摘要
中尺度降水模式预报具有很大的不确定性,为更好地描述与模式降水预报密切相关的物理过程关键参数的不确定性,基于中国气象局GRAPES (Global/Regional Assimilation and Prediction System)中尺度区域集合预报模式,从对模式降水预报不确定性有较大影响的积云对流、云微物理、边界层及近地面层等4个参数化方案中选取了18个关键参数,设计了一种随机参数扰动方案(Stochastically Perturbed Parameterization,SPP),并通过2015年6—7月总计10 d的随机扰动集合预报试验,对比分析了SPP方案对不同物理过程参数扰动敏感性、随机场时、空尺度敏感性、能量变化特征及其集合预报效果。结果显示,对所选择的任一物理过程参数化方案增加SPP扰动后,降水及等压面要素的概率预报技巧优于无SPP扰动的预报,而扰动积云对流和边界层过程中的参数较扰动云微物理过程中的参数影响更显著,且同时扰动积云对流、云微物理、边界层及近地面层参数化方案中的18个参数的集合预报效果优于扰动任何单一物理过程中的部分参数,表明SPP方案能够有效地提高中尺度降水概率预报技巧;从能量变化特征可知,不同物理过程的参数扰动对动能、内能和总能量的影响层次和特征有所不同,但总体而言,扰动前后各项能量基本相同;随机场时、空尺度敏感性试验发现,SPP扰动随机场时间、空间相关尺度对集合预报效果有明显影响,当扰动随机场选用12 h抗相关时间及截断波数20时,集合预报结果最优。上述结果表明,SPP随机参数扰动方案不仅能够有效提高集合概率预报效果,还能够提高集合降水概率预报技巧,具有良好的业务应用与发展前景。
There are great uncertainties in mesoscale precipitation model forecasting. To better describe the uncertainties of key parameters in the physical processes that are closely related to model precipitation forecasting, a stochastically perturbed parameterizations (SPP) scheme consisting of temporally and spatially varying perturbations of 18 key parameters in the cumulus convection, microphysics, boundary layer and surface layer parameterization schemes has been developed in the Global and Regional Assimilation and Prediction Enhanced System-Regional Ensemble Prediction System (GRAPES-REPS) of China Meteorological Administration. Sensitivities of parameter perturbations in different physical processes, spatial and temporal decorrelation scales, as well as energy evolution characteristics and ensemble prediction performance are analyzed by conducting sensitivity experiments for 10 summer days in June and July 2015. The main conclusions are as follows. Almost all the SPP experiments with parameter perturbations in selected physical parameterization schemes exhibit higher probabilistic forecasting skill and the results are better than that without SPP in the forecast of precipitation and other variables on isobaric surfaces. It is also found that perturbing parameters in the cumulus and boundary layer schemes has more significant impacts than perturbing parameters in the microphysics scheme. Furthermore, simultaneously perturbing parameters in the cumulus, microphysics, boundary layer and surface layer parameterization schemes can yield better ensemble prediction than perturbing some of the parameters in any single parameterization scheme. This result indicates that the SPP can effectively improve the probabilistic forecasting skill for mesoscale precipitation. The characteristics of energy evolution indicate that perturbing parameters in different physical processes affects energy at different levels and with different features, but overall the SPP scheme has little influence on the internal energy, kinetic energy and total energy of the atmosphere, and the energy before and after the perturbation is basically the same. By conducting sensitivity experiments on spatial and temporal decorrelation scales of random patterns, it is found that the choice of spatial and temporal decorrelation scale of random patterns has great impact on the ensemble prediction. The optimal ensemble prediction can be obtained when choosing the temporal decorrelation coefficient of 12 h and the truncated wave number of 20 in the stochastic perturbation field. In conclusion, the SPP scheme can not only effectively improve the performance of ensemble probability prediction, but also improve the ensemble prediction skill of precipitation forecasting. Therefore, it has a promising prospect for operational application and development.
作者
徐致真
陈静
王勇
李红祺
陈法敬
范宇恩
XU Zhizhen;CHEN Jing;WANG Yong;LI Hongqi;CHEN Fajing;FAN Yuen(Chinese Academy of Meteorological Sciences,Beijing 100081,China;Numerical Weather Prediction Center,China Meteorological Administration,Beijing100081,China;Central Institute for Meteorology and Geodynamics,Vienna 1040,Austria;Chengdu University of Information Technology,Chengdu 610225,China)
出处
《气象学报》
CAS
CSCD
北大核心
2019年第5期849-868,共20页
Acta Meteorologica Sinica
基金
国家重点研发计划项目(2018YFC1507405)
国家科技支撑计划项目(2015BAC03B01)
关键词
区域集合预报
随机参数扰动方案
时间尺度
空间尺度
Regional ensemble forecast
Stochastically perturbed parameterization
Temporal decorrelation scales
Spatial decorrelation scales
