Institute of Atmospheric Physics, Chinese Academy of Sciences
利用WRF模式，对1409号超强台风“威马逊”发展演变及登陆过程开展了高分辨率数值模拟，结合三维降水诊断方程和降水效率定义，重点针对“威马逊”临岸迅速加强为超强台风并登陆我国华南沿海这一时段的强降水物理过程开展了模拟诊断研究。结果表明，“威马逊”主体环流区域内一直维持很强的平均降水强度（PS），陆地和海洋格点PS的相对贡献基本呈反向变化，登陆期间陆面摩擦辐合的增强，有利于水汽更多地向陆地区域辐合（正值水汽通量辐散/辐合率QWVA），造成登陆前短时段内陆地格点上空局地大气增湿（水汽局地变化率QWVL为负值），借助云微物理过程快速转化为液相和固相云水凝物，促使陆地上空降水云系快速发展和降水强度增强，而当环流中心位于北部湾洋面时，海洋格点QWVA的相对贡献显著增强，登陆期间下垫面的变化导致水汽相关物理过程的明显变化，造成降水云系和强降水中心的显著变化；与陆地格点的表面蒸发率QWVE相比，海洋下垫面QWVE的作用更强，变化更明显；“威马逊”影响华南沿海期间，主体环流圈内平均的QCLL和QCIL（液相和固相水凝物局地变率的负值）均基本呈现“正-负-正”的变化特征，环流中心位于北部湾洋面时水凝物含量以增加为主，但液相和固相水凝物增长原因不同，而登陆期间，陆地格点QCLL和QCIL “先负后正” 的变化特征主要源于登陆前期陆面摩擦增强造成的陆地上空降水云系快速发展以及后期强降水的消耗；“威马逊”主体环流区域内一直维持高降水效率，从主体环流圈接触陆地开始，陆地格点降水效率迅速升高，而海洋格点降水效率在绝大多数积分时段内维持较高数值，只在第二和第三次登陆后有所降低。
The development evolution and landfall process of supertyphoon Rammasun (1409) was investigated using high-resolution simulation data produced by the Weather Research and Forecasting (WRF) model. The diagnostic and numerical study on physical process of strong rainfall was focusing on the period of the rapid enhancement and the landfall on South China Sea of Rammasun, using the three-dimensional surface precipitation equations and the definition of precipitation efficiency. The results showed that the strong average precipitation intensity（PS） had been maintained in the main circulation area of Rammasun, and the relative contribution of PS over the land and ocean was basically reversed. The enhancement of land surface friction was conducive to more water vapor convergence to the land (positive value of moisture advection QWVA), resulting in local atmospheric humidification over the land within a short period before the landfall (negative value the local change rate of water vapor QWVL). Water vapor was rapidly transformed into liquid-phase and ice-phase hydrometeors by means of cloud-related microphysical processes, which promoted the rapid development of clouds and the intensification of precipitation intensity over the land. When the center of the circulation was located in the Beibu Gulf, the relative contribution of QWVA over the ocean was significantly enhanced. The change of the underlying surface during the landfall period led to remarkable changes in the moisture-related microphysical processes, causing significant changes in the cloud system and the strong precipitation center. The surface evaporation (QWVE) over the ocean made more effect and more obvious changes, compared with the one over the land. The average QCLL and QCIL (the local change rate of liquid-phase and ice-phase hydrometeors) in the main circulation were basically “positive – negative - positive” within the period of Rammasun moving to the coastal region of South China. The content of hydrometeors was mainly increased when the center of the circulation was located in the Beibu Gulf, but the reasons for the growth of liquid-phase and ice-phase hydrometeors were different. During the landfall period, the characteristics of the “negative - positive” change of QCLL and QCIL over the land were mainly due to the rapid development of the cloud over the land caused by the enhancement of land surface friction in the early landfall period and the consumption of heavy precipitation in the later period. The high precipitation efficiency had been maintained in the main circulation area of Rammasun. From the contact of the main circulation to the land, the precipitation efficiency over the land rapidly increased, while the precipitation efficiency over the ocean maintained a high value during most of the integration period, but reduced only after the second and third landfall.