【作者】 周率；

【导师】 李泽椿；

【作者基本信息】 南京信息工程大学 ， 气象学， 2005， 博士

【摘要】 气象条件对人造卫星等航天器的发射具有直接而明显的影响,西昌发射场区气象保障的难点和重点是中尺度强对流天气,特别是强雷电天气。西昌场区位于青藏高原东南部、横断山脉东麓的安宁河谷中,独特的地理位置和地形环境使其强对流天气具有突发性、复杂性、局地性等特点,且全年各月均有发生、雷电强度很大,是制约发射时段的主要因子。本文在对西昌场区影响发射的强对流天气进行气候统计和天气分析的基础上,利用常规和非常规资料,对严重影响卫星发射任务的“10.1”和“11.4”两次中尺度强对流过程进行了大尺度环流背景分析、中尺度结构分析和下垫面热力及地形作用的数值模拟研究。 研究表明,西昌发射场区强对流天气具有明显的干、雨季对比及显著的日变化特征;雨季主要影响系统是西南涡和切变线,过渡季节和干季则是绕流冷空气和锋面过程;并且在场区所处的安宁河谷内,强对流天气有自北向南发展的特点。直接造成场区强对流的天气系统是形成于横断山脉东麓的中-β尺度切变线和低涡,配合场区北侧30°N附近有较强锋区。发生在雨季附近的过程降水量大、持续时间较长;主要发生在副高边缘的暖湿气团中;来自四川盆地和中南半岛的水汽使场区附近低空的湿度显著增加,导致抬升凝结高度和自由对流高度降低,造成对流有效位能(CAPE)迅速发展,为过程提供了层结稳定度条件并积累能量;而冷空气导致的场区低层中尺度锋生是强对流的触发机制之一。过渡季节和干季过程降水量小、持续时间较短,但其雷电强度不亚于雨季强对流过程;绕流冷空气造成西南准静止锋生成并向西推进,形成大尺度环流背景;而西北气流在高原东南边缘引起锋生作用,产生中-β尺度地形锋—高原东南边缘锋,是引发强雷电天气的直接原因;它与西南准静止锋一起构成独特的“双锋”型。地表感热和潜热通量的敏感性试验揭示,感热和潜热通量对场区强对流的产生都有重要贡献;尤其在过程初期,二者量级相当,这与潜热通量占主导作用的梅雨锋暴雨及华南暴雨等都有所不同;其作用一方面是导致近地层的大气变湿、变暖,产生深厚的大气不稳定层结;同时由于山脊和山谷的感热通量对比,引起局地热力环流,有利于中尺度系统形成。而中尺度山脉地形动力作用的敏感性试验揭示出,西北部和北部的山脉对河谷内的降水都有增幅作用;东部山脉则主要通过对绕流冷空气的阻挡而影响场区强对流过程;东南部和南部山脉都对水汽输送起阻挡作用,使发射场区降水减少,其影响的大小取决于水汽的主要来向。中尺度地形在场区强对流过程中起到重要作用,不仅影响或决定了气流走向,输送了过程所需的物质、能量;促成中β尺度系统的生成;更直接作为触发机制,导致过程发生;因此高原东南部特殊地形可能是导致西昌发射场区强对流天气的主要原因之一。更多还原

【Abstract】 Meteorological conditions have direct and obvious effect on spacecrafts’ launch, such as artificial satellites. It’s the meso-scale strong convective weather(SCW for short afterwards) which is the difficulty and emphases of meteorological support in XiChang Satellite Launch Site (XSLS for short), especially the thunder weather. XSLS lies at southeast of the Tibetan Pleateau and east of Hengduan mountains, where the particular position and topography surrounding result in SCW with characteristics of not only outburst, complexity and occur at local area, but also happened at every months of the year and with very strong thunder, which is the main factor to restrict the periods of usable launch time in XSLS. Based on the climatic statistics and analysis of SCW that affected the launch missions of XSLS, using kinds of conventional and unconventional data, two cases of SCW which seriously affected the launch missions are investigated by analysis of macro-scale surrounding, meso-scale structure, numerical simulations of surface heating effect and meso-scale mountains’ dynamic effect.The research proved that the SCW of XSLS with obvious differences in dry season and rainy season and distinctly changed with day time, are mainly affected by southwest vortex and shear in the rainy season and by cold air from Sichuan basin and cold fronts in other seasons. There is a local property of SCW in Anning valley which XSLS lies at that it was developed from north to south. The weather systems which directly cause the SCW are meso-P vortex and shear at east of Hengduan mountains and there are comparatively strong cold front at about 30°N. The SCW in rainy season and its about with big precipitation and longer duration are mainly happened at warm-moisture mass near subtropical high and the vapor from Sichuan basin and peninsula of central-southern China led the obviously increase of lower-level humidity near XSLS, and resulted in fell of the levels of ascending and free convective condensation to generate the rapidly development of CAPE which caused the unstable stratification and accumulated energy, and the frontogenesis induced by cold air near low level at XSLS is a triggering mechanism. The SCW in other seasons are with small precipitation, shorter duration, but nearly same strong thunder, whose macro-scale surrounding were mainly formed by strengthening and west-forwarding of the southwest quasi-stationary front conduced by NE cold air and the meso-P southeast brink front of the Tibetan Plateau caused by NW cold air and local topography directly caused the thunderstorm, so formed the unique "two-fronts" pattern to cause SCW of XSLS. A series of sensitivity experiments proved that the geographic thermal forcing, both including the sensible and latent flux played important roles in the cases, especially at the beginning that with almost the same quantities, which is obviously different with rainstorms of the Yangtse-Huaihe river district and south China where the latent flux are most important. They played the partes by causing the instable stratification and favorable backgrounds for meso-scale systems. Among the meso-scale mountains near XSLS, the northwestern and northern topography enhanced the precipitation of the valley, the eastern mountains mainly affected the SCW by blocking off the NE flow, and the southwestern and southern topography worked on by mainly affecting the vapor transportation to reduced the precipitation and obviously affected by the directions of the vapor. The mesoscale topography have significant actions by effect on the flows to transport substances and energy, and on development of meso-P systems, furthermore directly acted as triggering mechanisms, so it’s maybe one of the key factors for SCW in XSLS and its about.更多还原