偏离度法确定济南夏季对流边界层高度研究     

王栋成  邱粲  董旭光  曹洁 《气象与环境学报》2019,35(3):29-36

利用济南站边界层风廓线雷达（简称WPR）观测资料,对大气折射率结构常数（简称C_n²）确定对流边界层高度（简称CBLH）的技术难点进行了研究,通过对实测C_n²数据廓线进行求导变换突出其变量特征,提出了一种确定CBLH的方法,即e指数拟合曲线的偏离度法。结果表明：经案例分析和与实测对比,证实其判断的结果与L探空实测虚位温梯度法、湿度梯度法等的判断结果总体一致,平均值分别与后两者结果相差+10.4 m、-21.8 m,最小值差-70 m、-120 m,最大值差+50 m、+80 m,与后两者的相关系数分别达0.988、0.980。不同方法对比表明,31组样本中有7组的极大值法判断结果与偏离度法、虚位温梯度法存在较大差异,在CBLH判别时偏离度法总体优于极大值法。偏离度法能够将夏季CBLH确定结果的绝对误差降至近似WPR垂直分辨率水平。  相似文献   

2018年12号热带低压奇异路径分析     

祁丽燕  王冀  农孟松 《气象研究与应用》2019,40(1):20-23

分析2018年第12号热带低压的奇异路径及其在广西强降雨落区产生的原因,分析表明:(1)12号热带低压路径为逆时针旋转,主要是由于副热带高压位置偏北,引导气流偏弱,低压先受到11号热带低压的互旋作用而产生了逆时针旋转的路径,登陆后由于11号热带低压减弱,对其影响也逐渐减弱,之后受到自身内力作用转向西北方向移动。(2)广西上空的热力和水汽条件均有利于对流发展,但桂东南由于缺少有利的动力条件和触发条件,没有强降雨产生。由于低压中心随高度向西南方向倾斜,导致垂直运动随低压中心向西南倾斜,使低压西南方处于大尺度上升运动处。而沿海和桂南一带处于偏北风和偏西风的辐合处,触发对流产生。强降雨云团在沿海被触发并发展,在低压西南方得到进一步发展,并随着低压转向西北方向移动,在广西的南部和中西部产生了强降水。  相似文献   

冷涡底部一次弓状强飑线的演变和机理   总被引：1，自引：0，他引：1  

公衍铎  郑永光  罗琪 《气象》2019,45(4):483-495

综合利用多种观测资料和NCEP分析资料,分析了2016年6月30日发生在冷涡南部暖区的一次长生命史弓状飑线(以下简称飑线)的环境条件、触发、演变和维持机制以及预报难点。其发生环境条件为超过4000 J·kg~(-1)以上的对流有效位能(CAPE)、中等强度0～6 km垂直风切变,是超级单体形成和维持的有利条件;湿球温度0℃高度3. 6 km是有利大冰雹形成的融化层高度;整层相对干(对流层中层达28℃温度露点差)、大的垂直减温率和下沉对流有效位能(DCAPE)都是形成弓状回波和地面强风的有利条件。前期较大对流抑制能量(CIN)抑制了对流初生;随着地面温湿度增加CAPE显著增大、CIN减小,加之边界层辐合显著增强因而触发了对流。老的对流出流气流,环境低空西南气流增强为急流和上游的低空西北偏西气流增强了边界层辐合。飑线发展过程表现出以下特征:TBB演变表明飑线是由线状积云发展成为一个中尺度对流复合体,以正闪为主的闪电和地面大风主要分布于TBB低值处;可见光云图显示具有粗糙的纹理、显著的上冲云顶和旋转等特征;雷达反射率因子显示其由一个β中尺度线状对流系统发展成为一个α中尺度弓状飑线系统;成熟阶段具有显著的回波悬垂、有界弱回波区、中气旋、强中层后侧入流、后侧入流缺口、前侧入流缺口和中层径向速度辐合等特征,异常的垂直液态水含量值是产生大冰雹和雷暴大风的典型雷达回波特征;由于高层分流气流和其西侧不断有新生对流使其组织成非对称尖锥状。对流层中层大的温度露点差和强的后侧入流导致的强下沉辐散气流是形成弓状回波结构的主要原因。位于飑线前沿辐合区后侧的强前侧入流是飑线和弓状回波维持的主要原因。500 hPa风速初期偏弱后期增强、前期较大的CIN及后续迅速减小和抬升触发条件相对弱是该飑线的短期时效预报难点。  相似文献   

用于地震预警的三维实时定位方法     

韩雪君  马延路  刘瑞丰 《地震地磁观测与研究》2012,33(2):32-39

为了尽快定位地震,在“着未着”定位算法基础上,尝试引入三维地壳模型,构建具有三维空间格点分布的走时表.根据已触发台站的到时和未触发台站的位置信息设计概率分布函数,通过八叉树搜索方法,快速给出震源在三维空间的可能位置.使用波前追踪算法,计算中国几个地区三维地壳模型的走时网格,利用中国地震台网资料,对区域内发生的地震进行定位分析.结果显示,在一定的台网密度条件下,三维实时定位方法能在震后数秒给出震源位置,可满足地震预警要求.  相似文献   

宁夏地震灾情捕获系统设计与实现     

李万胜  吉祥  封德春  李自芮 《防灾减灾学报》2015,(4):79-82

破坏性地震发生后,各级政府、各级指挥部需要第一时间获取到地震现场及周边的灾情信息,包括灾情图片、图像。宁夏地震局立足于本区重点危险区、人口密集区、重要设施分布点、次生灾害多发区,利用现有超短波、3G通信链路,在宁夏境内建立基于P头触发、自动拍摄、自动上传、自动存储、自动分发的灾情捕获系统,解决震后对震区及周边灾情图像及时获取的需要,为震后指挥决策提供依据。  相似文献   

Landslide Activity Maps for Landslide Hazard Evaluation: Three Case Studies from Southern Italy   总被引：7，自引：0，他引：7  

Parise  M.  Wasowski  J. 《Natural Hazards》1999,20(2-3):159-183

This paper focuses on the application of landslideactivity maps for evaluating the mass movementhazard in selected areas of the Southern Apenninesof Italy: Bisaccia, Calitri, and Buoninventre. Theavailability of multi-year aerial photo coveragehelped to assess the morphological changes whichoccurred in the last 40 years. This information,integrated with historical data on slope instabilityand field checks, were used to produce landslideactivity maps. These maps represent a short-cut inthe assessment of mass movement hazard, because theyfocus on the effects of slope instability ratherthan on the causative conditions and processes;however, if kept simple and prepared at large scale,they may help the local administrators and land-useplanners to reduce the socio-economic costs oflandslides. Furthermore, the comparative study oflandslide activity represents a relativelyinexpensive and quick method for evaluating theperformance of the engineering control efforts.The quantification of landslide activity in terms ofareal frequency can represent an additional step,useful to determine the relative landslide hazard(zonation in more or less hazardous areas). Forexample, the estimates of areal frequency of activelandsliding for the last 40 years demonstrated thegreat influence of the 1980 Irpinia earthquake(M_s = 6.9) on the stability of slopes situatedclose to its epicenter (within a radius of about20 km).  相似文献   

An Observational Study of Wind Profiles in the Baroclinic Convective Mixed Layer     

Margaret a. Lemone  Mingyu Zhou  Chin-Hoh Moeng  Donald H. Lenschow  L. Jay Miller  Robert L. Grossman 《Boundary-Layer Meteorology》1999,90(1):47-82

A comprehensive planetary boundary-layer (PBL) and synoptic data set is used to isolate the mechanisms that determine the vertical shear of the horizontal wind in the convective mixed layer. To do this, we compare a fair-weather convective PBL with no vertical shear through the mixed layer (10 March 1992), with a day with substantial vertical shear in the north-south wind component (27 February). The approach involves evaluating the terms of the budget equations for the two components of the vertical shear of the horizontal wind; namely: the time-rate-of-change or time-tendency term, differential advection, the Coriolis terms (a thermal wind term and a shear term), and the second derivative of the vertical transport of horizontal momentum with respect to height (turbulent-transport term). The data, gathered during the 1992 STorm-scale Operational and Research Meteorology (STORM) Fronts Experiments Systems Test (FEST) field experiment, are from gust-probe aircraft horizontal legs and soundings, 915-MHz wind profilers, a 5-cm Doppler radar, radiosondes, and surface Portable Automated Mesonet (PAM) stations in a roughly 50 × 50 km boundary-layer array in north-eastern Kansas, nested in a mesoscale-to-synoptic array of radiosondes and surface data.We present evidence that the shear on 27 February is related to the rapid growth of the convective boundary layer. Computing the shear budget over a fixed depth (the final depth of the mixed layer), we find that the time-tendency term dominates, reflecting entrainment of high-shear air from above the boundary layer. We suggest that shear within the mixed layer occurs when the time-tendency term is sufficiently large that the shear-reduction terms – namely the turbulent-transport term and differential advection terms – cannot compensate. In contrast, the tendency term is small for the slowly-growing PBL of 10 March, resulting in a balance between the Coriolis terms and the turbulent-transport term. Thus, the thermal wind appears to influence mixed-layer shear only indirectly, through its role in determining the entrained shear.  相似文献   

A Homogeneous Langevin Equation Model, Part ii: Simulation of Dispersion in the Convective Boundary Layer     

John S. Nasstrom  Donald L. Ermak 《Boundary-Layer Meteorology》1999,92(3):371-405

We present a Lagrangian stochastic model of vertical dispersion in the convective boundary layer (CBL). This model is based on a generalized Langevin equation that uses the simplifying assumption that the skewed vertical velocity probability distribution is spatially homogeneous. This approach has been shown to account for two key properties of CBL turbulence associated with large-scale coherent turbulent structures: skewed vertical velocity distributions and long velocity correlation time. A 'linear-skewed' form of the generalized Langevin equation is used, which has a linear (in velocity) deterministic acceleration and a skewed random acceleration. 'Reflection' boundary conditions for selecting a new velocity for a particle that encounters a boundary were investigated, including alternatives to the standard assumption that the magnitudes of the particle incident and reflected velocities are positively correlated. Model simulations were tested using cases for which exact, analytic statistical properties of particle velocity and position are known, i.e., well-mixed spatial and velocity distributions. Simulations of laboratory experiments of CBL dispersion show that (1) the homogeneous linear-skewed Langevin equation model (as well as an alternative 'nonlinear-Gaussian' Langevin equation model) can simulate the important aspects of dispersion in the CBL, and (2) a negatively-correlated-speed reflection boundary condition simulates the observed dispersion of material near the surface in the CBL significantly better than alternative reflection boundary conditions. The homogeneous linear-skewed Langevin equation model has the advantage that it is computationally more efficient than the homogeneous nonlinear-Gaussian Langevin equation model, and considerably more efficient than inhomogeneous Langevin equation models.  相似文献   

1995年夏季青藏高原上及其邻域的对流活动   总被引：3，自引：2，他引：1  

朱国富  陈受钧 《高原气象》1999,18(1):9-19

通过统计分析１９９５年夏季６－８月每小时一次的ＧＭＳ红外资料,揭示了１９９５年夏生青藏高原及其邻域对流活动的一些天气候特征,得到以主要结果：（１）具有明显的区域性,喜马拉雅山分隔开孟湾－印度和青藏高原两个主要大值区,另一个主要大值区在老挝至雷州半岛,高原上最频繁的对流区在以３０°Ｎ,９０°Ｅ为中心的地区,而不在高原东部,而且喇叭口形的雅鲁藏布江出口区是一个小值区。高原和孟湾－印度两地的对流活动有不  相似文献   

强震前地气系统长波辐射（OLR）异常的成因   总被引：5，自引：2，他引：3       下载免费PDF全文

康春丽  韩延本  刘德富  曹忠权 《地球物理学进展》2008,23(6):1703-1708

本文针对2008年1月9日发生在西藏阿里地区的改则6.9级地震,分析了卫星遥感我国西部地区长波辐射(OLR)信息场的月际和日际变化特征,研究了临震前震中区附近长波辐射的显著增强与其所处大气压力变化的同步关联现象,认为震前长波辐射异常征象的成因可能源自大气而非地热,临震前的大气压力增强是改则6.9级地震发生的诱触发因素,而长波辐射变化信息可作为表征大气诱触发地震动力的一个重要指征物理量.  相似文献