Study of spatial distribution and occurrence frequency of ice jams in rivers of the Votkinsk reservoir catchment

In this paper, ice jams were studied and systemized for the first time for the Votkinsk reservoir catchment. For this purpose, observational and pooling data were used. The cartographic and attributive databases of sites where the jams occur were created by using GIS-technologies what allows obtaining their exact georeferences. Performed analysis of the studied river sections allowed revealing the main reasons of jamming.     

Environmentally allowable levels of impact on river ecosystems in the arctic region

Using a case study for the river ecosystems in the Russian Arctic, the methodological approaches are presented to the selection of hydrochemical and hydrobiological parameters and to the estimation of the limits of their variability at which the ecosystem conditions can be considered stable. The research is carried out using the classifiers of water ecosystem conditions developed at the Hydrochemical Institute. Based on the statistical processing of long-term monitoring information carried out by the National Service of Observation of Environmental Conditions, the environmentally allowable ranges of variations of hydrochemical and hydrobiological parameters are separated for the river ecosystems of the Arctic region. Determined are the allowable limits of variations of concentration of priority pollutants and the upper limits are considered as the environmentally allowable levels of impact.     

Forecasting the intrawater ice formation and ice jams in the Neva River

Considered is a dangerous ice phenomenon developing in the Neva River during its freezing, the formation of the intrawater ice resulting in the corking of water intakes, and ice jams causing a sharp water runoff decrease downstream of them and floods. Described are the forecasting techniques of the intrawater ice formation intensity, peak ice jam water levels, and thickness of ice jams.     

Possible Climate Change Impact on River Runoff in the Different Regions of the Globe

The possibility ofassessing changes in river runofftill 2100 for a number oflarge river basins of the world for a wide range of natural conditions is investigated. The assessment is based on the SWAP (Soil Water–Atmosphere–Plants) model using meteorological data as inputs which were simulated with different general atmosphere–ocean circulation models in accordance with the RCP climate change scenarios. The possible climatic changes in annual runoff for some rivers by the end of the 21st century are compared with the natural interannual variability of river runoff caused by weather noise.     

Estimation of possible climatic changes of river runoff in the Northern Dvina River basin in the 21st century

Presented is a method of studying possible climate-driven changes of river runoff characteristics, according to which the atmosphere-ocean general circulation models are used for computing the climate system impact, whereas the response of a watershed to given disturbance is estimated using the model of runoff formation in a river basin. The study is carried out for the Northern Dvina River basin. Estimates of possible changes (relative to the reference period) by the middle and late 21st century of such water regime characteristics as mean annual and maximum water discharge, as well as mean discharge values for the spring, summer-fall and winter seasons, are presented.     

一次“高影响天气”的弱降雪过程的数值研究

该文对2001年12月7日下午北京的一次弱降雪天气过程进行了诊断分析和数值模拟研究。诊断结果表明:北京地区由于受500 hPa小槽东移及850 hPa东移小高压后部带来的来自东海和南海的偏南暖湿气流共同影响，造成降雪。数值模拟结果显示:MM5模式对这次降雪过程具有较好的模拟能力，不仅模拟出了北京地区的降雪量，而且对这次过程大尺度背景场的演变、触发机制和水汽源有很好的表述。利用诊断分析和数值模拟结果，对这次弱降雪过程引起交通大阻塞的可能因素进行了探讨，说明建立城市预警系统的迫切性。     

包头山区流域面雨量的实现及最大洪峰流量的估计

利用T213数值预报产品建立包头市短期降雨预报方程,通过地理信息系统,在Citystar4.0版本软件的支持下,实现大青山区降水随高度的分布模式,计算出主要山区沟河的流域面雨量和降水总量,估计洪峰流量。在GIS(地理信息系统)环境下,研究山区面雨量的预报,通过建立包头市大青山区山体高度降雨量分布的经验公式,得到实现山区沟河流域面的面雨量,最终得到各个沟河流域的最大洪峰流量的估计。     

Climate Change and Water Resources

Current perspectives on global climate change based on recent reports of the Intergovernmental Panel on Climate Change (IPCC) are presented. Impacts of a greenhouse warming that are likely to affect water planning and evaluation include changes in precipitation and runoff patterns, sea level rise, land use and population shifts following from these effects, and changes in water demands. Irrigation water demands are particularly sensitive to changes in precipitation, temperature, and carbon dioxide levels. Despite recent advances in climate change science, great uncertainty remains as to how and when climate will change and how these changes will affect the supply and demand for water at the river basin and watershed levels, which are of most interest to planners. To place the climate-induced uncertainties in perspective, the influence on the supply and demand for water of non-climate factors such as population, technology, economic conditions, social and political factors, and the values society places on alternative water uses are considered.     

Estimating hydrological characteristics in the Amu Darya River basin under climate change conditions

Under consideration are results of solving the problem of the river water content estimation under conditions of uncertainties of climate change forecasts and the catchment state with a reference to the Amu Darya River basin. When constructing regional climate models, one selected a multimodel approach using the results of several global models and a statistical downscaling method that made the climate scenarios more detailed. The estimates demonstrated that in the medium- and long-term perspective, the Amu Darya River runoff is expected to decrease. As a result of the Bayesian ideology application, using the calculations got with a total probability formula, a prognostic probability curve of an annual river runoff supply of the basin rivers was derived based on different weights given to the estimates of a mean value for different climate scenarios. Prognostic characteristics of the annual runoff for the Amu Darya basin rivers are estimated in a form acceptable for hydrologic and hydroeconomic application.     

用反射率因子垂直廓线联合雨量计校准估测夏季区域强降水

提出了一种使用平均雷达反射率因子垂直廓线(VPR)联合雨量计校准估测地面降水的方法。选用2002年、2003年夏季长江中下游地区的宜昌和合肥新一代S波段多普勒雷达在几次大范围强降水过程中的部分时段体积扫描强度数据和周边100km范围内整理成10min一次的雨量资料，计算了区域上空短时平均VPR在地面的可能反射率因子值，并用此值反演降水，计算相对误差。同时，还分析了超短时强降水地区实时VPR的特征。结果表明:用最小二乘曲线拟合VPR数值，并联合雨量计平均校准因子估测降水，在大部分区域比较合理。与实测的降水比较可以看到，这种方法对提高估测区域性降水的精度都有效果；对于强对流性降水区域，只须用拟合法得到的地面反射率因子值估测地面降水。通过分析超短时强降水对应区域的实时VPR特征，有利于在无地面雨量计的地区通过分析VPR的特征来估测降水量的大小，结合其他要素分析降水的发展变化。     

An estimation of the probable maximum precipitation for river basins in the Czech Republic

The hydro-meteorological evaluation of a flood event in July 1997 (the Odra flood in Central Europe) demonstrated that new procedures to estimate design floods for the reservoir outflow structures in the Czech Republic (CR) were needed. Therefore, the techniques of the estimation of Probable Maximum Precipitation (PMP) were developed in a national research project (1998–2000), and the activity focused on the improvement of the area related PMP estimates was going on within a present national project. In the frame of the evaluation of the next extreme precipitation event in August 2002 (the Labe flood in the CR and Germany), we compared the catchments related precipitation with the PMP estimates. In this paper, an outline of the PMP estimation techniques is given and the use of data from the Czech gauges is described, the aim being the statistical derivation of the point and area PMP estimates for precipitation duration of 1 to 5 days. The use of radar data in assessing the maximized area reduction factor is discussed and the relationship resulting from the radar measurements over the CR territory is presented. An evaluation of the radar-based area rainfall enabled us to transform the point PMP to the area PMP estimate designed for the river basins in CR. In the last part of the paper, the results obtained by comparing the rainfalls in 1997 and 2002 flood events with the PMP estimates are presented. The comparison showed that the maximum area rainfalls over small Czech catchments (the 3rd order river basins) did not exceed 63% of the corresponding PMP values.     

汉江丹江口流域水文气象预报系统

汉江丹江口流域水文气象预报系统在GIS技术的支持下,以水文气象监测网、定量降水估算、定量降水预报、洪水预报技术为基础,通过雷达估算降水技术、中尺度数值模式预报技术获取高时空分辨率的降水信息输入水文模型来进行水文气象预报。以Web形式为基础的汉江丹江口流域水文气象预报系统平台在2010年7月以及2011年9月汉江丹江口两次洪水过程中及时、准确地显示了流域实况降水、预报降水,准确地预报了洪水入库过程。目前系统已成功移植到三峡区间、清江水布垭、淮河王家坝、漳河水库等流域开展汛期试验与服务,取得了较好的应用效果。     

漳河流域气象水文预报模型研究

通过对漳河产流、汇流、河道汇流和水库调洪演算,建立了漳河流域气象水文预报模型。本模型可根据实测降水量预报未来一定时期内入库洪水总量、洪峰、峰现时间、入库洪水过程,考虑水库出流及串联水库水量交换,经调洪演算得出水库水位变化过程。同时,也可输入气象预报的降水量或人工估算的未来可能降水量,进行水库未来洪水的可能发展趋势预测。     

佳木斯市雷暴的气候特征及其成因分析

根据佳木斯市常规地面气象观测记录,分析了雷暴的时空分布特征。雷暴主要集中在春夏之交及盛夏季节,且变化趋势比较平稳;地理分布是沿江低海拔地势,简要分析雷暴时空分布的原因。     

Uncertainties in the GSWP-2 precipitation forcing and their impacts on regional and global hydrological simulations

The Global Soil Wetness Project (GSWP) is an international initiative aimed at producing global data sets of soil wetness and energy and water fluxes by driving land surface models with state-of-the-art 1° by 1° atmospheric forcing and land surface parameters. It also provides a unique opportunity to develop and test land surface parameterizations at the global scale, using multi-year off-line simulations that are not affected by the systematic errors found in atmospheric models. Nevertheless, the accuracy and reliability of the 10?year GSWP-2 atmospheric forcing remain questionable. A first comparison using the high-resolution Rhône-AGGregation (Rhône-AGG) database reveals that the baseline GSWP-2 precipitation forcing is drastically overestimated over the Rhône river basin. Hydrological simulations driven with each dataset and using the ISBA land surface model and the MODCOU river routing model are also compared. The simulated river discharges are validated against a dense network of river gauges and are generally less realistic when using the GSWP-2 instead of the Rhône-AGG precipitation forcing. Secondly, the GSWP-2 precipitation forcing is compared with three alternative data sets (GPCP-2, CRU-2, CMAP) at the global scale. Moreover, the results of a global sensitivity study to the precipitation forcing conducted with six land surface models are shown. The TRIP river routing model is used to convert daily runoff from all models into river discharges, which are compared at 80 gauging stations distributed over the globe. In agreement with the regional evaluation, the results reveal that the baseline GSWP-2 precipitation forcing is generally overestimated over the mid and high latitudes, which implies systematic errors in the simulated discharges. This study reveals that the empirical wind corrections applied to the GSWP-2 precipitation forcing are exaggerated, whereas the GPCP satellite adjustments seem to be useful for simulating realistic annual mean river discharges over the East Siberian river basins.     

Modelling the Interaction Between a River Surface and the Atmosphere at the Bottom of a Valley

The role of a river of small dimensions in driving the surface exchange of sensible and latent heat fluxes at the bottom of a valley is investigated using large-eddy simulation (LES). Simulations were performed using different valley topographies, river widths and large-scale wind speed and direction. In all cases, the river acted as a sink of both sensible and latent heat during daytime. Despite the general agreement concerning the flux direction above the river surface, specific differences exist between the simulations. The topography enhances the wind divergence caused by the river, and the larger negative surface fluxes above the river occur when there are no slopes, a consequence of larger wind speeds above the river. For large-scale winds aligned with the valley axis, the surface fluxes depend on the large-scale wind speed, but this dependence is reduced if the large-scale wind is perpendicular to the valley axis. There is a minimum of temperature and a maximum of specific humidity above the river surface. The scalar budgets show that sensible heat flux converges above the river, being balanced by the warm air subsidence at the centre of the valley. Latent heat fluxes, on the other hand, converge above the river surface, and they are balanced by the horizontal advection of humidity towards the river margins.     

Errors in taking account of the runoff of the rivers with diurnal variations of the water level at the absence of increased-frequency observations

Estimated are additional errors in taking account of the river runoff during different phases of high water and snowmelt floods using the observational data from gaging stations at the absence of increased-frequency measurements of the water level (due to the lack or downtime of recorders). Described is a method for determination of these errors. Using the data collected on 118 gaging stations on 58 rivers in different regions of Russia and the former USSR for seven years of observations, determined are the possible additional errors of average daily, monthly and annual water flows of the rivers of different sizes as well as the total errors that take account of the additional errors.     

卫星雷达联合重构大尺度流域降水场

给出了一种用GMS-5卫星估计3h降水的方法,并利用地面测雨雷达和卡尔曼滤波器提取误差因子,用于在雷达探测范围以外校准卫星估计的降水,从而获得大尺度流域的(淮河流域)降水分布。在史灌河子流域的比较试验表明：卫星雷达联合重构的降水场具有比卫星估计降水更高的精度,3h降水估计的相对误差从31％下降到13％,和地面降水场的相关系数也有明显提高。     

石羊河流域1960～2009年参考蒸散量与蒸发皿蒸发量变化特征

以石羊河流域5个气象站点1960～2009年逐日气象资料为基础,从估算模型和统计角度计算分析了该流域参考蒸散量及蒸发皿蒸发量的变化趋势和变化原因。结果表明：过去50 a石羊河流域蒸散发呈增加趋势,个别站点达极显著水平（p＜0．01）,1960～2009年和1970～2009年不同时段的选择对分析结果有一定的影响。估算模型理论分析认为桑斯威特法计算的参考蒸散量变率主要由气温决定,蒸发皿蒸发量和彭曼蒙蒂斯公式计算的参考蒸散量变化则是辐射、气温、风速及空气饱和差共同作用的结果,而相关分析和突变检验的分析结果验证了上述结论,并得出过去50 a石羊河流域蒸发皿蒸发量和彭曼蒙蒂斯公式计算的参考蒸散量变化的主要决定因素是空气饱和差。