共查询到20条相似文献，搜索用时 15 毫秒
1.
S. S. Zilitinkevich 《Boundary-Layer Meteorology》1989,49(1-2):1-5
A logarithmic + polynomial approximation is proposed for the vertical temperature profile in a neutrally or stably stratified planetary boundary layer (PBL) in conditions of quasi-stationarity. Using this approximation with the asymptotic logarithmic + linear law of the Monin-Obukhov similarity theory for the near-surface layer and with the Zilitinkevich formula for the PBL thickness allows one to derive an analytical expression for the function C in the heat transfer law, which permits simple parameterization of the thermal interaction between the atmosphere and the underlying medium in terms of external parameters, such as the geostrophic wind velocity and the temperature difference across the PBL. 相似文献
2.
鞍型场是一种特殊的流场,鞍点附近气压梯度很小,风场很弱,引导气流不明显。当热带气旋进入鞍型场时,会表现为停滞、打转、突然转向等异常路径。采用NCEP资料对2011年热带气旋"梅花"路径和大尺度形势场分析结果表明,在其整个生命史中出现三次移动路径转折,热带气旋进入鞍型场后,出现在鞍点附近停滞、移动缓慢、突然转向等异常路径。利用理想变形场和兰金涡旋相结合的鞍型场作为背景场,用梯度风平衡构造了理想热带气旋,分别考虑了科氏参数为常数和β平面近似两种情况,利用二维浅水模式对热带气旋处于鞍点和收缩轴附近不同位置的情况进行了数值对比试验。当科氏参数为常数时,处于鞍点位置的热带气旋在鞍点停滞;而当采用β平面近似时,处于鞍点位置的热带气旋向东北低压一侧移动,并和低压合并。当初始热带气旋处于鞍点南侧的收缩轴上以及偏东或偏西100 km时,会出现三种截然不同的移动路径。试验结果表明:鞍型场对热带气旋有"陷阱"作用。当热带气旋进入到鞍型场区并接近鞍点时,在β漂移和弱引导气流作用下,可能陷入鞍点附近区域,移动缓慢,出现异常路径,也可能沿着膨胀轴向偏东或偏西方向移动,使得热带气旋突然转向。热带气旋的移动对其和收缩轴的相对位置十分敏感,数十千米的偏差可能会导致截然相反的移动路径。 相似文献
3.
S. S. Zilitinkevich 《Boundary-Layer Meteorology》1989,46(4):367-387
The logarithmic + polynomial approximation is suggested for vertical profiles of velocity components in a planetary boundary layer (PBL) at neutral and stable stratification. The resistance law functions A and B are determined on the basis of this approximation, using integral relations derived from the momentum equations, the Monin-Obukhov asymptotic formula for the wind profile in a stably stratified near-surface layer and the known expressions for the PBL depth. This result gives a realistic and convenient method for calculating the surface friction velocity and direction and the total dissipation rate of mean flow kinetic energy in terms of geostrophic velocity, buoyancy flux at the surface, the roughness parameter and the Coriolis parameter. In the course of these derivations a review is given of current views on the main problems of the neutral and stable PBL. 相似文献
4.
The effect of equatorially trapped waves on the movement of tropical cyclones (TC) is studied numerically based on a two-dimensional barotropic model in a beta-plane approximation. According to recent studies, equatorially trapped waves contribute to the genesis of TCs. It is thus natural to assume that these waves affect also the movement of the TC. The effect of three types of equatorially trapped waves, namely Kelvin, Rossby, and n = 0 eastward inertio-Gravity (EIG) waves, on the TC trajectory is investigated with a focus on the sensitivity on some key physical parameters such as the wavenumber and wavespeed. Using a simple barotropic model forced by a prescribed baroclinic flow, the barotropic response to equatorially trapped waves is simulated for a period of 50 days, under various wave parameter configurations. This response is then used as a background flow where TC’s can evolve and propagate. TC-like flows are injected into this wavefield background at arbitrary times during the simulation, and the TC trajectories are tracked and recorded for 48h after the injection time. The resulting TC trajectory patterns with respect to the injection times and wave parameters appear to be stochastic and the mean paths and the associated standard deviations are calculated and reported here. The statistics are different for different wave types. Kelvin waves make shorter length of TC trajectories and small divergence of direction. On the contrary, Rossby waves cause rather dramatic changes in the TC path and yield longer trajectories. Meanwhile, TCs in EIG waves maintain fairly the same direction and typically have longer trajectories though less dramatic. A robustness test using a random forcing instead has also been conducted.
相似文献5.
Numerical Simulation of Changes in Tropical Cyclone Intensity Using a Coupled Air-Sea Model 总被引：1，自引：0，他引：1
A coupled air-sea model for tropical cyclones （TCs） is constructed by coupling the Pennsylvania State University/National Center for Atmospheric Research mesoscale model （MM5） with the Princeton Ocean Model.Four numerical simulations of tropical cyclone development have been conducted using different configurations of the coupled model on the f-plane.When coupled processes are excluded,a weak initial vortex spins up into a mature symmetric TC that strongly resembles those observed and simulated in prior research.The coupled model reproduces the reduction in sea temperature induced by the TC reasonably well,as well as changes in the minimum central pressure of the TC that result from negative atmosphere-ocean feedbacks.Asymmetric structures are successfully simulated under conditions of uniform environmental flow.The coupled ocean-atmosphere model is suitable for simulating air-sea interactions under TC conditions.The effects of the ocean on the track of the TC and changes in its intensity under uniform environmental flow are also investigated.TC intensity responds nonlinearly to sea surface temperature （SST）.The TC intensification rate becomes smaller once the SST exceeds a certain threshold.Oceanic stratification also influences TC intensity,with stronger stratification responsible for a larger decrease in intensity.The value of oceanic enthalpy is small when the ocean is weakly stratified and large when the ocean is strongly stratified,demonstrating that the oceanic influence on TC intensity results not only from SST distributions but also from stratification.Air-sea interaction has only a slight influence on TC movement in this model. 相似文献
6.
In the first paper in this series, a variational data assimilation of ideal tropical cyclone (TC) tracks was performed for the statistical-dynamical prediction model SD-90 by the adjoint method, and a prediction of TC tracks was made with good accuracy for tracks containing no sharp turns. In the present paper, the cases of real TC tracks are studied. Due to the complexity of TC motion, attention is paid to the diagnostic research of TC motion. First, five TC tracks are studied. Using the data of each entire TC track, by the adjoint method, five TC tracks are fitted well, and the forces acting on the TCs are retrieved. For a given TC, the distribution of the resultant of the retrieved force and Coriolis force well matches the corresponding TC track, i.e., when a TC turns, the resultant of the retrieved force and Coriolis force acts as a centripetal force, which means that the TC indeed moves like a particle; in particular, for TC 9911, the clockwise looping motion is also fitted well. And the distribution of the resultant appears to be periodic in some cases. Then, the present method is carried out for a portion of the track data for TC 9804, which indicates that when the amount of data for a TC track is sufficient, the algorithm is stable. And finally, the same algorithm is implemented for TCs with a double-eyewall structure, namely Bilis (2000) and Winnie (1997), and the results prove the applicability of the algorithm to TCs with complicated mesoscale structures if the TC track data are obtained every three hours. 相似文献
7.
Summary Current understanding of tropical cyclone (TC) structure and intensity changes has been reviewed in this article. Recent studies in this area tend to focus on two issues: (1) what factors determine the maximum potential intensity (MPI) that a TC can achieve given the thermodynamic state of the atmosphere and the ocean? and (2) what factors prevent the TCs from reaching their MPIs? Although the MPI theories appear mature, recent studies of the so-called superintensity pose a potential challenge. It is notable that the maximum intensities reached by real TCs in all ocean basins are generally lower than those inferred from the theoretical MPI, indicating that internal dynamics and external forcing from environmental flow prohibit the TC intensification most and limit the TC intensity. It remains to be seen whether such factors can be included in improved MPI approaches.Among many limiting factors, the unfavorable environmental conditions, especially the vertical shear-induced asymmetry in the inner core region and the cooling of sea surface due to the oceanic upwelling under the eyewall region, have been postulated as the primary impediment to a TC reaching its MPI. However, recent studies show that the mesoscale processes, which create asymmetries in the TC core region, play key roles in TC structure and intensity changes. These include the inner and outer spiral rainbands, convectively coupled vortex Rossby waves, eyewall cycles, and embedded mesovortices in TC circulation. It is also through these inner core processes that the external environmental flow affects the TC structure and intensity changes. It is proposed that future research be focused on improving the understanding of how the eyewall processes respond to all external forcing and affect the TC structure and intensity changes. Rapid TC intensity changes (both strengthening and weakening) are believed to involve complex interactions between different scales and to be worthy of future research.The boundary-layer processes are crucial to TC formation, maintenance, and decaying. Significant progress has been made to deduce the drag coefficient on high wind conditions from the measurements of boundary layer winds in the vicinity of hurricane eyewalls by Global Positioning System (GPS) dropsondes. This breakthrough can lead to reduction of the uncertainties in the calculation of surface fluxes, thus improving TC intensity forecast by numerical weather prediction models. 相似文献
8.
In the case study of this paper, sensitivity experiments are carried out using the mesoscale non-hydrostatic Weather Research and Forecasting (WRF) model to investigate the impact of tropical cyclone (TC) Soudelor (2003) on the East Asian subtropical upper-level jet (EASJ) before TC Soudelor transformed into an extratropical cyclone. The physical mechanism for changes in the EASJ intensity and position caused by TC Soudelor is explored. Results indicate that TC Soudelor would warm the air in the middle and upper troposphere over the Japan Sea and the adjacent areas through stimulating northward propagating teleconnection pattern as well as releasing large amounts of latent heat, which led to increase (decrease) the meridional air temperature gradient to the south (north) below the EASJ axis. As a result, the geopotential height abnormally increased in the upper troposphere, resulting in an anomalous anticyclonic circulation belt along the EASJ axis. Correspondingly, the westerly winds to the north (south) of the EASJ axis intensified (weakened) and the EASJ axis shifted northward by one degree. The case study also suggests that before the extratropical cyclone transition of TC Soudelor, the TC activities had exerted significant impacts on the EASJ through thermodynamic processes. 相似文献
9.
能量频散是一个基础性的科学问题,与台风、暴雨以及地震等灾害密切相关,一直受到多学科研究人员和广大预报员的关注。孤立圆涡能量频散波列形成过程己经清楚。但是,造成天气灾害的往往是非孤立圆涡,这里,非孤立圆涡指的是:一个热带气旋(Tropical Cyclone,TC)涡旋和一个中尺度涡构成的复杂构型。非孤立圆涡能量频散波列的形成过程研究目前尚未见报道。本文用线性化的正压无辐散涡度方程,研究了复杂构型的非孤立圆涡能量频散波列的形成过程,并指出该形成过程由三个阶段构成:涡旋东西向非对称结构的形成;涡旋主体东侧,频散高值系统的出现、持续和发展;在频散高值系统的东侧,频散低值系统的出现和加强。这些结果在台风预测中具有应用前景。 相似文献
10.
This study investigates the potential use of a regional climate model in forecasting seasonal tropical cyclone (TC) activity. A modified version of Regional Climate Model Version 3 (RegCM3) is used to examine the ability of the model to simulate TC genesis and landfalling TC tracks for the active TC season in the western North Pacific. In the model, a TC is identified as a vortex satisfying several conditions, including local maximum relative vorticity at 850?hPa with a value?≥450?×?10?6?s?1, and the temperature at 300?hPa being 1°C higher than the average temperature within 15° latitude radius from the TC center. Tracks are traced by following these found vortices. Six-month ensemble (8 members each) simulations are performed for each year from 1982 to 2001 so that the climatology of the model can be compared to the Joint Typhoon Warning Center (JTWC) observed best-track dataset. The 20-year ensemble experiments show that the RegCM3 can be used to simulate vortices with a wind structure and temperature profile similar to those of real TCs. The model also reproduces tracks very similar to those observed with features like genesis in the tropics, recurvature at higher latitudes and landfall/decay. The similarity of the 500-hPa geopotential height patterns between RegCM3 and the European Centre for Medium-Range Weather Forecasts 40 Year Re-analysis (ERA-40) shows that the model can simulate the subtropical high to a large extent. The simulated climatological monthly spatial distributions as well as the interannual variability of TC occurrence are also similar to the JTWC data. These results imply the possibility of producing seasonal forecasts of tropical cyclones using real-time global climate model predictions as boundary conditions for the RegCM3. 相似文献
11.
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. 相似文献
12.
B. S. Yurchak 《Russian Meteorology and Hydrology》2018,43(9):581-590
The spiral signatures of infrared satellite images of the tropical cyclone Phanfone observed in the Northwest Pacific in August 2002 are analyzed using the hyperbolic-logarithmic model of a streamline in the Rankine vortex. Maximum wind speed Vmax and some other physical characteristics of the cyclone are estimated by identifying hyperbolic-logarithmic spirals (RLS) which “fit” into the geometric boundaries of the signatures. The comparison of temporal variations in Vmax with the data of meteorological services of the USA (JTWC) and Japan (RSMC) revealed satisfactory agreement of the time course of tropical cyclone intensity from the HLS estimates and JTWC data. The absolute estimates of intensity were within an interval between the corresponding JTWC and RSMC data. It seems that if the presented approach is enhanced, the HLS estimation may be a useful contribution to the empirical methods of tropical cyclone intensity determination by remote sensing means. 相似文献
13.
L. M. Leslie D. J. Karoly M. Leplastrier B. W. Buckley 《Meteorology and Atmospheric Physics》2007,97(1-4):171-180
Summary Knowledge of the variability in tropical cyclone (TC) frequency and distribution is essential in determining the possible
impact of natural or human-induced climate change. This variability can be investigated using the available TC data bases
and by carrying out long-term climate model simulations for both past and future climates.
A coupled ocean-atmosphere climate model (referred to here as the OU-CGCM) is described and applied with a higher resolution
(50 km) nested domain in the southwest Pacific region. Six-member ensembles of simulations with the OU-CGCM have been run
for 80 years, from 1970 to 2050. During the period 1970–2000, the OU-CGCM runs were compared with the observed TC data base.
For the period 2000–2050, two ensembles of simulations were performed, one with constant greenhouse gas concentrations and
the second with increasing greenhouse gases.
The OU-CGCM simulated well the observed TC frequency and distribution in the southwest Pacific during the period 1970–2000.
It also produced clear interannual and interdecadal TC variability in both the fixed and enhanced greenhouse gas simulations
during the period 2000–2050. The variability in TC frequencies was associated with the typical atmospheric and SST anomaly
patterns that occur in periods of quiet and active TC frequencies.
The main findings from the enhanced greenhouse gas scenario for the period 2000–2050 are: no change in the mean decadal number
of TCs relative to the control run, but a marked increase of about 15% in the mean decadal number of TCs in the most severe
WMO categories 4 and 5; the likelihood of TCs during the next 50-year period that are more intense than ever previously experienced
in the Australian region; a poleward extension of TC tracks; and a poleward shift of over 2 degrees of latitude in the TC
genesis region. 相似文献
14.
The power dissipation index (PDI), which is defined as the sum of the cube of tropical cyclone (TC) maximum wind speed during TC lifetime, is widely used to estimate the TC destructive potential. However, due to the lack of high-resolution observations, little attention has been paid to the contribution of TC size change to TC destructive potential in response to ocean warming. In this study, sensitivity experiments are performed by using the high-resolution Weather Research and Forecasting (WRF) model to investigate the responses of TC size and TC destructive potential to prescribed sea surface temperature (SST) increase under the present climate condition. The results show that TC size increases with the ocean warming. Possible reasons for TC size change are investigated with a focus on the outer air-sea moisture difference (ASMD). As SST increases, ASMD in the outer zone of the TC is larger than that in the inner zone, which increases the surface entropy flux (SEF) of the outer zone. This change in the radial distribution of SEF causes the increase of tangential wind in the outer zone, which further increases SEF, resulting in a positive feedback between outer-zone SEF and outer-zone tangential wind. This feedback leads to the increase of the radius of gale-force wind, leading to the expansion of TC size. Moreover, to estimate the contribution of TC size change to TC destructiveness, we calculate TC size-dependent destructive potential (PDS) as the storm size information is available in the model outputs, as well as PDI that does not consider the effect of TC size change. We find that PDS increases exponentially as SST increases from 1 to 4°C, while PDI increases linearly; hence the former is soon much greater than the latter. This suggests that the growth effect of TC size cannot be ignored in estimating destructiveness under ocean warming. 相似文献
15.
Summary Tropical cyclone (TC)—ocena feedbacks are studied using a coupled tropical cyclone-ocean model consisting of an eightlayer triply-nested movable grid model of a TC and a three-layer primitive equation ocean model. The numerical results indicate that the TC-ocean interaction influences intensities, structures, and the trajectories of tropical cyclones. Two possible mechanisms, barotropic and baroclinic, influencing TC tracks under TC-ocean interaction are suggested. The barotropic mechanism is related to the changes of the vertically averaged TC structure, induced by the TC-ocean coupling. The baroclinic mechanism is related to the asymmetry of the condensation heating within the TC caused by the asymmetry of heat and moisture fluxes at the sea surface. This asymmetry arises due to the asymmetry in sea surface cooling relative to the storm center. The experiments indicate that the influence of TC-ocean interaction on the TC tracks is the greatest for the case of a zero background flow. In the case of a non-zero background flow the sensitivity of storm tracks to the coupling with the ocean decreases. It is found that the influence of the ocean coupling on the TC track is quite sensitive to the method of convective heating parameterization in the TC model. The TC-ocean interaction also results in a change of the amount and spatial distribution of precipitation. 相似文献
16.
The extratropical transition (ET) of tropical cyclone (TC) Haima (2004) was simulated to understand the impact of TC on midlatitude frontal systems. Two experiments were conducted using the Advanced Research version of the Weather Research and Forecast (WRF) model. In the control run (CTL), a vortex was extracted from the 24-hour pre-run output and then inserted into the National Centers for Environmental Prediction (NCEP) global final (FNL) analysis as an initial condition, while TC circulation was removed from the initial conditions in the sensitivity run (NOTC). Comparisons of the experiments demonstrate that the midlatitude front has a wider meridional extent in the NOTC run than that in the CTL run. Furthermore, the CTL run produces convection suppression to the southern side of the front due to strong cold advection related to the TC circulation. The easterly flow north of the TC not only decelerates the eastward displacement of the front and contracts its zonal scale but also transports more moisture westward and lifts the air along equivalent potential temperature surfaces ahead of the front. As a result, the ascending motion and diabatic heating are enhanced in the northeastern edge of the front, and the anticyclonic outflow in the upper-level is intensified. The increased pressure gradient and divergent flow aloft strengthen the upper-level jet and distort the trough axis in a northwest-southeast orientation. The thermal contrast between the two systems and the dynamic contribution related to the TC circulation can facilitate scalar and rotational frontogenesis to modulate the frontal structure. 相似文献
17.
热带气旋眼墙非对称结构的研究综述 总被引：2，自引：0，他引：2
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。 相似文献
18.
Shaoying LI Jun PENG Weimin ZHANG Jianping WU Qiang YAO Xiangrong YANG Tengling LUO 《大气科学进展》2023,40(3):464-482
The accurate forecasting of tropical cyclones(TCs) is a challenging task. The purpose of this study was to investigate the effects of a dry-mass conserving(DMC) hydrostatic global spectral dynamical core on TC simulation. Experiments were conducted with DMC and total(moist) mass conserving(TMC) dynamical cores. The TC forecast performance was first evaluated considering 20 TCs in the West Pacific region observed during the 2020 typhoon season. The impacts of the DMC dynamical core on forecasts o... 相似文献
19.
一个与卫星TBB相匹配的人造台风构造方案 总被引：6，自引：4，他引：2
在台风数值预报中需要重点考虑的问题是初值条件,特别是人造台风的构造(typhoon bogusing)在当中起着重要作用.一个新的人造台风构造方案被提出,该方案在初值中引入了较真实的台风结构,尝试利用卫星探测TBB资料来改进人造台风中对流加热的分布,确定与卫星TBB协调一致的人造台风径向环流场,这能改善风-压平衡,使得模式对强加入的人造台风更协调. 相似文献
20.
It has been challenging to project the tropical cyclone(TC) intensity,structure and destructive potential changes in a warming climate.Here,we compare the sensitivities of TC intensity,size and destructive potential to sea surface warming with and without a pre-storm atmospheric adjustment to an idealized state of Radiative-Convective Equilibrium(RCE).Without RCE,we find large responses of TC intensity,size and destructive potential to sea surface temperature(SST) changes,which is in line with some previous studies.However,in an environment under RCE,the TC size is almost insensitive to SST changes,and the sensitivity of intensity is also much reduced to 3%?C-1–4%?C-1.Without the pre-storm RCE adjustment,the mean destructive potential measured by the integrated power dissipation increases by about 25%?C-1 during the mature stage.However,in an environment under RCE,the sensitivity of destructive potential to sea surface warming does not change significantly.Further analyses show that the reduced response of TC intensity and size to sea surface warming under RCE can be explained by the reduced thermodynamic disequilibrium between the air boundary layer and the sea surface due to the RCE adjustment.When conducting regional-scale sea surface warming experiments for TC case studies,without any RCE adjustment the TC response is likely to be unrealistically exaggerated.The TC intensity–temperature sensitivity under RCE is very similar to those found in coupled climate model simulations.This suggests global mean intensity projections under climate change can be understood in terms of a thermodynamic response to temperature with only a minor contribution from any changes in large-scale dynamics. 相似文献