海洋飞沫对台风“Morakot”结构影响的数值模拟研究

将海洋飞沫参数化引入到高分辨率、非静力中尺度模式中,并对0908号台风"Morakot"进行了数值模拟,研究了海洋飞沫对台风"Morakot"结构和强度的影响。结果表明:(1)不论是否考虑海洋飞沫作用,模式均能较好地模拟出台风"Morakot"的移动路径,说明海洋飞沫对其移动路径影响不大;(2)引入海洋飞沫参数化后,台风眼墙区域的切向风速、径向风速、垂直速度、涡度、云水混合比、雨水混合比等物理量均增强,表明飞沫对台风结构变化的影响明显;(3)海洋飞沫对台风"Morakot"演变的直接影响是在对流层低层,低层风速明显增大,大风速区的影响尤为显著;(4)飞沫的蒸发使台风范围内的潜热和感热通量明显增强,尤其是潜热通量,其大值区对应着台风中心附近的最大风速区。由于水汽和热量输送的增强,使台风眼壁附近的云水量与雨水量增多,因此降水强度明显增加。     

A Numerical Simulation Study of Typhoon Rananim（0414）

Using the high-resolution non-hydrostatic model ARPS (Advanced Regional Prediction System),the Typhoon Rananim (0414) was simulated by using the CINRAD Doppler radar data.The results before and after typhoon landfall show that model ARPS performs well to simulate the track,the variation of center pressure,as well as severe heavy rain of Rananim.Meanwhile,the simulated composite reflectivity was compared with the observed radar composite reflectivity.The numerical results reveal that the asymmetrical structure of Rananim plays an important role in its westward deflecting after landfall.The sensitivity simulation experiments of terrain effects on Rananim (0414) were also investigated,and the terrain of the southeastern China has important effects on Rananim turning right slightly of its track and increasing its intensity obviously,but when typhoon is far away from the coastline,the terrain only impacts slightly on the storm intensity during its landfall.The results show that topographic lifting contributes greatly to precipitation enhancement,and makes the distribution of precipitation more uneven.     

Typhoon Winnie （1997） with a Very Large Eye： High Resolution Numerical Simulation

Typhoon Winnie (1997) was one of the hurricanes that had extremely large eyewall ever recorded with a diameter of eyewall reaching 370 km. Using the Penn State University/National Center for Atmospheric Research mesoscale model MM5 with 3-km grid horizontal spacing on the finest nested mesh, Winnie was successfully simulated in terms of track, intensity, eye and concentric eyewalls. The dynamic and thermal structures of concentric eyewalls were studied based on the model output. It was found that the concentric eyewalls and their surrounding wind fields were asymmetric in observation as well as in simulation. Winnie's outer eyewall was associated with a maximum wind ring, a warm moist ring, and a high vorticity ring. The inner eyewall was associated with a secondary maximum wind ring and a warm moist ring. Upward motion dominated the whole layer of inner eyewall and the area above 2-km altitude of the outer eyewall. Downward motion was found inside the eye and the moat. Radial inflow happened in the boundary layer of the outer eyewall and the moat, but radial outflow dominated the middle and upper levels of the outer eyewall.     

海洋飞沫对热带气旋影响的数值试验

将最新版的Andreas海洋飞沫通量参数化方案与中尺度大气模式MM5V3耦合,对0514号热带气旋Nabi进行数值模拟,探讨海洋飞沫蒸发对热带气旋发展和演变的影响.模拟结果表明,考虑海洋飞沫的作用后,热带气旋范围内(气旋中心附近600 km左右范围内)的潜热和感热通量明显增强,尤其是潜热通量,最大值可提高35%～80%,潜热通量的大值区对应热带气旋眼墙处的最大风速区.无论是否考虑海洋飞沫作用,模式均能较好地模拟出热带气旋Nabi的移动路径,但考虑飞沫作用后,由于飞沫对海气界面通量交换的贡献,使得模拟热带气旋中心的最低海平面气压降低,最大风速增强,暖心结构更加明显.     

Analysis on a Severe Storm of Wenzhou Similar Tornado in The Outer-Region of the Super Typhoon ＇Sepat＇

利用NCEP/NCAR 1°×1°6h再分析资料、多普勒天气雷达资料及FY-2C卫星TBB资料,分析了2007年8月18日23：10（北京时,下同）～23：20在0709号超强台风＂圣帕（Sepat）＂外围温州市龙港镇诱生类龙卷。诊断分析表明,类龙卷发生地所处环境特征为高层辐散、低层辐合、从低层一直延展到高层的强烈上升运动、超低空强垂直风切变等;雷达连续跟踪探测到气旋式速度存在由中层向低层发展的现象,该中气旋中伴有明显的相邻方位角速度切变,尽管没有满足龙卷涡旋特征（TVS）的所有指标,但强烈的旋转风在极短时间由高层向低层迅速发展下传,进而产生超级单体龙卷。     

The Effect of Intensity： Typhoon-Induced SST Cooling on Typhoon The Case of Typhoon Chanchu （2006）

In order to investigate air-sea interactions during the life cycle of typhoons and the quantificational effects of typhoon-induced SST cooling on typhoon intensity, a mesoscale coupled air-sea model is developed based on the non-hydrostatic mesoscale model MM5 and the regional ocean model POM, which is used to simulate the life cycle of Typhoon Chanchu （2006） from a tropical depression to a typhoon followed by a steady weakening. The results show that improved intensity prediction is achieved after considering typhoon-induced SST cooling; the trend of the typhoon intensity change simulated by the coupled model is consistent with observations. The weakening stage of Typhoon Chanchu from 1200 UTC 15 May to 1800 UTC 16 May can be well reproduced, and it is the typhoon-induced SST cooling that makes Chanchu weaken during this period. Analysis reveals that the typhoon-induced SST cooling reduces the sensible and latent heat fluxes from the ocean to the typhoon＇s vortex, especially in the inner-core region. In this study, the average total heat flux in the inner-core region of the typhoon decrease by 57.2%, whereas typhoon intensity weakens by 46%. It is shown that incorporation of the typhoon-induced cooling, with an average value of 2.17℃, causes a 46-hPa weakening of the typhoon, which is about 20 hPa per 1℃ change in SST.     

积云参数化对0613号台风“珊珊”数值模拟的影响研究

使用W RF的ARW动力核心模拟台风"珊珊",以研究各种积云参数化方案对于台风路径,强度和降水分布等的影响。研究表明,环境场对积云参数化的选取不敏感,积云参数化对台风的强度和路径模拟有明显的影响,KF方案模拟的台风强度较强,增强过程明显,后期移速偏快。KF和BM J对降水的模拟较好,GD方案不够理想。     

Near-equatorial Typhoon Development： Climatology and Numerical Simulations

The climatology of near-equatorial typhoons over the western-north Pacific are fully investigated using the JTWC (Joint Typhoon Warning Center) typhoon record from 1951 to 2006. The result shows that there are seasonal and decadal variations, as well as a distinctive spatial distribution, of such events. Among them, Typhoon Vamei is an example of a near-equatorial typhoon that occurred near Singapore in December of 2001. Using the WRF (Weather and Research Forecast) model, we attempt to find out how the well known ``wind surge" of this event contributes to the development of Typhoon Vamei. It is found that the strong wind surge not only helps to provide advection of positive vorticity to Vamei between 800 and 500 hPa, but also increases the convective instability of the lower troposphere, and thus helps to induce convective outbreaks and rapid intensification. Furthermore, sensitivity experiments show that terrain and the land-sea distribution have very limited effects on the formation of Typhoon Vamei in the simulation, but an adequate Coriolis parameter ($f)$ is still needed for the development of Vamei.     

Finescale Spiral Rainbands Modeled in a High-Resolution Simulation of Typhoon Rananim （2004）

Finescale spiral rainbands associated with Typhoon Rananim(2004)with the band length ranging from 10 to nearly 100 km and band width varying from 5 to 15 km are simulated using the Fifth-Generation NCAR/Penn State Mesoscale Model(MM5).The finescale rainbands have two types:one intersecting the eyewall and causing damaging wind streaks,and the other distributed azimuthally along the inner edge of the eyewall with a relatively short lifetime.The formation of the high-velocity wind streaks results from the interaction of the azimuthal flow with the banded vertical vorticity structure triggered by tilting of the horizontal vorticity.The vertical advection of azimuthal momentum also leads to acceleration of tangential flow at a relatively high altitude.The evolution and structures of the bands are also examined in this study. Further investigation suggests that the boundary inflection points are related tightly to the development of the finescale rainbands,consistent with previous findings using simple symmetric models.In particular,the presence of the level of inflow reversal in the boundary layer is a crucial factor controlling the formation of these bands.The near-surface wavy peaks of vertical vorticity always follow the inflection points in radial flow.The mesoscale vortices and associated convective updrafts in the eyewall are considered to strengthen the activity of finescale bands,and the updrafts can trigger the formation of the bands as they reside in the environment with inflow reversal in the boundary layer.     

Roles of Mesoscale Terrain and Latent Heat Release in Typhoon Precipitation： A Numerical Case Study

The mesoscale orographic effects on typhoon Aere＇s precipitation are simulated using an Advanced Regional Eta-coordinate Model （AREM） version 3.0. In particular, the effects of the latent heat release are studied by two comparable experiments： with and without condensational heating. The results show that the typhoon rainfall is tripled by the southeastern China mesoscale terrain, and the condensational heating is responsible for at least half of the increase. One role of the latent heat release is to warm the atmosphere, leading to a depression of the surface pressure, which then causes a larger pressure difference in the zonal direction. This pressure gradient guides the water vapour to flow into the foothills, which in turn amplifies the water vapour flux divergence amplified, causing the typhoon rainfall to increase eventually. The other role of the latent heat release is to make the convection more organized, resulting in a relatively smaller rain area and stronger precipitation.     

Numerical Simulation of Long-Term Climate Change in East Asia

A 10-yr regional climate simulation was performed using the fifth-generation PSU/NCAR Mesoscale Model Version 3 (MM5V3) driven by large-scale NCEP/NCAR reanalyses. Simulations of winter and summer mean regional climate features were examined against observations. The results showed that the model could well simulate the 10-yr winter and summer mean circulation, temperature, and moisture transport at middle and low levels. The simulated winter and summer mean sea level pressure agreed with the NCAR/NCEP reanalysis data. The model could well simulate the distribution and intensity of winter mean precipitation rates as well as the distribution of summer mean precipitation rates, but it overestimated the summer mean precipitation over North China. The model's ability to simulate the regional climate change in winter was superior to that in summer. In addition, the model could simulate the inter-annual variation of seasonal precipitation and surface air temperature. Geopotential heights and temperature at middle and high levels between simulations and observations exhibited high anomaly correlation coefficients. The model also showed large variability to simulate the regional climate change associated with the El Nino events. The MM5V3 well simulated the anomalies of summer mean precipitation in 1992 and 1995, while it demonstrated much less ability to simulate that in 1998. Generally speaking, the MM5V3 is capable of simulating the regional climate change, and could be used for long-term regional climate simulation.     

边界层参数化方案对“莫兰蒂”台风（1614）登陆阶段影响的数值模拟研究

利用中尺度数值模式WRF v3.8中的YSU、MYJ、QNSE、ACM2、UW、GBM、Boulac七种不同边界层参数化方案,采用高分辨率（1.33 km）数值试验的方法研究了不同边界层方案对模拟台风“莫兰蒂”（1614）登陆减弱阶段的移动路径、强度、结构、降水量、近地层有关物理量场分布等方面的影响,结果表明:（1）“莫兰蒂”台风登陆减弱阶段,不同边界层方案对台风路径、强度、降水量模拟影响显著,24 h内模拟台风路径、最低气压、最大风速及24 h累积降水量极值的最大差异分别达80 km、11 hPa、27 m s?1及241 mm;（2）Boulac方案模拟台风路径与实况最为接近,GBM、YSU和MYJ方案分别次之,ACM2和UW方案再次之,而QNSE方案最差;UW和QNSE方案模拟的最低气压以及MYJ和QNSE方案模拟的最大风速与观测最为接近;不同边界层方案均模拟出台风登陆阶段最低气压逐渐升高以及其升高速率在台风登陆后大于登陆前的特征,这与实况一致,但台风登陆前各方案模拟最低气压升高速度均大于实况,而台风登陆后却又不及实况;（3）Boulac方案模拟的24 h降水分布、强降水落区、结构、强度和各量级降水TS评分均最优,MYJ方案次之;而QNSE、UW和ACM2方案雨带向西北方向推进过快,各量级降水TS评分均较差;（4）综合台风路径、强度和降水模拟,Boulac和MYJ方案相对最优,其中Boulac方案在台风路径和降水模拟上更优,而MYJ方案在台风强度模拟上更优;YSU和GBM方案次之,而QNSE、UW和ACM2方案相对较差;（5）不同边界层方案计算的近地层潜热通量、感热通量显著不同,进而影响台风路径、强度、降水量模拟存在显著差异。比较而言,QNSE方案潜热通量相对异常偏高,MYJ和Boulac方案量值适中,其余方案相对偏低;QNSE方案感热通量相对略偏高,MYJ方案适中,其他方案则相对显著偏低;（6）不同边界层方案模拟降水区边界层热、动力结构显著不同,其中Boulac方案具有较明显优势,尤其是对日间边界层结构的模拟。     

A Numerical Simulation Study of Impacts of Historical Land-Use Changes on the Regional Climate in China Since 1700

By using the improved regional climate model (BCC_RegCM1.0), a series of modeling experiments are undertaken to investigate the impacts of historical land-use changes (LUCs) on the regional climate in China. Simulations are conducted for 2 years using estimated land-use for 1700, 1800, 1900, 1950, and 1990. The conversion of land cover in these periods was extensive over China, where large areas were altered from forests to either grass or crops, or from grasslands to crops. Results show that, since 1700, historical LUCs have significant effects on regional climate change, with rainfall increasing in the middle and lower reaches of the Yangtze River Basin, Northwest China, and Northeast China, but decreasing by different degrees in other regions. The air temperature shows significant warming over large areas in recent hundred years, especially from 1950 to 1990, which is consistent with the warming caused by increasing greenhouse gases. On the other hand, historical LUCs have obvious effects on mean circulation, with the East Asian winter and summer monsoonal flows becoming more intensive, which is mainly attributed to the amplifled temperature difference between ocean and land due to vegetation change. Thus, it would be given more attention to the impacts of LUCs on regional climate change.     

Impacts of a GCM＇s Resolution on MJO Simulation

Long-term integrations are conducted using the Spectral Atmospheric Model （referred to as SAMIL）, which was developed in the Laboratory for Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG） in the Institute of Atmospheric Physics （IAP）, with different resolutions to inves-tigate sensitivity of the Madden-Julian Oscillation （MJO） simulations to the model＇s resolution （horizontal and vertical）. Three resolutions of the model, R15L9, R42L9 and R42L26, with identical physical processes, all produced the basic observed features of the MJO, including the spatiotemporal space-time spectra and eastward propagation. No fundamental differences among these simulations were found. This indicates that the model resolution is not a determining factor for simulating the MJO. Detailed differences among these modeling results suggest, however, that model resolution can substantially affect the simulated MJO in certain aspects. For instance, at a lower horizontal resolution, high frequency disturbances were weaker and the structures of the simulated MJO were better defined to a certain extent. A higher vertical resolution led to a more realistic spatiotemporal spectrum and spatial distribution of MJO precipitation. Meanwhile, increasing the model＇s resolution improved simulation of the climatology. However, increasing the resolution should be based on improving the cumulus parameterization scheme.     

海浪和海洋飞沫对“珊珊”台风影响的数值研究

台风是剧烈的天气系统,在开放的海上强风激起大浪,改变了海表粗糙度,同时,海浪顶端的白泡沫破碎,在海-气界面处会出现大量的海洋飞沫。基于共享内存的进程间通信技术应用到区域大气和海浪模式的耦合中,大气模式引入了Fairall和Andreas两种海洋飞沫参数化方案,对2006年珊珊台风进行了模拟对比试验,结果表明:耦合模式通过海-气相互作用,对台风的强度产生影响,由于耦合模式在海表粗糙度的计算上考虑了海表状况,使得耦合模式模拟的台风强度更接近实况,而对台风的移动路径影响不大;耦合模式中海-气相互作用主要通过动力因素来对台风产生影响,海表状况影响了海表粗糙度,从而使台风的动量输送发生变化,具体的台风强度增强还是减弱主要取决于海表状况与实况的符合程度;海洋飞沫参数化主要通过热力场的改变来影响动力场,Fairall方案中潜热通量和感热通量得到很大程度的加强,使得台风的热力结构得以改变,台风强度明显加强,从而影响了动力场结构;Andreas方案由于其界面通量算法在高相对湿度条件下计算界面通量时得到的量值较小,虽然高风速条件下感热通量加大,但总的潜热通量、感热通量较Fairall方案为弱,因此,模拟的台风强度不强;海洋飞沫参...     

Numerical Simulation and Comparison Study of the Atmospheric Intraseasonal Oscillation

Daily mean outputs for 12 yr (1978-1989) from two general circulation models (SAMIL-R42L9 and CAM2.0.2) are analyzed and compared with the corresponding NCEP/NCAR reanalysis dataset, and results in two models show clearly that the root-mean square errors (RMSEs) from the simulation of intraseasonal oscillation can take 30-40 percent of the total RMSE, particularly, the distributions of the RMSE in simulating intraseasonal oscillation are almost identical with that of the total RMSE. The maximum RMSE of intraseasonal oscillation height at 500 hPa is shown in the middle latitude regions, but there are also large RMSEs of intraseasonal oscillation wind over the tropical western Pacific and tropical Indian Oceans. The simulated ISO energy in the tropic has very large difference from the result of the NCEP/NCAR reanalysis dataset which means the simulation of tropical atmospheric ISO still possesses serious insufficiency. Therefore, intraseasonal oscillation in the weather and climate numerical simulation is very important, and thus, how to improve the ability of the GCM to simulate the intraseasonal oscillation becomes very significant.     

不同边界层参数化方案对台风“利奇马”模拟的影响研究

基于中尺度数值模式WRF,对比分析了六种大气边界层物理过程参数化方案（BouLac、MYJ、UW、YSU、ACM2、SH）对台风“利奇马”模拟结果的影响。结果表明,不同边界层方案对“利奇马”路径的模拟结果影响较小,但对其强度和结构演变的模拟结果影响显著。其中,局地闭合方案UW方案模拟的结果最强,局地闭合方案BouLac次之,而局地闭合方案MYJ和三种非局地闭合方案YSU、ACM2和SH的模拟强度都较弱。这些方案中,BouLac模拟的海平面最低气压与实况最为接近。通过对比这些边界层方案的模拟结果发现,由于台风强度的差异受到热力和动力的共同影响,边界层方案如模拟得到的地表潜热通量和边界层中湍流扩散系数较大,将导致较大的径向风和低层辐合,从而模拟得到较强的台风强度;反之,则台风强度较弱。     

WRF模式中微物理和积云对流参数化方案对台风“莫拉克”模拟敏感性分析

基于WRF模式,研究了不同微物理和积云对流参数化方案对0908号台风"莫拉克"的路径移动、强度变化和降水过程模拟的敏感性。结果显示,积云对流参数化方案对台风"莫拉克"的路径和强度模拟起主导作用,采用Kain-Fritsch积云对流方案模拟的72 h平均路径误差较小;降水量的模拟主要取决于微物理参数化方案,而降水分布的好坏更依赖于积云对流参数化方案,而采用Thompson微物理和Grell-Devenyi积云对流方案的试验导致累积降水极值的偏干误差较大。积云对流方案对环境场和潜热释放模拟存在差异,导致路径和强度、温度廓线和垂直运动的模拟结果不同,而微物理方案对不同相态降水粒子的垂直分布结构模拟存在差异,从而导致降水模拟的差别。此外,由不同试验构造的集合平均能减少单个成员模拟路径和降水的不确定性,特别在强降水方面能减小空报数和漏报数,提高TS评分,改善模拟效果。     

WRF模式对高影响浙江型台风微物理和边界层参数化方案的优化试验

选取近年来在浙江和福建登陆高影响浙江的9个西太平洋台风,利用WRF中尺度数值模式,选取多种微物理和边界层参数化方案,量化评估不同方案下的台风路径、强度和降水的模拟性能。结果表明,Kessler和SBU-YLin微物理方案对台风路径和强度模拟较好;而SBU-YLin在浙江降水上比Kessler评分相对更优、误差更小、相关性更佳,但其漏报率相对较高。MYNN2和BouLac边界层方案的最优台风路径和强度比例较高,而BouLac对浙江降水有更好的表现,其降水误差更小、相关性更好,且有更高的TS评分,特别是大雨以上量级或台风登陆前12 h。因此,SBU-YLin微物理和BouLac边界层方案相对更适合浙江台风模拟。此外,浙江沿海地区模拟雨量比实况偏少,且绝对误差较大,内陆反之;雨量误差与浙江地形有较好的对应关系。