摘要
摘要:利用WRF模式，结合三维降水诊断方程和降水效率定义，针对1409号超强台风“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高分辨率数值模拟诊断研究。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（P_S），陆地和海洋P_S的相对贡献基本呈反向变化，登陆期间陆面摩擦辐合增强，有利于水汽更多地向陆地区域辐合（Q_WVA代表垂直积分的三维水汽通量辐合/辐散率，此时段Q_WVA为正值），造成登陆前短时段内陆地上空局地大气增湿（Q_WVL代表垂直积分的水汽局地变化率的负值，此时段Q _WVL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（Q_CLL和Q_CIL分别代表垂直积分的液相和固相云水凝物局地变化率的负值，此时段Q_CLL和Q_CIL为负值），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Q_WVA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明显变化，进而造成降水云系和强降水中心的显著变化；与陆地相比，海洋表面蒸发的作用更强，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Q_CLL和Q_CIL均基本呈现“正—负—正”的变化特征，当环流中心位于北部湾洋面（三次登陆时期）时水凝物含量以增加（减少）为主；“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，陆地降水效率迅速升高，而海洋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。
关键词:登陆热带气旋/
主体环流圈/
强降水物理过程/
降水效率/
三维降水诊断方程
Abstract:The development evolution and landfall process of typhoon Rammasun (1409) was investigated using high-resolution simulation produced by the WRF (weather research and forecasting) model. The diagnostic and numerical study on the physical process of strong rainfall focused on the period of Rammasun featuring the rapid enhancement of land surface friction and the landfall in the South China Sea, using three-dimensional surface precipitation equations and the definition of precipitation efficiency. The results showed that a strong average precipitation intensity (P_S) was maintained in the main circulation area of Rammasun, and the relative contributions of P_S over the land and ocean were opposite. The enhancement of land surface friction was conducive to more water vapor convergence to the land (Q_WVA represented vertically integrated three-dimensional flux convergence/divergence rate of moisture, and Q_WVA was positive), resulting in local atmospheric humidification over the land within a short period before the landfall (Q_WVL represented vertically integrated negative local change rate of water vapor , and Q_WVL was negative during the duration). The water vapor was rapidly transformed into liquid-phase and ice-phase hydrometeors by cloud-related microphysical processes (Q_CLL and Q_CIL represented vertically integrated negative local change rate of liquid-phase and ice-phase hydrometeors respectively, and they were negative during the duration), 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 Q_WVA over the ocean was significantly enhanced. The change in 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 over the ocean caused more effect and more significant changes, compared with the one over the land. The average Q_CLL and Q_CIL in the main circulation were basically “positive–negative–positive” within the period of Rammasun movement to the coastal region of South China. The content of hydrometeors was mainly increased (decreased) when the circulation center was located in the Beibu Gulf (during the landfall). A high precipitation efficiency was 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 landfalls.
Key words:Landfalling tropical cyclone/
Main circulation ring/
Physical process of strong precipitation/
Precipitation efficiency/
Three-dimensional WRF-based surface precipitation equation



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