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短期集合预报技术在梅雨降水预报中的试验研究
Experiment and Research of Short-range Ensemble Forecasting Techniques in Forecasting Meiyu Precipitation
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摘要: 数值预报的误差来源于初始场和模式的误差，集合预报技术是减小这些误差的有效方法。该文以MM5模式作为试验模式框架，模式的积云参数化方案分别取Anthes-Kuo、Grell、Kain-Fritsch和Betts-Miller方案，边界层参数化方案分别取MRF和Eta方案，通过组合4种积云参数化方案和两种边界层参数化方案产生8个集合成员，对1999年华东地区梅雨期间3个降水个例进行48 h集合预报试验。结果显示不同集合成员的预报结果各不相同，积云参数化方案对降水的影响比边界层参数化方案对降水的影响大；不同集合成员预报降水的偏差也各不相同，大多存在湿偏差，量级小的降水的湿偏差程度比量级大的降水的湿偏差程度小；对于不同个例，各成员中预报效果相对较好的成员是不同的，集合平均后可以得到一个比较稳定的预报结果；从集合预报结果中还能得到客观化和定量化的降水概率预报，它能对可能发生的天气现象发出信号。Abstract: Numerical weather prediction errors come from the initial conditions and model errors. Ensemble forecasting technique is an effective way to diminish the errors. Short-range ensemble forecasting experiments are made for three precipitation cases during the 1999 Meiyu period in the East China area. The MM5 model is used as the experimental model configuration. Eight ensemble members are created by choosing four kinds of cumulus parameterization schemes and two kinds of PBL parameterization schemes. The four kinds of cumulus parameterization schemes are Anthes-Kuo, Grell, Kain-Fritsch and Betts-Miller schemes. The two kinds of PBL parameterization schemes are MRF and Eta schemes.The resul ts indicate that different ensemble members have dif ferent forecasting result s . For the precipi tation fo recast ing results , the inf luence of cumulus parameterization scheme is larger than the influence of the PBL parameterization scheme .For the bias sco re , most ensemble members have a “wet” bias .The bias score is larger for large precipitation than that for small precipitation .The ef fects of ensemble averaging increase the bias score for small precipitation and reduce the bias sco re for large precipitation .Fo r different cases, the member w ho has the best precipitation forecasting results is not the same one .Af ter ensemble averaging , stable precipi tation fo recasting results can be got ten .Also the objective and quantitative precipitation probability fo recasts can be obtained f rom the ensemble forecasting .
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Key words:
- Ensemble forecasting;
- Meiyu;
- Precipitation
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图 1 1999年6月份3个暴雨个例08:00 24 h实况雨量分布 (mm)
(a) 个例1, 9~10日; (b) 个例1, 10~11日; (c) 个例2, 15~16日; (d) 个例2, 16~17日; (e) 个例3, 24~25日; (f) 个例3, 25~26日
图 3 1999年6月3个暴雨个例的6 h发生0.1 mm以上和10 mm以上降水的TS评分 (集合平均预报:粗实线成员1:实线成员2:长虚线成员3:短虚线成员4:长短虚线成员5:点线成员6:点虚线成员7:点点虚线成员8:粗短虚线)
(a) 个例1(0.1 mm), (b) 个例1(10 mm), (c) 个例2(0.1 mm), (d) 个例2(10 mm), (e) 个例3(0.1 mm), (f) 个例3(10 mm)
图 4 集合预报的1999年6月3个暴雨个例08:00的24 h降水概率分布
(a) 个例1(10~11日), 降水量大于0.1 mm; (b) 个例1(10~11日), 降水量大于50 mm; (c) 个例2(15~16日), 降水量大于100 mm; (d) 个例3(25~26日), 降水量大于100 mm
表 1 集合预报成员的构成
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[1] Brooks H E, Stensrud D J, Doswell C A. Application of short-range NWP model ensembles to severe storm forecasting. Preprints, 18th Conf. Severe Local Storm, San Francisco, Amer. Meteor. Soc., 1995. [2] Brooks H E, Cortinas J V, Janish P R, et al. Application of short-range numerical ensembles to the forecasting of hazardous winter weather. Preprints, 11th Conf. on Numerical Weather Prediction, Norfolk, Amer. Meteor. Soc., 1996. 70～71. [3] Hamill T M, Colucci S J. Eta/RSM ensemble usefulness for short-range forecasting. Preprints, 11th Conf. On Numerical Weather Prediction, Norfolk, Amer. Meteor. Soc., 1996. 43～45. [4] Hamill T M, Colucci S J. Verification of Eta-RSM short-range ensemble forecasts. Mon. Wea. Rev., 1997, 125: 1312～1327. [5] Du J , Mullen S L, Sanders F .S hort-range ensemble forecast ing of quantit at ive precipit at ion .Preprin ts , 11th Conf .on Numerical Weather Prediction , Norfolk , Amer.Met eor .Soc., 1996 .46～49 . [6] Du J , Mullen S L , Sanders F.S hort-range ensemble forecast ing (SREF)of quantit ati ve precipitation .Mon .Wea . Rev ., 1997 , 125 :2427～2459 . [7] S tensrud D J , Bao J W , Warner T T .Using init ial condition and model physics perturbat ions in short-range ensem ble simulations of mesoscale convecti ve systems .Mon .Wea .Rev ., 2000 , 128 :2077～2107 . [8] Mesoscale and Microscale Meteorology Division .PSU/ NCAR Mesoscale Modeling System Tu torial Class Not es and User' s Guide :MM5 Modeling System Version 2 .NCAR T echnical Note , June 1999 . -
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