Impacts of Horizontal and Vertical Resolutions on the Microphysical Structure and Boundary Layer Fluxes of Typhoon Hato

We set four sets of simulation experiments to explore the impacts of horizontal resolution (HR) and vertical resolution (VR) on the microphysical structure and boundary layer fluxes of tropical cyclone (TC) Hato (2017). The study shows that higher HR tends to strengthen TC. Increasing VR in the upper layers tends to weaken TC, while increasing VR in the lower layers tends to strengthen TC. Simulated amounts of all hydrometeors were larger with higher HR. Increasing VR at the upper level enhanced the mixing ratios of cloud ice and cloud snow, while increasing VR at the lower level elevated the mixing ratios of graupel and rainwater. HR has greater impact on the distributions of hydrometeors. Higher HR has a more complete ring structure of the eyewall and more concentrated hydrometeors along the cloud wall. Increasing VR at the lower level has little impact on the distribution of TC hydrometeors, while increasing VR at the upper level enhances the cloud thickness of the eyewall area. Surface latent heat flux (SLHF) is influenced greatly by resolution. Higher HR leads to larger water vapor fluxes and larger latent heat, which would result in a stronger TC. A large amount of false latent heat was generated when HR was too high, leading to an extremely strong TC, VR has a smaller impact on SLHF than HR. But increasing VR at the upper-level reduces the SLHF and weakens TC, and elevating VR at the lower-level increases the SLHF and strengthens TC. The changes in surface water vapor flux and SLHF were practically identical and the simulation results were improved when HR and VR were more coordinated. The friction velocity was greater with higher VR. Enhancing VR at the lower level increased the friction velocity, while increasing VR at the upper level reduced it.     

Sea-Salt Aerosol Effects on the Simulated Microphysics and Precipitation in a Tropical Cyclone

We investigate the effects of sea-salt aerosol(SSA) activated as cloud condensation nuclei on the microphysical processes, precipitation, and thermodynamics of a tropical cyclone(TC). The Weather Research and Forecasting model coupled with Chemistry(WRF-Chem) was used together with a parameterization of SSA production. Three simulations, with different levels of SSA emission(CTL, LOW, HIGH), were conducted. The simulation results show that SSA contributes to the processes of autoconversion of cloud water and accretion of cloud water by rain,thereby promoting rain formation. The latent heat release increases with SSA emission, slightly increasing horizontal wind speeds of the TC. The presence of SSA also regulates the thermodynamic structure and precipitation of the TC.In the HIGH simulation, higher latent heat release gives rise to stronger updrafts in the TC eyewall area, leading to enhanced precipitation. In the LOW simulation, due to decreased latent heat release, the temperature in the TC eye is lower, enhancing the downdrafts in the region; and because of conservation of mass, updrafts in the eyewall also strengthen slightly; as a result, precipitation in the LOW experiment is a little higher than that in the CTL experiment.Overall, the relationship between the precipitation rate and SSA emission is nonlinear.     

Impact of Different Cloud Microphysics Parameterization Schemes on Typhoon Intensity and Structure

The impact of different cloud microphysics parameterization schemes on the intensity and structure of the Super-strong Typhoon Rammasun (1409) in 2014 is investigated using the Weather Research and Forecasting model version 3.4 with eight cloud microphysics parameterization schemes. Results indicate that the uncertainty of cloud microphysics schemes results in typhoon forecast uncertainties, which increase with forecast time. Typhoon forecast uncertainty primarily affects intensity predictions, with significant differences in predicted typhoon intensity using the various cloud microphysics schemes. Typhoon forecast uncertainty also affects the predicted typhoon structure. Greater typhoon intensity is accompanied by smaller vortex width, tighter vortex structure, stronger wind in the middle and lower troposphere, greater height of the strong wind region, smaller thickness of the eyewall and the outward extension of the eyewall, and a warmer warm core at upper levels of the eye. The differences among the various cloud microphysics schemes lead to the different amounts and distributions of water vapor and hydrometeors in clouds. Different hydrometeors have different vertical distributions. In the radial direction, the maxima for the various hydrometeors forecast by a single cloud microphysics scheme are collocated with each other and with the center of maximum precipitation. When the hydrometeor concentration is high and hydrometeors exist at lower altitudes, more precipitation often occurs. Both the vertical and horizontal winds are the strongest at the location of maximum precipitation. Results also indicate that typhoon intensities forecast by cloud microphysics schemes containing graupel processes are noticeably greater than those forecast by schemes without graupel processes. Among the eight cloud microphysics schemes investigated, typhoon intensity forecasts using the WRF Single-Moment 6-class and Thompson schemes are the most accurate.     

热带气旋眼墙非对称结构的研究综述

热带气旋的眼墙非对称结构与其发展过程密切相关。在热带气旋移动过程中,非对称风场伴随着边界层内非对称摩擦而引起的辐合,影响着热带气旋眼墙内的对流分布。此外,风垂直切变作为影响热带气旋强度的重要因子,将上层暖心吹离表层环流,引起眼墙垂直运动的非对称,导致云、降水在方位角方向的非均匀分布。当存在平均涡度的径向梯度时,罗斯贝类型的波动可以存在于涡旋内核区域,影响眼墙非对称结构。海洋为热带气旋提供潜热和感热形式的能量,是热带气旋发展的重要能量来源,关于海洋如何影响热带气旋眼墙非对称结构的相关研究较少。文中着重回顾了热带气旋与海洋相互作用的研究成果,并提出海洋影响热带气旋眼墙非对称结构的机制。海洋对热带气旋最显著的响应特征是冷尾效应,该效应通过降低海表温度,减少海洋向大气输送的潜热和感热,从而影响热带气旋眼墙非对称结构。此外,海浪改变海表粗糙度,通过边界层影响移动热带气旋的眼墙结构。     

Impacts of the Lowest Model Level Height on Tropical Cyclone Intensity and Structure简

Variable thicknesses in the lowest half-ηmodel level （LML） are often used in atmospheric models to compute surface diagnostic fields such as surface latent and sensible heat fluxes.The effects of the LML on simulated tropical cyclone （TC）evolution were investigated in this study using the Weather Research and Forecasting （WRF） model.The results demonstrated notable influences of the LML on TC evolution when the LML was placed below 12 m.The TC intensification rate decreased progressively with a lowering of the LML,but its ultimate intensity change was relatively small.The maximum 10-m winds showed different behavior to minimum sea level pressure and azimuthally-averaged tangential winds,and thus the windpressure relationship was changed accordingly by varying the LML.The TC circulation was more contracted in association with a higher LML.Surface latent heat fluxes were enhanced greatly by elevating the LML,wherein the wind speed at the LML played a dominant role.The changes in the wind speed at the LML were dependent not only on their profile differences,but also the different heights they were taken from.Due to the enhanced surface heat fluxes,more intense latent heat release occurred in the eyewall,which boosted the storm＇s intensification.A higher LML tended to produce a stronger storm,and therefore the surface friction was reinforced,which in turn induced stronger boundary layer inflow together with increased diabatic heating.     

利用TMI反演的水汽凝结物对热带气旋潜热结构分布的探索研究

本文利用热带测雨卫星TRMM（Tropical Rainfall Measuring Mission）微波成像仪TMI（TRMM Microwave Imager）2A12 水汽凝结物（Hydrometeor）反演资料,对西北太平洋地区从1998～2009 年的236 个热带气旋个例的1776 个“快照”（snapshot）的水汽凝结物的结构特征进行了分析,并探讨了水汽凝结物的时空变化与热带气旋强度演变联系。研究结果表明:（1）TMI 2A12 水汽凝结物资料显示出了热带气旋内部的细致结构及变化特征,水汽凝结物的峰值集中于数十公里到一百多公里的热带气旋眼壁及云墙区;在热带气旋发展过程中,随着热带气旋强度的增强,水汽凝结物增多且往其中心靠拢,从发展阶段到成熟阶段,水汽凝结物的大值中心基本上集中在距离热带气旋中心约50 km 区域,而且强度越强的热带气旋,水汽凝结物的大值中心与热带气旋中心的距离越近;在热带气旋消亡的过程中,水汽凝结物不断减弱且往外围扩散,逐渐扩展到远离中心的区域;（2）热带气旋强度与水汽凝结物的分布关系密切,热带气旋强度变化与热带气旋中心附近200 km 范围内的水汽凝结物含量存在显著的正相关,而200 km 以外的外围水汽凝结物含量存在负相关;（3）热带气旋强度变化与水汽凝结物的变化存在时间差,水汽凝结物的变化超前于热带气旋强度的变化,在热带气旋迅速发展之前数小时,热带气旋中心0～50 km 环状区域的水汽凝结物含量就已经提前增加了,在热带气旋减弱前数小时到十数小时,即使热带气旋还处于它强度的鼎盛时期,其中心0～50 km 环状区域的水汽凝结物含量就已经提前显著减少了,这种水汽凝结物的变化超前于热带气旋强度的变化的现象,可能是热带气旋强度预报的潜在线索。     

西北太平洋海温增暖对热带气旋潜在破坏力的影响:高分辨模式个例分析

以三个西北太平洋热带气旋（TC）为例,利用WRF（Weather Research and Forecasting）模式进行了一系列海表温度（SST）敏感性数值试验,揭示了西北太平洋SST增暖对TC的强度、尺度及潜在破坏力的影响及其机理。结果表明,在距TC中心100 km以内区域的SST升高有利于TC强度增加,但会减小TC内核尺度;而在距TC中心100 km以外的SST升高并不会使TC强度明显增加甚至使TC强度减弱,但同时会增加TC内核尺度。伴随着低层向眼墙的入流,升高的外区SST会使TC区表层的大气温度和湿度升高,造成眼墙附近海气温差和湿度差及向内的气压梯度力减小,进而减少进入TC眼墙内的感热和潜热,不利于TC增强,但有利于眼墙向外移动,使TC内核尺度增加。内区SST升高与外区SST升高对TC强度及尺度变化的作用机理相反。因此,当TC移过冷或暖洋面时,TC的强度和尺度的变化不仅取决于局地洋面的冷或暖状况,还取决于TC内区和外区SST的差异。由于TC内区和外区SST对TC强度和内核尺度的不同作用,可能存在一个临界范围,当暖池范围在这个临界范围之内时TC潜在破坏力随暖池范围的扩大而增大,但当暖池范围超过这个临界范围时TC潜在破坏力便不会随着暖池范围的继续扩大而增大,甚至会有所减小。      

Formation and Replacement Mechanism of the Concentric Eyewall of Super Typhoon Muifa (1109)

Based on high-fidelity numerical simulation by using the Weather Research and Forecast (WRF) model, we analyzed the formation and replacement mechanism of the concentric eyewall of Super Typhoon Muifa (1109) from the aspects of the potential vorticity (PV), dynamic/ thermodynamic structure change, sea surface flux, and water vapor content. Observational data and sensitivity tests were also adopted to verify the results. We found that: (1) The abnormal increase of the PV in the rain zone is mainly due to the condensation latent heat. Sufficient water vapor conditions are beneficial to the formation of the outer eyewall structure, and when the environmental water vapor content is larger, the intensity of the outer eyewall becomes greater. (2) After the formation of the typhoon’s outer eyewall, in the area where the outer eyewall is located, the increase of inertial stability contributes to the decrease of the intensity of the inner eyewall. When the intensity of the outer eyewall is larger, the divergence and subsidence motion in the upper layer of the outer eyewall has a greater weakening effect on the intensity of the inner eyewall. (3) The increase of potential temperature of the outer eyewall is mainly due to the condensation latent heat release and the warming of dry air subsidence motion in the moat area. (4) The increase of sea surface heat flux can prolong the concentric eyewall replacement process.     

次千米至次百米高分辨率模拟的热带气旋眼墙低层极端上升运动特征分析

观测发现热带气旋(TC)眼墙附近低层(3 km以下)存在着强烈的上升运动,严重威胁低空观测飞机的安全,由于对实际TC观测的样本非常有限,目前对极端上升运动(大于10 m/s)的了解不多。通过三个水平分辨率自次千米(333 m)至次百米(37 m)大涡数值试验模拟眼墙附近低层上升运动的分布特征。结果表明,TC眼墙附近的最强上升运动主要分布在眼墙处最大风速半径(RMW)内侧,并且主要出现在台风眼墙强对流的一侧。对比不同试验发现,在大涡试验中,随着模式水平分辨率的提高,模式可以模拟出更强的上升运动,且极端上升运动最大频数的分布高度随着水平分辨率的提高而降低。研究表明,与现有观测结果比较,当大涡试验水平分辨率到达111 m时,可以模拟出与实际观测比较相似的极端上升运动空间分布和强度。      

2010年6月中旬浙闽赣地区暴雨特征和冰云热力效应的数值模拟分析

以2010年6月19日发生在浙闽赣地区的一次强降水过程为例,利用中尺度WRF模式进行模拟,用模拟资料对该地区降水收支特征和冰云热力作用进行分析。依据局地水汽/热量变化项、水汽/热量辐合辐散项和云凝物辐合辐散项这3个因子可将降水分为8类,其中局地水汽变干和大气变暖、水汽辐合和热量辐散以及云凝物辐合时,降水强度(雨强)最强,而局地水汽变湿和大气变冷、水汽辐合和热量辐散以及云凝物辐合时,降水覆盖率最大。冰云热力效应包括辐射和潜热两部分。基准试验与敏感性试验对比分析表明冰云辐射减弱降水,而冰云潜热增强降水。热量收支对比分析发现冰云辐射造成辐射冷却的减弱在对流层中低层随高度增加,减弱大气不稳定和降水;而冰云潜热造成潜热增强在对流层中高层随高度减小,增强大气不稳定和降水。     

SENSITIVITY OF LANDFALLING TYPHOON STRUCTURE AND PRECIPITATION TO VARYING CLOUD MICROPHYSICAL PROCESSES

Typhoon KROSA in 2007 is simulated using GRAPES, a mesoscale numerical model, in which a two-parameter mixed-phase microphysics scheme is implanted. A series of numerical experiments are designed to test the sensitivity of landfalling typhoon structure and precipitation to varying cloud microphysics and latent heat release. It is found that typhoon track is sensitive to different microphysical processes and latent heat release. The cloud structures of simulated cyclones can be quite different with that of varying microphysical processes. Graupel particles play an important role in the formation of local heavy rainfall and the maintenance of spiral rainbands. Analysis reveals that the feedback of latent heat to dynamic fields can significantly change the content and distribution of cloud hydrometeors, thus having an impact on surface precipitation.     

海温及海浪对台风眼墙中尺度涡的影响

本文利用包括海气耦合、气浪耦合及浪流耦合的完全耦合系统,着重研究了2006年“格美”(Kaemi)台风眼墙内的中尺度涡结构。中尺度涡作为影响台风眼墙非对称结构的内部因子,与风垂直切变密切相关,其发展过程受台风下垫面海洋状况的影响。在顺切变右侧,垂直气流逐渐增强,在顺切变左侧达到最大后逐渐减弱。当不考虑海表温度的冷涌反馈作用时,海气间的热通量输送较大,由此引起眼墙内的中尺度对流加强,但集中爆发区仍然位于顺切变方向,不受热通量输送变化的影响。当不考虑海浪对海表粗糙度的影响时,在较小的海表粗糙度条件下,眼墙非对称性减弱,使得中尺度对流涡在切向方向上的分布较为均匀。     

登陆台风“凡亚比”(1011)合力散度特征诊断研究——垂直分布特征

本文利用2010年1011号台风“凡亚比”登陆过程高分辨率数值模拟资料,诊断分析了“凡亚比”台风环流合力散度的垂直分布及其演变特征。结果指出,合力散度的显著区一直与台风系统相伴随,可以有效地示踪热带气旋（Tropical Cyclone,简称TC）的移动,并能较好地识别TC强度、结构的发展演变。台风中心偏东一侧流入层的合力散度异常信号首先出现并发展,反映出环流的非对称特征。随着台风趋于成熟,合力散度逐渐增强,高度扩展,对称性也逐渐增加;台风中心上空为合力辐合,外围为合力辐散,垂直方向上合力辐合与辐散相间的结构对应上升运动极值区及强降水,即对应台风眼墙位置。合力散度面积指数和强度指数的分析指出,垂直方向上辐合与辐散面积指数负相关;各层的合力辐合强度指数普遍大于辐散强度指数,垂直方向上两强度指数呈显著的正相关关系;结合面积指数与强度指数,可知垂直方向上合力辐合与辐散此消彼长。运用合力散度方程对该垂直分布特征的成因展开分析,发现风速u分量平流随经度变化项和风速v分量平流随纬度的变化项是TC眼区合力辐合部分的主要贡献项,垂直运动项决定了TC眼墙的合力辐合与辐散相间的垂直分布特征。     

A possible new mechanism for northward propagation of boreal summer intraseasonal oscillations based on TRMM and MERRA reanalysis

Boreal summer intraseasonal oscillations (BSISOs) manifest in the active and break spells and act as the primary building block of the Indian summer monsoon. Although recent research has evolved a basic framework for understanding the scale selection and northward propagation of the BSISO, the role of different hydrometeors in modulating these processes remains poorly explored. In this study, TRMM-2A12 retrievals and Modern Era Retrospective-analysis for Research and Applications reanalysis data are examined to establish relationship between cloud hydrometeors and other atmospheric dynamical parameters with the northward propagation of the BSISOs. The study reveals that the cloud liquid water leads the deep convection during the northward propagation of BSISOs in the lower troposphere, while the cloud ice slightly lags the convection. This distribution indicates the occurrence of a possible mechanism of the lower level moistening through the large scale moisture advection in lower atmosphere and boundary layer (PBL) convergence, followed by triggering of the deep convection. The analyses of moisture advection and the dynamical fields with respect to the convection center show that low level moistening is a manifestation of the barotropic vorticity and PBL convergence of moisture anomaly north of the convection center. A new internal dynamical-thermodynamical mechanism is unraveled to understand the reason behind the middle tropospheric heating maximum and its role on the northward propagation. It is shown that the enhanced moisture perturbation in lower levels together with the heat transport by the sub-grid scale eddies within the PBL induces lower level instability required to precondition the lower atmosphere for triggering the deep convection. Vigorous upward motion inside the deep convection uplifts the liquid hydrometeors to upper levels and the formation of precipitable ice leads to the heating maxima in the middle troposphere. To check the robustness of the proposed hypothesis, similar analysis is performed for the weak northward propagating BSISO cases.     

Implementation of a new cumulus parameterization scheme based on an explicit time-dependent tilting cloud model in ARPS model

A one-dimensional Explicit Time-dependent Tilting cloud Model (ETTM) that separates updraft and downdraft columns and takes into account the effect of cloud tilting on precipitation is introduced and incorporated into the Advanced Regional Prediction System (ARPS). Results of the stand-alone ETTM are compared with that of cloud resolving simulations using the ARPS mesoscale model. Inter-comparison is performed by qualitative examination of simulated parameters such as vertical distribution of fluxes of mass, heat, and moisture. Although there is a great degree of similarity between the vertical profiles, ETTM systematically underestimates magnitudes of all fluxes. Sensitivity tests carried with ETTM show that the effect of varying cloud radius and tilting angle is considerable on the simulated cloud behavior. Increasing the cloud radius, results in a corresponding increase in fluxes of mass, heat, and moisture, while increasing the cloud tilt angle has the opposite effect. Since ETTM showed promise as a suitable sub-grid cumulus parameterization scheme; it was incorporated into ARPS as an additional cumulus parameterization scheme (CPS) to be available for the wider community. Results of simulations using ETTM and other CPSs already available in ARPS were compared for 2, 4 and 10 km grid spacings to assess its utility. Simulation results of the 2 km grid showed that at this resolution, the simulated time series of updraft velocities using the new scheme (ETTM) compared well with the results of other schemes in the ARPS model. The simulations with horizontal resolution of 4 km that was compared with the convection resolving reference run (No-CPS-2KM) showed almost consistent results for all schemes except for one using KF scheme. The results of the simulation with the ETTM scheme and other schemes in the model with resolution of 10 km showed that at this resolution, there is not significant difference between the uses of these schemes.     

Can crop albedo be increased through the modification of leaf trichomes,and could this cool regional climate?

Managing the land surface to increase albedo to offset regional warming has received less attention than managing the land surface to sequester carbon. We test whether increasing agricultural albedo can cool regional climate. We first used the Community Atmosphere Model (CAM 3.0) coupled to the Community Land Model (CLM 3.0) to assess the broad climatic effects of a hypothetical implementation of a strategy in which the albedo of cropland regions is increased using high albedo crops. Simulations indicate that planting brighter crops can decrease summertime maximum daily 2 m air temperature by 0.25°C per 0.01 increase in surface albedo at high latitudes (>30°). However, planting brighter crops at low latitudes (<30°) may have negative repercussions including warming the land surface and decreasing precipitation, because increasing the land surface albedo tends to preferentially decrease latent heat fluxes to the atmosphere, which decreases cloud cover and rainfall. We then test a possible method for increasing crop albedo by measuring the range of albedo within 16 isolines of soybeans that differ only with trichome color, orientation, and density but find that such modifications had only minor impacts on leaf albedo. Increasing agricultural albedo may cool high latitude regional climate, but increasing plant albedo sufficiently to offset potential future warming will require larger changes to plant albedo than are currently available.     

利用WRF-Chem模式模拟分析人为气溶胶对台风Fitow(1323)强度及降水的影响

利用气象与化学模块在线耦合的模式WRF-Chem V3.5(Weather Research and Forecasting Model coupled to Chemistry Version 3.5) 对1323号台风Fitow进行了模拟,设计无人为排放源、含人为排放源和人为排放源增加的三组模拟试验,对比分析了人为气溶胶对台风的影响。结果表明:人为气溶胶对台风移动路径影响较小。人为气溶胶增加,台风强度减弱,台风主体总累积降水量减少,靠近陆地阶段台风主体降水率减少。气溶胶的增多可提供更多的凝结核,台风外围云水增加,更多的云水可上升至冻结层以上形成过冷水,促进冰相粒子的形成,释放的潜热增加,使外围对流增强,降水增加。台风外围对流的发展,使低层入流的暖湿空气更多的在外围上升,向台风中心的入流减弱,眼墙的发展减弱,降水减少,台风强度减弱。台风外围的对流发展弱于眼墙的对流,降水仍以眼墙区为主,使累积降水量和降水率整体上表现为减少。     

海洋对大气加热场的区域性年变化特征

本文研究了热带和中纬度一些海表面温度年变化较强的区域中海洋对大气加热场的年度化特征。结果表明海洋向大气提供热通量的强度在冷海区呈年周期性变化,而在暖海区呈半年周期性变化。与潜热的湍流输送及海表面向上的长波辐射通量相比,感热的湍流输送量很小。在暖海区潜热输送总大于长波辐射,并且前者有较强的年变化而后者较弱;在冷海区二者的量级相当,年变化幅度也相当。海表风场和云的变化对海洋对大气加热场年变化的影响非常重要。     

Sensitivity of tropical cyclone intensity and structure to vertical resolution in WRF

In this paper the impacts of vertical resolution on the simulations of Typhoon Talim (2005) are examined using the Weather Research and Forecasting (WRF) model, with cumulus parameterization scheme representing the cumulus convection implicitly. It is shown that the tropical cyclone (TC) track has little sensitivity to vertical resolution, whereas the TC intensity and structure are highly sensitive to vertical resolution. It is partly determined by the sensitivity of the planetary boundary layer (and the surface layer) and the cumulus convection processes to vertical resolution. Increasing vertical resolution in the lower layer could strengthen the TC effectively. Increasing vertical resolution in the upper layer is also beneficial for the storm intensification, but to a lesser degree. In contrast, improving the midlevel resolution may cause the convergence of environmental air, which inhibits the TC intensification. The results also show that the impacts of vertical resolution on features of the TC structure, such as the tangential winds, secondary circulations and the evolution of the warm-core structure, are consistent with the impacts on the TC intensity. It is suggested that in the simulations of TCs, the vertical levels should be distributed properly rather than the more the better, with higher vertical resolution being expected both in the lower and upper layer, while the middle layer should not hold too many levels.     

8807号登陆台风的数值研究：内核结构及能量水汽收支

使用PSU/NCAR研制的非静力中尺度模式MM5对登陆后维持较久的典型个例8807号台风(Bill)进行了数值模拟。模拟采用了网格距分别为18和6 km的两重双向嵌套网格。通过给定初始涡旋和选择合适的物理过程,模式不仅比较好地模拟了Bill的强度变化过程,而且再现了风暴的移动轨迹,对降水量的模拟也相当成功。文中利用细网格的模拟结果,分析台风登陆前后的内核结构特征和能量水汽收支,揭示Bill登陆后维持较久的可能原因。分析表明,Bill台风登陆后出现了中低层的稳定度特别是湿稳定度显著加大、表面热通量和水汽通量明显减小、摩擦耗散的动能显著增加等不利于台风维持的特征。但是台风登陆后眼墙结构长时间维持,在登陆初欺眼墙区的上升气流乃至较登陆前更强;台风登陆后通过低层辐合获得了大量水汽,眼墙区强劲的上升运动将低层辐合的水汽向中上层输送,在眼墙附近凝结产生大量的非绝热加热;非绝热加热不仅增暖气柱、增加位能还影响位能向动能的转换,虽然台风登陆后陆面摩擦显著加大,但气压梯度力所做的正功足以补偿摩擦耗散的动能,因而Bill能在登陆后长时间维持。