改进的客观分析诊断图形软件   总被引：1，自引：1，他引：0  

郑永光  陈炯  沃伟峰  韩雷  陶祖钰 《气象》2011,37(6):735-741

客观分析诊断图形系统是一款面向气象科研,得到广泛应用的二维气象绘图软件。根据气象科研工作和强对流天气分析研究的新需求,对该软件进行了改进,主要包括增加新数据接口、增加新算法、改进算法、简化操作等。改进的软件增加了静止卫星、新一代天气雷达和二进制格式点加工数据GRIdded Binary 2(GRIB2)等多种数据接口,...  相似文献   

复杂地形下雷暴增强过程的个例研究   总被引：12，自引：2，他引：10  

陈双  王迎春  张文龙  陈明轩 《气象》2011,37(7):802-813

本文基于多普勒雷达变分同化分析系统（VDRAS）反演的对流层低层热力和动力场,并结合多种稠密观测资料,对北京地区2009年7月22日一次弱天气尺度强迫下雷暴在山区和平原增强的机理进行了较深入的分析。研究结果表明：雷暴过程受大尺度天气系统影响不明显,对流前期地面弱冷锋,是此次雷暴新生的触发机制,高层冷平流、低层偏南暖湿气流的稳定维持和对流不稳定能量的聚集是本次雷暴增强的必要条件。雷暴从河北北部移进北京西北山区后,在下山和到达平原地区时,经历了两次明显的发展增强阶段。雷暴第一阶段下山增强,地形强迫起着主要作用,具体表现在三个方面：（1）地形斜坡使得雷暴冷池出流下山加速与稳定维持的偏南气流形成了强的辐合区;（2）地形抬升使得偏南暖湿入流强烈地上升,从而加剧了对流的发展;（3）地形抬高了冷池出流高度,使得出流与近地面偏南气流构成随高度顺转的低层垂直风切变,低层暖空气之上有冷平流叠加,使得雷暴前方的动力和热力不稳定增强。雷暴第二阶段在平原地区再次增强的主要原因是：组织完好的雷暴到达平原地区后,其冷池与低层暖舌在城区（朝阳地区）的对峙,产生了强的扰动温度梯度;强的冷池出流与势力相当的偏南暖湿气流相互作用产生了强的辐合上升气流,并与下沉气流在较长时间内共存;冷池出流形成的负涡度与低层切变产生的正涡度达到近似平衡状态。运用RKW理论,三者导致雷暴前方低层的辐合抬升最强,最有利于雷暴的维持发展。  相似文献   

强对流风暴中同质冻结增温的直接探空观测     

徐小红  余兴  戴进  刘贵华  朱延年  岳治国 《南京气象学院学报》2011,34(4):416-422

通过两个强对流风暴个例,利用探空资料辅以卫星反演方法,揭示了强对流风暴中同质冻结增温这一事实。探空观测到在强风暴中同质冻结潜热释放造成该层内的空气增温达5℃以上,风暴中强上升气流使云滴没有足够的时间长大,云水向雨水转化和云的晶化会被推到更高的高度,在到达同质冻结高度之前,异质核化过程没有太多的时间消耗大量云水,多数云滴被带到同质冻结高度以上时迅速冻结,造成潜热的集中释放,使周围的空气增温。NOAA卫星观测到的云顶的大量由同质冻结形成的小冰粒子以及过顶现象,进一步证实了同质冻结潜热增温。当探空仪靠近风暴、对流层顶又距同质冻结高度层较近时,同质冻结增温作用有可能被探空仪观测到。  相似文献   

磁层顶日下点距离R_0与磁暴D_（st）指数的相关性     

程国胜  苑顺周  赵蕾 《南京气象学院学报》2011,34(4):504-509

利用2004—2006年ACE、WIND卫星观测的太阳风数据和相应时期反映磁暴大小的Dst指数,针对200个不同级别的磁暴事件,分析了磁层顶日下点距离R0与磁暴Dst指数的线性相关性。分析显示,在极端太阳风条件下,Dst指数时间序列比借助于Chao Model计算出的磁层顶日下点距离R0的时间序列延迟了约3h。经修正时间延迟后,对磁层顶日下点距离R0与磁暴Dst指数的线性相关性进行分析。结果表明：发生超级磁暴时,二者线性相关系数的均值为0.77;大磁暴时,线性相关系数的均值为0.74;中等磁暴时,线性相关系数的均值为0.47。此外,用最小二乘数据拟合得到了不同级别磁暴时的R0-Dst关系图。  相似文献   

A Case Study of a Typical Dust Storm Event over the Loess Plateau of Northwest China          下载免费PDF全文

LING Xiao-Lu  GUO Wei-Dong  ZHAO Qian-Fei  ZHANG Bei-Dou 《大气和海洋科学快报》2011,4(6):344-348

Enhanced observational meteorological elements,energy fluxes,and the concentration of dust aerosols collected from the Semi-Arid Climate Observatory and Laboratory(SACOL) during a typical dust storm period in March 2010 at Lanzhou were used in this paper to investigate the impact of dust aerosols on near surface atmospheric variables and energy budgets.The results show that the entire dust storm event was associated with high wind velocities and decreasing air pressure,and the air changed from cold and wet to warm and dry and then recovered to its initial state.The response of energy fluxes occurred behind meteorological elements.At high dust concentration periods,the net radiation was significantly less in the daytime and higher at night,while the heat fluxes displayed the same trend,indicating the weakening of the land-atmosphere energy exchange.The results can be used to provide verification for numerical model results in semi-arid areas.  相似文献   

磁暴主相多阶发展行星际起因的初步分析          下载免费PDF全文

佟亚男  刘四清  张效信  林瑞淋  龚建村 《地球物理学报》2011,54(6):1439-1456

本文利用1998～2006年与磁云有关的80起中强磁暴(Dst*≤-50 nT),对其主相期间不同发展阶数磁暴的行星际起因进行了统计分析.重点研究了鞘区磁场单独作用、磁云本体单独作用、鞘区与磁云共同作用以及其他复杂行星际结构在磁暴主相多阶发展中的相对重要性,并对导致磁暴主相增加一阶的行星际起因做了初步分析.统计结果表明...  相似文献   

The influence of alongshore and cross‐shore wave energy flux on large‐ and small‐scale coastal erosion patterns     

Elsayed M. Galal  Satoshi Takewaka 《地球表面变化过程与地形》2011,36(7):953-966

A strong low‐pressure system traveled along the Japanese main island Honshu in October 2006. High waves and storm surge attacked the Kashima Coast resulting in huge erosion over the area. Airborne laser data measured in October 2005 and November 2006 were analyzed to estimate cross‐sectional changes within the subaerial zone. The results of the alongshore distribution of the changes of cross‐sectional area indicate that the amount of erosion of the 38 km‐long northern and 15 km‐long southern parts decreased toward the south in each part and that the amount of erosion was smaller in protected areas with artificial headlands than in unprotected areas. The local alongshore variation of the erosion and accretion patterns showed wavy fluctuations of several hundreds of meters. The total amounts of the estimated eroded volume of the subaerial zone over the northern and southern parts were 620 000 m³ and 600 000 m³, respectively. The Simulating Waves Nearshore (SWAN) wave model was applied to estimate wave conditions along the coast during the storm. The computational results were verified, and then the alongshore distribution of wave energies, expressed as the alongshore and cross‐shore components of the wave energy flux, was compared with the alongshore distribution of cross‐sectional change. The results show that the distribution of energy flux explains the distribution of erosion well: The alongshore variability in the cross‐shore energy flux is responsible for the large‐scale variability in erosion, and shorter‐scale variability is due to gradients in the alongshore energy fluxes, especially for the areas without coastal works. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Discontinuous Galerkin methods for modeling Hurricane storm surge   总被引：1，自引：0，他引：1  

Clint Dawson  Ethan J. KubatkoChristopher Mirabito  Craig MichoskiNishant Panda 《Advances in water resources》2011,34(9):1165-1176

Storm surge due to hurricanes and tropical storms can result in significant loss of life, property damage, and long-term damage to coastal ecosystems and landscapes. Computer modeling of storm surge can be used for two primary purposes: forecasting of surge as storms approach land for emergency planning and evacuation of coastal populations, and hindcasting of storms for determining risk, development of mitigation strategies, coastal restoration and sustainability.Storm surge is modeled using the shallow water equations, coupled with wind forcing and in some events, models of wave energy. In this paper, we will describe a depth-averaged (2D) model of circulation in spherical coordinates. Tides, riverine forcing, atmospheric pressure, bottom friction, the Coriolis effect and wind stress are all important for characterizing the inundation due to surge. The problem is inherently multi-scale, both in space and time. To model these problems accurately requires significant investments in acquiring high-fidelity input (bathymetry, bottom friction characteristics, land cover data, river flow rates, levees, raised roads and railways, etc.), accurate discretization of the computational domain using unstructured finite element meshes, and numerical methods capable of capturing highly advective flows, wetting and drying, and multi-scale features of the solution.The discontinuous Galerkin (DG) method appears to allow for many of the features necessary to accurately capture storm surge physics. The DG method was developed for modeling shocks and advection-dominated flows on unstructured finite element meshes. It easily allows for adaptivity in both mesh (h) and polynomial order (p) for capturing multi-scale spatial events. Mass conservative wetting and drying algorithms can be formulated within the DG method.In this paper, we will describe the application of the DG method to hurricane storm surge. We discuss the general formulation, and new features which have been added to the model to better capture surge in complex coastal environments. These features include modifications to the method to handle spherical coordinates and maintain still flows, improvements in the stability post-processing (i.e. slope-limiting), and the modeling of internal barriers for capturing overtopping of levees and other structures. We will focus on applications of the model to recent events in the Gulf of Mexico, including Hurricane Ike.  相似文献   

基于MODIS数据定量判识沙尘暴方法的对比研究     

陶然  于曼竹 《地理信息世界》2011,9(3):51-54

利用MODIS数据,结合具体实例,对比研究当前几种利用光谱特征定量判识沙尘暴的方法。从理论上剖析各方法的原理,分析其优劣,并提出一套新的算法的组合方式。研究结果表明,新的组合算法有不小的改进：①大大降低了单一算法在不同时间或地区图像中阈值取值不稳定的影响,减少了图像噪声造成的误判,增强了其通用性和稳定性;②明显减弱了太...  相似文献   

Temporal variations in aerosol composition at Lanzhou City,Northwestern China     

Feng She  YiFan Cheng  ShiGong Wang  YongTao Guo  JinYan Wang  MinJing M  KeZheng Shang 《寒旱区科学》2011,3(3):0252-0263

Although Lanzhou is one of the most heavily polluted cities in China, the composition of its air pollutants have not yet been studied in detail. The data of four months on the concentrations and compositions of ions from daily air-filter samples in the winter and spring during 2007–2008 were analyzed to investigate temporal trends and their possible causes. The results indicate that mean concentrations of almost all the aerosol components are greater in winter than in spring due to stronger emissions in winter and weaker localized dispersion. Spring dust storms are the major cause of the highest peak PM10 concentrations recorded during the study period; however, these elevated levels were transient. Ion concentrations related to coal combustion show the greatest reduction from winter to spring, while the concentrations of strong crustal components show a less-pronounced reduction. Strong cycles in the levels of particulate matter (PM) and all ions are also observed during the winter months due to meteorological conditions. Depending on the season, nine different ions accounted for 20%–50% of the PM concentration. The particle size of polluting ions was constant at times of increasing PM concentrations (particularly during winter), whereas the particle size of crustal ions increased dramatically during spring dust storms. Local meteorological conditions (especially wind speed) have a strong influence on the levels of pollutants. Four dust storms were noted, including one during winter. In summary, the regional transport of desert dust from the Gobi can significantly affect air quality and the chemical composition of aerosols in Lanzhou. The dust storms can strongly increase concentration of crustal ions, which are characteristics of deserts in northwestern China. This observation is in agreement with back-trajectories, which show reduced levels of pollutant ions during dust storms. Data on nitrate:sulfate ratios indicate that stationary point sources are the main source of ions rather than mobile sources.  相似文献