AMDAR资料在北京数值预报系统中的同化应用
Assimilation Application of AMDAR Data to the Operational NWP System of Beijing
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摘要: 该文针对北京市气象局业务快速更新循环同化预报系统 (BJ RUC),通过对有无飞机观测资料参加同化的预报试验客观要素预报均方根误差和降水量TS评分的对比分析,探讨了飞机观测资料对短期数值天气预报的影响。结果表明:飞机观测资料的同化对于前9 h预报时效内的高空风和温度预报有明显的正面影响。其中,对风预报的正面影响集中在925~250 hPa高度上;而对温度预报的正面影响主要体现在850~400 hPa之间的各层内。在快速更新循环的暖启动模式下,飞机观测资料同化比冷启动模式下带给预报结果更明显的正面贡献。飞机观测资料参加同化对于降水预报技巧的提高也有正面效应,对24 h和12 h累积降水量TS评分以及12~18 h和18~24 h时段内的6 h累积降水TS评分有明显提高,提高的最大幅度达50%,并对相应阈值和时段内无飞机观测资料参加同化的试验中雨区偏大现象有改善。分析增量分布特征与同化带来的风温要素3 h预报改进的垂直特征基本对应,表明飞机观测资料参加同化对初始场中风场和温度场质量的改进。Abstract: AMDAR data has been widely proved valuable in improving accuracy of numerical weather forecast. But assimilation application of AMDAR data in operational NWP model is seldom accessed in China. BJ RUC, the operational rapid update and cycling NWP system of Beijing Meteorological Bureau, is used to evaluate the impacts of assimilating AMDAR data on forecast performance. Durative experiments with and without AMDAR data are conducted from 15 Jul to 15 Aug, 2007. The average RMSE difference and average precipitation scores difference of AMDAR and NOAMDAR experiments are compared to discuss the impacts of AMDAR on short range numerical weather forecast.Analysis shows that the assimilation of aircraft data has remarkable positive impacts on the first 9 hours forecast especially on upper levels. Forecasts of wind on the levels of 925 hPa to 250 hPa and temperature on the levels of 850 hPa to 400 hPa are improved. The assimilation of AMDAR data contributes more in rapid updated cycle mode than in cold start mode. It has positive impacts on the threshold score of accumulated precipitation forecast of 0—12 hours, 0—24 hours, 12—18 hours, and 18—24 hours. It also improves the overestimating in the NOAMDAR experiments. The increment analysis shows parallel characteristics with the horizontal distribution of AMDAR data and the vertical improvement characteristic of the 3 hours forecast. The comparability indicates the improvement of wind and temperature in first guess field made by assimilating AMDAR data. The relative observation errors of AMDAR against Beijing radiosonde are discussed and proved reliable. It suggests that determining AMDAR observation errors properly in assimilation can help make better use of AMDAR data.Experiments on AMDAR data assimilating application in the operational BJ RUC system show that AMDAR assimilating has important positive impacts on improving the upper temperature, wind and precipitation forecast. Reasonable amendment of observation errors will bring more efficient utilization of AMDAR data, so priority is assigned to adjusting the AMDAR observation errors in BJ RUC.
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Key words:
- AMDAR;
- data assimilation;
- numerical weather prediction
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图 1 2007年7月15日-8月15日飞机观测数据分布
(a)7月15日12:00 27 km区域空间分布,(b) D3区域资料平均高度分布,(c) D3区域资料时间分布
Fig. 1 AMDAR distribution from 15 July to 15 August 2007
(a) AMDAR spatial distribution in domain of 27 km resolution at 12:00 15 Jul 2007, (b) averaged vertical distribution of AMDAR data in D3, (c) averagedtemporal distribution of AMDAR data in domain of D3
图 3 冷启动模式 (a,b) 和暖启动模式 (c,d) 模式下风速 (a,c) 和温度 (b, d)6 h预报均方根误差在2007年7月15日-8月15日针对北京探空站的平均垂直廓线
Fig. 3 Vertical profile of averaged root mean square error of wind (a, c) and temper ature (b, d)6-hour valid forecast within the duration of 15 Jul to 15 Aug 2007 under cold start mode (a, b) and warm start mode (c, d) respectively
表 1 2007年8月1日不同时次D2和D3同化系统读入和同化的飞机观测资料数目
Table 1 Input and assimilated AMDAR report of different time on 1 Aug 2007 in D2 and D3
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