九华山区下垫面对局地降水的影响分析

Influences of Underlying Surface on Local Precipitation in Jiuhua Mountains

利用安徽中尺度自动气象站的探测数据和多年统计数据,对九华山区下垫面影响降水的地理分布及强度进行讨论,分析下垫面物理过程在降水天气中的作用。结果表明:山区的湿热条件及不稳定能量均强于周边地区,非均匀下垫面的热力作用和山区地形作用形成地面中尺度风场辐合线及其所造成的上升运动对低空急流起加强作用,这些均影响强对流天气的形成和发展。山区降水地理分布受地形影响很大,山区的降水量、降水日数及降水强度均明显多于周边丘陵地区,并有迎风坡降水明显及在一定高度内山体越高降水量越大的特点。逐小时地面自动站资料分析对山区强降水的形成、发展和消散具有很好的临近预报指示作用。

By using observation data of mesoscale automatic station in Anhui and statistic data,the influence of Jiuhua Mountain underlying surface on the distribution and intensity of precipitation has been discussed, and the role played by underlying surface physical processes in the precipitation has been analyzed. The results show that the heat and humid conditions and its unstable energy in mountainous area are stronger than in surrounding areas.The thermodynamic effects of non-uniform underlying surface and the mountainous topography lead to ground wind field convergence,and the resulting vertical ascending motion strengthens low-level jet,which affects the formation of strong convective weather and development.The topography in mountainous area has an obvious effect on the rainfall distribution.The mean annual precipitation, precipitation days and intensity are significantly stronger than others in the peripheral hilly area. Precipitation is significantly enhanced at the windward slope and greater at higher mountains.The study on automatic weather station data gives a good indication of nowcasting for the formation,development and decay phases of a rainfall event in mountain.