Vol.13, NO.1, 2002

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THE DEVELOPMENT AND APPLICATION OF THE OPERATIONAL ENSEMBLE PREDICTION SYSTEM AT NATIONAL METEOROLOGICAL CENTER
Li Zechun, Chen Dehui
2002, 13(1): 1-15.
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Abstract:
The basic concepts of the Ensemble Prediction System (EPS) are addressed. A brief review is given on the development and implementation of the operational EPS at National Meteorological Center (NMC): the main components and their functions of the EPS/NMC, the interpretation of the EPS’ products and the routine uses in the Weather Forecast Offices (WFO). The future development issues of the EPS, the national-wide uses of the EPS products in the provincial WFO over China are discussed.
PRESENT SITUATION AND PROSPECTS OF ENSEMBLE NUMERICAL PREDICTION
Jun Du
2002, 13(1): 16-28.
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Abstract:
Over the past few years ensemble prediction has come to the fore as a major element in defining the future of numerical weather prediction (NWP) and operational weather forecasting. This stems basically from convergence of increasing recognition of the importance of explicitly addressing the intrinsic uncertainties in forecasts (originated from both initial conditions and model physics) with rapid advance in expanding capability to provide quantitative estimates of those uncertainties. It is widely agreed that ensemble based probabilities and measures of confidence hold the best potential for enhancing the ability to make user dependent informed decisions. Indeed, the U. S. National Weather Service is requiring that many forecast products evolve to probabilistic in nature, especially for quantitative precipitation forecasting. In this paper, the basic concepts, outstanding issues and recent development of ensemble technique are briefly described, which include (1) how to establish and validate an ensemble forecasting system; (2) how to correctly represent intrinsic uncertainties in both initial conditions and model physics; and (3) how to extract useful information out of an ensemble of forecasts and how to interpret and evaluate ensemble products especially probabilistic forecasts. Besides its application to direct weather forecasting, application of ensemble technique to adaptive observation and data assimilation are also mentioned.
THE VERIFICATION FOR ENSEMBLE PREDICTION SYSTEM OF NATIONAL METEOROLOGICAL CENTER
Huangfu Xueguan
2002, 13(1): 29-36.
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Abstract:
The various diagnostics, e. g. , Talagrand probability distrbution, spread, Brier score (BS), Brier Skill score (BSS), hit rate and false alarm rate are applied to the Ensemble Prediction System (the singular vector version, 32 members) at the National Meteorological Center, Beijing, China from June to October in 2000. The comparison also is conducted between Singular Vector (SV) and Lagged Averaging Forecast (LAF) methods.
APPLICATION OF THE DISTANCE OF DISPLACEMENT AND MAXIMUM CORRELATION ON THE PRODUCTS OF ECMWF ENSEMBLE PREDICTION SYSTEM
Yang Xuesheng, Jean Nicolau, Nicole Girardot
2002, 13(1): 37-46.
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Abstract:
A new method named the Displacement and Maximum Correlation,which is used to interpret the products of ECMWF Ensemble Prediction System(EPS) automatically, is proposed. The basic assumption is that in a certain degree, the EPS members represent the future weather situations based on the conception of weather regimes defined by the forecasters of the Medium-Range Section in Meteo France. The 500 hPa geopotential height fields from ECMWF EPS are classified. It is shown that the predictability of the atmosphere is relevant to the forecast time and the weather patterns. The new classification method is succinct and intuitive, and the large amount of information contained in the EPS is condensed dramatically. The weather regimes that influence France such as warm blocked flow (BCA), cold blocked flow (BFA), straight flow (RE) and perturbation (PE) are well predicted, but the predictability for the undulating flow (OND) is relatively poor because of its variability.
THE DEVE LOPMENT OF ENSEMBLE PRODUCTS BASED ON THE SHENWEI MEDIUM-RANGE ENSEMBLE PREDICTION SYSTEM
Mao Hengqing, Chen Yi, Chen Dehui
2002, 13(1): 47-55.
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Abstract:
Based on 32 forecast members of the Shenwei Medium-Range Ensemble Prediction System and the need of operational forecast, some new ensemble products are developed. These products include the clusters of 500 hPa height trajectories, “spaghetti” charts of special 500 hPa height contours, probability “plumes” and ensemble mean charts of 850 hPa temperature, and weather element forecasts from provincial capitals of China.
THE OPERATIONAL APPLICATION OF THE SHENWEI MEDIUM-RANGE ENSEMBLE PREDICTION PRODUCTS
Mao Hengqing, Chen Yi, Chen Dehui
2002, 13(1): 56-61.
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Abstract:
The products issued by the Shenwei Medium-range Ensemble Prediction System include the ensemble mean of 500 hPa height fields, the probabilities of 850 hPa temperature anomalies, and probabilities of rainfall. The ensemble-mean of 500 hPa height fields has been used in the forecast of the Eurasia circulation pattern, the sandstorm in spring, the rain process, and the change tendency of the subtropical high in summer. The probabilities of 850 hPa temperature anomalies are very useful in the forecast of temperature change tendency and cold air processes. The probabilities of rainfall have been used by forecasters directly.
THE COMPARISON EXPERIMENTS OF SV AND LAF INITIAL PERTURBATION TECHNIQUES USED AT THE NMC ENSEMBLE PREDICTION SYSTEM
Yang Xuesheng, Chen Dehui, Leng Tingbo, Huang Zhuo
2002, 13(1): 62-66.
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Abstract:
The Ensemble Prediction System (EPS) at NMC is briefly described. It mainly includes such seven parts as the data pre-processing, optimal interpolation analysis, the forecasting model (T106L19), the computation of initial perturbations based on singular vectors, post-processing, the generation of ensemble products and the system monitoring. The configuration of EPS compromises one control forecast started from the unperturbed analysis and 31 perturbed forecasts started from the perturbed analysis. Then the lagged average forecasting (LAF) scheme with 12 members is proposed and implemented at the SW-1 computer. The comparison experiments are conducted by using different initial perturbation techniques. One is SV (singular vectors), the other is LAF. The results show that the performance of SV is better than that of LAF in most of the verified regions and lead times, both for the anomaly correlation coefficients and the root mean square errors.
CLIMATOLOGICAL CHARACTERISTICS OF MOISTURE TRANSPORT OVER YANGTZE RIVER BASIN
Xie An, Mao Jiangyu, Song Y any un, Ye Qian
2002, 13(1): 67-77.
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Abstract:
Climatological characteristics of moisture transport over the Yangtze River basin during summer monsoon are investigated based on NCEP/NCAR reanalysis data for the period of 1973—1998. The differences between drought and flood years, and especially some features of moisture transport over the Yangtze River basin in the course of flood in 1998 are examined. The results show that the characteristics of horizontal moisture transport over the Yangtze River are different from month to month. Moisture transport from the Bay of Bengal and South China is main sources of the Yangtze River basin precipitation. Droughts or floods over the Yangtze River are closely related with the onset time of summer monsoon over the South China Sea. Yangtze River basin floods chiefly resulted from the long-term maintenance of moisture transport from the South China Sea and the Bay of Bengal to the Yangtze River basin in 1998.
NUMERICAL STUDY ON CLOUD PHYSICAL PROCESSES OF HEAVY RAINFALL IN SOUTH CHINA
Wang Pengyun, Ruan Zheng, Kang Hongwen
2002, 13(1): 78-87.
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Abstract:
The heavy rainfall IOP case of the HUAMEX project during 23—24 May 1998 is simulated by using the non-hydrostatic meso-scale model MM5 (V2). Results show that the cold cloud process in which ice phase is coexisted with super-cooled liquid phase of cloud water plays the most important role in the formation and development of convective heavy rainfall in South China. The warm process (condensation and aggregation of liquid droplets) for the formation and development of rains in South China may play a role only for the non-convective precipitation with larger scale but not very strong intensity.
ANALYSIS OF ANOMALOUS FREQUENCY OF TROPICAL CYCLONE IN EAST CHINA
Jiang Leyi, Ying Ming
2002, 13(1): 88-95.
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Abstract:
Based on 1958—1997 monthly mean data of 500 hPa height and 1000 hPa wind, temperature, sea surface temperature and outgoing long-wave radiation, the features in the former autumn-winter season for anomalous frequency of tropical cyclone affecting East China are discussed with the composition analysis method. It is shown that these different features relate to the anomalous winter monsoon. Therefore, winter monsoon has influence on the frequency of tropical cyclones affecting East China. Finally, a diagnostic conceptual model is constructed. The prediction experiments are conducted and the results show that the conceptual model has reference value to forecasting the anomalous frequency of tropical cyclones.
NEW APPROACH TO DYNAMIC DATA MODELING AND ITS APPLICATION TO PRECIPITATION FORECASTING
Jia Xiaojing, Cao Hongxing, Feng Guolin
2002, 13(1): 96-101.
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Abstract:
By use of an observed data series a new dynamic data modeling has been proposed. Taking a nonlinear ordinary differential equation which is retrieved from the data series based on the bilateral difference principle as a dynamic kernel, with the self-memorization principle a forecast model can be established, which is called the DAta-based Mechanistic Self-memory Model (DAMSM). Some computing cases show that the forecasting accuracy of the DAMSM is quite satisfactory. An example of inter-annual precipitation prediction in summer in the Yangtze delta is given.
STUDY ON THE PARALLELIZATION OF METEOROLOGICAL FORECASTING MODELS WITH OPENMP AND COMPARISION TO MPI METHOD
Zhu Zhenghui, Shi Peiliang, Yan Hong
2002, 13(1): 102-108.
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Abstract:
A portable shared memory parallel application program interface (API) OpenMP is introduced. By conducting parallel experiments on a shallow water model and a nested finemesh model over the complex topography, its feasibility for the parallelization of meteorological forecasting models discussed with comparison to Message Passing Interface (MPI).
PATTERN RECOGNITION METHOD AND APPLICATION IN MEDIUM-RANGE FORECAST OF SNOW DISASTER
Chen Jing
2002, 13(1): 109-116.
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Abstract:
Combined the computer pattern recognition and the numerical weather model products, the method of pattern recognition to predict the medium-range weather processes and the process of the pattern primitive element recognition are introduced. With the NWP products of ECMWF, the concept model of medium-range forecast of snow disasters in the northwestern plateau in Sichuan Province is established. The computer imitates the thinking process of forecasters, automatically classifies and judges the different categories to determine whether a snow disaster will occur in the future 3—5 days and which day it will occur. The results of the medium-range forecast of snow disasters are rather good.
ANALYSIS ON THE SENSITIVITY OF RUNOFF IN YELLOW RIVER TO CLIMATE CHANGE
Wang Guoqing, Wang Yunzhang, Kang Lingling
2002, 13(1): 117-121.
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Abstract:
Effects of climate change on runoff in Yellow River are studied with hypothetical scenarios using the monthly hydrological model. The results show that runoff is less sensitive to temperature change but more sensitive to precipitation change, and runoff in the middle reaches is more sensitive to climate change than that in upper reaches. While temperature increases 1℃, runoff in Yellow River decreases 5%; while precipitation changes 10%, runoff changes about 17%.
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