First record of Prorocentrum lima (Dinophyceae) inside harbor areas and along the Abruzzo region coast, W Adriatic     

Cristina Ingarao  Giovanna Lanciani  Carmen Verri  Tommaso Pagliani 《Marine pollution bulletin》2009,58(4):596-600

Prorocentrum lima (Ehrenberg) Dodge has been found for the first time during the summer of 2007 inside Ortona harbor and along the coast of the Abruzzo region, a slightly eutrophic area influenced by runoff from a nearby river. The investigations were conducted in two harbors and at six coastal sampling stations. Samplings were conducted using a phytoplankton net and with a pump. Average P. lima cellular concentrations were 3.2 × 10⁴ cells L⁻¹. Other well-known toxic and potentially toxic phytoplankton species have been considered. The number of toxic cells from net samples were higher than the numbers of toxic cell samples collected without the net. Occurrences of P. lima with abiotic factors revealed that temperature was positively correlated with P. lima abundance (p = 0.01), while salinity was highly negatively correlated with P. lima presence (p = 0.001). The total phytoplankton community was studied.  相似文献   

75th anniversary of strong motion observation—A historical review     

Mihailo D. Trifunac 《Soil Dynamics and Earthquake Engineering》2009

This review describes the experience accumulated in the field of recording earthquake motions up to the early 1900s, and then it discusses the key players who contributed to the first successful strong motion observation program in earthquake engineering in the 1930s. It begins by summarizing the accomplishments of the preceding seismological observations, which provided the stepping-stone ideas on how to construct the first strong motion accelerograph. Next, it describes the lack of optimism among the engineers in the early 1900s, who doubted that structural response could ever be calculated for irregular earthquake ground motion—this was, of course, half a century before the appearance of fast digital computers—but also their realization that something needed to be done to reduce the hazards from earthquakes. The roles of the two pioneers Kyoji Suyehiro and John Freeman, whose vision, leadership, and perseverance launched the strong motion observation program in 1932, are then briefly discussed. Finally, the mechanical characteristics of the first strong motion accelerograph are outlined. The review is completed by illustrating the growth of the strong motion observation programs in selected seismic areas of the world and the fruits of these programs—the cumulative number of uniformly processed strong motion records in southern California.  相似文献   

黄河上游夏季流量对气候变化的响应及未来趋势预估     

刘彩红  杨延华  王振宇 《地理科学进展》2012,31(7):846-852

本文从气候变化的角度出发, 研究黄河上游龙羊峡水库夏季流量与流域气候条件的响应关系及流量预估模型, 并根据区域气候模式输出数据降尺度生成的未来气候情景, 对未来龙羊峡夏季水库流量进行了预估。结果表明:近35 年来, 黄河上游夏季气温升高、蒸发增大, 降水略有减少;黄河上游龙羊峡水库平均入库流量呈递减趋势, 夏季流量对流域降水量、平均最高气温及最低气温的响应显著;未来两个时期(2020s、2030s)龙羊峡夏季流量均较基准期(1988-2010 年)减少, 但在不同气候变化情景下流量变化有所差异, 其中A2 情景下夏季平均流量分别减少23.9%(2020s)和19.8%(2030s), B2 情景下分别减少14.4%(2030s)和17.3%(2030s), 据此, 未来气候变化对黄河上游流域夏季流量的可能影响将弊大于利, 但仍具有较大不确定性。  相似文献   

2D acoustic‐elastic coupled waveform inversion in the Laplace domain     

Ho Seuk Bae  Changsoo Shin  Young Ho Cha  Yunseok Choi  Dong‐Joo Min 《Geophysical Prospecting》2010,58(6):997-1010

Although waveform inversion has been intensively studied in an effort to properly delineate the Earth's structures since the early 1980s, most of the time‐ and frequency‐domain waveform inversion algorithms still have critical limitations in their applications to field data. This may be attributed to the highly non‐linear objective function and the unreliable low‐frequency components. To overcome the weaknesses of conventional waveform inversion algorithms, the acoustic Laplace‐domain waveform inversion has been proposed. The Laplace‐domain waveform inversion has been known to provide a long‐wavelength velocity model even for field data, which may be because it employs the zero‐frequency component of the damped wavefield and a well‐behaved logarithmic objective function. However, its applications have been confined to 2D acoustic media. We extend the Laplace‐domain waveform inversion algorithm to a 2D acoustic‐elastic coupled medium, which is encountered in marine exploration environments. In 2D acoustic‐elastic coupled media, the Laplace‐domain pressures behave differently from those of 2D acoustic media, although the overall features are similar to each other. The main differences are that the pressure wavefields for acoustic‐elastic coupled media show negative values even for simple geological structures unlike in acoustic media, when the Laplace damping constant is small and the water depth is shallow. The negative values may result from more complicated wave propagation in elastic media and at fluid‐solid interfaces. Our Laplace‐domain waveform inversion algorithm is also based on the finite‐element method and logarithmic wavefields. To compute gradient direction, we apply the back‐propagation technique. Under the assumption that density is fixed, P‐ and S‐wave velocity models are inverted from the pressure data. We applied our inversion algorithm to the SEG/EAGE salt model and the numerical results showed that the Laplace‐domain waveform inversion successfully recovers the long‐wavelength structures of the P‐ and S‐wave velocity models from the noise‐free data. The models inverted by the Laplace‐domain waveform inversion were able to be successfully used as initial models in the subsequent frequency‐domain waveform inversion, which is performed to describe the short‐wavelength structures of the true models.  相似文献   

A note on the L’Aquila earthquake of 6 April 2009: Permanent ground displacements obtained from strong-motion accelerograms     

R. Rupakhety  R. Sigbjörnsson 《Soil Dynamics and Earthquake Engineering》2010

On 6 April 2009, 01:32 GMT, an M_w 6.3 earthquake hit the Abruzzi region of central Italy causing widespread damage in the City of L’Aquila and its nearby villages. The mainshock of this earthquake was recorded by 57 digital strong-motion instruments, four of which are located on the hanging wall of the Paganica Fault near L’Aquila. These stations are no more than 6 km from the epicentre. We use accelerometric data from these four stations to estimate permanent ground displacements caused by the mainshock. Our numerical results reveal south-east and downwards directed permanent co-seismic displacements which are in fair agreement with the outcomes of GPS and InSAR measurements reported in preliminary Istituto Nazionale di Geofisica e Vulcanologia (INGV) reports.  相似文献   

井水位长周期事件记录及其机理的讨论   总被引：13，自引：1，他引：12  

张淑亮  范雪芳 《地震》2003,23(4):85-90

选择了几口具有代表性的观测井, 并对这些井孔在强震前记录到长周期波现象的特征进行了分析。从理论上对地震前的长周期事件给出了较为合理的解释, 认为地震前一些敏感井水位长周期事件可能反映了断层蠕动、静地震与慢地震、断裂的预扩展和地震成核等。井— 含水层系统像一个长周期地震仪, 它为记录到有价值的前兆低频波提供了最佳的频率响应范围。  相似文献   

对虾样品中Pb、cd的微波消解与常规消解分析方法比较研究   总被引：8，自引：0，他引：8  

徐维海  江志刚  朱校斌  王新亭  马绪丽 《海洋科学》2005,29(6):38-41

采用微波消解与常规消解2种方法消解对虾样品,石墨炉原子吸收法(GFAAS)测定其Pb、Gd的含量,对样品中Pb、Cd的微波消解与常规消解分析方法做了系统的比较。结果表明。微波消解法准确度、精密度以及回收率的准确度等与常规消解法相比均有较大幅度的提高。  相似文献   

基于长短期记忆神经网络的风速超短期快速滚动预报技术          下载免费PDF全文

方楠  姜舒婕  闫晓敏  阮小建  马辛宇 《气象科技》2022,50(6):842-850

利用甘肃省某风电场2017—2020年测风数据，基于长短期记忆神经网络（LSTM）模型，通过评估不同输入数据和模型时间窗口长度下的预报精度，设计一套适用于风电场的风速超短期快速滚动预报方案。结果表明：通过输入不同的特征变量，在风速的超短期(未来4 h内)预报中，风速自身变化起主导作用，模型输入变量中只加入各高度层的风速能得到更好的模拟效果。通过评估LSTM模拟时间窗口长度L对模拟效果的影响，当时间窗口长度L≤24 h时，模拟效果较好，说明超短期风速变化主要和风速自身临近时刻的变化有关；当L>24 h时，模拟效果快速下降，说明过长的L会削弱模拟能力，降低模拟精度。 通过分析LSTM在未来4 h内的风速模拟能力，发现随着预报时长的增加，模拟精度逐步下降，但在未来2 h内的风速均方根误差RMSE均小于2 m〖DK〗·s-1，结果较为理想，且该方法对计算资源要求不高，经济实用性强，在业务中具有较高的应用潜力。  相似文献   

基于人工神经网络的沿海风速多步预测研究          下载免费PDF全文

刘志丰  丁锋 《气象科技》2022,50(6):851-858

基于气象历史观测资料，将长短期记忆网络LSTM方法和Transformer模型结合提出了混合短期风速多步预测模型BLSTM TRA。以山东半岛南部沿海6个台站为研究区域，通过气象台站观测数据构建数据集。经与2018年ECMWF模式6 h预报结果对比分析，得出如下结论：构建的BLSTM TRA多步预测模型可大幅度降低风速误差，BLSTM TRA的1 h单步预测结果和ECMWF预报模式结果对比，其RMSE平均降低了58.9%，MAE平均降低了63.2%；风速误差和大风统计过程分析发现，BLSTM TRA模型具有一定的抗干扰能力，可以抓住短时大风等敏感信息，对于大风预报结果明显优于ECWMF模式和传统LSTM模型。  相似文献   

山东中西部一次长生命史超级单体雷达回波特征和触发机制分析          下载免费PDF全文

朱义青  胡顺起 《沙漠与绿洲气象(新疆气象)》2021,15(1):54-61

利用常规观测资料、多普勒雷达产品、NCEP/NCAR再分析资料和加密自动站等资料分析了2016年6月14日山东中西部地区一次长生命史超级单体的环境条件和雷达回波结构演变。结果表明,强对流发生在华北冷涡天气背景下,中层有中空急流配合的冷槽叠加在低层低空急流配合的暖脊上,中低层之间水汽和热量的平流差异不断增大。地面露点锋生和中尺度辐合线触发的对流云团在深厚的垂直风切变和强的垂直不稳定层结作用下逐渐发展成超级单体风暴。超级单体低层反射率因子呈现明显"V"型缺口,反射率因子垂直剖面呈现典型的有界弱回波区,回波悬垂和回波墙,相应的中高层径向速度呈现出一个强中气旋,旋转速度达29 m/s,中气旋的发展和维持使得超级单体发展和维持。6月,当最大反射率因子值达到60 dBZ,出现中等强度以上中气旋且VIL值和VIL密度分别达59 kg/m2和4.7 g/m3以上时,在强对流预报业务中需要注意大冰雹的出现。冰雹发生在风暴单体强中心所在高度和回波顶高下降期间。  相似文献