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1.
一次爆发性气旋的发展与湿位涡关系的研究 总被引：13，自引：3，他引：13
通过对一次陆地爆发性气旋的数值模拟与湿位涡的诊断分析发现，气旋的爆发与湿位涡的平流关系密切，气旋的发展并不是在湿位涡中心位于气旋上空时才开始，而是当湿位涡中心位于气旋的后部，并在200hPa对下有明显的倒圆锥形下伸区时，才有利于气旋的发展。当湿位涡中心位于气旋上空时，气旋发展开始减慢。湿位涡局地变化的大小与水平方向位涡梯度的大小有关。湿斜压位涡负值区的上下贯通与气旋发展也有明显的关系。 相似文献
2.
The singular vector (SV) initial perturbation method can capture the fastest-growing initial perturbation in a tangent linear model (TLM). Based on the global tangent linear and adjoint model of GRAPES-GEPS (Global/Regional Assimilation and Prediction System—Global Ensemble Prediction System), some experiments were carried out to analyze the structure of the moist SVs from the perspectives of the energy norm, energy spectrum, and vertical structure. The conclusions are as follows: The evolution of the SVs is synchronous with that of the atmospheric circulation, which is flow-dependent. The moist and dry SVs are located in unstable regions at mid-to-high latitudes, but the moist SVs are wider, can contain more small- and medium-scale information, and have more energy than the dry SVs. From the energy spectrum analysis, the energy growth caused by the moist SVs is reflected in the relatively small-scale weather system. In addition, moist SVs can generate perturbations associated with large-scale condensation and precipitation, which is not true for dry SVs. For the ensemble forecasts, the average anomaly correlation coefficient of large-scale circulation is better for the forecast based on moist SVs in the Northern Hemisphere, and the low-level variables forecasted by the moist SVs are also improved, especially in the first 72 h. In addition, the moist SVs respond better to short-term precipitation according to statistical precipitation scores based on 10 cases. The inclusion of the large-scale condensation process in the calculation of SVs can improve the short-term weather prediction effectively. 相似文献
3.
以发展基于奇异向量技术为初值扰动的GRAPES全球集合预报系统为目的,在GRAPES模式及其干动力框架下的切线性、伴随模式基础上开展了以总能量模为权重算子的奇异向量计算技术研究,建立奇异向量的计算求解模块,并通过奇异向量检验方法和切线性近似方法验证了奇异向量求解的正确性.通过对中高纬度的GRAPES奇异向量水平结构的线性演变分析,证实了在最优时间间隔内GRAPES奇异向量能够快速增长,并能描述中高纬度大气的斜压不稳定特征.分析在初始时刻和最优化时间间隔时刻的GRAPES奇异向量总能量及其分量(动能和势能)的垂直分布特征,发现在中高纬度区域,GRAPES奇异向量能够描述对流层不同层次的斜压不稳定增长特征. 相似文献
4.
伴随技术是四维变分同化（4DVar）系统中计算代价函数梯度的最佳办法,切线性和伴随模式的效果和效率直接影响着4DVar系统的发展。基于GRAPES（Global and Regional Assimilation PrEdiction System）全球切线性和伴随模式1.0版本,利用GRAPES全球模式2.0版本在并行框架和性能等方面的改善,重新优化和设计了GRAPES全球切线性伴随模式2.0版本,提高了GRAPES全球切线性和伴随模式的效果和效率,优化了切线性模式程序结构,使其计算时间最优可控制在非线性模式的1.2倍以内;采用在切线性模式中保存基态的方法,重构了伴随模式的程序结构,使其计算时间最优控制在非线性模式的1.5倍以内;在GRAPES全球切线性物理过程的设计中,将线性物理过程的轨迹基态计算和切线性扰动计算解耦,提高了GRAPES全球切线性和伴随模式的计算效果和效率。 相似文献
5.
《大气与海洋》2013,51(4):423-443
Abstract The sensitivity of forecast errors to initial conditions obtained from the adjoint of a numerical weather prediction model provides new insights into the analysis errors responsible for poor short‐range to mediumrange forecasts. In recent years, we have developed a sensitivity analysis system based on the tangent linear and adjoint of the Global Environmental Multiscale model, in which an iterative procedure minimizing the shortrange forecast errors leads to the so‐called key analysis errors. These errors are dominated by a small number of atmospheric structures, those growing the most rapidly. The algorithm has proven very useful in understanding improvements to the three‐dimensional variational data assimilation (3D‐Var) system implemented in the Canadian Meteorological Centre operational suite in December 2001. The main difference between the old and the new 3D‐Var systems is the assimilation of temperature and surface pressure from surface and upper air stations as opposed to geopotential heights, additional Tiros Operational Vertical Sounder channels, new sources of observations such as temperature observations from aircraft, and wind and temperature from dropsondes. In this paper, we examine key analysis errors of the old 3D‐Var analysis, which led to a very poor 3‐day forecast of a severe winter storm that struck eastern Canada on 10 February 2001. In this case, the same 3‐day forecast from the new 3D‐Var analysis is much better. We compare the difference between the two 3D‐Var analyses and the key analysis errors. We find that the main key analysis errors, in terms of potential vorticity, is located along the west shore of southern California and is characterized by a strong baroclinic structure that has its maximum amplitude in the upper part of the troposphere. The difference between the two analyses is three times more energetic than the key analysis errors and its structure is much more barotropic in the troposphere. However, we show that the large improvement in the new 3D‐Var analysis stems mainly from the reduction of the analysis errors that project onto the key analysis structures. 相似文献
6.
Using the data of ECMWF (European Center for Medium-range Weather Forecasts) to undertake composite diagnoses of 16 explosive cyclones occurring at the Atlantic and the Pacific Oceans,it is found that there are a lot of obvious discrepancies on the basic fields between these strong and weak explosive cyclones.The major reasons why the explosive cyclones over the Atlantic are stronger than those over the Pacific Ocean are that the non-zonal upper jet and the low-level warm moist flow over the Atlantic are stronger.The non-zonal upper jet offers stronger divergence,baroclinicity and baroclinic instability fields for explosive cyclones.Anticyclonic curvature at the high level of strong explosive cyclones is easy to make the inertia-gravitational wave developing at the moment of northward transfer of energy and stimulate the cyclones deepening quickly.Warm advection and diabatic heating can cause the upper isobaric surface lifting,as a result,the anticyclone curvature of cyclones enlarges,and wave energy develops easily as well.The most powerful period of the development of explosive cyclones is just the time when the positive vorticity advection center is located over the low vortex.At the upper level,when the distribution of potential vorticity contours changes suddenly from rareness to denseness,and the large values of the potential vorticity both in the west and north sides of cyclones extend downwards together,then cyclones are easy to explosively develop.The formation of strong explosive cyclones is closely related with the non-zonality of upper jet and the anticyclonic curvature. 相似文献
7.
Sei-Young Park Hyun Mee Kim Tae-Young Lee Michael C. Morgan 《Meteorology and Atmospheric Physics》2013,120(3-4):107-122
To investigate the statistical sensitivity distributions of tropical cyclone (TC) forecasts over the Korean Peninsula, total energy (TE) singular vectors (SVs) were calculated and evaluated over a 10-year period. TESVs were calculated using the fifth-generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5) and its tangent linear and adjoint models with a Lanczos algorithm over a 48-h period. Chosen cases were 21 TCs that affected the Korean Peninsula among 230 TCs that were generated in the western North Pacific from 2001 to 2010. Sensitive regions indicated by TESVs were mainly located near mid-latitude troughs and TC centers but varied depending on TC track and environmental conditions such as subtropical high and mid-latitude trough. The cases were classified into three groups by clustering TC tracks based on the finite mixture model. The two groups that passed through the western and southern sea of the Korean Peninsula had maximally sensitive regions in the mid-latitude trough and largely sensitive regions around the TC center, while the other group that passed straight through the eastern sea of the Korean Peninsula had maximally sensitive regions near the northeastern region of the TC center. Vertically, the former two clustered groups had the westerly tilted TESVs and potential vorticity structures under the mid-latitude troughs at the initial time, indicating the TCs were in a baroclinic environment. Conversely, the straight-moving TCs were not in a baroclinic environment. Based on the results in the present study, the TCs moving toward a fixed verification region over the Korean Peninsula have different sensitivity regions and structures according to their moving tracks and characteristic environmental conditions, which may provide guidance for targeted observations of TCs affecting the Korean Peninsula. 相似文献
8.
MOIST POTENTIAL VORTICITY DIAGNOSIS OF A MEIYU FRONTAL HEAVY RAIN PROCESS SIMULATION DURING SUMMER,1991 
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下载免费PDF全文 In this paper,the heavy rain process from June 30 to July 2,1991,has been simulated by MM4.and three-dimensional moist potential vorticity distribution of the simulation results has beencalculated.It is shown that moist potential vorticity is an important physical variable to reveal heavyrain structure and dynamic mechanisms.Negative moist potential vorticity corresponds to the Meiyufront-wind shear line system and the negative center corresponds to the heavy rain center.Negativemoist potential vorticity mainly attributes to the effects of meridional baroclinic term and convectiveunstable term.The former is favourable to the maintenance of zonal precipitation and the latter is themechanism of the heavy rain center propagating along the rain belt.The heavy rain is contributed bythe cooperative effects of conditional convective instability,baroclinic instability and upper air inertialinstability. 相似文献
9.
MOIST POTENTIAL VORTICITY DIAGNOSIS OF A MEIYU FRONTAL HEAVY RAIN PROCESS SIMULATION DURING SUMMER, 1991 下载免费PDF全文
下载免费PDF全文 In this paper,the heavy rain process from June 30 to July 2,1991,has been simulated by MM4.and three-dimensional moist potential vorticity distribution of the simulation results has been calculated.It is shown that moist potential vorticity is an important physical variable to reveal heavy rain structure and dynamic mechanisms.Negative moist potential vorticity corresponds to the Meiyu front-wind shear line system and the negative center corresponds to the heavy rain center.Negative moist potential vorticity mainly attributes to the effects of meridional baroclinic term and convective unstable term.The former is favourable to the maintenance of zonal precipitation and the latter is the mechanism of the heavy rain center propagating along the rain belt.The heavy rain is contributed by the cooperative effects of conditional convective instability,baroclinic instability and upper air inertial instability. 相似文献
10.
基于WRF四维变分伴随模式建立数值预报敏感初始误差计算流程并对台风北冕 (0809) 进行了分析。结果表明:基于线性化近似的伴随敏感分析方法对台风系统在24 h内适用。构造敏感初始误差的参考系数存在一个合理的取值范围,参考系数取为0.08效果最好。在初始场中去除敏感初始误差能够有效减少预报误差,改善台风路径预报效果,依据24 h预报误差计算出的敏感初始误差订正对24 h后台风数值预报效果也有明显影响。另外,敏感初始误差分布在台风中心附近,伴随台风系统环流且各物理量分布形态相似。对流层下层和中上层的敏感初始误差均对数值预报效果有所影响,对流层中上层的作用略大于对流层下层。敏感初始误差中各物理量对数值预报改善的贡献各不相同,相对而言,风场的贡献最大。 相似文献
11.
The development mechanisms of the explosive cyclone that occurred during 3–4 April 2012 over East Sea (Sea of Japan) are examined through numerical simulation and sensitivity experiments using the Weather and Research Forecasting (WRF) model. The characteristics of this explosive cyclone are different from typical cyclonic features observed in this region, including its intensity, deepening rate, and formation time. Numerical simulation, reanalysis data, upper and surface weather charts, and satellite data indicate that the strong baroclinic instability and temperature advection associated with upper-level cut-off low and the interaction of potential vorticity (PV) anomalies between the lower- and upper-level are essential to explosive cyclogenesis.The sensitivity experiments of the explosive cyclone show that latent heat release (LHR) is an important factor in explosive cyclogenesis. The intensification, extent, and movement speed of the cyclone are amplified by LHR as well as the formation of an upper-level cut-off low. The role of LHR is primary important in the generation and evolution of the cyclone. Especially, the LHR contributes to roughly 50% of decrease in sea level pressure (SLP) and 50% of the central cyclone’s low-level PV generation in initial stage. During a 48-h simulation, the contributions of the LHR, surface heat flux, and their interaction on the decrease of SLP of the cyclone are found to be 40.6, −8.2, and 10.5%, respectively. These results reveal that the explosive cyclone has larger deepening rates than OJ cyclones, and develops with a large amount of LHR near the cyclone center. 相似文献
12.
Regional-Eta-Coordinate-Model(REM)中尺度模式对中国区域性降水显示出公认的较高预报能力,建立其四维变分资料同化系统是完善该模式,进一步提高其预报效果的重要工作。本研究编写了REM模式的切线性模式和伴随模式,介绍了建立REM模式伴随系统的过程,并利用实际天气个例资料,分别对REM模式的切线性模式、伴随模式及定义的目标函数梯度进行了正确性检验,检验结果表明对REM模式的切线性模式及伴随模式编写是成功的。利用REM模式的伴随系统,对1998年06月08日00时到09日00时和2000年08月01日00时到02日00时两个实际天气个例进行了四维变分资料同化试验。从数值试验的结果分析可以看到,进行四维变分资料同化后,两个天气个例在预报结束时刻其预报结果对风场和湿度场的预报都有明显改善,对温度场和高度场的预报也有所改善。对于累积降水的预报,两个个例利用四维变分资料同化后得到的初始场进行的预报结果则有较大不同,在个例1中,变分同化后对降水中心的位置和降水强度的预报都有明显改善,预报结果更接近于观测场;个例2中,变分同化后对降水中心位置和强度的预报则没有改善,产生这种现象的原因可能是由于定义的目标函数中没有加进背景场项,也可能是由于采用的观测资料时次比较少,还需要进一步进行研究和试验。 相似文献
13.
The Regional Eta-coordinate Model(REM) has performed well in forecasting heavy rainfalls in China in recent years.A four-dimensional variational assimilation system(4DVar) is developed to improve the forecast skill of the REM.The tangent linear model and adjoint model codes are written according to thecode to coderule,and the establishment of the REM adjoint modeling system is introduced in detail in this paper.The tangent linear and adjoint models of the REM are validated against the observational data,... 相似文献
14.
《气象科学》2014,(2)
Based on diagnostic analysis of reanalysis data for 58-year,the distribution characteristics of decadal variability in diabatic heating,transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature(SST)anomalies over the North Pacific,as well as their relationship with anomalous atmospheric circulation have been investigated in this paper.A linear baroclinic model(LBM)was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies,and then to compare relative roles of different kinds of forcing in terms of geopotential height responses.The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic.The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow,as well as to the vertical profile of heating.The response to the idealized deep heating over the eastern North Pacific,mimicking the observed heating anomaly,is baroclinic.The atmospheric response to the mid-latitude vorticity forcing is always barotropic,resulting in a geopotential low that is in phase with the forcing.The atmospheric responses to the realistic heat and vorticity forcing show the similar results,suggesting that diabatic heating,transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies. 相似文献
15.
Mid-latitude atmospheric responses to heat and vorticity forcing using a linear baroclinic model 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 Based on diagnostic analysis of reanalysis data for 58-year, the distribution characteristics of decadal variability in diabatic heating, transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature (SST) anomalies over the North Pacific, as well as their relationship with anomalous atmospheric circulation have been investigated in this paper. A linear baroclinic model(LBM) was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies, and then to compare relative roles of different kinds of forcing in terms of geopotential height responses. The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic. The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow, as well as to the vertical profile of heating. The response to the idealized deep heating over the eastern North Pacific, mimicking the observed heating anomaly, is baroclinic. The atmospheric response to the mid-latitude vorticity forcing is always barotropic, resulting in a geopotential low that is in phase with the forcing. The atmospheric responses to the realistic heat and vorticity forcing show the similar results, suggesting that diabatic heating, transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies. 相似文献
16.
台风暴雨作为台风引起的最主要灾害之一,一直被人们关注。台风常被认为是对称结构,但从实际状况来看台风的非对称性非常明显,所以有必要研究斜压性涡度在台风中的表现。在高分辨率数值模拟的基础上,通过引入斜压涡度的概念,分析和总结了斜压涡度在2009年台风“莫拉克”暴雨过程中的表现。通过模拟与分析得到如下的结果:斜压涡度和MPV对比,可以看出在登陆前和登陆后,明显低层斜压涡度有更强的异常信号,围绕台风内核呈现正负正的位相特点;从沿着台风中心时间剖面可以看出,登陆前斜压涡度低层多为负正负的位相,并且随着时间的推移,斜压涡度有从大气的高层向台风的移动中心传递的趋势,即在台风即将到达时原先的正涡度被替换为负涡度,所以对其移动有一定指示意义;在台风“莫拉克”过台湾岛时,其斜压涡度表现为负涡度消失,在山地附近有正涡度生成,完成过岛,台风中心被替换;斜压涡度的异常值主要位于大气的低层时,一般会产生较强的降水。 相似文献
17.
七十年代,谢义炳教授指出:湿大气动力学和干大气动力学特征有明显差异。结合我们的天气实践,注意到经常造成鄂北强降水的西南低涡处于对流层低层,在这一层次内不仅流场辐合明显,而且水汽丰沛,空气为强烈的对流性不稳定,这些因子对低涡的生消移动必然有较大的影响。本文的目的是,引入水汽因子后,通过简化涡度方程在湿斜压大气中的应用,并考虑湿静力稳定度σ_m既为P的函 相似文献
18.
Summary Linearization and adjoint-model derivation for the solar radiation transfer codes in the NMC spectral model have been carried out. Verification of the validity of resulting tangent linear model and the correctness of the corresponding adjoint have been performed. Applications of derived adjoint model are considered, including parameter estimation for inputs to solar radiation codes with aid of the physics (i.e., the solar radiation codes) and a sensitivity study of the downward solar radiation flux at the earth surface with respect to water vapor amount at various heights.With 5 Figures 相似文献
19.
In this study, the characteristics of moist potential vorticity （MPV） in the vicinity of a surface cyclone center and their physical processes axe investigated. A prognostic equation of surface absolute vorticity is then used to examine the relationship between the cyclone tracks and negative MPV （NMPV） using numerical simulations of the life cycle of an extratropical cyclone. It is shown that the MPV approach developed herein, i.e., by tracing the peak NMPV, can be used to help trace surface cyclones during their development and mature stages. Sensitivity experiments are conducted to investigate the impact of different initial moisture fields on the effectiveness of the MPV approach. It is found that the lifetime of NMPV depends mainly on the initial moisture field, the magnitude of condensational heating, and the advection of NMPV. When NMPV moves into a saturated environment at or near a cyclone center, it can trace better the evolution of the surface cyclone due to the conservative property of MPV. It is also shown that the NMPV generation is closely associated with the coupling of large potential temperature and moisture gradients as a result of frontogenesis processes. Analyses indicate that condensation, confluence and tilting play important but different roles in determining the NMPV generation. NMPV is generated mainly through the changes in the strength of baroclinicity and in the direction of the moisture gradient due to moist and/or dry air mass intrusion into the baroclinic zone. 相似文献
20.
Structures of adjoint sensitivities to potential vorticity for specific initial and final norm are investigated for a short-range cyclone forecast in a three-dimensional quasigeostrophic (QG) model. Moreover, adjoint sensitivities to potential vorticity are compared with nonlinear sensitivities calculated for the same cyclogenesis case in the QG model. The adjoint sensitivities using different initial and final norms (e.g., total QG disturbance energy and potential enstrophy) show approximately similar characteristics for the horizontal and vertical structures and evolutions. Consistent with previous studies, the horizontal structure of the adjoint sensitivity is smaller for the energy norm than for the potential enstrophy norm. The dynamical mechanism of cyclone development by adjoint sensitivity coincides with that of nonlinear sensitivity, with slight differences in the region of sensitivity maxima over the upstream (nascent) low for the adjoint (nonlinear) sensitivity. The adjoint sensitivities show different vertical distributions from the nonlinear sensitivities. Consistent with the sensitive regions denoted by singular vectors and error evolution in the QG model, maxima of the adjoint sensitivities are located at both the upper and lower boundaries, with prominent secondary peaks in the lower to mid-troposphere of the domain. The level of the secondary maxima changes depending on the initial and final norm used. The secondary peak is located in the lower to mid- (mid-) troposphere for the total QG disturbance energy (potential enstrophy) as the initial and final norm. Based on the correspondence in the level of the sensitivity maxima in the interior of the domain between the adjoint and nonlinear sensitivities, adjoint sensitivities may serve as an alternative to nonlinear sensitivities given the enormous computing expenses in nonlinear sensitivity calculation. 相似文献