- 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
作為對比，本文還對2002年6月24 - 25日發生在北京地區的強地形雨進行了分析，并討論陜南、北京地區兩地暴雨的異同點以及地形作用的共性和個性，為兩地暴雨預報提供有益的參考，得出了一些很有意義的結果： 1大尺度環流背景分析表明： ( 1 ) “ 02 . 6 ”強降水與6月上旬越赤道氣流和季風爆發密切相關，攜帶大量水汽的偏南氣流與冷空氣于6月8日交匯在西北地區東部，導致了這次強降水的發生； ( 2 ) 200hpa的副熱帶西風急流、 500hpa副高以及850hpa的低空急流的配置非常有利于本文分析之陜西強降水的發展與維持。大尺度形勢分析表明，東高西低形勢場、低空急流的建立和高低空形勢的配置決定了這場降雨出現在西北地區東部。與暴雨區相聯系，存在一支橫越低空急流的經向垂直環流，暴雨區處于該垂直環流的上升支； ( 3 )偏南和偏東氣流水汽通道在西北地區東部交匯，水汽的輻合積聚主要在對流層低層和行星邊界層內完成； ( 4 )整層的視熱源< q _ 1 >高值區在暴雨區附近呈東北-西南向分布，與切變線走向非常一致，降水產生的凝結潛熱釋放是強降水區大氣的主要熱源。
- 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
中尺度結構分析表明，本次暴雨具有明顯的中尺度特征，是由三支氣流共同作用的結果，分析發現( 1 )地面東南風和地形在這次大暴雨過程起主要作用； ( 2 )東路冷空氣主要是通過中低層侵入陜南地區的，并與地面冷式錮囚鋒的形成密不可分； ( 3 )夜博士論文:中尺度地形對陜南暴雨的影響研究間垂直次級環流發展加強可能有兩個原因，一個是由于地形山谷風的作用，另一個是降水的潛熱釋放激發了上升運動: ( 4 )位勢不穩定層結的形成與低層暖濕平流的發展有很好的對應關系; ( 5 )本次暴雨的水汽主要靠偏南風急流將孟加拉灣和中國南海的水汽輸送至西北地區東部，為暴雨的發生提供了必要熱力條件。
- It's difficult to find secondary circulation in a sentence. 用secondary circulation造句挺難的