基于LiDAR观测的长江河口南汇南滩近期动力地貌研究     

王杰  戴志军  魏稳  葛振鹏  庞文鸿  马彬彬  梅雪菲  于亚文 《海洋与湖沼》2018,49(4):756-768

南汇潮滩是长江河口重要的后备国土资源,其地貌的动态变化过程可敏锐反映河海相互作用的强弱。本文利用地面LiDAR获取了南汇南滩2016年4月—2017年5月逐月大潮低潮期间滩面地貌高分辨率点云数据,根据平均小潮高、低潮位将潮滩划分为上、中和下部,由此结合水文泥沙资料分析区域潮滩动力地貌演变过程。结果表明:(1)潮滩在观测期间整体向海淤涨,其一年间垂向淤积值为10 cm,其中潮滩中部面积增大,而潮滩上部和下部的面积均减小;(2)滩面变化具有明显的夏秋季弱侵蚀调整、冬春季强淤积推进的季节性特征,潮滩地貌侵蚀-淤积则呈现明显的空间分异。在潮滩上部中侧-中部西侧形成贯通的冲刷带(10—80cm),上部沿堤西侧植被区出现强淤积带(20—85cm),整个滩面中东部潮滩出现大面积的弱淤积(5—30cm);(3)南汇南滩并未因长江入海泥沙的剧烈减少而遭受侵蚀,这可能受控于局地基本未变的动力环境和悬浮泥沙浓度,冲刷-淤积的纵向分带性则与区域海堤导致的潮流流向发生改变有关。  相似文献   

东南极中山站陆缘固定冰2011/2012年度的时空变化     

赵杰臣  杨清华  程斌  LEPP&#;RANTA Matti  谢苏锐  陈猛  于亦宁  田忠翔  李明  张林  惠凤鸣 《海洋学报(英文版)》2019,38(5):51-61

Annual observations of first-year ice(FYI) and second-year ice(SYI) near Zhongshan Station, East Antarctica,were conducted for the first time from December 2011 to December 2012. Melt ponds appeared from early December 2011. Landfast ice partly broke in late January, 2012 after a strong cyclone. Open water was refrozen to form new ice cover in mid-February, and then FYI and SYI co-existed in March with a growth rate of 0.8 cm/d for FYI and a melting rate of 2.7 cm/d for SYI. This difference was due to the oceanic heat flux and the thickness of ice,with weaker heat flux through thicker ice. From May onward, FYI and SYI showed a similar growth by 0.5 cm/d.Their maximum thickness reached 160.5 cm and 167.0 cm, respectively, in late October. Drillings showed variations of FYI thickness to be generally less than 1.0 cm, but variations were up to 33.0 cm for SYI in March,suggesting that the SYI bottom was particularly uneven. Snow distribution was strongly affected by wind and surface roughness, leading to large thickness differences in the different sites. Snow and ice thickness in Nella Fjord had a similar "east thicker, west thinner" spatial distribution. Easterly prevailing wind and local topography led to this snow pattern. Superimposed ice induced by snow cover melting in summer thickened multi-year ice,causing it to be thicker than the snow-free SYI. The estimated monthly oceanic heat flux was ～30.0 W/m2 in March–May, reducing to ～10.0 W/m2 during July–October, and increasing to ～15.0 W/m2 in November. The seasonal change and mean value of 15.6 W/m2 was similar to the findings of previous research. The results can be used to further our understanding of landfast ice for climate change study and Chinese Antarctic Expedition services.  相似文献   

Field estimation of specific yield in a central Iowa crop field     

S. D. Logsdon  K. E. Schilling  G. Hernandez‐Ramirez  J. H. Prueger  J. L. Hatfield  T. J. Sauer 《水文研究》2010,24(10):1369-1377

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CO2 absorption of sandy soil induced by rainfall pulses in a desert ecosystem          下载免费PDF全文

Ke‐Yu Fa  Jia‐Bin Liu  Yu‐Qing Zhang  Bin Wu  Shu‐Gao Qin  Wei Feng  Zong‐Rui Lai 《水文研究》2015,29(8):2043-2051

Soil CO₂ flux is strongly influenced by precipitation in many ecosystem types, yet knowledge of the effects of precipitation on soil CO₂ flux in semi‐arid desert ecosystems remains insufficient, particularly for sandy soils. To address this, we investigated the response of sandy soil CO₂ flux to rainfall pulses in a desert ecosystem in northern China during August–September 2011. Significant changes (P < 0.05) were found in diel patterns of soil CO₂ flux induced by small (2.1 mm), moderate (12.4 mm) and large (19.7 mm) precipitation events. Further analysis indicated that rainfall pulses modified the response of soil CO₂ flux to soil temperature, including hysteresis between soil CO₂ flux and soil temperature, with F_s higher when T_s was increasing than when T_s was decreasing, and the linear relationship between them. Moreover, our results showed that rainfall could result in absorption of atmospheric CO₂ by soil, possibly owing to mass flow of CO₂ induced by a gradient of gas pressure between atmosphere and soil. After each precipitation event, soil CO₂ flux recovered exponentially to pre‐rainfall levels with time, with the recovery times exhibiting a positive correlation with precipitation amount. On the basis of the amounts of precipitation that occurred at our site during the measurement period (August–September), the accumulated rain‐induced carbon absorption evaluated for rainy days was 1.068 g C m^?2; this corresponds approximately to 0.5–2.1% of the net primary production of a typical desert ecosystem. Thus, our results suggest that rainfall pulses can strongly influence carbon fluxes in desert ecosystems. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

柴达木盆地欧南凹陷上石炭统克鲁克组海陆过渡型烃源岩有机质组成及生烃特征     

施辉  李宗星  彭博  孙玉琦  张浩  杨元元  胡俊杰  方欣欣  魏小洁 《地质学报》2023,97(1):179-196

柴达木盆地北缘东段欧南凹陷上石炭统克鲁克组海陆交互混积型储层中获得良好油气发现,但该层段内烃源岩海陆混合型生物有机质组分及类型、生烃差异性等基础性问题的认识尚不清楚。选择尕海南山南坡柏树沟剖面克鲁克组烃源岩开展有机地球化学、XRD、岩石薄片、SEM等分析测试,研究了岩性及组分、丰度质量及类型、可溶有机质族组分及生烃母质等,结果表明：克鲁克组烃源岩残余有机质丰度总体较高,原始生烃能力强,处于高成熟演化阶段,残留腐殖型(Ⅲ型)为主的干酪根,可溶有机质主要来源于海洋低等水生生物有机质母质(Ⅱ型),反映出海陆两相混源生物有机质的特征,海相有机质在前次生烃过程中对生烃量的贡献相对高于陆源生物。大量放射虫等浮游硅质生物是克鲁克组烃源岩海相有机质的主要组分,是海相干酪根的主力生烃物质;晚石炭世,欧南凹陷南部古陆和北部海槽分别向凹陷提供陆相高等植物和海洋低等水生生物或富硅上升流,海相有机质的富集与硅质生物活动直接相关。该研究认识为探索石炭系有机质富集机制和优质烃源岩分布规律提供了参考依据,也对区域性油气勘探部署具有指导意义。  相似文献   

1215号“布拉万”台风暴雨及降水非对称性分布的成因分析   总被引：9，自引：4，他引：5  

孙力  董伟  药明  朱丹  李倩 《气象学报》2015,73(1):36-49

利用中尺度非静力模式WRF对2012年第15号台风“布拉万”在中国东北地区造成的暴雨过程进行了数值模拟,结合观测资料对模拟结果进行了验证,利用模式输出的高分辨率资料,对“布拉万”台风造成的强降水及其非对称性分布的成因进行了诊断分析。结果表明,模式很好地再现了台风登陆过程中的路径、强度变化和降水分布,受中纬度西风槽带来的干冷空气影响,“布拉万”台风登陆后的降水和环流结构具有明显的不对称性,降水主要集中在台风中心西北侧的能量锋区附近。水汽散度通量和水汽螺旋度能够较好地描述强降水过程的发生、发展及其非对称性分布的时空特征,在强降水区,水汽散度通量表现为正值强信号,而水汽螺旋度表现为负值强信号,在非降水区和弱降水区,两者均表现为弱信号。等熵位涡分析显示,对流不稳定只是此次台风暴雨前期和初始阶段的不稳定条件,而湿位涡(MPV)的湿斜压项(MPV₂)则是暴雨增强和出现非对称性分布的主要机制。在暴雨形成过程中,由于冷空气侵入造成了在台风环流西北侧湿等熵面的陡立倾斜和水平风垂直切变的增强,导致了气旋性涡度的显著增强,气旋性涡度增强造成的强烈上升运动将降水区东南侧输送过来的暖湿空气向上输送,从而导致了暴雨的发生,这其中条件性对称不稳定是降水得以加强的一种重要不稳定机制。  相似文献   

Evaluation of CMIP5 Climate Models in Simulating 1979–2005 Oceanic Latent Heat Flux over the Pacific     

Ning Cao  Baohua Ren  Jianqiu Zheng 《大气科学进展》2015,32(12):1603-1616

The climatological mean state,seasonal variation and long-term upward trend of 1979–2005 latent heat flux(LHF) in historical runs of 14 coupled general circulation models from CMIP5(Coupled Model Intercomparison Project Phase 5) are evaluated against OAFlux(Objectively Analyzed air–sea Fluxes) data. Inter-model diversity of these models in simulating the annual mean climatological LHF is discussed. Results show that the models can capture the climatological LHF fairly well,but the amplitudes are generally overestimated. Model-simulated seasonal variations of LHF match well with observations with overestimated amplitudes. The possible origins of these biases are wind speed biases in the CMIP5 models. Inter-model diversity analysis shows that the overall stronger or weaker LHF over the tropical and subtropical Pacific region,and the meridional variability of LHF,are the two most notable diversities of the CMIP5 models. Regression analysis indicates that the inter-model diversity may come from the diversity of simulated SST and near-surface atmospheric specific humidity.Comparing the observed long-term upward trend,the trends of LHF and wind speed are largely underestimated,while trends of SST and air specific humidity are grossly overestimated,which may be the origins of the model biases in reproducing the trend of LHF.  相似文献   

晚秋与后冬间欧亚遥相关型波列反相现象探究   总被引：3，自引：0，他引：3       下载免费PDF全文

乔少博  张志森  王晓娟  封国林 《Acta Meteorologica Sinica》2015,73(4):711-724

围绕1979/1980—2013/2014年晚秋(11月)与后冬(次年1、2月)间欧亚遥相关(EU)型波列关系展开研究,揭示了晚秋与后冬间欧亚遥相关指数存在显著负相关,即二者主要呈反位相变化。对比晚秋与后冬间欧亚遥相关型呈反位相和同位相变化时的环流演变规律发现,反位相变化年晚秋环流异常对后冬有显著的指示意义,而同位相变化年晚秋环流异常对后冬指示意义较弱。就可能的外部成因而言,反位相与同位相变化过程均与北大西洋湍流热通量(NATU)异常有较好的对应关系。具体物理过程表现为:当北大西洋湍流热通量正(负)异常时,有利于北大西洋50°N附近上升(下沉)运动及对流层中低层水汽含量显著增多(减少),相应北大西洋上空高度场乃至整个欧亚遥相关型波列表现为负(正)异常。  相似文献   

利用TLS技术与伪单点监测模式进行滑坡变形测量     

郭献涛  黄腾  贾燕  张荣春 《测绘通报》2021,(6):106-111

针对传统离散点监测模式不适用于TLS变形监测,以及现有基于TLS技术变形监测的一维性与仅适用于特定几何对象分析等不足,本文提出了一种基于TLS技术的伪单点变形监测模式,并基于该监测模式提出了一种以表面匹配技术为核心的变形计算新方法。通过构建广义高斯-马尔可夫模型匹配搜索估计伪单点对象的全三维变形参数,利用TLS多期点云的高密度性,实现了高精度提取全三维变形信息,尤其适用于滑坡等灾害监测领域。试验表明在扫描距离约240 m时,该方法可达到1 cm级的变形提取精度,对推动变形监测从点测绘向形测绘的转变具有一定的价值。  相似文献   

淮北煤田现今地温场特征及大地热流分布          下载免费PDF全文

彭涛  吴基文  任自强  徐胜平  张海潮 《地球科学》2015,40(6):1083-1092

淮北煤田的高温热害问题愈发突出,但目前对该区系统的地温场特征及大地热流分布研究非常稀少.在系统分析淮北煤田大量地面钻孔井温测井数据和井下巷道围岩温度测试数据的基础上,结合72块岩石样品的热导率测试结果,全面阐述了该区现今地温梯度和大地热流的分布特征.研究表明:淮北煤田现今地温梯度众值介于1.80~2.80 ℃/100 m之间,平均地温梯度为2.42 ℃/100 m;大地热流值变化范围为39.52~74.12 mW/m2,平均热流值为55.72 mW/m2,地温梯度和热流值均低于同处华北板块的其他盆地以及南部的淮南煤田;大地热流受地温梯度控制明显,两者分布较为相似,整体表现为南高北低、西高东低的特点.结果表明,区内现今地温场和热流分布主要受区域地质背景和区内构造格局的控制.   相似文献