基于谱逼近和地面资料同化的降尺度模拟研究  

Dynamic Downscaling Simulation using Spectral Nudging and Three-dimensional Assimilation of Surface Observation

作　　者：李洪兵 邵爱梅[1] 李兰倩 LI Hongbing;SHAO Aimei;LI Lanqian(College of Atmosphere Sciences/Key Laboratory for Semi-Arid Climate Change of the Ministry of Education,Lanzhou University,Lanzhou 730000,Gansu,China)

机构地区：[1]兰州大学大气科学学院/半干旱气候变化教育部重点实验室,甘肃兰州730000

出　　处：《高原气象》2021年第4期919-931,共13页Plateau Meteorology

基　　金：科技基础资源调查专项(2017FY100900);国家自然科学基金项目(41275102)。

摘　　要：谱逼近方法和变分资料同化方法都是提高动力降尺度模拟效果的有效手段,其中谱逼近方法通过引入分析或再分析资料来订正长时间连续积分造成的大尺度偏差问题,其模拟输出有望为变分同化提供质量较好的背景场。为此,本文通过WRF模式对2015年夏季秦巴山区实施水平分辨率为5 km的短期气候动力降尺度模拟,探讨在谱逼近方法的基础上利用三维变分(3DVar)同化方法同化地面观测资料的降尺度模拟效果,以期为获取复杂地形下高精度的高分辨率降尺度数据集提供一种有效途径。结果表明,在动力降尺度过程中使用谱逼近方法能够改善2 m温度、10 m风速和降水的模拟结果。只同化地面观测资料对模拟的2 m温度和10 m风速有明显改善,但对降水模拟有负作用。谱逼近方法和地面资料同化方法的结合使用能够得到2 m温度、10 m风速的最佳模拟效果,对降水的模拟结果也优于只同化地面观测资料的试验效果。使用谱逼近方法能够有效地对风场和水汽场做出合理调整,这是其降水模拟精度提高的原因之一。Both spectral nudging and variational data assimilation are effective approaches to improve the simulation effects of dynamic downscaling.The spectral nudging can introduce analysis or reanalysis data and consequently correct the large-scale bias caused by long-term continuous integration,which may provide a better background field for the variational assimilation.For this,a short-term climatic dynamic downscaling simulation is conducted by using the WRF model with a horizontal resolution of 5 km in the Qinling-Daba Mountains in the summer of 2015.The roles of surface observation data assimilation by combining spectral nudging and three-dimensional variation(3DVar)assimilation method are investigated in order to obtain an effective approach to producing high-precision and high-resolution downscale datasets in complex terrain.The results show that the spectral nudging technique can improve the simulation accuracy of 2 m temperature,10 m wind speed and precipitation.Surface observations assimilation without spectral nudging has a significant improvement on the simulated 2 m temperature and 10 m wind speed but results in a negative effect on the simulation of precipitation.The combine use of two methods can obtain the best simulations on 2 m temperature and 10 m wind speed,and the combined approach is also better than surface data assimilation method in simulating precipitation.The use of the spectral nudging can reasonably modify the wind and water vapor fields,which is one of the reasons for improving the simulation accuracy of precipitation.

关 键 词：动力降尺度 谱逼近 地面观测 复杂地形 WRF模式 

分 类 号：P435[天文地球—大气科学及气象学]