Monthly Extended Predicting Experiments with Nonlinear Regional Prediction.PartⅠ:Prediction of Zonal Mean Flow

Systematic errors have recently been founded to be distinct in the zonal mean component forecasts, which account for a large portion of the total monthly-mean forecast errors. To overcome the difficulty of numerical model, the monthly pentad-riean nonlinear dynamic regional prediction models of the zonal mean geopotential height at 200, 300, 500, and 700 hPa based on a large number of historical data (NCEP/NCAR reanalysis data) were constituted by employing the local approximation of the phase space reconstruction theory and nonlinear spatio-temporal series prediction method. The 12-month forecast experiments of 1996 indicated that the results of the nonlinear model are better than those of the persistent, climatic prediction, and T42L9 model either over the high- and mid-latitude areas of the Northern and Southern Hemispheres or the tropical area. The root-mean-square of the monthly-mean height of T42L9 model was considerably decreased with a change of 30.4%, 26.6%, 82.6%, and 39.4%, respectively, over the high- and mid-latitudes of the Northern Hemisphere, over the high- and mid-latitudes of the Southern Hemisphere, over the tropics and over the globe, and also the corresponding anomaly correlation coefficients over the four areas were respectively increased by 0.306-0.312, 0.304-0.429, 0.739-0.746, and 0.360-0.400 (averagely a relative change of 11.0% over the globe) by nonlinear correction after integration, implying that the forecasts given by nonlinear model include more useful information than those of T42L9 model.     

地带性与非地带性夷平面*

夷平面是指由剥蚀和夷平作用所产生的,以截面形式横切所有在年龄上先于它的地层和构造的一种平缓地形。前人普遍认为,夷平面是在构造相对稳定条件下经过长期外营力作用形成的一个接近基准面的平坦地形,是地貌长期演化的终极产物。 流水侵蚀是夷平面形成的动力学基础。"夷平面"一直是解释新生代以来大的构造格局和地貌演化的重要理论依据,如我国青藏高原隆升的研究。 基于气候地貌学原理,文章提出了寒冻夷平面和干旱夷平面的概念;从坡地演化过程理论模型入手,探讨了寒冻、干旱夷平面和流水夷平面的形成机理;提出有别于传统"构造侵蚀旋迴"理论的"构造隆升和地面剥夷动态平衡"的气候夷平地貌假说;此外,还简要分析了这三类夷平面的全球分布规律。     

镁铁质-超镁铁质岩浆岩中单斜辉石的智能分析研究

区分不同构造环境中岩浆作用是认识地幔中岩浆形成过程的基本手段。目前较为成熟的是利用全岩去区分判别,而利用造岩矿物去判别构造环境、演绎岩浆演化的研究还不够深入。本文运用机器学习的方法,以全球新生代大洋中脊、洋岛以及岛弧构造背景中的镁铁质-超镁铁质岩浆岩中单斜辉石的地球化学数据为研究对象,试图区分这3 种不同构造环境的单斜辉石。通过机器学习方法中K-邻近（K-Nearest Neighbor,KNN）和随机森林（Random Forest,RF）的计算和比较,认为RF 是一种有效的地球化学区分方法,它的结果不仅可用来判别构造环境,同时还能够提取特征元素。同时我们发现,在镁铁质-超镁铁质岩浆岩单斜辉石构造环境判别图解中,Rb、La、Ba、Cr、Sr、Yb、V、Ti、Nd、Eu、Gd等微量元素具有较高的贡献率,而主量元素贡献率较低。在此基础上,我们结合前人的对单斜辉石的构造环境判别图的研究成果,提出几个判别效果较好的判别图解。但是整个研究由于缺少进一步可视化的成果,限制了机器学习方法的推广,这也是今后需要进一步研究的课题。     

贵州革东地区带状热储赋存规律研究

通过对贵州革东变质岩地区地热水的水化学、氢氧同位素及地热井的地温场垂向变化的分析,结果表明:(1)区域地热井热储呈带状(Ⅱ-2型);(2)区域大地热流量供热,补给来源为大气降水,补给高程下限1100m,地热水循环深度下限2400m,围岩与上层地下水影响其化学组分;(3)挽近期革东活动断层具有导热导水性,经循环的地热水沿断层上盘构造裂隙向上运移在此断层破碎带富集,位于断层上盘3km范围内的地热钻孔揭穿该断裂带深度约1200m,均有流量约994m3/d、井口水温40℃的地热水。研究结果可为黔东南地区带状热储的开发与利用提供参考。     

Identifying the characteristic signatures of fold-accommodation faults

Hand-specimen and outcrop scale examples of folds are analyzed here to identify the characteristic signatures of fold-accommodation faults. We describe and analyze the geometric and kinematic relationships between folds and their associated faults in detail including the structural position and spatial distribution of faults within a fold, the displacement distribution along the faults by applying separation–distance plots for the outcrop scale examples, and the change of cut-off angle when the fault cut across folded layers. A comparison between fold-accommodation faults and fault related folds based on their separation–distribution plots and the problem of time sequence between faulting and folding are discussed in order to distinguish fold-accommodation faults from the reverse faults geometrically and kinematically similar to them. The analysis results show that fold-accommodation faults originate and terminate within a fold and usually do not modify the geometry of the fold because of their limited displacement. The out-of-syncline thrust has a diagnostically negative slope (separation value decreasing away from the upper fault tip) in the separation–distance graph. The change of cut-off angle and the spatial distribution of faults display a close relationship with the axial surface of the fold. Our analyses show that fold-accommodation faults are kinematically consistent with the flexural slip of the fold. The interbedded strata with competence contrast facilitate formation of fold-accommodation faults. These characteristic signatures are concluded as a set of primary identification criteria for fold-accommodation faults.     

Intraseasonal variability of the surface zonal current in the equatorial Indian Ocean: Seasonal differences and causes

Using observations and numerical simulations, this study examines the intraseasonal variability of the surface zonal current(u ISV) over the equatorial Indian Ocean, highlighting the seasonal and spatial differences, and the causes of the differences. Large-amplitude u ISV occurs in the eastern basin at around 80°–90°E and near the western boundary at 45°–55°E. In the eastern basin, the u ISV is mainly caused by the atmospheric intraseasonal oscillations(ISOs), which explains 91% of the standard...     

The Impact of an Abnormal Zonal Vertical Circulation in Autumn of Super El Ni?o Years on Non-tropical-cyclone Heavy Rainfall over Hainan Island

This study reveals a significant positive connection between autumn non-tropical-cyclone heavy rainfall on Hainan Island and the intensity of Eastern Pacific (EP) El Ni?o events. That is, the amount of rainfall in super EP El Ni?o years is more than that in normal EP El Ni?o years. Comparing EP El Ni?o years of different intensities, the cooler sea surface temperature in the northwestern Pacific during super EP El Ni?o years stimulates a negative surface latent heat flux (LHF) anomaly and abnormal anticyclonic circulation at 850 hPa. Under these conditions, an abnormal zonal vertical circulation develops in the northern South China Sea once a positive LHF anomaly and abnormal cyclonic circulation (ACC) at 850 hPa occur in the Beibu Gulf. The abnormal zonal vertical circulation further strengthens the ascending motion over Hainan Island, as the critical factor that leads to excessive rainfall. Further analysis shows that the positive LHF anomaly, which can be attributed to the increased latent heat transfer which resulted from the increased surface wind speed, is an important trigger for the ACC. However, the ACC is also the supplier of favorable moisture conditions because it intensifies vapor convergence over Hainan Island and meridionally transports moisture from the South China Sea to northeastern Hainan Island, thereby generating heavy rainfall. This paper emphasizes that the impact of El Ni?o events, especially super El Ni?o events, on rainfall over Hainan Island cannot be ignored, even if the traditional view is that frequent rainfall occurs mainly in La Ni?a years.     

Cyclonic-anticyclonic asymmetry and a new soliton concept for rossby vortices in the laboratory,oceans and the atmospheres of giant planets

Abstract

It is demonstrated in laboratory experiments with rotating shallow water that large scale Rossby vortices, greater than the Rossby-Obukhov radius in size, have dispersive and non-linear properties that are fundamentally different for the two possible polarities. We call this “cyclonic-anticyclonic asymmetry”. This asymmetry manifests itself in the following way: first, anticylones, unlike cyclones, do not undergo the dispersive spreading inherent in a linear wave packet. and therefore, having a considerably longer natural lifetime, are obvious candidates for Rossby solitons; second, dipolar vortices are, because of the comparatively rapid decay of a cyclone, transformed into anticyclonic solitons; third, anticyclones are much more readily generated by zonal flows of the type existing in planetary atmospheres. The evident dominance of anticyclones amongst the long-lived vortices in the atmospheres of giant planets strongly suggests that the cyclonic-anticyclonic symmetry plays a decisive role in the atmospheric cyclogenesis of large planets.

According to our concept, the Rossby soliton is a “real” vortex; unlike a wave, it retains some fluid particles within it throughout its lifetime. Two similar solitons can merge by mutual collisions. This picture of a “vortical” soliton differs in an essential way from the earlier idea due to Maxworthy and Redekopp (1976) of purely “wave-like” Rossby solitons that can freely pass through one another.

Laboratory experiments were performed by us to simulate the new Rossby solition, with special reference to naturally-occurring vortices of the same general type as Jupiter's great red spot. The experimental data presented contradict the idea of “pure wave solitons” but confirm our concept of “vortical solutions”.     

Effect of pressure gradients and line-tying on the magnetic stability of coronal loops

Abstract

In this paper we study the stability of an idealised magnetostatic coronal loop, incorporating both the effect of line-tying, due to the dense photosphere, and of pressure gradients. The stability equations may be solved analytically for our particular equilibrium. From the marginally stable case, the critical conditions separating instability from stability are derived. It is found that stretching or twisting a loop eventually makes it kink unstable.     

华北地区中强地震时间间隔特征与目前大形势分析

针对目前华北地区5、6级地震持续平静的复杂形势,分析了华北地区1484年以来M≥5、M≥6级地震的时间间隔特征,结果表明:①1731～1814年地震平静期的5、6级地震的平均时间间隔明显长于1484～1730年及1815年以来2个地震活动期的平均时间间隔,说明华北地区地震起伏交替轮回的韵律性是客观的;②华北地区2个地震活动期中相邻活动幕的幕间M≥5地震(含平静幕里发生的地震)平均时间间隔(86月)与1731～1814年平静期内单次M≥5级地震平均时间间隔(90月)一致,90月可做为华北地区5级地震异常平静的标志性时间;③类比500多年华北地区5、6级地震的时间间隔特征认为,当前华北地区正处于2000年以来的平静幕后期,该平静幕已持续169月,已经随时有可能发生5、6级地震,开始进入新一轮的地震活动幕.