地形影响下海河流域北系强降水成因分析   总被引：1，自引：0，他引：1  

尉英华  陈宏  刘一玮 《气象与环境科学》2018,41(3):83-90

利用区域自动站观测和NCAR/NCEP 1°×1°再分析资料,对比2012-2014年海河流域北系4次强降水过程成因,重点分析地形对强降水过程的影响。分析结果表明,4次强降水过程均属于低槽类暴雨,高空槽是影响流域北系强降水的主要影响系统,副热带高压、低层辐合系统对暴雨强度、位置及持续时间存在明显影响。此外,除能量及水汽的积聚外,地形对海河流域北系降水强度有明显增幅作用。风场与地形相配合的地形抬升是降雨增幅的动力因子。在水平方向上,呈"V"形分布的上升运动区,对应燕山山脉迎风坡坡度较大地区;在垂直方向上,地形强迫引起的低层上升运动中心与天气系统抬升引起的中高层上升运动中心逐渐合并加强。地形阻挡导致的水汽通量辐合也是迎风坡降雨增幅的重要因子,低层地形引起的水汽辐合明显强于中层天气系统引起的水汽辐合。  相似文献   

Evaluation of WRF-based convection-permitting multi-physics ensemble forecasts over China for an extreme rainfall event on 21 July 2012 in Beijing     

Kefeng Zhu  Ming Xue 《大气科学进展》2016,33(11):1240-1258

On 21 July 2012, an extreme rainfall event that recorded a maximum rainfall amount over 24 hours of 460 mm, occurred in Beijing, China. Most operational models failed to predict such an extreme amount. In this study, a convective-permitting ensemble forecast system (CEFS), at 4-km grid spacing, covering the entire mainland of China, is applied to this extreme rainfall case. CEFS consists of 22 members and uses multiple physics parameterizations. For the event, the predicted maximum is 415 mm d^-1 in the probability-matched ensemble mean. The predicted high-probability heavy rain region is located in southwest Beijing, as was observed. Ensemble-based verification scores are then investigated. For a small verification domain covering Beijing and its surrounding areas, the precipitation rank histogram of CEFS is much flatter than that of a reference global ensemble. CEFS has a lower (higher) Brier score and a higher resolution than the global ensemble for precipitation, indicating more reliable probabilistic forecasting by CEFS. Additionally, forecasts of different ensemble members are compared and discussed. Most of the extreme rainfall comes from convection in the warm sector east of an approaching cold front. A few members of CEFS successfully reproduce such precipitation, and orographic lift of highly moist low-level flows with a significantly southeasterly component is suggested to have played important roles in producing the initial convection. Comparisons between good and bad forecast members indicate a strong sensitivity of the extreme rainfall to the mesoscale environmental conditions, and, to less of an extent, the model physics.  相似文献   

深海水泵与储料罐组合采矿硬管输送系统研究     

徐绍军  徐海良 《海洋工程》2007,25(3):73-77,82

通过对沙浆泵接力输送和水泵与储料罐组合输送两种深海采矿输送方法进行分析,可知采用沙浆泵对矿石流体进行接力输送的方法,沙浆泵容易磨损破坏,安装维护困难;而水泵与储料罐组合的输送方法在理论上具有扬程高,输送量大,能长期可靠地工作,当应用于深海硬管采矿系统时,输送设备的主水泵和主要动力设备安装于采矿船上,相对于深海工作,在技术上易于实现,工作可靠,操作和维修方便。并对四种输送系统参数进行分析,水泵与储料罐组合的输送方法在理论上可行,采用现有技术容易实现,是一种具有应用前景的深海采矿输送方法。  相似文献   

深海采矿锰结核泵的试验研究   总被引：1，自引：1，他引：0  

唐达生  阳宁  龚德文  肖红  夏建新 《海洋工程》2015,33(4):101-107

锰结核泵是深海采矿扬矿系统中的关键设备,为了研究泵结核矿浆工作性能,在实验室构建了一套高30 m、内径204 mm,可提供最大管网阻力2.5 MPa的泵矿浆性能试验系统,采用不同模拟结核粒径进行了泵矿浆工作特性试验。试验结果表明,锰结核泵基本上达到了预期设计指标,分析了模拟结核粒径d≤50 mm矿浆回流试验泵流道堵塞的原因,初步讨论了锰结核泵的环形格栅通道和泵流道问题,可作为我国中试多级锰结核泵的设计依据。  相似文献   

Microstructure of Turbulence in the Stably Stratified Boundary Layer   总被引：1，自引：1，他引：0  

Zbigniew Sorbjan  Ben B. Balsley 《Boundary-Layer Meteorology》2008,129(2):191-210

The microstructure of a stably stratified boundary layer, with a significant low-level nocturnal jet, is investigated based on observations from the CASES-99 campaign in Kansas, U.S.A. The reported, high-resolution vertical profiles of the temperature, wind speed, wind direction, pressure, and the turbulent dissipation rate, were collected under nocturnal conditions on October 14, 1999, using the CIRES Tethered Lifting System. Two methods for evaluating instantaneous (1-sec) background profiles are applied to the raw data. The background potential temperature is calculated using the “bubble sort” algorithm to produce a monotonically increasing potential temperature with increasing height. Other scalar quantities are smoothed using a running vertical average. The behaviour of background flow, buoyant overturns, turbulent fluctuations, and their respective histograms are presented. Ratios of the considered length scales and the Ozmidov scale are nearly constant with height, a fact that can be applied in practice for estimating instantaneous profiles of the dissipation rate.  相似文献   

地表几何形态对冲断带构造特征影响的物理模拟实验研究          下载免费PDF全文

谢玉华  赵坤  周建勋  王利  王雪芹 《沉积与特提斯地质》2010,30(1):89-92

设计了基底均匀的水平砂层单测挤压砂箱模型,包括水平砂层上无砂丘以及砂丘分别位于距左侧活动挡板5 cm、10 cm、15 cm、20 cm、25 cm、30 cm时的7组实验,通过实验着重对水平砂层在受单侧挤压时不同位置砂丘对冲断带的影响问题进行研究。实验结果表明,砂丘在不同位置时,冲断带的形成规模、几何形状都发生相应变化:砂丘距左侧活动挡板10～25 cm时,冲起构造发育,且冲断带的构造特征明显;而砂丘距左铡活动档板5 cm、30 cm时不发育冲起构造,主要发育逆冲断层。  相似文献   

CZ-1200型冲击钻机的开发与应用          下载免费PDF全文

高甲  陈毅斌  王振奎 《探矿工程》2002,(2):33-34

针对目前国内防渗墙、灌注桩桩孔施工及水井钻凿的主要设备CZ－22型钢绳冲击式钻机在使用过程中的一些不足之处，研制开发了CZ－1200型冲击钻机。介绍了钻机的结构特点及其在防渗墙、水井施工中的应用。  相似文献   

无卷扬机液压缸升降式钻机          下载免费PDF全文

夏志明  杨宝鑫  李冰  刘晓鹏  薛军 《探矿工程》2011,38(7):9-11

目前,液压动力头岩心钻机大多采用液压缸给进,液压卷扬机提升。近年来,国外多个国家以液压技术见长的公司,研发了无卷扬机液压缸升降式钻机,它与传统钻机设计理念不同,液压缸不单是给进机构也作为提升机构。这种钻机取消了结构复杂而笨重的卷扬机、天车、游动滑车组。液压缸提升系统井架不承受提升载荷,井架尺寸小,轻便;整个设备体积小、质量轻、成本低、技术经济指标先进。它为研发液压动力头钻机提供了一种新机型。介绍了瑞典山特维克浅钻和挪威MH公司RamRig深孔钻机的结构和其他一些国家研发和应用情况。阐述了双液压缸提升和液压缸-钢丝绳倍速机构两种不同系统的工作原理及应用特点。  相似文献   

On the Mechanism of a Terrain-Influenced Snow Burst Event during Midwinter in Northeast China   总被引：1，自引：0，他引：1  

Na LI  Baofeng JIAO  Lingkun RAN  Xinyong SHEN  Yanbin QI 《大气科学进展》2021,38(5):800-816

Short-duration snow bursts with heavy snow represent one type of hazardous weather in winter which can be easily missed by the winter weather warnings but often results in great hazards.In this paper,the mechanism for the occurrence of such events was investigated with the aid of a localized terrain-influenced snow burst event in Northeast China.The snow burst was produced by an eastward-moving cold-frontal snowband which encountered the downstream complex terrain of the Changbai Mountains and intensified.To ascertain the role of orography on the snow burst,numerical experiments,together with a parallel sensitivity experiment removing Changbai Mountains,were performed to attempt to distinguish the contributions of cold-frontal system and orographic effects to produce the heavy snow.Diagnosis showed that without the influence of Changbai Mountains,the release of conditional instability(CI)and inertial instability(II)within a weak frontogenetical environment was responsible for the snowband maintenance.Orographic effects played important roles in enhancing the snowband and increasing the snowfall intensities.The enhancement mechanism was related to the interactions of the cold-frontal snowband and the topography.On the one hand,orographic frontogenesis and persistent ascent,created by orographic gravity waves over the terrain,greatly enhanced the orographic lifting.The intensification of the lifting promoted the release of CI and thus enhanced the snowfall.On the other hand,pre-existing orographic instabilities were released due to the passing of the cold-frontal snowband,which could also serve to intensify the snowband over terrain and thus increase the snowfall.  相似文献   

深海扬矿系统中颗粒过泵回流试验研究     

王英杰  阳宁  金星 《海洋工程》2012,30(2):100-104

两相流过泵回流试验是模拟水力提升系统紧急停泵情况下垂直管道中颗粒运动状态,紧急停泵时,可能会出现堵管、难于输送等现象。为提高管道水力输送安全性,采用三种不同的模拟结核颗粒(粒径分别为d≤10 mm,d≤20 mm,d≤50 mm),两种不同浓度(CV=5%,CV=8%),在两级泵额定流量Q=420 m3/h条件下进行了过泵回流试验,分析了试验结果,从多个方面总结了堵管原因。认为实际工程中应该严格控制颗粒上限粒径,采用合适的颗粒级配,并对管道定期进行清洗,尽量减少管道的大角度转弯和断面突变。  相似文献