九寨沟“8.8”地震背景下火花海钙华坝体无损探测分析     

罗尧东  代群威  董发勤  王富东  赵学钦  廖传康  崔杰  李琼芳  王安平 《中国岩溶》2021,40(1):147-156

为研究震后九寨沟钙华景区的溶洞、裂隙、暗流等地质特性,丰富钙华景区岩溶洞穴无损探测技术,探讨了多物探技术在多孔疏松钙华地区作业的可靠性。首次运用地质雷达法及高密度电法相结合的无损探测技术,在九寨沟景区火花海特定区域进行了现场勘查和无损探测试验。结合对比两种无损探测成果与测区内出露地质剖面3组勘探数据,结果发现:高密度电法与地质雷达法相结合,两者能优劣互补,相互佐证,在解决钙华区域浅部溶洞、暗流、裂隙等工作中,对探测目标体具有极高的识别度。两种方法探测数据与震后出露剖面地质特征保持极高的一致性,验证了两种无损检测方法在多孔疏松介质条件下数据的真实可靠性,解决了多物探技术在多孔疏松介质地区施工的疑点和难点,丰富了工程物探领域技术。   相似文献   

京津冀地区低层局地大气环流的气候特征研究   总被引：3，自引：0，他引：3       下载免费PDF全文

曾佩生  朱蓉  范广洲  李泽椿  王月冬 《气象》2019,45(3):381-394

本文采用2007-2016年的中尺度数值模拟结果和15个地面气象站观测资料,定义了局地风场表征风速,研究京津冀平原地区局地大气环流日变化的气候特征,并对区域大气污染及其输送的影响进行分析。此外,对2016年12月30日至2017年1月7日北京地区跨年大气重污染过程进行了个例分析。得到结论:京津冀平原地区低空风场变化是天气系统与局地大气环流共同作用的结果,山谷风环流致使太行山和燕山沿线平原地区大气边界层内的长年主导风向为偏北和偏南;太行山和燕山沿线地区山谷风环流本身呈顺时针旋转的日变化特征,夜间至早晨谷风转向山风,午后至夜间山风转向谷风;在午后谷风向山风转向期间,容易形成沿太行山东麓和燕山南麓、自南向东北的"弓形"气流输送通道,此气流输送通道在1月于21时左右形成,持续时间大约3 h,在7月于18时左右形成,持续时间可达9 h;冬季午后至晚间盛行谷风时,受山体的阻挡,污染物容易在山前累积,导致污染浓度增高;夏季同样的情况会发生在后半夜。  相似文献   

Generation of oceanic internal gravity waves by a cyclonic surface stress disturbance     

《Dynamics of Atmospheres and Oceans》2019

Atmospheric cyclones with strong winds significantly impact ocean circulation, regional sea surface temperature, and deep water formation across the global oceans. Thus they are expected to play a key role in a variety of energy transport mechanisms. Even though wind-generated internal gravity waves are thought to contribute significantly to the energy balance of the deep ocean, their excitation mechanisms are only partly understood.The present study investigates the generation of internal gravity waves during a geostrophic adjustment process in a Boussinesq model with axisymmetric geometry. The atmospheric disturbance is set by an idealized pulse of cyclonic wind stress with a Rankine vortex structure. Strength, radius and duration of the forcing are varied. The effect upon wave generation of stratification with variable mixed-layer depth is also examined.Results indicate that internal gravity waves are generated after approximately one inertial period. The outward radial energy flux is dominated by waves having structure close to vertical mode-1 and with frequency close to the inertial frequency. Less energetic higher mode waves are observed to be generated close to the sea floor underneath the storm. The total radiated energy corresponds to approximately 0.02% of the wind input. Deeper mixed-layer conditions as well as weaker stratification reduce this fraction.The low energy transfer rates suggest that other processes that drive vertical motion like surface heat fluxes, turbulent motion, mixed region collapse and storm translation are essential for significant energy extraction by internal gravity waves to occur.  相似文献   

Nature,origin and evolution of a Late Pleistocene incised valley‐fill,Sunda Shelf,Southeast Asia          下载免费PDF全文

Faisal A. Alqahtani  Howard D. Johnson  Christopher A.‐L. Jackson  Mohd Rapi B. Som 《Sedimentology》2015,62(4):1198-1232

Understanding the stratigraphic fill and reconstructing the palaeo‐hydrology of incised valleys can help to constrain those factors that controlled their origin, evolution and regional significance. This condition is addressed through the analysis of a large (up to 18 km wide by 80 m deep) and exceptionally well‐imaged Late Pleistocene incised valley from the Sunda Shelf (South China Sea) based on shallow three‐dimensional seismic data from a large (11 500 km²), ‘merge’ survey, supplemented with site survey data (boreholes and seismic). This approach has enabled the characterization of the planform geometry, cross‐sectional area and internal stratigraphic architecture, which together allow reconstruction of the palaeo‐hydrology. The valley‐fill displays five notable stratigraphic features: (i) it is considerably larger than other seismically resolvable channel forms and can be traced for at least 180 km along its length; (ii) it is located in the axial part of the Malay Basin; (iii) the youngest part of the valley‐fill is dominated by a large (600 m wide and 23 m deep), high‐sinuosity channel, with well‐developed lateral accretion surfaces; (iv) the immediately adjacent interfluves contain much smaller, dendritic channel systems, which resemble tributaries that drained into the larger incised valley system; and (v) a ca 16 m thick, shell‐bearing, Holocene clay caps the valley‐fill. The dimension, basin location and palaeo‐hydrology of this incised valley leads to the conclusion that it represents the trunk river, which flowed along the length of the Malay Basin; it connected the Gulf of Thailand in the north with the South China Sea in the south‐east. The length of the river system (>1200 km long) enables examination of the upstream to downstream controls on the evolution of the incised valley, including sea‐level, climate and tectonics. The valley size, orientation and palaeo‐hydrology suggest close interaction between the regional tectonic framework, low‐angle shelf physiography and a humid‐tropical climatic setting.  相似文献   

C波段雷达在新疆区域数值预报系统中的应用初探     

马秀梅 《沙漠与绿洲气象(新疆气象)》2015,9(6):19-26

基于新疆区域数值预报系统（Desert Oasis Gobi Rapid Analysis Forecast System,下称DOGRAFS）,开展了同化C波段雷达资料对2010年10月6日发生在新疆的一次强降水过程预报结果影响的试验分析。其中设计包括不同化任何资料、同化常规资料、同化雷达反射率因子、同化雷达径向风、同时同化反射率因子和径向风五组试验,重点分析了雷达资料同化对此次天气过程降水、温度以及风速模拟效果的影响。结果表明：（1）同化雷达径向风和同时同化径向风和反射率因子相对于其他三组试验,对降水预报的TS和ETs评分更高;（2）相对于其他三组试验,同化雷达径向风和同时同化径向风和反射率因子对模式垂直方向上的温度、风速预报偏差具有一定的改善效果;（3）对于地面2 m温度和10 m风速而言,同化常规观测资料比其他四组试验预报的平均偏差和均方根误差更小;其它四组试验误差相当,差别不明显,表明同化雷达对近地面层温度和风的影响不明显。本研究旨在探索C波段雷达观测资料在新疆区域数值预报系统中的适用性,为今后雷达观测资料在业务系统中的应用提供参考。  相似文献   

一种改进的TSI3563积分浊度误差校正方法          下载免费PDF全文

马楠  周秀骥  颜鹏  赵春生 《应用气象学报》2015,26(1):12-21

TSI3563型积分式浊度计是一种性能出色的气溶胶散射系数观测仪器,然而由于仪器设计所固有的限制,TSI3563型浊度计观测结果包含有角度截断和非朗伯体光源两项系统性误差,会使观测结果较真值偏小10%左右。因此,需要对TSI3563型浊度计的观测结果进行校正才能得到较为精确的散射系数观测值。该研究利用2009年华北平原HaChi气溶胶外场观测数据测试了现有校正方法,结果显示,传统的校正方法在我国华北平原这样的高气溶胶污染地区并不适用。为此,提出一种改进的校正方法,利用同时观测的PM₁和PM₁₀数据,在校正方案中加入超微米粒子体积比这一参量,对于不同体积比采用不同的校正函数。利用实际观测数据检验后发现,改进方法的校正效果相对于传统方法有很大改善。  相似文献   

COMPARISONS OF CIRCULATION ANOMALIES BETWEEN THE DAILY PRECIPITATION EXTREME AND NON-EXTREME EVENTS IN THE MIDDLE AND LOWER REACHES OF YANGTZE RIVER IN BOREAL SUMMER   总被引：1，自引：1，他引：0  

韩洁  管兆勇  李明刚 《热带气象学报(英文版)》2015,21(2):131-142

Based on the NCEP/NCAR reanalysis dataset and in situ meteorological observations of daily precipitation in boreal summer from 1979 to 2008, the features of circulation anomalies have been investigated using the composite analysis for the extreme events and non-extreme events of regional mean daily rainfall(RMDR) occurring over the midand lower- Yangtze valley(MLYV). The extreme RMDR(ERMDR) events are the events at and above the percentile99 in the rearranged time-series of the RMDR with ascending order of rainfall amount. The non-extreme RMDR events are those at the percentiles 90-85 and 80-75 separately. Our results suggest that the threshold value is 25 mm/day for the ERMDR at percentile 99. Precipitation at all the percentiles is found to occur more frequently in the Meiyu rainfall season in MLYV, and the ERMDR events have occurred with higher frequency since the 1990 s. For the percentiles-associated events, the MLYV is under the control of an anomalous cyclonic circulation in the mid- and lower- troposphere with vastly different anomalous circulation at higher levels. However, at both low and high levels, the ERMDR events-related anomalous circulation is stronger compared to that linked to the non-ERMDR events. The dominant sources of water vapor differ between the ERMDR and non-ERMDR events. During the ERMDR events plentiful water vapor is transported from the Bay of Bengal into the MLYV directly by divergence while there is distinctly increased water vapor from the South China Sea(SCS) in non-RMERMDR episodes. The diabatic heating rates < Q1>, < Q2> and< Q1>- < Q2> have their anomalous patterns and are consistent with each other for these percentiles but their strength decreases markedly with the drop of rainfall intensity. For the precipitation at percentiles 99 and 90-85, the sea surface temperature anomalies(SSTA) in the Pacific distribute positively(negatively) in the south(north), and are stronger when the ERMDR emerges, with little or no SSTA as the events at percentile 80-75 occur. Besides, these results suggest that the genesis of the ERMDR event is directly related to intense local circulation anomalies and the circulation anomalies over the Pacific and SCS in tropical to mid-latitudes, and probably linked with the Pacific SSTA closely while the non-ERMDR events are mainly associated with the anomalous circulation on a local basis. The findings here help understand and predict the happening of ERMDR events over the MLYV.  相似文献   

THE EFFECTS OF THE PLATEAU''S TOPOGRAPHIC GRADIENT ON ROSSBY WAVES AND ITS NUMERICAL SIMULATION     

何钰  李国平 《热带气象学报(英文版)》2015,21(4):337-351

By using barotropic model equations, this article analyzed the characteristics of Rossby waves, the propagation features of wave energy and the influence of dynamic and thermal effects of the Tibetan Plateau on Rossby waves, and the focus is on discussing the plateau's topographic gradient effects on atmospheric Rossby waves. Then based on the WRF3.2 and the NCEP/NCAR FNL reanalysis data, we devised comparative tests of changing the plateau's topographic gradient and simulated a process of persistent heavy rain that happened in May 2010 in South China. The results are shown as follows. The Tibetan Plateau’s topography is conducive to the formation of atmospheric Rossby waves. while the plateau's terrain, its friction and heating effects can all make the atmospheric Rossby waves develop into the planetary waves; The effects of plateau's north and south slopes on the Rossby wave’ phase velocity is opposite, and when the slope reached a certain value can the quasi-steady normal fluctuations be generated; Simultaneously, due to the plateau's topographic gradient, descending motion appears at the west side of the plateau while ascending motion appears at the east side, and the vertical movement increased with the amplification of topographic gradients. The plateau's topographic gradient also obviously amplified the precipitation in South China, and the rainfall area increased with the amplification of topographic gradients and gradually moved from south to north and from west to east, which is conducive to the occurrence and development of convective activities in the downstream areas of the Tibetan Plateau; Moreover, for the plateau’s dynamic and thermal effects, the Rossby wave’ propagation shows upstream effects of energy dispersion, so the plateau can then affect the weather in downstream areas. Moreover, the wave group velocity increased with the degree of topographic slope.  相似文献   

华北-华东地区高温热浪与土壤湿度的关系研究   总被引：2，自引：1，他引：1  

王丽伟  张杰 《气象科学》2015,35(5):558-564

利用观测站点的日最高气温、土壤湿度旬观测资料以及土壤湿度再分析资料等,分析了华北-华东地区高温热浪次数的时空变化特征及其与土壤湿度的关系。结果表明:1960s以及1990-2010年为高温热浪次数的高值期,1970s-1980s为低值期。利用旋转经验正交函数分解得到土壤湿度的3个气候分区,分区内前期(3-5月)和同期(6-7月)的土壤湿度与6、7月份高温热浪次数基本呈负相关关系,并且同期相关性更显著。在华北-华东北部与中部,5月下旬土壤湿度与6月高温热浪次数、6月上、中旬平均土壤湿度与6月高温热浪次数、7月平均土壤湿度与7月高温热浪次数的相关性均显著。  相似文献   

近50a东北冷涡异常特征及其与淮河流域降水的关系   总被引：1，自引：0，他引：1  

李超  韩桂荣  孙燕 《气象科学》2015,35(2):216-222

利用美国国家环境预报/大气研究中心(NCEP/NCAR)再分析月平均数据分析了1960—2009 年夏季东北冷涡的异常特征,研究了夏季东北冷涡与同期淮河流域降水的关系,发现:东北冷涡偏强时,淮河流域的降水很可能偏多,东北冷涡偏弱时,淮河流域的降水很可能偏少。东北冷涡异常强年,淮河流域高低层环流具有斜压性,且低层有显著的正涡度发展,促进了上升对流运动活跃发展。而东北冷涡活动异常频繁,有利于引导潮湿阴冷的北方气流南下,与东亚夏季盛行的西南暖湿气流在淮河流域上空交汇,在上升运动的触发下,导致淮河流域降水明显增多;东北冷涡弱年的情况正好相反。  相似文献