宁波地区海-陆下垫面差异对雷暴过程影响的数值模拟

利用耦合Noah陆面过程的WRF模式对2009年6月5日傍晚发生在宁波地区的一次雷暴过程进行数值模拟，通过改变下垫面覆盖类型的敏感性试验，探讨了海洋和陆地下垫面对雷暴过程的影响。结果表明，WRF模式能够较合理地模拟出雷暴的发生、发展过程。雷暴发生前期，由于海-陆强烈的热力差异，海风特征明显，海风引起的抬升运动触发了雷暴，海风形成的强辐合区对应雷暴过程累积降水量的大值区。当研究区域全部被替换成陆地后，地表的粗糙度增大，在研究区域东部由于摩擦辐合加强，产生了强烈的上升运动，多个发展旺盛的对流单体在上升运动区生成，使雷暴产生的降水区域东扩、降水量增大、雷暴维持时间延长。当研究区域所有陆地被替换成水体后，白天地表通量减小，大气边界层中湍流运动减弱，边界层高度降低，大气层结变得稳定，不利于对流发展。

Numerical study of the impact of differences between sea and land underlying surface on thunderstorm in the Ningbo area

The thunderstorm process is simulated by the WRF model coupled with the Noah land-surface model. In this paper, the impact of sea-land underlying surface on thunderstorm is studied by changing the land cover type of underlying surface. The results show that the development process of thunderstorm is successfully captured by the WRF model. Before the thunderstorm takes place, since thermal contrast between the sea surface and the land surface is so strong that there is a distinct sea breeze circulation caused. Then the thunderstorm is triggered by lifting movement. The strong surface convergence is coinciding with the accumulated precipitation core produced by the thunderstorm. When water is replaced with land, uplifting movement become stronger in the east part of the study area for the increased land surface roughness. Several powerful convective cells form in the east part of the uplifting area, which expanded the rain area, increased the accumulated rainfall and extended the duration of the thunderstorm. When land is replaced with water, surface fluxes decrease in the daytime and turbulent motion becomes weak. So boundary layer becomes low, the atmospheric stratification turns to being stable and the thunderstorm is not easy to develop.