霍振华,李晓莉,陈静,刘永柱. 2021. GRAPES全球模式静力平衡奇异向量改进及应用试验[J]. 气象学报, (0):-, doi:10.11676/qxxb2021.009
GRAPES全球模式静力平衡奇异向量改进及应用试验
The improved computation scheme of singular vectors based on the hydrostatic equilibrium and the related application experiments with the GRAPES global model
投稿时间:2020-06-28  修订日期:2020-08-24
DOI:10.11676/qxxb2021.009
中文关键词:  奇异向量,静力平衡关系,GRAPES模式,集合预报
英文关键词:singular  vectors, hydrostatic  equilibrium, GRAPES  model, ensemble  forecasts
基金项目:国家自然科学基金项目(41805081)
作者单位E-mail
霍振华 国家气象中心 hzh11hzh@126.com 
李晓莉 国家气象中心 lixl@cma.gov.cn 
陈静 国家气象中心 chenj@cma.gov.cn 
刘永柱 国家气象中心 liuyzh@cma.gov.cn 
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中文摘要:
      [背景] 采用线性化物理过程方案的GRAPES全球模式奇异向量(Singular Vectors,SVs)初始扰动在进行非线性模式积分时会有部分成员出现崩溃问题,这说明SVs结构可能存在扰动变量之间不协调之处,需要对奇异向量扰动的计算方法优化,[目的] 进而改进基于奇异向量的集合预报初值扰动,提高GRAPES全球集合预报效果。[资料和方法] 基于原有的GRAEPS全球SVs计算方法,在求解SVs时,对气压扰动的处理进行改进,将初始时刻的气压扰动分量通过位温扰动根据静力平衡关系导出获得,其它保持一致,发展了静力平衡奇异向量改进方法。基于有两个台风过程的个例(2019年8月8日12 UTC),分别采用原奇异向量方法和静力平衡奇异向量改进方法进行热带气旋目标区SVs的计算求解,并进行相应奇异向量初始扰动的非线性模式积分,对比分析SVs初始扰动非线性积分的稳定性。进而,对比分析奇异向量求解方法改进前后热带气旋奇异向量的结构特征和初值扰动特征,开展了集合预报试验,评估改进后的奇异向量求解方法对GRAPES全球集合预报系统预报性能的影响。[结果/结论] 试验结果表明,静力平衡奇异向量改进方法,通过产生协调的气压扰动和位温扰动场,解决了奇异向量初始扰动非线性积分崩溃的问题,消除了原来不利于积分稳定性的气压扰动过于局地化的小尺度结构。静力平衡奇异向量改进方法对奇异向量中位温扰动分量和纬向风扰动分量结构影响较小,使得气压扰动分量的的大值区位于台风附近,更好地描述热带气旋初值不确定性,与位温扰动分量的分布更为协调。采用静力平衡奇异向量改进方法,可以提高GRAPES全球集合预报在北半球和南半球等压面要素集合预报技巧和中国地区24小时累计降水概率预报技巧,增加台风路径集合离散度。
英文摘要:
      The singular vectors (SVs) based on the linearized physical processes have been applied in the Global and Regional Assimilation PrEdiction System (GRAPES) global ensemble forecast system to generate the initial perturbations. However, for the nonlinear integration of the initial perturbations of SVs, some members may break down occasionally. This means that there may exist discordance between different perturbed varaibles and the computation method of SVs should be improved, which could further improve the SVs-based initial perturbations and the GRAPES global ensemble forecasts. Based on the original computation scheme for the GRAPES global SVs, when computing SVs, the pressure perturbation component at the initial time is obtained through the potential temperature perturbation component according to the hydrostatic equilibrium relation, and others remain the same. The tropical cyclone SVs (TCSVs) are sensitive to the linearized physical processes, so based on one case with two typhoon processes (the initial time is 12 UTC at August 8, 2019), the TCSVs are computed separately with the original SVs computation scheme and the improved computation scheme of SV based on the hydrostatic equilibrium, and the nonlinear integrations of the initial perturbations of TCSVs are given to analyze the stability of the nonlinear integrations for the initial perturbations of TCSVs. Further the structure characters of the TCSVs and the initial perturbations are analyzed, the ensemble forecasting experiments are conducted, and the influence of the improved computation method of SVs on the GRAPES global ensemble prediction skills. The experiments show that the improved computation method of SV based on the hydrostatic equilibrium solves the breakdown problem of the nonlinear integrations of the initial perturbations of SVs, and eliminates the original small-scale structure which is too local and may result in the nonlinear integration instability, through generating the coordinated pressure perturbation and potential temperature perturbation. The improved computation method of SV based on the hydrostatic equilibrium has small effect on the structures of potential perturbation and zonal wind perturbation, makes the maximum values of pressure perturbation locate near the tropical cyclone, which could better describe the initial uncertainty of the tropical cyclone and make the pressure perturbation and the potential temperature perturbation more coordinating. With the improved computation method of SV based on the hydrostatic equilibrium for the GRAPES global ensemble forecasts, the Northern and Southern isobaric variables ensemble forecasts and the probability forecast skill of 24 hour accumulated precipitation in China is increased, and the tropical cyclone track ensemble spread is increased.
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