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.     

The effect of meteorological conditions prior to ice run on the extent of ice jam floods on the Lena River

Generalized information about frequency, extent, and consequences of ice-jam floods in the Middle Lena River is presented. Demonstrated is the possibility of estimation of their probability with the use of data on air temperature in the period preceding the beginning of flood and ice run.     

Modeling fields of river runoff (a case study for the Lena River basin)

The potential of the model approach to the construction of mean annual fields (maps) of specific runoff for large territories from meteorological data is demonstrated for the Lena River basin. The ECOMAG (ECOlogical Model for Applied Geophysics), the physically based distributed model of river runoff formation is used to simulate hydrological parameters. Methodological aspects of calibration of the spatial fields of model parameters are discussed. The results of runoff hydrograph calculations are compared with the data of hydrometric observations at 12 gaging stations for the period of 1966-2009. The field of mean annual specific runoff in the Lena River batin computed with the ECOMAG model is compared with the map of specific runoff constructed from the data on water discharge in the river network. The comparative analysis of consistency between the fields is provided, and the possible sources of errors are considered.     

Peculiarities of the flow front structure in the Buor-Khaya Bay (the Laptev Sea) in winter

Hydrological flow front whose location and structure depend on the value of the Lena River water flow forms in winter under the ice in the Buor-Khaya Bay. The flow front is characterized by the baroclinic and thermocline components. Under the lens of desalinated waters, the layers of increased temperature and salinity alternate with the layers of decreased salinity and temperature. On the periphery of the front, the thermocline stratification results in the formation of the cold isopycnic intrusion at intermediate levels. The cross section of the cold intrusion in the bay amounted to ??50?C85 km and its thickness, from 3?C5 to 15 m. The waters of cold intrusions are rich with oxygen and favor the ventilation of the bay waters. The winter flow increase results in the significant widening of the river impact zone, warming of the coastal zone waters, and stratification intensification.     

Sensitivity Study of Anthropogenic Aerosol Indirect Forcing through Cirrus Clouds with CAM5 Using Three Ice Nucleation Parameterizations

Quantifying the radiative forcing due to aerosol–cloud interactions especially through cirrus clouds remains challenging because of our limited understanding of aerosol and cloud processes. In this study, we investigate the anthropogenic aerosol indirect forcing (AIF) through cirrus clouds using the Community Atmosphere Model version 5 (CAM5) with a state-of-the-art treatment of ice nucleation. We adopt a new approach to isolate anthropogenic AIF through cirrus clouds in which ice nucleation parameterization is driven by prescribed pre-industrial (PI) and presentday (PD) aerosols, respectively. Sensitivities of anthropogenic ice AIF (i.e., anthropogenic AIF through cirrus clouds) to different ice nucleation parameterizations, homogeneous freezing occurrence, and uncertainties in the cloud microphysics scheme are investigated. Results of sensitivity experiments show that the change (PD minus PI) in global annual mean longwave cloud forcing (i.e., longwave anthropogenic ice AIF) ranges from 0.14 to 0.35 W m^–2, the change in global annual mean shortwave cloud forcing (i.e., shortwave anthropogenic ice AIF) from–0.47 to–0.20 W m^–2, and the change in net cloud forcing from–0.12 to 0.05 W m^–2. Our results suggest that different ice nucleation parameterizations are an important factor for the large uncertainty of anthropogenic ice AIF. Furthermore, improved understanding of the spatial and temporal occurrence characteristics of homogeneous freezing events and the mean states of cirrus cloud properties are also important for constraining anthropogenic ice AIF.     

Variability and conjugacy of ice conditions in the system of east arctic seas (the Laptev, East Siberian, and Chukchi Seas)

The analysis of the long-term variability and spatiotemporal conjugacy of formation processes of ice conditions in the water areas of the Laptev, East Siberian, and Chukchi seas is carried out on the basis of the available data on the ice cover conditions in the above seas. On the whole, the type of relationships between the ice processes in the system of East Arctic seas indicates the existence of certain mechanisms generating the wave processes in the climatic system of the Arctic Basin manifested in the phase opposition in the development of ice conditions on the western and eastern peripheries of the basin under consideration. The statistical analysis of series of the ice coverage of water areas under consideration demonstrated that the existence of the long-term trend of this characteristic in some seas has its spatiotemporal features: the probability of the trend existence increases from west to east (from the Laptev Sea to the Chukchi Sea) and the trends are of opposite signs.     

黄河下游凌情变化的气象成因分析

概述黄河下游凌汛,分析了气温时空差异与凌汛形成和凌情变化的关系,根据冬季气温变化过程特点,并结合1968－1969年度凌汛实例,分析讨论了气温变化过程对凌情的影响。     

Forming conditions and probable values of maximum water levels of the Lena River near Yakutsk

The genesis of the formation of maximum water levels of the Lena River near Yakutsk is considered. Recovery techniques of series of hydrological characteristics is briefly stated. Observational data on maximum water levels are reduced to the long-term period, an estimation of their homogeneity and stationarity is carried out. The recomputation of maximum water levels of 1% probability taking account of extreme historical levels is executed. As a result, the mark of calculated 1% maximum water level (97.34 m, Baltic System) is obtained, which is 0.98 m higher than the one given in hydrological handbooks [1, 6].     

Atmospheric inversion strength over polar oceans in winter regulated by sea ice

Low-level temperature inversions are a common feature of the wintertime troposphere in the Arctic and Antarctic. Inversion strength plays an important role in regulating atmospheric processes including air pollution, ozone destruction, cloud formation, and negative longwave feedback mechanisms that shape polar climate response to anthropogenic forcing. The Atmospheric Infrared Sounder (AIRS) instrument provides reliable measures of spatial patterns in mean wintertime inversion strength when compared with available radiosonde observations and reanalysis products. Here, we examine the influence of sea ice concentration on inversion strength in the Arctic and Antarctic. Correlation of inversion strength with mean annual sea ice concentration, likely a surrogate for the effective thermal conductivity of the wintertime ice pack, yields strong, linear relationships in the Arctic (r?=?0.88) and Antarctic (r?=?0.86). We find a substantially greater (stronger) linear relationship between sea ice concentration and surface air temperature than with temperature at 850?hPa, lending credence to the idea that sea ice controls inversion strength through modulation of surface heat fluxes. As such, declines in sea ice in either hemisphere may imply weaker mean inversions in the future. Comparison of mean inversion strength in AIRS and global climate models (GCMs) suggests that many GCMs poorly characterize mean inversion strength at high latitudes.     

Freezing types and winter runoff of small rivers

Investigations carried out in the Northern Dvina River basin revealed that the decrease in the ice thickness on small rivers is of significant importance in the increase in the water content of rivers in winter in recent decades. This process resulted in the improvement of the channel capacity as a result of the decrease in the ice formation intensity on the rivers and of the increase in the fraction of ground waters participating in the winter river runoff formation. It is proposed to consider the initial winter ice conditions as a separate important factor of this process as they define the types of river freezing influencing on the winter river runoff formation as well.     

对流云中冰相过程的三维数值模拟——Ⅱ:繁生过程作用

在可压缩三维冷云数值模式里对冰晶繁生过程进行了参数化,显式考虑了过冷滴冻结破裂和Hallett-Mossop两个繁生机制,并对冰晶浓度进行了订正。对暖底孤立积云的模拟实例表明繁生作用对对流系统宏观特征没有显著改变,地面总降水略有增加,最大雨强增大且时间提前。繁生过程的主要作用是改变了云的微物理结构特征,使云中冰化时间提早,冰化程度大大加强,引起云上部增暖并抬高云顶。在所考虑的两个繁生机制中,冻结破裂繁生机制是引起微物理结构发生变化的主要过程。还对各冰相微物理过程的相对作用进行了分析。     

To what extent can atmospheric deposition influence the natural background of metals in ground waters? A case study in the Czech Republic

In harmony with requirements of Water Framework Directive the natural backgrounds of selected metals were established on the territory of Czech Republic. This paper is intended to provide characteristics and results of testing methods focused on quantification of the impacts of anthropogenic activities based on data of regional monitoring and their separation from acid atmospheric deposition including an appropriate discussion regarding the natural backgrounds of relevant metals. The results indicate that even in regions extremely affected by acid atmospheric deposition as is the territory of the Czech Republic this acid deposition will not have direct impact on the quality of ground waters on a regional scale. Consequently, the proved changes in quality of ground waters seem to have been caused by secondary processes, specifically by mobilization of metals in a rock environment due to increased acidity.     

The role of winter flaw polynyas in the formation of ice and hydrologic conditions in the Siberian shelf seas in the summer period

This paper analyzes the influence of flaw polynyas of the seas of the Siberian shelf on the formation of ice conditions in summer based on the ten-day data on the areas of flaw polynyas for 1978–2002 obtained by satellite image processing. The results of forecasts of summer ice conditions in the seas of the Siberian shelf are presented. The correspondence between the forecasts and observed data is 94.7% on average. The interrelation of atmospheric and ice processes is shown for the case when winter atmospheric processes determine ice conditions for the following summer and fall.     

不同浓度污染气溶胶对一次暴雨的影响

本文应用WRF-Chem模式耦合人为排放源,模拟了2011年8月13日的一次强降水过程,研究了正常（试验Norm）和两种极端情况（试验High和试验Low）下3种排放强度的人为污染气溶胶对微物理过程和降水的影响。结果表明:不同排放强度下降水开始的时间没有变化,低排放情况下降水区域未发生变化,暴雨前期试验Low的降水增强,后期减弱,降水中心强度减弱,周边降水增强,降水分散;高排放情况下降水区域明显减小,降水强度和各个量级的降水区域都减少。雨水和霰含量的变化是导致降水发生变化的原因,不同强度的污染气溶胶通过影响微物理过程影响大气的热力和动力过程,大气动力过程的变化反过来又通过微物理过程影响降水粒子的增长,从而影响地面降水。影响机理可概括为:当污染气溶胶的排放浓度增强,水汽凝结和冰晶凝华增长过程的减弱导致微物理过程的大气加热减弱,可用于发展对流的能量减少,上升运动减弱,对流强度的减弱抑制了了雨水和霰收集云水的增长,导致了可降水粒子含量的减少,降水减弱。     

Long term changes in ice and discharge regime of rivers in the Baltic region in relation to climatic variability

The river ice regime is considered a sensitive indicator of climate change and within this study long term changes (in case of River Daugava starting from 1530, but for other studied rivers starting from first half of twentieth century) river ice regimes in the Baltic region have been studied. The ice cover duration on the rivers (17 rivers) in the Baltic countries and Belarus has decreased during the recent decades. In addition to this, long term observational records of ice break on the rivers of the studied region exhibit a pattern of periodic changes in the intensity of ice regime. Both the ice regime and the seasonal river discharge are shown to be strongly influenced by large-scale atmospheric circulation processes over North Atlantic that manifests through close correlation with North Atlantic Oscillation index.     

Some features of sea ice formation in Antarctic coastal waters

Considered are the peculiarities of fast ice formation in the Antarctic coastal waters. It is noted that the fine-crystalline ice with the chaotic orientation of crystals is mainly developed in the surface layers of the ice cover as well as the ice formed due to the infiltration of the sea water and its subsequent freezing in the lower layers of the snow cover. It is demonstrated that under the conditions of coastal Antarctic, the lamination of the structure during the period of ice cover formation and its subsequent development is the result of heavy precipitation in the form of snow and the formation of the large amount of snow sludge and crystals of intrawater ice (frazil ice) on the open water. The main distinctive feature of the Antarctic sea ice is its seasonal stratification with the formation of the surface layer of recrystallized ice and underlying destructive layers including the water interlayer in the ice column. The provision of the safety of overice movement of machinery requires the development of methods of continuous remote control of the snow-ice stratum of the fast ice.     

Long-term effects of anthropogenic CO<Subscript>2</Subscript> emissions simulated with a complex earth system model

A new complex earth system model consisting of an atmospheric general circulation model, an ocean general circulation model, a three-dimensional ice sheet model, a marine biogeochemistry model, and a dynamic vegetation model was used to study the long-term response to anthropogenic carbon emissions. The prescribed emissions follow estimates of past emissions for the period 1751–2000 and standard IPCC emission scenarios up to the year 2100. After 2100, an exponential decrease of the emissions was assumed. For each of the scenarios, a small ensemble of simulations was carried out. The North Atlantic overturning collapsed in the high emission scenario (A2) simulations. In the low emission scenario (B1), only a temporary weakening of the deep water formation in the North Atlantic is predicted. The moderate emission scenario (A1B) brings the system close to its bifurcation point, with three out of five runs leading to a collapsed North Atlantic overturning circulation. The atmospheric moisture transport predominantly contributes to the collapse of the deep water formation. In the simulations with collapsed deep water formation in the North Atlantic a substantial cooling over parts of the North Atlantic is simulated. Anthropogenic climate change substantially reduces the ability of land and ocean to sequester anthropogenic carbon. The simulated effect of a collapse of the deep water formation in the North Atlantic on the atmospheric CO₂ concentration turned out to be relatively small. The volume of the Greenland ice sheet is reduced, but its contribution to global mean sea level is almost counterbalanced by the growth of the Antarctic ice sheet due to enhanced snowfall. The modifications of the high latitude freshwater input due to the simulated changes in mass balance of the ice sheet are one order of magnitude smaller than the changes due to atmospheric moisture transport. After the year 3000, the global mean surface temperature is predicted to be almost constant due to the compensating effects of decreasing atmospheric CO₂ concentrations due to oceanic uptake and delayed response to increasing atmospheric CO₂ concentrations before.     

边界层过程对"98·7"长江流域暴雨预报影响的数值试验研究

通过ETA模式对"98@7"长江流域暴雨过程的数值试验研究,讨论了行星边界层过程对暴雨数值预报的影响,结果表明边界层过程在这次暴雨预报中有重要作用.具体结论为:(1)降水大范围落区是受大尺度流场所决定的,但边界层过程对暴雨预报具有重要的作用;(2)不考虑边界层过程会影响对天气系统的正确预报,包括影响大气低层的运动场、水汽及大气不稳定度,从而影响暴雨的预报;(3)从时间层次上看,由于地表通量有着显著的日变化,边界层过程的作用不仅与暴雨本身发生发展及消亡的阶段有关,也与各阶段的时间(白天或夜间)有联系;(4)在空间范围内,边界层过程对大气的影响是通过大气流场重新分布来影响降水的环境条件,故地表通量分布和低层流场的相互配置作用十分重要.长江南北的情况有所不同,长江流域南侧区是地表通量的大值区,也是长江流域雨区水汽和不稳定能量的源区,它对长江流域的暴雨可能有着更为重要的作用.