A study on the early-warning technique concerning debris flow disasters

According to the principle of the eruption of debris flows, the new torrent classification techniques are brought forward. The torrent there can be divided into 4 types such as the debris flow torrent with high destructive strength, the debris flow torrent, high sand-carrying capacity flush flood torrent and common flush flood by the techniques. In this paper, the classification indices system and the quantitative rating methods are presented. Based on torrent classification, debris flow torrent hazard zone mapping techniques by which the debris flow disaster early-warning object can be ascertained accurately are identified. The key techniques of building the debris flow disaster neural network (NN)real time forecasting model are given detailed explanations in this paper, including the determination of neural node at the input layer, the output layer and the implicit layer, the construction of knowledge source and the initial weight value and so on. With this technique, the debris flow disaster real-time forecasting neural network model is built according to the rainfall features of the historical debris flow disasters, which includes multiple rain factors such as rainfall of the disaster day, the rainfall of 15 days before the disaster day, the maximal rate of rainfall in one hour and ten minutes. It can forecast the probability, critical rainfall of eruption of the debris flows, through the real-time rainfall monitoring or weather forecasting. Based on the torrent classification and hazard zone mapping, combined with rainfall monitoring in the rainy season and real-time forecasting models, the debris flow disaster early-warning system is built. In this system, the GIS technique, the advanced international software and hardware are applied, which makes the system′s performance steady with good expansibility. The system is a visual information system that serves management and decision-making, which can facilitate timely inspect of the variation of the torrent type and hazardous zone, the torrent management, the early-warning of disasters and the disaster reduction and prevention.     

Ekman motion in shallow open sea in the presence of time-harmonic variation of water depth

The time variation of the wind-induced flow in a homogeneous unbounded sea region has been analytically investigated. The time-dependent Ekman solution in a homogeneous, shallow open sea has been further extended by taking into account the time variation in water depth which might be caused by either tidal motion or change in the mixed layer thickness. The solution approach taken in this study is based on the Galerkin-eigenfunction method originally developed by Heaps [1972. On the numerical solution of three-dimensional hydrodynamical equations for tides and storm surges. Memoires de la Societe Royale des Sciences de Liege Serie 6(2), 143–180]. A series of calculations have been made with emphasis on the influence of the time variation in water depth upon the build-up of Ekman spirals in the presence of oscillatory variations in water depth. It has been found that two oscillations contribute to the wind drift current, the inertial oscillation and the depth-variation-induced oscillation; the inertial oscillation decays with time, but the depth-variation-induced oscillation remains undamped despite the presence of bottom friction. The presence of time-harmonic variation produces peculiar forms of hodograph with a curled or circular pattern according to the angular frequency of the water depth variation.     

基于航空客流的中国城市层级结构分析

基于1995、2000和2003三个年份的航空客运统计数据,分析中国城际航空客流的结构,并以优势流(dominant flow)方法为主,辅以距离平方和聚类法,分析中国主要城市在国内客运航空网络中的层级及其变化。研究表明,通过航空客运方式产生的空间联系主要集中于东部地区,中部地区在航空网络的重要性方面落后于西部,北京、上海、广-深3个顶点组成全国航空网络的主干;从主导航空客流角度观察,自1995至2003年,一个高度集中的城市层级在3个全国性中心的控制下形成和发展,航空客运网络层级体系中的顶层结构业已清晰,而以下各层次的结构尚处于分化发展之中。     

The interannual variability of East Asian Winter Monsoon and its relation to the summer monsoon

1.IntroductionOvertheEastAsiaregion,themostprominentsurfacefeatureofthewintermonsoonisstrongnortheasterliesalongtheeastflankoftheSiberianhighandthecoastofEastAsia.At500hPathereisabroadtroughcenteredaboutatthelongitudesofJapan.Thedominantfea-tureat2O0hPaistheEastAsianjetwithitsmaximumlocatedatjustsoutheastofJapan.Thisktisassociatedwithintensebaroclinicity,largeverticalwindshearandstrongadvectionofcoldair(StaffmembersofAcademiaSinica,l957,LauandChang,1987;BoyleandChen,1987;Chenetal.,1991…     

The role of the hyporheic zone across stream networks

Many hyporheic papers state that the hyporheic zone is a critical component of stream ecosystems, and many of these papers focus on the biogeochemical effects of the hyporheic zone on stream solute loads. However, efforts to show such relationships have proven elusive, prompting several questions: Are the effects of the hyporheic zone on stream ecosystems so highly variable in place and time (or among streams) that a consistent relationship should not be expected? Or, is the hyporheic zone less important in stream ecosystems than is commonly expected? These questions were examined using data from existing groundwater modelling studies of hyporheic exchange flow at five sites in a fifth‐order, mountainous stream network. The size of exchange flows, relative to stream discharge (Q_HEF:Q), was large only in very small streams at low discharge (area ≈ 100 ha; Q < 10 l/s). At higher flows (flow exceedance probability > 0·7) and in all larger streams, Q_HEF:Q was small. These data show that biogeochemical processes in the hyporheic zone of small streams can substantially influence the stream's solute load, but these processes become hydrologically constrained at high discharge or in larger streams and rivers. The hyporheic zone may influence stream ecosystems in many ways, however, not just through biogeochemical processes that alter stream solute loads. For example, the hyporheic zone represents a unique habitat for some organisms, with patterns and amounts of upwelling and downwelling water determining the underlying physiochemical environment of the hyporheic zone. Similarly, hyporheic exchange creates distinct patches of downwelling and upwelling. Upwelling environments are of special interest, because upwelling water has the potential to be thermally or chemically distinct from stream water. Consequently, micro‐environmental patches created by hyporheic exchange flows are likely to be important to biological and ecosystem processes, even if their impact on stream solute loads is small. Published in 2011 by John Wiley & Sons, Ltd.     

Multiparametric infrared Tully-Fisher relation as a tool for mapping cosmic flows

The peculiar velocity field for 907 galaxies with heliocentric radial velocities V_H ≤ 3000 km/s is examined. The data are divided into three samples, organized according to the principles behind the method for determining the distance to the galaxies: the luminosity of the tip of the red giant branch (TRGB), fluctuations in the surface brightness, and the infrared Tully-Fisher relation for spiral galaxies viewed edge-on. The latter sample includes 410 galaxies. For determining the distance to the galaxies in this sample, additional regressors were introduced into the Tully-Fisher relation, in particular the “color index” K-m₂₁, which make it possible significantly to reduce the dispersion with respect to the regression curve. All three samples showed good agreement in the peculiar velocity distribution. Based on each of these samples, as well as on the combined sample, detailed maps of the field of peculiar velocities of the galaxies are constructed for V_H ≤ 3000 km/s. An analysis shows that most of the observed features of this map can be explained by large-scale density variations in the galactic distribution. __________ Translated from Astrofizika, Vol. 51, No. 3, pp. 409–422 (August 2008).     

Controls on debris-flow initiation on burned and unburned hillslopes during an exceptional rainstorm in southern New Mexico,USA

AbstractUsing observations from 688 debris flows, we analyse the hydrologic and landscape characteristics that influenced debris-flow initiation mechanisms and locations in a watershed that had been partially burned by the 2012 Whitewater-Baldy Complex Fire in the Gila Mountains, southern New Mexico. Debris flows can initiate due to different processes. Slopes can fail as discrete landslides and then become fluidized and move downstream as debris flows (landslide initiated) or progressive bulking of sediment from a distributed area can become channelized and concentrated as it moves downslope (runoff generated). In this study, we have an unusual opportunity to investigate both types of debris-flow initiation mechanisms in our observations of debris flows, triggered by an exceptional rainstorm in the autumn of 2013. Additionally, we compare our observations with those of a dataset of 1138 debris flows in the Colorado Front Range, triggered during the same weather system. We found that runoff-generated debris flows dominated in burn areas, and runoff required to start these flows could be well characterized by the Shields stress. Landslide-initiated debris flows were dominant in unburned areas. Debris-flow densities were tied to total rainfall and precipitation intensities. Like the observations in the Colorado Front Range, debris-flow initiation locations were found primarily in areas of relatively sparse vegetation on south-facing slopes between 25 and 40°, and with upslope contributing areas less than 1000 m². In terms of preferential locations for debris-flow initiations, 2013 vegetation coverage, approximated by Green–Red Vegetation Index metrics, proved to be more influential than the 2012 burn-severity designation. The uniformity of observations between our study area and those in the Colorado Front Range indicate that the underlying hydrologic and landscape patterns of the debris-flow initiation locations documented in these studies could be applicable to the wider southwest and Rocky Mountain regions. © 2019 John Wiley & Sons, Ltd.     

基于NCEP风向数据的中国夏季降水估算研究

提出一个基于NCEP风向数据估算全国夏季降水的模型。根据NCEP地面气压、经纬向风数据计算得到全国1971—2000年夏季各月盛行风向;并将盛行风向与宏观坡向夹角的余弦值作为降水的坡向因子,以此区分山体迎风坡和背风坡降水的空间分布。利用站点观测资料、数字高程模型数据、坡向、坡度因子,采用逐步回归分析法,建立估算夏季降水的回归方程,得到全国1971—2000年夏季各月及总降水量的空间分布图,并对模型结果进行检验与对比分析。结果表明,此方法估算夏季总降水量的平均绝对误差为27 mm,平均相对误差为11.8%。模型结果能体现迎风坡与背风坡的雨量差,符合客观规律,能够定性、定量地再现中国夏季降水的实际空间分布特征。     

THE RELATIONSHIP OF THE PRECEDING WINTER MJO ACTIVITIES AND THE SUMMER PRECIPITATION IN YANGTZE-HUAIHE RIVER BASIN OF CHINA

The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO strength,according to which active(or inactive) years of preceding winter MJO are divided.By utilizing the data provided by NCEP/NCAR,CMAP and China’s 160 stations from 1979 to 2008,we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation,i.e.when the preceding winter MJO is relatively active,the summer precipitation in the basin decreases,and vise verse.We also analyzed the causes.When the preceding winter MJO is relatively active,its release of potential heat facilities Inter-Tropical Convergence Zone(ITCZ) to strengthen and locate northward in winter and propagate northeastward.This abnormal situation lasts from winter to summer.In mid-May,ITCZ jumps northward to the South China Sea,the western Pacific subtropical high withdraws eastward,and the South China Sea summer monsoon sets off and strengthens.In summer,ITCZ propagates to South China Sea-subtropical western Pacific,the zonal circulation of subtropical Pacific strengthens,and a local meridional circulation of the South China Sea to the basin area forms,giving rise to the East Asia Pacific teleconnection wave-train.An East Asian monsoon trough and the Meiyu front show opposite features from south to north,the East Asian summer monsoon strengthens and advances northward.As a result,the summer monsoon is weakened as the basin is controlled by the subtropical high continually,with less rain in summer.On the contrary,when the preceding winter MJO is inactive,ITCZ weakens and is located southward,the subtropical high is located southward in summer,and the basin is in a region of ascending airflow with prevailing southwest wind.The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases.     

中尺度非均—边界层气候的数值研究——(Ⅱ)夏季的数值试验

用修改的 Nickerson 等提出的中尺度模式,对我国北方夏季非均一下垫面上的边界层气候特征进行了研究。结果表明,在晴朗、静风和无扰动系统的条件下,下垫面的非均一性对边界层气候起着决定性的影响。边界层气候特征和低空急流强度与局地环流关系密切。干燥裸地上边界层内出现的逆湿现象,是由下垫面非均一的湿度场和中尺度平流共同引起的。