不同要素谱逼近对高分辨区域数值模式梅雨模拟的改进

Improving the Meiyu Simulation Using Spectral Nudging of Single-Element and Multi-Element in High-Resolution Regional Numerical Model

为改进高分辨率区域数值天气预报模式雨带模拟偏差,利用WRF模式探讨了不同要素及其组合谱逼近方法对2015年浙江典型梅雨天气预报性能的影响。结果表明:(1)不同单要素逼近对梅雨模拟效果影响差异明显,风场逼近对模拟结果改进较大,高度场逼近对结果略有改善,而温度场逼近主要表现为负效应;风场组合了其他要素的逼近效果与单要素类似,故将水平风场谱逼近确定为最优方案。(2)最优方案对梅雨期间形势场各要素改进程度的排序为纬向风、经向风、相对湿度、温度场和高度场;三个特征层850、500、200 hPa各要素平均的均方根误差(相关系数)分别降低了(增加了)24.1%(13.6%)、22.7%(21.7%)和13.0%(12.2%);且改进幅度随预报时效的延长而增加,这主要与区域模式内部大尺度系统的误差随积分时间增长有关。(3)典型个例分析显示,最优方案在较好订正低层风场及切变线动力条件的基础上,经过数值模式各物理过程的协同积分也修正了高湿区等关键热力因子,最终改进了高分辨率区域模式的梅雨模拟。

To improve the simulation in precipitation location,the impact from spectral nudging(SN)technique of single-element and multi-elements on the Meiyu weather simulation are investigated by using the Weather Research and Forecasting(WRF)model.The results show that:(1)the contributions of SN with different meteorological elements and their combination to Meiyu simulation are obviously different.On the whole,the SN with wind field obviously improves Meiyu precipitation simulation,while there is a little benefit and even deterioration in SN with geopotential height and temperature,respectively.Also,it is the similar effect in simulations with multi-elements SN.Therefore,the spectral nudging with wind field is chosen as the optimal scheme for the following analysis.(2)During Meiyu period,the sort of improvement in synoptic elements is zonal wind,meridional wind,humidity,temperature and geopotential height.On average,compared to the control experiment,the root mean square error(correlation coefficient)of all elements decreases(increases)by about 24.1%(13.6%),22.7%(21.7%)and 13.0%(12.2%)at 850 hPa,500 hPa,and 200 hPa in the optimal experiment respectively.Meanwhile,the longer lead time is,the better improvement could be in the simulation,which is related to larger-scale error growth in interior domain with the integration time.(3)Typical case diagnosis illustrates that wind field spectral nudging can amend efficiently the dynamic factors such as low-level wind shear line,and thus correct the key thermodynamic factors like high humidity region by physical process interaction and modulation during integration,which could result in the better simulation in Meiyu event finally.