共查询到20条相似文献,搜索用时 218 毫秒
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积云对流参数化对一交梅雨锋暴雨过程影响的模拟检验 总被引:12,自引:10,他引:2
应用1988年版日本谱模式JSM,对比分析了Arakawa-Sckawa-Schubert、Kain-Fritsch、KuoAnthes和Gadd-Keers等几种积云对流参数化方案在梅雨锋暴雨对流系统模拟中的表现。 相似文献
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介绍了Spencer P L和Stensrud D J关于下曳气流在暴洪中作用的模拟结果。Spencer和Stensrud利用Kain-Frisch对流参数化方案及其3种修改方案即最大降水效率方案(MPE)、无下曳气流方案(NDD)和滞后下曳气流方案(DDD)对暴洪个例进行模拟试验。结果表明:利用种修改了的对流参数化方案模拟出的24h最大降水量的结果与未修改的最大降水量均比实测的小,但是DDD所模 相似文献
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修正的ECMWF质量通量积去参数化方案的预报试验 总被引:1,自引:4,他引:1
用一个有限区域业务预报模式,以1995年7-8月西北地区几次大范围的降水天气过程为试验个例,对经过修改的ECMWF质量通量积云参数化方案和模式中的原Kuo型积云型数化方程进行了13例48h的批量对比预报试验。 相似文献
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非绝热物理过程在模拟飑线系统中β尺度结构中的作用 总被引:1,自引:0,他引:1
利用经改进的中尺度模式,对一次飑线过程进行了多种对流参数化和显式水汽方案及地面加热过程的敏感性试验,结果表明中尺度对流性天气系统的成功预报,不仅取决于次网格尺度对流,而且取决于可分辨尺度相变过程及地面加热引起的边界层日变化。计入湿下沉的Fritsch-Chappell对流参数化方案和计入可分辨尺度凝结蒸发冻结融化等相变过程的预诊性显式方案的结合使用,对于真实模拟飑线等中尺度对流系统和减少或消除与中尺度涡旋及其降水过度加强相联系的类CISK不稳定是十分必要和有效的。 相似文献
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澳大利亚气象局热带分析预报系统的动力张弛逼近初值化方案Davidson.N.EPuri.K.1引言近年来中纬度地区的数值天气预报能力在稳定提高,然而低纬度地区的预报改善甚少。其主要原因归因于如下几个方面:1)低纬度数值预报对于参数化对流加热的四维结构... 相似文献
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蒸发—风反馈机制的进一步研究 总被引:2,自引:0,他引:2
对蒸发-风反馈的作用进行了简单动力学研究。结果表明,蒸发-风反馈不能像波动-CISK那样改变热带大气波动的性质,不可能单独成为激发热带大气内振荡的动力学机制。在积云对流加热的蒸发-风反馈的共同作用下,CISK-Kelvin波和CISK-Rossby波可以不稳定发展,共同作用比单独和积云对流加热反馈作用能更全面合理地解释热带大气内振荡的活动。 相似文献
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Mauro Dall’Amico Lesley J. Gray Karen H. Rosenlof Adam A. Scaife Keith P. Shine Peter A. Stott 《Climate Dynamics》2010,34(2-3):381-398
In most climate simulations used by the Intergovernmental Panel on Climate Change 2007 fourth assessment report, stratospheric processes are only poorly represented. For example, climatological or simple specifications of time-varying ozone concentrations are imposed and the quasi-biennial oscillation (QBO) of equatorial stratospheric zonal wind is absent. Here we investigate the impact of an improved stratospheric representation using two sets of perturbed simulations with the Hadley Centre coupled ocean atmosphere model HadGEM1 with natural and anthropogenic forcings for the 1979–2003 period. In the first set of simulations, the usual zonal mean ozone climatology with superimposed trends is replaced with a time series of observed zonal mean ozone distributions that includes interannual variability associated with the solar cycle, QBO and volcanic eruptions. In addition to this, the second set of perturbed simulations includes a scheme in which the stratospheric zonal wind in the tropics is relaxed to appropriate zonal mean values obtained from the ERA-40 re-analysis, thus forcing a QBO. Both of these changes are applied strictly to the stratosphere only. The improved ozone field results in an improved simulation of the stepwise temperature transitions observed in the lower stratosphere in the aftermath of the two major recent volcanic eruptions. The contribution of the solar cycle signal in the ozone field to this improved representation of the stepwise cooling is discussed. The improved ozone field and also the QBO result in an improved simulation of observed trends, both globally and at tropical latitudes. The Eulerian upwelling in the lower stratosphere in the equatorial region is enhanced by the improved ozone field and is affected by the QBO relaxation, yet neither induces a significant change in the upwelling trend. 相似文献
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An Improved Velocity Volume Processing Method 总被引:3,自引:0,他引:3
Velocity volume processing (VVP) retrieval of single Doppler radar is an effective method which can be used to obtain many wind parameters. However, due to the problem of an ill-conditioned matrix arising from the coefficients of equations not being easily resolved, the VVP method has not been applied adequately and effectively in operation. In this paper, an improved scheme, SVVP (step velocity volume processing), based on the original method, is proposed. The improved algorithm retrieves each group of components of the wind field through a stepwise procedure, which overcomes the problem of an ill-conditioned matrix, which currently limits the application of the VVP method. Variables in a six-parameter model can be retrieved even if the analysis volume is very small. In addition, the source and order of errors which exist in the traditional method are analyzed. The improved method is applied to real cases, which show that it is robust and has the capability to obtain the wind field structure of the local convective system. It is very helpful for studying severe storms. 相似文献
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A method for selecting optimal initial perturbations is developed within the framework of an ensemble Kalman filter (EnKF). Among the initial conditions generated by EnKF, ensemble members with fast growing perturbations are selected to optimize the ENSO seasonal forecast skills. Seasonal forecast experiments show that the forecast skills with the selected ensemble members are significantly improved compared with other ensemble members for up to 1-year lead forecasts. In addition, it is found that there is a strong relationship between the forecast skill improvements and flow-dependent instability. That is, correlation skills are significantly improved over the region where the predictable signal is relatively small (i.e. an inverse relationship). It is also shown that forecast skills are significantly improved during ENSO onset and decay phases, which are the most unpredictable periods among the ENSO events. 相似文献
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INFLUENCE OF INTERACTION BETWEEN LOW AND MIDDLE LATITUDES ON ENSO VARIABILITY IN THE CANE-ZEBIAK MODEL* 下载免费PDF全文
Ni Yunqi 《Acta Meteorologica Sinica》1996,10(2):160-174
In this paper,an error source in the atmospheric component of the CZ(Cane-Zebiak) model is discussed,which is missing a free mode in "the exact solutions".However,the improved scheme is proposed,which is the computational scheme with adjusted wind or observed u and v as lateral boundaries.The simulations show that the simulated surface wind by the improved scheme strongly bears resemblance to the observation except for the area near the west and the east boundaries of the integrated area.These results support the conclusion that the wind stress simulated by the improved scheme with lateral boundaries is much better than that simulated by the CZ model,and show that interaction between low and middle latitudes has an important influence on the ENSO variability in the CZ model.Therefore,considering its impact on the CZ model can improve capability of the CZ model for simulating ENSO variability. 相似文献
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A computational scheme for an improved Mellor–Yamada(M–Y) Level-3 model with condensation physics is proposedand its performance is examined against large-eddy-simulationdata on radiation fog. The improved M–Y model greatlycorrects several shortcomings of the original M–Y model:the underestimations of the mixed-layer depth and themagnitude of turbulent kinetic energy, and the discrepanciesin the formation and dissipation times of the fog. Inaddition the improved M–Y model can reproduce theoccurrence of Kelvin–Helmholtz instability and periodicoscillations due to its energy cycle. It is shown that theoptimization of both the closure constants and the masterlength scale is required for this improvement.The improved M–Y model has an improvement also in theLevel-2.5 version. Although the performance of theLevel-2.5 version is not so good as that of the Level-3version, the former has the advantage of relatively lowcomputational cost and is popularly used in operationalweather forecasts. Our computational scheme for theimproved M–Y model allows us to switch its hierarchylevels easily according to the purpose. 相似文献
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Nonlinear stability criteria for quasi-geostrophic zonally symmetric flow are improved by establishing an optimal Poincar′e inequality. The inequality is derived by a variational calculation considering the additional invariant of zonal momentum. When applied to the Eady model in a periodic channel with finite zonal length, the improved nonlinear stability criterion is identical to the linear normal-mode stability criterion provided the channel meridional width is no greater than 0.8605· · · times its channel length (which is the geophysically relevant case). 相似文献
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介绍了小波变换和维纳滤波相结合的图像小波域维纳滤波去噪算法,在分析该算法最小均方误差期望的基础上提出一种改进算法。指出在进行维纳滤波之前,阈值化处理可以有效提高维纳滤波的性能。用标准测试图像的处理结果来比较改进前后两种算法的效果。 相似文献
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文章推导出了改进的大气声散射截面σ(θ)表达式,确定了大气声散射系数αs的解析表达式,并得出改进的大气声折射指数脉动结构系数c2n表达式。实测结果表明,在潮湿大气中,湿度脉动和温湿相关脉动与温度脉动一样是影响声散射衰减的重要因子,而在干燥大气中,湿度脉动的影响可以忽略。 相似文献
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An urban boundary layer model (UBLM) is improved by
incorporating the effect of buildings with a sectional drag coefficient and
a height-distributed canopy drag length scale. The improved UBLM is applied
to simulate the wind fields over three typical urban blocks over the Beijing
area with different height-to-width ratios. For comparisons, the wind fields
over the same blocks are simulated by an urban sub-domain scale model
resolving the buildings explicitly. The wind fields simulated from the two
different methods are in good agreement. Then, two-dimensional building
morphological characteristics and urban canopy parameters for Beijing are
derived from detailed building height data. Finally, experiements are
conducted to investigate the effect of buildings on the wind field in
Beijing using the improved UBLM. 相似文献
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IVAP和扩展VAP技术是在常用的VAD和VAP技术基础上发展起来的单Doppler雷达风场反演技术.在IVAP和扩展VAP技术基础上,进一步改进IVAP技术,将IVAP技术反演假定从局地均匀扩展到局地风速均匀、风向随方位角线性变化,进而提高IVAP技术的反演能力.使用涡旋流场试验表明,改进后的IVAP技术对于风速稳定,而风向变化的风场的反演能力有明显提高.由于改进后的IVAP技术保持了IVAP技术反演时可不对原始资料进行平滑预处理,对于小尺度扰动具有滤波作用,其应用更为广泛. 相似文献