPa isobaric surface over the Plateau.it isfavourable to typhoon's westward movement:on the contrary,large scale anticyclone over thePlateau is favourable to typhoon's recurvature.We simulated the typhoon under these two flowpatterns with MM5 model.Numerical simulation results showed that:(a)Longwave trough on500 hPa surface over the Plateau makes subtropical high extended westward so as to typhoon southto high moves westward in easterly steering flow.(b)Anticyclone over the Plateau will bringabout the longwave trough developing along the east coast of Asia,it'will usually cause typhoonrecurring in front of the developed trough.In addition,the results of dynamic diagnosis show the physical mechanism on impact ofsynoptic system over the Plateau on the downstream synoptic system,that is,the transport ofdisturbance kinetic energy over the upstream Plateau makes the downstream trough developed.And then it affects the steering flow of typhoon.Because of existence of the high ridge over thePlateau.the energy transport channel moves to north.On the contrary,the trough exists over thePlateau,the energy transport channel moves to south.The southerly in front of trough over thePlateau and the southerly in the east part of typhoon transport low potential vorticity of lowlatitude into subtropical high.That is beneficial to development of subtropical high and affectstyphoon's movement.These results fully reflect the impact of interaction between mid-latitude andlow latitude on synoptic system.     

0713号台风韦帕路径预报难点分析

0713号台风韦帕各家都预报在台湾岛北部海上北折,在120°E以东向偏北方向移动,与台风实际在浙闽交界处登陆后在120°E以西转向北上路径存在较大误差.为认识这种预报偏差的原因,应用各种资料对影响台风韦帕北折的可能原因进行探讨.指出:(1)欧洲气象中心天气形势预报误差较大,西风槽底预报比实况偏南,是本次台风路径转折预报失误的主要原因.(2)欧亚500hPa高度场为两脊一槽形势,西风指数从低指数向高指数演变和副热带高压处周期性加强均不利于台风韦帕在台湾东北部海区折向偏北方向移动.(3)地形的影响造成的趋岸左折和港湾"吸引",以及动力场和热力场的分布均有利于台风韦帕在台湾东北部海区折向偏西方向移动.     

RECONSTRUCTION OF EL NINO EVENT CHRONOLOGY FOR THE LAST 600 YEAR PERIOD

The El Nino events for 1870—1989 were identified according to the sea surface temperature(SST)over the easternequatorial Pacific(0—10°S,90—180°W)and Southern Oscillation Index.The chronicle of the El Nino events in histori-cal time(14708—1879)was reconstructed by using of a series of proxy data such as Australian droughts,Nile floods,Peruvian floods,numbers of landing typhoon in China,cool summers in East Asia,SOI calculated from tree ring data,and El Nino events identified mainly from meteorological and oceanographical conditions along the Ecuador and Perucoast.Finally,114 El Nino events were found for the period 1470—1989.The mean return interval was 4.5 years.The fre-quency of the events seems to have a cyclical variation of 70 years.No close relationship was found between the globalwarming and the frequency of El Nino events.     

THE FORMATION MECHANISM OF CONCENTRIC DOUBLE EYEWALL TYPHOON——PART Ⅱ:NUMERICAL SIMULATIONS*

In the context of a non-hydrostatic axisymmetric compressible numerical model,the concentric double eyewall structure of the typhoon was replicated well to discuss the formation mechanism of concentric eyewall with the aid of gradient wind adjustment.Evidence suggests that in the weakening phase of the typhoon,the heterogeneous radial distribution of the sensible and convective latent heating over the sea surface will induce the gradient wind unbalance accompanied by mutual gradient wind adjustment between the thermodynamic field and dynamic fields,which results in a two-peak tangential wind and concentric double eyewall structure.     

东海登陆台风的地面结构及降水分析

本文根据大陆上此较完善的地面观测资料,着重地对1953—1956年四次较强的登陆台风,此较细致地分析了台风中的气压、风、降水量和中心附近的气象状况的分布以及其相互联系.主要的结果如下:(i)台风范围内气压分布的特点随其移动方向的改变有显著不同.台风低压的填塞为其半径的函数,而且其六小时填塞率和当地气压日变化一致.(ii)台风范围风速的分布不仅和其气压分布相适应,而且受到海陆、地形的显著影响.地面风的辐合分布和台风降水分布的配合较好.(iii)台风登陆后的降水分布大致按其发展程度分为三种类型:对称型、侧偏型、对锋面型.(iv)台风刚刚登陆,其中心附近可有两种截然不同的天气状况:一类中心天气晴晴朗平静,一类中心狂风大雨.总的来说,登陆台风的地面结构一方面从东风带到西风带发生显著的变化,一方面受到海陆、地形的重大影响.     

THE IMPACT OF MID-LATITUDE CIRCULATION OVER THE TIBETAN PLATEAU ON THE TRACK OF TYPHOON OVER THE NORTHWEST PACIFIC*

There is a close relationship between variation of middle latitude synoptic system over the Tibetan Plateau and movement of typhoon over the Northwest Pacific.This paper tries to discuss the mechanism of it through the numerical simulation and dynamic diagnosis.25-year statistical results during the period from 1970 to 1995 indicate that the relationship between middle latitude circulation over the Plateau and the track of typhoon over the Northwest Pacific are as follows.When longwave trough in 500 hPa isobaric surface over the Plateau.it is favourable to typhoon's westward movement:on the contrary,large scale anticyclone over the Plateau is favourable to typhoon's recurvature.We simulated the typhoon under these two flow patterns with MM5 model.Numerical simulation results showed that:(a)Longwave trough on 500 hPa surface over the Plateau makes subtropical high extended westward so as to typhoon south to high moves westward in easterly steering flow.(b)Anticyclone over the Plateau will bring about the longwave trough developing along the east coast of Asia,it'will usually cause typhoon recurring in front of the developed trough.In addition,the results of dynamic diagnosis show the physical mechanism on impact of synoptic system over the Plateau on the downstream synoptic system,that is,the transport of disturbance kinetic energy over the upstream Plateau makes the downstream trough developed.And then it affects the steering flow of typhoon.Because of existence of the high ridge over the Plateau.the energy transport channel moves to north.On the contrary,the trough exists over the Plateau,the energy transport channel moves to south.The southerly in front of trough over the Plateau and the southerly in the east part of typhoon transport low potential vorticity of low latitude into subtropical high.That is beneficial to development of subtropical high and affects typhoon's movement.These results fully reflect the impact of interaction between mid-latitude and low latitude on synoptic system.     

A CASE STUDY OF NUMERICAL SIMULATION OF SEA FOG ON THE SOUTHERN CHINA COAST

This study uses numerical simulations to examine a case of sea fog that was observed from 20 to 22 March2011 on the southern China coast. The observation dataset includes observatory data, cloud-top temperature from MODIS, GPS sonde, and data from the Integrated Observation Platform for Marine Meteorology(IOPMM). The simulations are based on the Weather Research and Forecasting(WRF) model with four distinct parameter settings.Both the observations and simulations focus on the characteristics of the fog extent, boundary layer structure, and meteorological elements near the air-sea interface. Our main results are as follows:(1) The extent of mesoscale sea fog can be well simulated when the sea surface temperature has at least 0.5 ×0.5 horizontal resolution.(2) To accurately model the vertical structure of the sea fog, particularly the surface-based inversion, vertical levels must be added in the boundary layer.(3) When these model conditions are met, the simulations faithfully reproduce the measured downward shortwave radiation, downward longwave radiation, and surface sensible heat flux during the sea fog period.