Identification of physical processes inherent in artificial neural network rainfall runoff models

The emergence of artificial neural network (ANN) technology has provided many promising results in the field of hydrology and water resources simulation. However, one of the major criticisms of ANN hydrologic models is that they do not consider/explain the underlying physical processes in a watershed, resulting in them being labelled as black‐box models. This paper discusses a research study conducted in order to examine whether or not the physical processes in a watershed are inherent in a trained ANN rainfall‐runoff model. The investigation is based on analysing definite statistical measures of strength of relationship between the disintegrated hidden neuron responses of an ANN model and its input variables, as well as various deterministic components of a conceptual rainfall‐runoff model. The approach is illustrated by presenting a case study for the Kentucky River watershed. The results suggest that the distributed structure of the ANN is able to capture certain physical behaviour of the rainfall‐runoff process. The results demonstrate that the hidden neurons in the ANN rainfall‐runoff model approximate various components of the hydrologic system, such as infiltration, base flow, and delayed and quick surface flow, etc., and represent the rising limb and different portions of the falling limb of a flow hydrograph. Copyright © 2004 John Wiley & Sons, Ltd.     

An integrated hydrological model for rain‐induced landslide prediction

This paper describes an extension to the Combined Hydrology And Stability Model (CHASM) to fully include the effects of vegetation and slope plan topography on slope stability. The resultant physically based numerical model is designed to be applied to site‐specific slopes in which a detailed assessment of unsaturated and saturated hydrology is required in relation to vegetation, topography and slope stability. Applications are made to the Hawke's Bay region in New Zealand where shallow‐seated instability is strongly associated with spatial and temporal trends in vegetation cover types, and the Mid‐Levels region in Hong Kong, an area subject to a variety of landslide mechanisms, some of which may be subject to strong topographic control. An improved understanding of process mechanism, afforded by the model, is critical for reliable and appropriate design of slope stabilization and remedial measures. Copyright © 2002 John Wiley & Sons, Ltd.     

Momentum transport of wave zero during March: A possible predictor for the Indian summer monsoon

Analysis of monthly momentum transport of zonal waves at 850 hPa for the period 1979 to 1993, between ‡S and ‡N for January to April, using zonal (u) and meridional (v) components of wind taken from the ECMWF reanalysis field, shows a positive correlation (.1% level of significance) between the Indian summer monsoon rainfall (June through September) and the momentum transport of wave zero TM(0) over latitudinal belt between 25‡S and 5‡N (LB) during March. Northward (Southward) TM(0) observed in March over LB subsequently leads to a good (drought) monsoon season over India which is found to be true even when the year is marked with the El-Nino event. Similarly a strong westerly zone in the Indian Ocean during March, indicates a good monsoon season for the country, even if the year is marked with El-Nino. The study thus suggests two predictors, TM(0) over LB and the strength of westerly zone in the Indian Ocean during March.     

Water and sediment outbursts from advanced Franz Josef Glacier,New Zealand

The Franz Josef Glacier, Westland, New Zealand, has a history of catastrophic sediment‐laden outburst ?oods associated with extreme rainfall events when the glacier toe is advanced over its own sediments. Consideration of these events and inspection of recent sediment deposits suggest that there are three distinct modes of outburst. The ?rst is associated with fans fed by over?ow along the glacier margin. As the glacier has advanced across its own fore?eld gravels, it is inferred that the primary drainage conduit has developed a reach of negative slope. In high ?ows massive boulders can block the conduit, trapping lesser clasts. The resulting backup of water causes over?ows through marginal moulins, producing the fan type of deposit. The second type of outburst deposits massive imbricated boulders at a greater or lesser distance from the glacier portal. In this case, pressure buildup drives the blockage out of the portal where the boulders deposit. Smaller materials are generally carried away. The third type consists of very shallow ?ows, and produces massive gravel deposits of uncertain provenance. In this condition, the excess pressure in the conduit results in slight uplift of the glacier and widespread discharge of water and sediment below the glacier snout; gravels and smaller sediments are laid down in a massive deposit across the fore?eld. The massive, boulder‐veneered deposit from the December 1995 outburst is interpreted in the light of the above mechanisms as a hyperconcentrated ?ow deposit from hydraulic jacking, overlain by boulders emplaced by a subsequent conduit outburst. A possible association of outbursts with the present advanced position of the glacier is suggested. Copyright © 2003 John Wiley & Sons, Ltd.     

月降水量的神经网络混合预报模型研究

以均生函数表征预报量自身周期变化，结合500hPa月平均高度场和月平均海温场预报因子，采用神经网络方法建立了一种新的短期气候预报模型。分别以广西桂北、桂中和桂南6月降水量作为预报对象进行预报试验，结果表明，这种新的预报方法比均生函数回归预报模型及高度场、海温场预报因子的回归预报模型，具有更好的物理基础和预报能力。     

山西省主要河流流域面雨量预报业务流程

以T213、HLAFS模式、MM5中尺度模式输出的格点资料以及日本降水量格点资料为基础，将影响山西降水的天气动力模型归纳为诊断模型，从中引出多个能够全面反映降水模型特征的综合物理因子；根据各种数值模式输出的降水量预报性能和质量优劣特点，依据数值模式的形势场预报优于要素场预报的现实，构造在不同环流形势背景下，启动不同预报方程的面雨量预报业务流程，有效地遏止了在环流形势调整时预报输出不能快速响应的弱点，提高了点和面雨量预报的准确度。     

TRMM卫星微波成像仪分级产品及其反演降水算法

文章叙述了获取定量降水信息的意义，简要介绍了对热带测雨卫星TRMM(Tropical Rainfall Measurement Mission)的仪器、美国国家宇航局提供的微波成像仪TMI(TRMM Microwave Imager)分级产品。对比了物理方法和经验方法反演降水的特点，并对一些经验方法以及倾斜对流系统对反演降水的影响、动态聚类分析、神经网络反演方法的研究成果进行了介绍。     

不同对流参数化方案和初值场组合对四川两次暴雨影响的数值模拟

针对2004年9月2~6日四川盆地东北部一次持续性暴雨过程和2004年6月30日成都地区暴雨过程,利用MM5中尺度数值模式,进行了Grell、Kuo、KF及BM四种积云对流参数化方案与T213模式分析值及NCEP再分析值两种初始值组合的数值试验,分析了不同积云方案和初值组合的模拟性能。比较结果表明,MM5模式较好地再现了这两次强降水过程。在同一模式中,不同对流参数化方案和不同初值组合在降水落区和强度模拟上存在一定程度的差异。初步模拟表明NCEP资料模拟的降水强度较T213资料模拟的降水强度偏弱,但降水落区较T213资料模拟的更接近实况,T213资料模拟的降水空报现象较严重。以T213资料模拟得到的高度、温度场都较NCEP资料更有利于影响系统的加强,模拟的湿度场、散度场和垂直运动场都较NCEP资料更有利于强降水的发生。相对而言,NCEP资料模拟结果更接近实况,Kuo和Grell方案对初值表现出更为敏感。     

一次大气河背景下华北地区暴雨的诊断分析

利用2018年5月15-16日的ERA5再分析资料和观测资料,对大气河背景下一次华北地区暴雨过程的天气形势、大气河在暴雨过程中的作用及其在暴雨前后的演变特征以及结构特征进行了诊断分析.结果 表明此次降水过程的直接影响系统是位于华北地区的高空槽、低空切变线、地面冷锋和高低空急流,这些系统使得华北地区低层辐合高层辐散,带来...     

我国华北地区春季降水的年代际变化特征及其可能成因的探讨

利用我国160个台站1951~2000年逐月和华北地区80个台站逐日降水观测资料,分析了我国,特别是华北地区春季降水的年代际变化特征。分析结果表明:华北地区春季降水具有明显的年代际变化,1951~1965年华北地区春季降水略偏少,1966~1976年华北地区春季降水更加偏少,春旱较严重,1977~2000年为华北春季降水明显偏多,这时期5~6月降水比1966~1976年有明显增多;并且,分析结果也表明了华北地区和黄河流域春季降水存在着与夏季降水相反的年代际变化特征。另外,作者还利用欧洲中心ERA40资料集的1958~2000年月平均700 hPa风场再分析资料,分析了东亚上空春季700 hPa风场的年代际异常情况,从而来探讨华北地区春季降水年代际变化的成因。其分析结果表明:1965年以前,蒙古高原上空存在着明显的反气旋距平环流,我国华北地区有偏北风距平,这使得我国华北地区在1965年以前春季降水偏少;1966~1976年,我国华北地区仍为偏北风距平,且我国东部沿海到南海上空的偏北风距平增强,这使得华北地区春季降水进一步减少;1977~2000年,东亚上空700 hPa环流场发生了一个明显的变化,华北地区出现偏南风距平,且我国东部沿海到南海上空的偏南风距平增强,这使得我国南方暖湿气流易输送到华北地区,从而造成我国华北地区春季降水增加。