副热带高压自身变化周期和形态结构对入梅的影响

针对2010年江淮入梅预报出现偏差情况,利用2008、2010、2011年降水实况资料和6-7月NCEP再分析资料,分析了预报出现偏差的原因,讨论了副热带高压水平移动和垂直结构对降水落区的影响,分析了局地入梅的预报方法和参考指标.研究发现:副热带高压(以下简称“副高”)和南亚高压的自身双周振荡规律在预报中不可忽略,在对大尺度系统和较长时间系统的变化判断时,高层系统的预报可信度可能更高.另外,在对梅雨预报时,副高垂直结构的变化对降水落区有一定影响,当500 hPa副高脊线越过20°N,副高脊线自上而下向南倾斜时,底层脊线在20°N以南,不利于江淮地区降水发生.副高上下结构垂直度较大时,利于降水落区北移.副高西脊点自高空到低空呈自西向东倾斜,500 hPa西脊点偏西也不利于江淮梅雨期的开始.

Influence of subtropical high's variation period and structure on plum rain onset

With regard to the forecast error about Plum rain in Yangtze-Huaihe basin in 2010, this paper, based on rainfall data of 2008, 2010 and 2011, as well as the analyzed data of NCEP, has explored the reasons of this error, discussed the influence of subtropical high's horizontal movement and vertical structure on rainfall region. The research has found that two-week periodic vibration rules of subtropical high and south Asia high can not be ignored in forecasting the beginning of Plum rain, and that when judging the changes of large-scale system and long-time system, forecast of high level system is more reliable. Moreover, the research has also confirmed that in forecasting Plum rain, vertical structure's variation must be considered besides proper attention to advance and retreat rule of horizontal movement. When 500 hPa subtropical high ridge moves to the north of 20 °N, subtropical ridge leans southward from top to bottom, and subtropical high ridge at low level moves to the south of 20 °N, there is no advantage for precipitation in Yangtze-Huaihe basin. As subtropical high remains vertical from bottom to top, it is beneficial to rainfall region moving to the north. When west ridge of subtropical high leans from west to east from high altitude to the low and the 500 hPa subtropical high ridge moves westward, the onset of Plum rain season in Yangtze-Huaihe basin will be delayed.