华南地区中尺度模式预报的初值影响分析

IMPACT OF THE INITIALIZATION ON MESOSCALE MODEL PREDICTION IN SOUTH CHINA

基于GRAPES3D-Var同化系统,介绍了根据静力平衡关系由高度场的增量来计算温度场的增量的方法,并结合常规探空资料同化,针对影响华南地区的一次冷空气过程的个例,分析了常规观测资料对初始场的影响。采用GRAPES区域中尺度模式进行了控制试验和同化试验,观测资料的检验表明,资料同化对GRAPES中尺度模式预报有正面影响,初始时刻预报敏感性较大并且变化较快,靠近地面的低层预报敏感性较为复杂,常规探空资料对高层大气预报能力的提高相对于中低层较小。

Based on the GRAPES 3D-Var system, this paper introduced a method to calculate the temperature increment by geopotential increment using the hydrostatic equilibrium equation. The impact of initialization is studied in the South China area during a course of cold wave by assimilating the sounding data. The control and assimilation experiments of GRAPES regional mesoscale model prediction are verified with observations. Results show that the assimilation of sounding data has positive impact on GRAPES regional mesoscale model. The initial forecast sensitivities are greater than later time and vary fast, the lower levels forecast sensitivity are more complex than the upper levels, and the sounding data assimilation can do little to improve the upper levels forecast while improving the lower and middle levels forecast much better.