陈丽芳,高 坤 . 2006. 梅雨锋结构的数值模拟[J]. 气象学报, 64(2):164-179, doi:10.11676/qxxb2006.016
梅雨锋结构的数值模拟
THE SIMULATION OF THE UNEVEN CHARACTERISTICS OF MEIYU FRONT STRUCTURE
投稿时间:2005-05-31  修订日期:2005-11-24
DOI:10.11676/qxxb2006.016
中文关键词:  梅雨锋结构,中层锋区,边界层锋区
英文关键词:Structure of meiyu front, Intermediate layer front, Boundary layer front.
基金项目:973国家重点基础研究发展规划项目(G1998040907),国家自然科学基金资助项目(40075009),杭州市科技发展计划项目(200214 B03)
作者单位
陈丽芳 杭州市气象局 杭州 310008 
高 坤 浙江大学地球科学系杭州310027 
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中文摘要:
      利用1999年6月下旬持续性梅雨锋降水过程的全程四维同化模拟结果,深入分析梅雨锋结构的时空不均匀变化特征及其与低涡降水强度的密切关系。结果表明,梅雨锋呈现明显的中层锋和边界层锋两段锋的特征,中层梅雨锋区对降水的影响比边界层锋更为关键,中层锋的加强、锋坡增大趋于垂直、锋区垂直环流的加强和与高空急流锋区的上下贯通,有利于梅雨锋降水的加强,强降水并不出现于中层锋区最强的时段,而是发生于大范围锋区强度达峰值之后约16—24 h。中低层总变形加强与梅雨锋的加强有密切关系。组成低空急流的中低层 u,v 分量呈现不同的分布和演变特征,强南风中心位于900—800 hPa,呈明显的低空急流状特征,贴近暴雨区还可能出现较小尺度的急流;而强西风中心出现于中层锋前700—500 hPa,表现为高空强西风区沿锋区上界的向下延伸;低空南风急流通常与总变形同时加强。强锋段的锋前饱和高湿高能气柱、锋前中低层急流状南风区和中层西风均匀大值区等要素场呈现高度组织化的特征。梅雨锋的低层特性,如辐合、锋区强度、总变形和南风分量及降水强度等要素呈现显著的中尺度扰动特征,有明显的日变化且受长江中下游中尺度地形影响,扰动特征有随时间上传的趋势。
英文摘要:
      A simulation of the heavy rainfall process along meiyu front was conducted using the NCAR/PSU mesoscale model with a four-dimensional data assimilation. The model output of high temporal and spatial resolution was used to investigate the uneven characteristics of the structure of meiyu front, which was closely responsible to the heavy rainfall. The results indicate that the meiyu front consists of two segments vertically, the middle layer front and boundary layer front. The vortex and associated heavy rainfall along meiyu front were more sensitive to the middle layer front than to the boundary layer front. The intensified, steeper of the middle layer front and intensification of the vertical circulation across the frontin the middle layer are favorable to the later enhancement of precipitation along the meiyu front. The peak intense of prcipitation did not occurred at the same time while the middle layer front reaching its peak intensity, but the former has a lag of about 16-24 hours. The total deformation fields at middle and low layer were closely associated with the development of front. The distribution and evolution of u and v components were significant different. The southerly jet stream center was at 900-800 hPa, and the strong westerly flow was at middle level of 700-500 hPa ahead of the front, appearing as the downward extension of upper level westerly along the upper boundary of the front. The vertical saturated warm moist air column, southerly low layer jet and westerly middle level jet ahead of the front show highly organized features at the intense front segment. Some low layer fields along Meiyu front, such as convergence, front intensity, deformation and southerly wind, show evident mesoscale orographic features and with significant daily variation.
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