摘要
应用非静力平衡中尺度模式MM5(V3.6),对0414号台风Rananim在登陆期间移动路径和所产生的降水进行了数值模拟研究,模式较好地再现了台风Rananim的移动路径和所产生的降水,但模拟的过程降雨量与实况值还有所偏差。多普勒雷达探测资料表明,台风Rananim登陆期间,强回波带出现在台风移动的右前方,螺旋云带中镶嵌着大量的对流云团;垂直液态水含量的高值区出现在台风中心的西北侧。作者通过在浙江、福建东部沿海一带进行有无地形的数值对比试验,着重讨论了台风登陆期间地形对台风降水、台风结构特征变化的影响。结果表明(1)台风登陆期间,地形的影响对台风降雨量有明显的增幅作用。由地形强迫产生的降雨量和地形走向相一致,迎风坡降雨量增加,背风坡降雨量减少,地形影响使浙江东部一带增加的平均降雨量约占该地区模拟平均总降雨量的40%左右。(2)台风登陆期间,地形的强迫作用有利于在低层台风眼的西北侧形成明显的辐合带,高层为明显的辐散区;在中尺度环流场上,地形的影响有利于台风中心西北侧低层中尺度气旋性涡旋系统的发生发展,从而激发中尺度对流云团,形成中尺度雨团,造成了台风中心南北雨区和雨量的不对称分布。(3)地形的强迫作用,可以使台风流场局部发生改变。当地形强迫产生与台风环流同向的中尺度扰动时,将使台风环流局部明显增强;当地形强迫产生与台风环流反向的中尺度扰动时,将使台风环流局部明显减弱。(4)台风登陆期间,地形的影响可以使台风靠近陆地一侧眼壁内的垂直上升速度增大,位涡明显增强,从而造成台风涡旋的增强。
Numerical simulation has been carried out on the track and precipitation of typhoon Rananim （0414） using the non-hydrostatic version 3.6 of the Pennsylvania State University/NCAR mesoscale numerical model （MM5）.The model can well simulate the track and precipitation of typhoon Rananim though the precipitation is underestimated in comparison with observatiorL However, the model can basically capture the characteristics of intensity change of typhoon Rananim, especially its weakening during landfall. Other features like the heavy rain pattern and the mesoscale rain-band can also be well simulated by the model, though their locations are slightly deviated from observation.
During landfall of typhoon Rananim, the base reflectivity of Doppler radar at Wenzhou indicates that the strong echo bands are located in the right front along the typhoon moving direction, with a lot of mesoscale convective cloud masses in the spiral echo bands, and the high value of vertically integrated liquid （VIL） in the northwest of the typhoon eye. These characters are closely related to the effect of orography. The sensitivity experiments of orographic effect on the changes of precipitation and structure of typhoon Rananim during its landfall by keeping/removing mountains in the eastern area of Zhejiang and Fujian provinces show that： 1） there exists significant increase of rainfall. The precipitation pattern is consistent with orientation of orography, i.e. the rainfall increases on the windward side, while deceases on the lee side. 2） In the northwest of the typhoon eye, there occur many significant convergence zones and mesoscale convective systems in the lower layer, and divergence ones in the upper layer. Mesoscale convective cloud masses are generated and resulted in heavy rain with its distribution highly asymmetric from northwest to southeast. These phenomena are consistent with observations by Doppler radar at Wenzhou. 3） The circulation of typhoon Rananim can be partly changed as the result of orographic forcing. The local circulation of typhoon will be enhanced obviously when mesoscale turbulences initiated by orographic forcing is in phase with the local circulation of typhoon, and vice versa. 4） The vertical motion on the side of the eye wall of the typhoon close to land will be increased, with significant enhancement of potential vorticity leading to strengthening of the typhoon vortex.
出处
《大气科学》
CSCD
北大核心
2007年第2期233-244,共12页
Chinese Journal of Atmospheric Sciences
基金
温州市科技局社会发展科技计划项目S2003A011
浙江省气象局重大科技项目2004ZD03
2004ZD03
关键词
台风
地形影响
数值模拟
typhoon, orographic effect, numerical simulation
