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21.
The Decadal Shift of the Summer Climate in the Late 1980s over Eastern China and Its Possible Causes 总被引：2，自引：0，他引：2 
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下载免费PDF全文 In this paper, it is pointed out that a notable decadal shift of, the summer climate in eastern China occurred in the late 1980s. In association with this decadal climate shift, after the late 1980s more precipitation appeared in the southern region of eastern China （namely South China）, the western Pacific subtropical high stretched farther westward with a larger south-north extent, and a strengthened anticyclone at 850 hPa appeared in the northwestern Pacific. The decadal climate shift of the summer precipitation in South China was accompanied with decadal changes of the Eurasian snow cover in boreal spring and sea surface temperature （SST） in western North Pacific in boreal summer in the late 1980s. After the late 1980s, the spring Eurasian snow cover apparently became less and the summer SST in western North Pacific increased obviously, which were well correlated with the increase of the South China precipitation. The physical processes are also investigated on how the summer precipitation in China was affected by the spring Eurasian snow cover and summer SST in western North Pacific. The change of the spring Eurasian snow cover could excite a wave-train in higher latitudes, which lasted from spring to summer. Because of the wave-train, an abnormal high appeared over North China and a weak depression over South China, leading to more precipitation in South China. The increase of the summer SST in the western North Pacific reduced the land-sea thermal contrast and thus weakened the East Asian summer monsoon, also leading to more precipitation in South China. 相似文献
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This study on the temporal and spatial variability of the viscosity and some chemical parameters in the sea surface microlayer (SML), the relationship between the viscosity and chemical parameters, and the influence of the viscosity on the mass transfer coefficient (K) in the flux of materials through the air-sea interface revealed that: The values of viscosity and some chemical parameters in the SML are higher than those in the sub-surface layer (SSL), and at daytime are higher than those at night. The viscosity has positive corelation with chemical oxygen demand (COD),dissolved organic carbon (DOC) and salinity. The “SML effect“ on K need not be considered because the SML effect on materials concentration is so small. 相似文献
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Based on the data obtained during the 15th Antarctic Expedition of China between November 1998 and February 1999,the paper discusses the water masses distributed on both sides of the Continental Water Boundary(CWB) as well as the spacial variability of the physical characteristics of the central location,the frontal width,the frontal strength,the vertical depth,and the vertical thickness for CWB,The above results are compared with the results from the data obtained during the 9th Antarctic Expedition of China between December 1992 and February 1993,and the temporal variabiltiy of those characteristics is discussed.In addition,the inhomogeneity of the kinematic characteristics and the patterms of the dynamic heights for those water masses located on both sides of CWB are illustrated.As it is pointed out in the paper,the trough in the dynamic height field is identified with the frontal location of CWB and the oceanic current shear.Furthermore,the dynamic reason for the upwelling of the circumpolar deep water can be understood by the explanation described in the paper. 相似文献
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A new North Atlantic Oscillation index and its variability 总被引：31，自引：4，他引：27
A new North Atlantic Oscillation (NAO) index, the NAOI, is defined as the differences of normalized sea level pressures regionally zonal-averaged over a broad range of longitudes 80°W-30°E. A comprehensive comparison of six NAO indices indicates that the new NAOI provides a more faithful representation of the spatial-temporal variability associated with the NAO on all timescales. A very high signal-to-noise ratio for the NAOI exists for all seasons, and the life cycle represented by the NAOI describes well the seasonal migration for action centers of the NAO. The NAOI captures a larger fraction of the variance of sea level pressure over the North Atlantic sector (20°-90°N, 80°W-30°E), on average 10% more than any other NAO index. There are quite different relationships between the NAOI and surface air temperature during winter and summer. A novel feature, however, is that the NAOI is significantly negative correlated with surface air temperature over the North Atlantic Ocean between 10°-25°N and 相似文献
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基于主观判断和有限资料解释的概率地震危险性研究的输入(地震震源区、地震发生率、衰减函数等)都是不确定的。面对这些不确定性,我们要考虑:(a)如何“合理地”确定单值概率地震危险性图中所标示的地震运动水平;(b)计算得到的地面运动水平的不确定性在这种图上可以明确地表达到何种程度。如果单个震源区的地震发生率、古登堡-里克特公式中的b值,以及最大震级的最佳猜测估计值被看作是不相关的并且每一参数中的不确定性可以看作是关于估计值对称的,那么,使用这些最优估计计算的概率地面运动水平表达了最可能的值和近似的均值。另一方面,根据不同震源区方案计算的地面运动大小,可能集中于每一方案的不同的中心值周围,而且,根据最可能方案计算出的地面运动水平可显著不同于所有方案计算出的地面运动水平的平均。我们得出结论(因为至少在美国东部和中部对地震过程是缺乏了解的),要得到单一的危险性估计结果,假定未来地震将趋向于发生在过去已经发生过地震的地区,并且具有与过去相当的发生率是合理的(在美国西部当单条断层上存在古地震资料时,这些信息是可以结合使用的)。在有多种震源区方案的情况下,使用不同的地面运动衰减关系得到的危险性估计,彼此会显著不同。人们或许考虑采用数个衰减关系的平均,但是,这样一来技术上的问题(例如,如何平均那些采用不同距离量度的关系式,如何估计σ,等等)会使操作非常困难,而且当包含一个与其它衰减关系离散较大的衰减关系时,它对均值会产生很大的影响。为了简化和可操作起见,使用单一的、不被认为是“极值”的衰减关系似乎是合理的,并且这一做法已获得危险性分析人员的接受。 相似文献
26.
综合20世纪90年代初在霍山山前断裂和近年在绵山西侧断裂和太谷断裂获取的最新调查资料，讨论了1303年山西洪洞8级地震地表破裂带的展布和位移特征. 如果太谷断裂、绵山西侧断裂与霍山山前断裂在1303年洪洞地震中同时活动，则该次地震的地表破裂带长163 km，分为3段，即霍山山前断裂段、绵山西侧断裂段和太谷断裂段. 各段长度分别为50，35和70 km，3段之间存在4和8 km的阶区. 该地震地表破裂带具右旋走滑特征，北段和中段右旋走滑位移量6～7 m，南段最大为10 m. 在山西断陷带盆地边界的单条断裂一般只对应7级地震，而该次8级特大地震则突破两个盆地之间的障碍体，显示了强震地表破裂尺度的可变特征. 相似文献
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工业指标的“多年一贯制”不利于合理充分地利用矿产资源．文章提出适合经济规律的工业指标制定办法，建议地质技术人员按照矿山年总成本和矿产品市场价格及时修正工业指标，以便使项目上马决策趋于正确。 相似文献
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Pongsak Kholkhuntod Jian-Ning Fu Chayan Boonyarak Kanokwan Marak Li Chen Shi-Yang Jiang 《中国天文和天体物理学报》2007,7(3):421-427
Time-series photometry was made for the large-amplitude δ Scuff star AD CMi in 2005 and 2006. High-quality photometric data provided in the literature were used to analyze the pulsation of the star, with the derived multiple frequencies fitted to our new data. Besides the dominant frequency and its harmonics, one low frequency （2.27402 c d^-1） is discovered, which provides a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light. Combining the nine new times of light maxima determined from the new data with the 64 times collected from the literature, we analyzed the long-term variability of AD CMi with the O - C technique. The results provide the updated value of period of 0.122974478 days, and seem to be in favor of the model of combination of the evolutionary effect and light-time effect of a binary system, of which some parameters are hereby deduced. 相似文献
30.
We introduce a new physical parameter, the optical variability amplitude, to the well-established Eigenvector 1 space of quasars and test a sample of long-term B-band light curves of 42 Palomar-Green quasars monitored by Giveon et al. We find that the optical variability amplitude strongly correlates with the intensity ratio of Fell to Hβ,Hβwidth and peak luminosity at 5007A. We briefly discuss the physical meaning of our findings and suggest that the Eddington ratio may be a key factor in determining a quasar's variability. 相似文献