彭飞,李晓莉. 2019. GRAPES全球集合预报系统模式扰动随机动能补偿方案初步探究[J]. 气象学报, (0):-, doi:10.11676/qxxb2019.009
GRAPES全球集合预报系统模式扰动随机动能补偿方案初步探究
A Stochastic Kinetic Energy Backscatter Scheme for Model Perturbations in the GRAPES Global Ensemble Prediction System
投稿时间:2017-11-23  修订日期:2018-04-18
DOI:10.11676/qxxb2019.009
中文关键词:  GRAPES全球集合预报,模式扰动,随机动能补偿方案,局地动能耗散率
英文关键词:GRAPES global ensemble prediction, Model perturbations, Stochastic Kinetic Energy Backscatter (SKEB) Scheme, Local kinetic energy dissipation rate
基金项目:中国气象局公益性行业科研专项(GYHY201506005)、国家科技支撑计划课题(2015BAC03B01)
作者单位E-mail
彭飞 国家气象中心 pengf@cma.cn 
李晓莉 国家气象中心 lixl@cma.gov.cn 
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中文摘要:
      为了体现次网格尺度能量升尺度转换过程中存在的不确定性,本文将随机动能补偿(Stochastic Kinetic Energy Backscatter,SKEB)方案应用于GRAPES(Global/Regional Assimilation and Prediction System)全球集合预报系统(GRAPES-GEPS)中,以更好的表征模式误差并且增加集合离散度。本文使用的SKEB方案基于具有一定时空相关特征的随机型以及由数值扩散导致的局地动能耗散率来构造随机流函数强迫。并根据流函数与水平风速旋转分量之间的关系,将SKEB方案中的流函数强迫转化为适用于GRAPES全球模式的水平风速扰动。研究结果表明,SKEB方案的使用一方面能够提高GRAPES模式对大气动能谱的模拟能力;另一方面能够改善GRAPES-GEPS的集合离散度与集合平均误差之间的关系,增加了集合离散度,并在一定程度上减小了集合平均误差,尤其是在热带地区这种改进最为显著。而且该方案使得热带地区连续分级概率评分(CRPS评分)显著减小。就降水预报而言,从Brier评分与相对作用特征面积AROC(Area under the Relative Operating Characteristics)的结果来看,SKEB方案有助于改善中国地区小雨(>=0.1mm/24h)、中雨(>=10mm/24h)与大雨(>=25mm/24h)量级降水的概率预报技巧,而对暴雨(>=50mm/24h)量级降水预报技巧影响很小。总体上,模式扰动随机动能补偿方案提高了GRAPES-GEPS的概率预报技巧。
英文摘要:
      For describing uncertainties in the subgrid-scale energy upscaling transfer, a Stochastic Kinetic Energy Backscatter (SKEB) scheme was introduced into the Global/Regional Assimilation and Prediction System (GRAPES) global ensemble prediction system (GEPS), so as to represent model errors more reasonably and increase the ensemble spread. In this research, the SKEB scheme employed the stochastic patterns with temporally and spatially correlated characteristics along with the estimated local kinetic energy dissipation rates caused by numerical diffusion to construct the stochastic streamfunction forcing. Then, according to the relationship between the streamfunction and the rotational component of horizontal winds, the streamfunction forcing in the SKEB scheme was transformed into the horizontal wind perturbations, which were suitable for the GRAPES global model. The results indicated that on the one hand the application of the SKEB scheme improved the simulations of the atmospheric kinetic-energy spectra in the GRAPES model; and on the other hand it led to a better spread-error relationship, increased the spread of the ensemble and reduced the root-mean-square error of the ensemble mean to some extent and in the tropics the improvement was the most pronounced. This scheme also contributed to a significant improvement of the continuous rank probability score (CRPS) in the tropics. In terms of precipitation forecast, the results from the Brier score and Area under the Relative Operating Characteristics (AROC) showed that the SKEB scheme helped to improve probabilistic forecast skills of rainfall in China for light rain (>=0.1mm/24h), moderate rain (>=10mm/24h)and heavy rain (>=25mm/24h); however, it played little role in the forecast of rainstorm (>=50mm/24h). On the whole, the introduction of the SKEB scheme ameliorated the probabilistic prediction skills of the GRAPES-GEPS.
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