地形对台风“海燕”暴雨增幅作用的观测与模拟

Observation and Simulation of Effect of Terrain on Rainstorm Amplification in Typhoon Haiyan

1330号台风"海燕"过程影响海南岛的强降水落区和强降水极值点(毛感乡)均位于南部地区,利用海南省区域加密自动站、三亚多普勒雷达以及0.25°×0.25°ERA-interim再分析资料对强降水成因进行观测分析,应用WRF Ver3.1.1模式对"海燕"进行模拟试验。结果表明:(1)"海燕"从海南岛南部近海北上阶段,其外围的偏东风或偏南风与五指山、吊罗山形成向南开口的"厂"字形地形正交,加密自动站和多普勒雷达在五指山区及"厂"字形地形南侧均探测到多个β中尺度风向辐合切变线或气旋性辐合涡旋,毛感乡附近存在明显的风向辐合,地面辐合中心与小时雨量大值区基本吻合。(2)"厂"字形地形迎风坡的强迫抬升导致气流垂直速度增大,毛感乡附近存在的水平的β中尺度辐合切变和垂直的β中尺度环流,有利于边界层辐合和中高层辐散增强,降水显著增幅。(3)数值模拟的强降水落区和降水极值点与实况基本一致,极值雨量较实况偏小;地形对山区及山脉迎风(背风)坡的雨量增(减)幅作用明显;有地形时,在五指山区及"厂"字形地形南侧容易产生β中尺度风向辐合区。

The heavy rainfall area and maximum precipitation point were located in the southern Hainan Island during Typhoon Haiyan(1330).The causes of heavy precipitation are analyzed by using the intensive automatic weather station data,Doppler Radar data in Sanya and 0.25°×0.25°ERA-interim reanalysis data,and the WRF model is applied in the simulation experiment.The results show:(1)The easterly or southerly winds on the periphery of the typhoon were orthogonal to the south-orientedΓ-shaped topography in the Wuzhi and Diaoluo Mountains while moving northward nearby the southern Hainan Island,and the multipleβ-mesoscale featured shear lines and cyclonic convergences were observed by the intensive automatic weather station and Doppler Radar in the Wuzhi Mountain and Maogan Village,where had an obvious wind direction convergence.The ground convergence center was basically consistent with the strong hourly rainfall area.(2)The local rainfall enhancement of Maogan Village was a result of interactions of the increasing of vertical velocity by theΓ-shaped topographical lifting,formatting ofβ-mesoscale horizontal and vertical circulations,developing of boundary-layer convergence and upper-level divergence.(3)The simulated strong precipitation area and extreme precipitation distributions of Haiyan were basically consistent with the observations,but the amount was less.The complex topography has positive(negative)contributions to rainfall increase(decrease)in the windward(lee)slope of mountains.It is easy to produce the β-mesoscale convergence in Wuzhi Mountain and the south side of the Γ-shaped topography.