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Search Results: 1 - 10 of 22923 matches for " 纪立人 Ji Liren "
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Analysis of the Dependence of Predictability on Spatial and Temporal Scales from Operational Forecasts
实际预报可预报性的时空依赖性分析

Li Zhijin,Ji Liren,
李志锦
,立人

大气科学 , 1996,
Abstract: The 1--day through 5--day forecasts of the 500 hPa height field made at the National Meteorological Center of China from the 1st January 1990 to the 29th February 1992 are used to examine the predictability of the spectral coefficients of spherical harmonics and empirical orthogonal functions (EOFs) The analysis of spherical harmonics that the predictability does not increase monotonically with the increase of spatial scales, but the predictability is largest when total wave number n is about 5. The predictability dramatically depends on total wave number n, so zonal wave number and wave number a long the Merifional large circle are equally important. It is found through the examination of the EOFs that the predictability tends to decrease with the increase of the EOF index. The spherical harmonic decomposition of the EOFs shows that the leading EOFs consist of the spherical harmonics which are more predictable. It is also confirmed that the most predictable components are characterized by slow evolution. These results are importat to the application of forecast products and to extended--range forecasting.
The forcing of steady perturbation in summer by diabatic heating and orographic effect of the Qinghai-Xizang Plateau
夏季青藏高原动力和热力的强迫定常扰动

Xu Feiya,ji Liren,
徐飞亚
,立人

大气科学 , 1985,
Abstract: 本文应用一个球面和σ坐标原始方程线性定常模式,模拟夏季青藏高原的动力和热力强迫作用下的定常扰动.计算得到的定常扰动,在对流层上层槽脊分布和实况基本相符,但南亚高压的位置稍偏东,中太平洋高空槽较弱.在对流层中层计算的扰动振幅较实况强,特别是西太平洋副高.对偏差的可能原因进行了讨论.文中比较了不同基本气流、热源的垂直分布和热力耗散的影响,结果表明不同的热源垂直分布可以影响定常扰动的位相分布;还指出线性模式中,随高度增强的热力耗散机制对解释定常扰动的位相和结构可能是重要的.
Observational study of dipole blocking in the atmosphere
大气中偶极子阻塞的观测研究

Luo Dehai,Ji Liren,
罗德海
,立人

大气科学 , 1991,
Abstract: In this paper, the 5-day mean 500 hPa geopotential height maps were used to carry out a statistical study on dipole blocking in the Northern Hemisphere during 1969 to 1984, and the seasonal and geographical variation of dipole blocking was discussed. Also the latitude distribution of dipole blocking was discussed and some useful results were obtained.
A Study of Information on the Extraction to Reduce Errors in Dynamic Extended (Monthly) Numerical Weather Prediction
动力延伸(月)数值天气预报中的信息提取和减小误差试验

Zhang Daomin,Ji Liren,
张道民
,立人

大气科学 , 2001,
Abstract: A number of monthly numerical weather prediction cases based on a global spectral model have been used to study the extraction of useful information in the predicted results. Spectral analysis of model prediction errors shows that the zonal symmetric part (" wave-number zero" ) accounts for a large portion of the total error. Using climatic tendency, two approaches have been tested to reduce this part of error. The first is to correct the final forecast result by replacing the zonal symmetric component by its climatic counterpart. The second is to proceed the correction of this part during the integration pro- cess. Both approaches prove effective.
Atmospheric Teleconnection Pattern over the Northern Hemisphere Connected with the Activity of the Asian Summer Monsoon
亚洲夏季风活动激发的北半球大气环流遥相关型

Li Weibiao,Ji Liren,
黎伟标
,立人

大气科学 , 1997,
Abstract: 亚洲季风区是全球热力变化最为显著的区域,亚洲夏季风活动必定会对其它环流系统产生影响。本文通过夏季风指数与北半球环流的相关计算以及强、弱季风候北半球环流异常合成的分析发现,亚洲夏季风的活动会激发北半球夏季大气环流遥相关型,其主要相关中心均出现在季风区的下游地区,即从亚洲经太平洋至北美洲一带,除了表现出正负中心交替出现的波列状结构外,该遥相关型在太平洋地区还表现为一对南北向的偶极子异常型,我们将这一遥相关型称为亚洲太平洋北美(APN)型。
The Application of the Digital Filtering Method in Monthly Numerical Weather Prediction. Part I: The Impact of Filtering the Initial Field
数字滤波方法在月尺度数值预报中的应用 I. 初始场滤波的作用

Yang Yan,Ji Liren,
杨燕
,立人

大气科学 , 1997,
Abstract: 本工作将数字滤波方法用于T42L9谱模式的月预报实验。为了去除高频扰动误差的影响,保留对月预报有意义且可预报性较强的低频过程,用滤波器对观测资料的序列进行处理,得到10天以上的低频分量作为初始场进行预报。结果说明,与不进行滤波的控制实验相比,误差增长明显减慢,预报效果在10~20天时段内提高最显著。进一步分析表明,延伸预报效果随时间的变化主要是由其中低频分量的预报效果决定的。初始场滤波后预报效果的提高也主要是由于其低频分量报得更好,而在此低频背景下新产生出来的高频扰动误差也相应较小,因而总体的预报效果好于控制实验。而如果在控制实验预报后提取低频分量进行检验,则对逐日预报的改进不明显。经过初始场滤波后对1~10天至1~30天平均场的预报也有较显著的提高。对旬平均预报改进最大的是在第二个10天。对500 hPa环流形势的预报也更接近实际。本工作的结果说明,在中长期预报中如果能用适当的方法提取出低频过程的信息,则可望提高预报水平。
Preferred Perturbations of Growth in the Barotropic Atmosphere and Dynamics of Teleconnection
正压大气有利发展扰动型与遥相关型的建立

Li Zhijin,Ji Liren,
李志锦
,立人

大气科学 , 1995,
Abstract: The goal of this study is to determine whether the generation of teleconnection patterns can resultsolely from the internal barotropic processes of the zonally varying climatoloical flow in the northern summer. The results of analysis of normal modes indicate that the growth rate of unstable normal modes is insufficient to explain the generation of realistic teleconnection patterns. Then, a concept of preferred Perturbation of growth is introduCed. An approach to find the prefeed perturbances of growth is described in detail. The results of calculations show that the amplification rate of the leading preferred perturbations of growth is consistent with that of realistic teleconnection patterns. Moreover,they evolve into the structure of realistic teleconnection patterns. The preferred perturbation of growth possesses highly localized spatial structures with the wavetrain appearance, most of them are localized to the south of regions of the jet cores. It is suggested that at least some of teleconnection patterns can form as a consequence of internal barotiopic processes of the zonally asymmetrical basic state , but de pend on the preferred perturbations of growth, which have larger growth rate than that of unstable normal modes.
Mechanisms of the atmospheric Teleconnection Associated with the Activity of the Asian Summer Monsoon. Part II: Optimal Forcing and Atmospheric Responses
亚洲夏季风活动激发北半球大气遥相关的物理机制探讨 II.最优强迫模及其响应

Li Weibiao,Ji Liren,
黎伟标
,立人

大气科学 , 1999,
Abstract: The external mechanism by which the activity of the Asian summer monsoon (ASM) develops the atmospheric teleconnection is investigated by using the methods of the complete orthonormal forcing mode. It is found that, during boreal summe the most optimal forcing modes are mainly centered over the ASM region, and exhibiting similar features to the anomalous OLR related to the activity of the ASM. Moreover, the atmospheric responses to the most optimal forcing bear much resemblance to the anomalous circulation patterns lagging behind the strong monsoon pentads. These results suggest that, as an optimal forcing, the thermal variation in the ASM region can lead to the atmospheric teleconnection over the Northern Hemisphere.
Mechanisms of the Atmospheric Teleconnection Associated with Activity of the Asian Summer Monsoon. Part I: Analyses of the Normal Modes and the Finite-Time Unstable Singular Vectors
亚洲夏季风活动激发北半球大气遥相关的物理机制探讨 I.正规模及有限时间不稳定奇异矢量分析

Li Weibiao,Ji Liren,
黎伟标
,立人

大气科学 , 1999,
Abstract: 造成大气环流异常的原因可以有两个方面, 一是大气内部的物理过程,另一方面则可能由大气外强迫引起。在线性框架内,该文的第I部分利用正规模(normal mode)以及有限时间不稳定奇异矢量(singular vectors)理论,对亚洲夏季风(ASM)活动激发北半球夏季遥相关型的大气内部物理机制进行了探讨。结果表明,亚洲季风区的扰动最有效地激发了它下游地区不稳定模态的发展,从而导致了从亚洲到北美洲一带的大气环流异常。关于从大气外强迫角度对这一问题的探讨,将在本文的第II部分发表。
The Application of the Digital Filtering Method in Monthly Numerical Weather Prediction. Part II:_The Comparison of the Forecast Skill with the Different Low Frequency Processes
数字滤波方法在月尺度数值预报中的应用 II. 保留不同低频过程的效果比较

Yang Yan,Ji Liren,
杨燕
,立人

大气科学 , 1997,
Abstract: 用数字滤波方法对观测资料序列进行处理,得到初始场用于T42L9全球谱模式的月预报,以去除误差增长较快的高频扰动对低频过程的影响,并且利用多时刻的观测资料提取低频过程的信息。对冬季和夏季两个不同个例进行了实验,并比较了取不同长度的观测序列,截取不同周期的过程作为初值对预报效果的影响。结果说明,经过滤波后对低频分量和平均场的预报都有较显著的改进。而且对于较长时效的预报,应保留更低频的过程(比如10 d以上周期)。最显著的改进是在第2旬。冬季个例经过滤波的初始场在第2旬对北太平洋阻塞形势的预报能力有较明显提高。
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