风压平衡关系对高分辨率区域模式地面资料同化的影响分析

Analysis of the Impact of Mass–Wind Balance Relationships on Surface Data Assimilation of High Resolution Regional Model

中文关键词:  高分辨率区域模式同化  多重网格方法  风压平衡约束关系

英文关键词:high-resolution regional model assimilation  multigrid method  Mass–wind balance constraints

中文摘要:

      随着模式分辨率的提高，数值模式可分辨的短波信息增加，以地转平衡为基础的风压平衡约束关系，不能完全满足低纬度地区及对流尺度高分辨率模式资料同化的需求。本文提出了基于多重网格方法构建1km分辨率数值模式变分同化风压平衡约束关系的方案，基于GRAPES（Global Regional Assimilation and PrEdiction System）三维变分（Three-Dimensional Variational Data Assimilation，简称3DVAR）和1km分辨率中尺度区域模式开展了单点同化试验和典型个例分析。单点同化试验表明，气压和风的同化结果在没有平衡约束关系条件下比线性平衡约束下更接近观测。针对地面自动站资料同化试验表明新风压平衡约束关系将明显增加模式低层几十公里尺度的分析增量，其次是增加100至200公里左右尺度的分析增量。新风压平衡约束试验的同化分析增量相对于线性平衡约束的控制试验可以描述出更多的增量中心位置，更好描述低层水汽辐合，对模式初始0-3小时降水、0-6小时地面10米风和地面气压的模拟有改进。研究表明在大尺度风压平衡约束的基础上增加局地无风压平衡约束的订正，可以提高对流尺度天气系统地面短波信息的同化能力，改进高分辨率模式短临预报。

英文摘要:

      With the improvement of model resolution, the recognizable shortwave information of numerical models increases. The mass–wind balance constraints based on geostrophic balance cannot fully meet the needs of data assimilation in low latitude regions and high-resolution convective scale models. This article proposes a mass–wind balance constraints in 1km resolution variational assimilation system based on the multigrid method , which adds correction without mass-wind constraints on the basis of large-scale mass–wind balance. Single point assimilation experiments and typical case studies were conducted based on the GRAPES (Global Regional Association and PrEducation System) three-dimensional variational system and mesoscale regional model. The experimental results indicate that the new mass–wind balance relationship will significantly increase the analysis increment of several tens of kilometers scale in the lower layer of the model, followed by an increase in analysis increment of about 100 to 200 kilometers scale. The assimilation analysis increment of the new mass–wind balance experiment can describe more increment center positions compared to the control experiment of linear balance constraint, better describing the low-level water vapor convergence, and improving the simulation of initial 0-3 hour precipitation ,0-6 hour 10 meter wind and surface pressure. Results of the study indicate that adding local correction without wind mass–wind balance constraints on the basis of large-scale mass–wind balance constraints can improve the assimilation ability of shortwave information in convective systems and improve high-resolution models for short-term forecasting.