- Rifled or other pipe wall corrugation may change the flow from a hetero－generous to a homogeneous regime by introducing a secondary circulation .
- The analysis of the large - scale synoptic situation shows that strong precipitation is closely related to the explosion of monsoon and the intensification of cross - equatorial flow which bring a lot of vapor and meet with cold masses at the eastern of northwest district on 8th , june causing extremely heavy rainfall ; that subtropical high - level jet at 200hpa , subtropical high at 500hpa and low - level jet at 850hpa are the weather backgrounds favorable to strong precipitation ; that the pattern of eastern highs and western lows and the establishment of a low - level jet and the coupling between upper - and low - level patterns that determine that the rain occurred in the east of the northwest china ( on average , this is the rainy season for the south of china , but not for the northwest china ) ; that water vapor comes from southerly and easterly flow which converge at the eastern of northwest district with convergence mainly in lower levels and pbl ; that the high value of the whole - level apparent heat source < q1 > is near the area of large rainfall in the direction of northeasterly - southwesterly agreeable to shear line very well and the condensation latent heat releasing is main heat source with vertical advection item playing key role in q1 and q2 ; that there is a vertical secondary circulation crossing low - lever jet whose ascending branch is at the area of large rainfall ; that the construction of convection instability and conditional symmetry instability results that there is not only deep thermal instability , but also moisture influx and triggering mechanism of thermal instability causing strong torrential rain
作为对比，本文还对2002年6月24 - 25日发生在北京地区的强地形雨进行了分析，并讨论陕南、北京地区两地暴雨的异同点以及地形作用的共性和个性，为两地暴雨预报提供有益的参考，得出了一些很有意义的结果： 1大尺度环流背景分析表明： ( 1 ) “ 02 . 6 ”强降水与6月上旬越赤道气流和季风爆发密切相关，携带大量水汽的偏南气流与冷空气于6月8日交汇在西北地区东部，导致了这次强降水的发生； ( 2 ) 200hpa的副热带西风急流、 500hpa副高以及850hpa的低空急流的配置非常有利于本文分析之陕西强降水的发展与维持。大尺度形势分析表明，东高西低形势场、低空急流的建立和高低空形势的配置决定了这场降雨出现在西北地区东部。与暴雨区相联系，存在一支横越低空急流的经向垂直环流，暴雨区处于该垂直环流的上升支； ( 3 )偏南和偏东气流水汽通道在西北地区东部交汇，水汽的辐合积聚主要在对流层低层和行星边界层内完成； ( 4 )整层的视热源< q _ 1 >高值区在暴雨区附近呈东北-西南向分布，与切变线走向非常一致，降水产生的凝结潜热释放是强降水区大气的主要热源。
- The analysis for the evolution of the upper westerly field , north - south wind field show that the upper jet stream is a good indication to sandstorm - occurring areas , the strong sandstorm appears at the right side of the entry domain of the jet stream and the ascension domain of secondary circulation
- A transverse secondary circulation is produced by the coupling of high and low jets , while the sinking branch of the secondary circulation providing the dynamic conditions for the dry intrusion air . during the period of the heavy rain process , dry intrusion descends southward along the intense constant potential temperature lines , which promotes the lower cyclone . in addition , the pouring of upper - level dry air not only decreases ground temperature behind the front but also increases surface pressure and velocity
- The above analysis showed that this heavy rainfall event took on obvious meso - scale characters and was the combination of the three flows , so we can deduce : ( 1 ) surface southeasterly wind and topography may play the main role in this event ; ( 2 ) the easterly cold air rushing into the southern shaanxi province in the lower troposphere was strongly relative to the form of surface cold - front type of occlusion ; ( 3 ) there were two reasons for the secondary circulation ' s strengthen in the evening , one was the effect of a mountain - valley wind and the other may be latent heat leading to ascending motion ; ( 4 ) the shape of potential instability stratification corresponded well with the development of the warm - moisture advection ; and ( 5 ) the vapor providing essential thermodynamics was transported by a southwesterly low - level jet from the bay of bengal and the south china sea . furthermore , with the effect of terrain , the southern shaanxi province became the center of this extremely heavy rain process
中尺度结构分析表明，本次暴雨具有明显的中尺度特征，是由三支气流共同作用的结果，分析发现( 1 )地面东南风和地形在这次大暴雨过程起主要作用； ( 2 )东路冷空气主要是通过中低层侵入陕南地区的，并与地面冷式锢囚锋的形成密不可分； ( 3 )夜博士论文:中尺度地形对陕南暴雨的影响研究间垂直次级环流发展加强可能有两个原因，一个是由于地形山谷风的作用，另一个是降水的潜热释放激发了上升运动: ( 4 )位势不稳定层结的形成与低层暖湿平流的发展有很好的对应关系; ( 5 )本次暴雨的水汽主要靠偏南风急流将孟加拉湾和中国南海的水汽输送至西北地区东部，为暴雨的发生提供了必要热力条件。
A secondary circulation is a circulation induced in a rotating system. For example, the primary circulation of Earth's atmosphere is zonal.