The Establishment and Verification of the Operational Ensemble Forecast System for Shanghai Regional Precipitation

Wang Chenxi; Yao Jianqun; Liang Xudong

Vol.18, NO.2, 2007

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Article Navigation > Journal of Applied Meteorological Science > 2007 > 18(2): 173-180

Wang Chenxi, Yao Jianqun, Liang Xudong. The establishment and verification of the operational ensemble forecast system for Shanghai regional precipitation. J Appl Meteor Sci, 2007, 18(2): 173-180.

Citation:

Wang Chenxi, Yao Jianqun, Liang Xudong. The establishment and verification of the operational ensemble forecast system for Shanghai regional precipitation. J Appl Meteor Sci, 2007, 18(2): 173-180.

Wang Chenxi, Yao Jianqun, Liang Xudong. The establishment and verification of the operational ensemble forecast system for Shanghai regional precipitation. J Appl Meteor Sci, 2007, 18(2): 173-180.

Citation:

Wang Chenxi, Yao Jianqun, Liang Xudong. The establishment and verification of the operational ensemble forecast system for Shanghai regional precipitation. J Appl Meteor Sci, 2007, 18(2): 173-180.

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The Establishment and Verification of the Operational Ensemble Forecast System for Shanghai Regional Precipitation

1.
Shanghai Typhoon Institute, Laboratory of Typhoon Forecast Technique, CMA, Shanghai 200030
2.
Shanghai Meteorological Center, Shanghai 200030

Received Date: 2005-12-19
Rev Recd Date: 2006-10-19
Publish Date: 2007-04-30

Abstract

Abstract

The operational ensemble forecast system for Shanghai regional precipitation is established. The model is based on MM5 in the system, with a one way two nesting procedure. The coarse grid domain of 101×101 grid points has a horizontal grid spacing of 45 km, while the inner grid domain of 70×70 grid points has a horizontal grid spacing of 15 km. Both domains have 21 vertical sigma levels. Eight different configurations of MM5 are used to produce an 8 member ensemble forecast. The approach to generating eight members is to use different convective parameterization schemes and different PBL parameterization schemes of the inner grid domain. In this system, all steps from data collection, data processing and model running to output automatically are carried out by computer. The system starts operating on August 1, 2005. The system operates twice everyday and each time it runs to 48 h forecast. The forecasts are then displayed on Website. Since the start of the operation, the system has shown stability and reliability. The forecasts from August to October are verified in the fields of ensemble mean, probabilistic forecast and spread. The results show the ensemble means of precipitations of low thresholds are more skillful than the ensemble means of precipitations of high thresholds. For precipitations of low thresholds, the larger the forecasting probability is, the larger the usefulness of probabilistic forecast is. For precipitations of high thresholds, the smaller the forecasting probability is, the larger the usefulness of probabilistic forecast is. The results also show the system has the problem of too small spread. In conclusion, the performance of the system is alright in forecasting precipitation. The precipitation forecasts of low thresholds seem better than the forecasts of high thresholds. The products of the system, especially the products of probability forecasts can be used as a reference. However, there are still some problems in the system, which should be improved in the future.
- ensemble prediction system;
- precipitation;
- verification

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References(14)

Figures and Tables

图 1 2005年8月和9月08:00起报的0~24 h集合平均对4个不同量级以上降水的ETS评分

Fig. 1 ETSs of 0—24 h ensemble mean precipitation from 08:00 ensembles in August anDseptember of 2005 for four thresholds

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图 2 2005年8月08:00起报的0~24 h集合平均与各成员对中雨 (a) 和大雨 (b) 以上降水的ETS评分

Fig. 2 ETSs of 0—24 h ensemble mean and each member precipitation from 08:00 ensemble in August of 2005 for the 10 mm threshold (a) and 25 mm threshold (b)

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图 3 2005年8月和9月08:00与20:00起报的0~24 h与24~48 h集合平均对4个不同量级以上降水的预报可信度

Fig. 3 Skillful percent of 0—24 h and 24—48 h ensemble mean precipitation from 08:00 and 20:00 ensembles in August anDseptember of 2005 for four thresholds

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图 4 2005年8月08:00与20:00起报的0~24 h与24~48 h对小雨 (a)、中雨 (b)、大雨 (c) 和暴雨 (d) 以上降水不同预报概率对应的ETS评分

Fig. 4 ETSs of 0—24 h and 24—48 h precipitation probability from 08:00 and 20:00 ensembles in August of 2005 for the 0.1 mm threshold (a), 10 mm threshold (b), 25 mm threshold (c) and 50 mm threshold (d)

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图 5 2005年8月08:00与20:00起报的0~24 h与24~48 h对小雨 (a)、中雨 (b)、大雨 (c) 和暴雨 (d) 以上降水不同预报概率对应的预报可信度

Fig. 5 Skillful percent of 0—24 h and 24—48 h precipitation probability from 08:00 and 20:00 ensembles in August of 2005 for the 0.1 mm threshold (a), 10 mm threshold (b), 25 mm threshold (c) and 50 mm threshold (d)

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图 6 2005年8月和10月08:00与20:00起报的所有测站0~24 h与24~48 h降水的平均D/D_s

Fig. 6 D/D_s of 0—24 h and 24—48 h precipitation from 08:00 and 20:00 ensembles in August and October of 2005

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图 7 2005年8月和10月08:00与20:00起报的所有测站0~24 h与24~48 h降水的Talagrand分布

Fig. 7 Talagrand diagrams of 0—24 h and 24 — 48 h precipitation from 08:00 and 20:00 ensembles in August and October of 2005

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表 1 系统集合成员的构成

Table 1 The formation of ensemble members of the system

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