Observations of Slantwise Convective instability in Winter Cyclones
Observations of Slantwise Convective instability in Winter Cyclones
复制标题
冬季气旋倾斜对流不稳定性的观测
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
M. Yau
中科院分区：
文献类型：
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作者：
G. Reuter;M. Yau
摘要研究了加拿大大西洋风暴计划(CASP)期间观测到的七个降水带，以评估倾斜对流不稳定的重要性。利用常规探空站和特殊探空站每小时一次的探空资料，建立了θe*(饱和等效位温)、M(绝对角动量)、θe(等效位温)和M表面的垂直截面。常数M、θe和θe*表面的斜率的比较表明，存在位势和条件倾斜不稳定性。本文主要研究了稳定场的时间演化及其对中性态的调节。在分析的7例病例中发现了一致的结果。大气中含有浅层空气，对条件性倾斜对流来说，特别是在风切变明显的地区，这些空气层略有不稳定。在高层，不稳定的潜势通常只是一种潜势，因为缺乏湿气使不稳定不可能发生。
Abstract Seven precipitation bands observed during the Canadian Atlantic Storms Program (CASP) are studied to assess the importance of slantwise convective instability. Using three-hourly radiosonde data from regular and special stations, vertical cross sections of θe*(saturated equivalent potential temperature) and M,(absolute angular momentum) and θe(equivalent potential temperature) and M surfaces are constructed. A comparison of the slopes of constant M,θe and θe* surfaces indicates the presence of potential and conditional slantwise instability. This study focuses on the time evolution of the stability field and on the adjustment to its neutral state. Consistent results were found in seven cases analyzed. The atmosphere is shown to contain shallow layers of air that are slightly unstable for conditional slantwise convection, particularly in regions having pronounced windshear. In the upper levels, the potential for instability usually remains only a potential because the lack of moisture precludes th...