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Search Results: 1 - 10 of 103573 matches for " ZHANG Daomin "
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An Approach to Extract Effective Information of Monthly Dynamical Prediction-The Use of Ensemble Method

Yang Hui,Zhang Daomin,Ji Liren,
Yang Hui
,Zhang Daomin,Ji Liren

大气科学进展 , 2001,
Abstract: The approach of getting useful information of monthly dynamical prediction from ensemble forecasts is studied. The extended range ensemble forecasts (8 members, the initial perturbations of the lagged average forecast (LAF)(0000, 0600, 1200 and 1800 GMT in two consecutive days) of the 500 hPa height field with the global spectral model (T63L16) from January to May 1997 are provided by the National Climate Center of China. The relationship between the spread of ensemble measured by root-mean-square deviation of ensemble member from ensemble mean and forecast skill (the anomaly correlation or the root-mean-square distance between the ensemble mean forecast and the observation) is significant. The spread of ensemble can evaluate the useful forecast days N for the best estimate of 30 days mean. Thus, a weighted mean approach based on ensemble spread is put forward for monthly dynamical prediction. The anomaly correlation of the weighted monthly mean by the ensemble spread is higher than that of both the arithmetic mean and the linear weighted mean. Better results of the monthly mean circulation and anomaly are obtained from the ensemble spread weighted mean.
Development and Test of Hydrostatic Extraction Scheme in Spectral Model
Zhang Daomin,Sheng Hua,Ji Liren,
Zhang Daomin
,Sheng Hu,Ji Liren

大气科学进展 , 1990,
Abstract: The introduction of “hydrostatic extraction” scheme, or “standard stratification approximation”, into spectral model gained some advantages compared with commonly used schemes. However, computational instability may occur for high vertical resolution versions if the stratification parameterC 0 taken as a constant. In this paper, the possible cause leading to the instability is discussed and an improved scheme presented whereC 0 is generalized to be a function of both height and latitudes. Hence the reference atmosphere gets closer to the real atmosphere and the temperature deviation field to be expanded becomes smoother everywhere. Test by real case forecasts shows good computational stability of the new scheme and better prediction performance than usual schemes of spectral model. This work has been carried out under the support of the Medium-range Numerical Weather Forecast research project.
A Study of Information on the Extraction to Reduce Errors in Dynamic Extended (Monthly) Numerical Weather Prediction

Zhang Daomin,Ji Liren,

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.
张道民 Zhang Daomin,纪立人 Ji Liren
大气科学 , 2001, DOI: 10.3878/j.issn.1006-9895.2001.06.05
Abstract: 用一个全球谱模式通过较多个例的月数值天气预报试验,研究了预报结果的有用信息提取问题.模式预报误差的谱分析表明,纬向平均(零波)场误差占很大比例,试验了两种用气候倾向改善纬向平均(零波)场误差的方案,一是对逐日预报结果进行订正,二是在积分过程中进行订正,两种方案都取得了一定成效.
Systematic Errors of Zonal-Mean Flow in Dynamical Monthly Prediction and Its Improvement

CHEN Bomin,JI Liren,YANG Peicai,ZHANG Daomin,
CHEN Bomin
,JI Liren,YANG Peicai,ZHANG Daomin

大气科学进展 , 2003,
Abstract: An analysis of a large number of cases of 500 hPa height monthly prediction shows that systematicerrors exist in the zonal mean components which account for a large portion of the total forecast errors, andsuch errors are commonly seen in other prediction models. To overcome the difficulties of the numericalmodel, the authors attempt a "hybrid" approach to improving the dynamical extended-range (monthly)prediction. The monthly pentad-mean nonlinear dynamical regional prediction model of the zonal-meangeopotential height (wave number 0) based on a large amount of data is constituted by employing thereconstruction of phase-space theory and the spatio-temporal series predictive method. The dynamicalprediction of the numerical model is then combined with that of the nonlinear model, i.e., the pentad-mean zonal-mean height produced by the nonlinear model is transformed to its counterpart in the numericalmodel by nudging during the time integration. The forecast experiment results show that the above hybridapproach not only reduces the systematic error in zonal mean height by the numerical model, but alsomakes an improvement in the non-axisymmetric components due to the wave-flow interaction.
Zhu Baozhen,Chen Jiabin,Zhang Daomin,Li Zechun,Ge Aifen,
Zhu Baozhen
,Chen Jiabin,Zhang Daomin,Li Zechun,Ge Aifen

大气科学进展 , 1984,
Abstract: A 5-layer primitive equation Northern Hemisphere operational model in a modified σ-coordinate system is developed in BMC, NMB. Finite difference schemes are constructed to conserve the total energy without imposing any constraints on the difference scheme of hydrostatic equation and pressure gradient term.The physical factors of orography, friction, horizontal diffusion and various non-adiabatic heatings are included.The model has been under development since the beginning of 1980, and became operational in September 1981. Preliminary results for selected series of 40 prognosis are summarized and the verifications are encouraging.
Infrared Remote Observation of the Vertical Distribution of Atmospheric Humidity

Li Chongyin,Zhang Daomin,Zeng Qingcun,

大气科学 , 1976,
Abstract: 本文讨论了在气象卫星上用红外方法遥测大气湿度垂直分布的几个基本问题。分析了红外测湿和红外测温的原则区别,指出遥测湿度垂直分布应根据其特殊性按“最佳信息层”概念选择遥测通道,国外笼统地把测温的一套办法搬到测湿中并不合理。根据湿度遥测的“最佳信息层”概念,分析了红外测湿的重要局限。
Comparison of global and hemispheric versions of a spectral model

Zhang Daomin,Ji Liren,Wu Wanli,

大气科学 , 1990,
Abstract: 本文将标准层结扣除下的谱模式用全球、北半球和全球、北半球交替方案对春、夏、秋、冬共5个实例做了5天的预报试验,比较了它们的预报结果,并做了一些理论分析。
Seasonal Variability and Systematical Error in Dynamical Extended Range Forecast Experiments with the IAP Global Spectral Model

Zhang Daomin,Ji Liren,Li Jinlong,

大气科学 , 1997,
Abstract: 本文用中国科学院大气物理研究所的全球谱模式(T42L9)和国家气象中心提供的1994年3月到1995年2月36个例子(每月3个)的全球客观分析资料做了较系统的动力延伸(月)预报试验,检验了预报结果,分析了模式的气候漂移,并对预报结果进行了系统误差订正,结果表明预报评分有明显的季节变化,冬季较高,夏季较低,动力预报高度距平相关系数北半球各个季节的平均都明显高于持续性预报和气候预报。
An Experimental Study on Monthly Numerical Weather Prediction

Zhang Daomin,Ji Liren,Li Jilong,

大气科学 , 1996,
Abstract: Experiments of monthly dynamical extended-rang prediction with the global spectralmodel developed by Lab II, IAP are performed. The results show that the 30-day mean 500 hPa heightforecasts are obviously superior not only to the persistence but also to climate forecasts. In this paper,we also discuss how to get a better monthly mean height forecast from day-by-day prediction, whichindicates that forecast skill is enhanced markedly when weighted mean forecast is used instead of arithmetic one.
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