Wind-induced motion of water in shallow-water closed basins

The motion of water induced by tangential wind stresses in a circular basin of finite depth is studied by the finite-element method. The dependences of vertical displacements of the surface of the basin and the field of horizontal wave currents on the topography of the bottom and the direction of the wind are analyzed. The transformations of wind-induced disturbances observed after termination of the wind action are investigated.Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 35–44, September–October, 2004.This revised version was published online in May 2005 with corrections to cover date.     

On the possible mechanism of the intensification of the vertical exchange in the ocean during earthquakes

In recent years, some papers reported events of the lowering of the temperature of the sea surface subsequent to earthquakes. This paper is devoted to a discussion of the possible mechanism of the intensification of the mixing of seawater under earthquakes. The possible role of the intensive turbidity flows that are sometimes generated in the near-bottom layer over a sloping bottom subsequent to earthquakes is discussed. The estimates made on the basis of a semiempirical theory of turbulence show that the shear currents caused by these flows can lead to a fast turbulization and mixing of rather thick water layers.     

Field measurements of the vertical shears for a drift current

We describe the procedure of field experiments aimed at measuring the vertical profiles of the vectors of a drift current with the help of quasi-Lagrangian drifters. We present the data on the vertical shears of the current at depths of 0.5–5 m obtained under the conditions of neutral stratification in the upper 5-m layer of the sea in the presence of weak and moderate winds. The correspondence of the obtained data to the concept according to which the subsurface layer of the sea is regarded as a near-wall turbulent layer with Ekman current located below is analyzed. A conclusion is made that the results of measurements correspond, on the average, to the classical concepts demonstrating both the region of logarithmic sublayer and its transition into the Ekman spiral. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 32–44, January–February, 2007.     

Climatic trends in temperature,zonal flow,and stationary planetary waves from NCEP/NCAR reanalysis data

A detailed analysis of climatic trends in the longitudinally averaged temperature, zonal wind velocity, and activity of a stationary planetary wave with the zonal wave number 1 (SPW1) is made for January. The results of analysis indicate that marked climatic temperature variations having opposite signs in the low and high latitudes are observed. These variations cause the relevant variations in the intensity and arrangement of maxima of tropospheric jet flows and, thereby, are responsible for changes in SPW1 propagation conditions. SPW1 propagation from the troposphere into the upper atmosphere is calculated with a linearized model by using the distributions of zonal mean flow that are characteristic of the 1960s and the early 21st century. These calculations indicate that, over the past 40 years, the propagation conditions have improved “on average” and the calculated SPW1 amplitude in the stratosphere and mesosphere of the winter hemisphere has increased substantially. Analysis of the amplitudes of the zonal wind velocity for SPW1 that were obtained from the NCEP/NCAR data is consistent with the results of simulation and shows that some enhancement of SPW1 activity in the lower stratosphere has been actually observed in recent years. These variations in the amplitudes are also accompanied by the enhancement of SPW1 interannual variability.     

Structural health monitoring of bridges in the State of Connecticut

A joint effort between the Connecticut Department of Transportation and the University of Connecticut has been underway for more than 20 years to utilize various structural monitoring approaches to assess different bridges in Connecticut. This has been done to determine the performance of existing bridges, refine techniques needed to evaluate different bridge components, and develop approaches that can be used to provide a continuous status of a bridge＇s structural integrity. This paper briefly introduces the background of these studies, with emphasis on recent research and the development of structural health monitoring concepts. This paper presents the results from three different bridge types： a post-tensioned curved concrete box girder bridge, a curved steel box-girder bridge, and a steel multi-girder bridge. The structural health monitoring approaches to be discussed have been successfully tested using field data collected during multi-year monitoring periods, and are based on vibrations, rotations and strains. The goal has been to develop cost-effective strategies to provide critical information needed to manage the State of Connecticut＇s bridge infrastructure.     

Time changes of atmospheric precipitation in Russia from the corrected data during 1936–2000

Homogeneous time series of atmospheric precipitation with corrected systematic errors of measurements at 100 stations in Russia for the period of 1936–2000 are obtained. Combined effects are considered of all kinds of systematic errors of standard network precipitation-measuring instruments (the raingauge with the Nifer shield and the Tret’yakov raingauge) on the measured precipitation totals. Comparative analysis is carried out of the measured and corrected long-term mean characteristics of precipitation amounts (annual totals, warm and cold season totals, and different types of precipitation). On the basis of the obtained archives of precipitation homogeneous time series, linear trends are estimated for the period under consideration with estimation of their statistical significance. Schematic charts are plotted and analyzed of time changes in the annual precipitation amounts and in the amounts of different types of precipitation.     

Medium-range forecast of air temperature and of some dangerous phenomena using the technique of the hydrometcenter of Russia

The improved forecasting technique is presented of weather element computation developed at the Hydrometcenter of Russia for the medium-range forecasting on the basis of statistical interpretation of the results of integration of hydrodynamic atmospheric models. The methodology of numerical forecasting algorithms is described. The methods of forecasting the air temperature for ten-day periods and the extreme air temperature detailed for every day for the territory of Russia are realized on the basis of the weather element computation technique. According to the resolution of the Central Methodical Committee for Hydrometeorological and Heliogeophysical Forecasts, these methods are introduced into the operational practice as the basic ones. The examples of forecasts and the data on their accuracy are given. The approach is developed to the solution of the problem of the dangerous phenomena forecast (of anomalously cold and anomalously hot weather) with the earliness of 48–96 h within the frameworks of this technique.     

Mass Transfer Velocity and Momentum Vertical Exchange in Simulated Deep Street Canyons

A box model to simulate mass transfer inside deep street canyons and with atmospheric flow above is introduced and discussed. Two ideal deep street canyons with aspect ratios of 3 and 5 (the aspect ratio being the ratio between building height and street width H/W) are considered. This range of aspect ratios, found in many densely populated historical centres in Mediterranean cities as well as in other cities around the world, potentially creates high air pollutant concentration levels. Our model is based on a combination of analytical solutions and computation fluid dynamics (CFD) simulations using carbon monoxide (CO) as a tracer pollutant. The analytical part of the model is based on mass transfer velocity concepts while CFD simulations are used both for a preliminary validation of the physical hypothesis underlying the model (steady-state simulations) and to evaluate the concentration pattern with time (transient or wash-out simulations). Wash-out simulation curves were fitted by model curves, and mass transfer velocities were evaluated through a best-fitting procedure. Upon introducing into the model the contribution of traffic-produced turbulence, the modelled CO concentration levels became comparable with those obtained in real-world monitoring campaigns. The mass transfer rate between the canyon and the above atmosphere was then expressed in terms of an overall mass transfer velocity, which directly allows the evaluation of the mass transfer rate between the bottom volume of the canyon (pedestrian level) with the above atmosphere. Overall mass transfer velocities are reported as a function of the operating conditions studied (H/W = 3–5 and wind speeds = 2–8 ms⁻¹). Finally, a simple expression is reported for determining pollutant concentrations at the pedestrian level based on the overall mass transfer velocity defined.     

Mass concentration of PM10 and PM2.5 fine-dispersed aerosol fractions in the Eastern Gobi Desert

Results are presented of monitoring measurements of the mass concentration of PM₁₀ (particles with the size of less than 10 μm) and PM_2.5 (less than 2.5 μm) fine-dispersed aerosol fractions at the Sainshand and Zamyn-Üüd stations located in the Gobi Desert of Mongolia. Revealed are the annual variations of the mass concentration of PM₁₀ and PM_2.5 fine-dispersed aerosol fractions at these stations in 2008. The maximum values of monthly mean concentration during the year were observed in May in the period of dust storms. On the days with the steady calm weather, the mass concentrations of PM₁₀ and PM_2.5 varied within 5–8 μg/m³ (PM₁₀) and 3–5 μg/m³ (PM_2.5) at the Sainshand station. During the dust storms, the maximum values of concentration exceeded 1400 μg/m³ (PM₁₀) and 380 μg/m³ (PM_2.5) that is by 28 (PM₁₀) and 15 (PM_2.5) times higher than the maximum permissible concentration for the European Union. Results are given of studying the frequency and duration of dust storms in recent 20 years (1991–2010) in the Eastern Gobi Desert.     

Stratospheric temperature trends: impact of ozone variability and the QBO

In most climate simulations used by the Intergovernmental Panel on Climate Change 2007 fourth assessment report, stratospheric processes are only poorly represented. For example, climatological or simple specifications of time-varying ozone concentrations are imposed and the quasi-biennial oscillation (QBO) of equatorial stratospheric zonal wind is absent. Here we investigate the impact of an improved stratospheric representation using two sets of perturbed simulations with the Hadley Centre coupled ocean atmosphere model HadGEM1 with natural and anthropogenic forcings for the 1979–2003 period. In the first set of simulations, the usual zonal mean ozone climatology with superimposed trends is replaced with a time series of observed zonal mean ozone distributions that includes interannual variability associated with the solar cycle, QBO and volcanic eruptions. In addition to this, the second set of perturbed simulations includes a scheme in which the stratospheric zonal wind in the tropics is relaxed to appropriate zonal mean values obtained from the ERA-40 re-analysis, thus forcing a QBO. Both of these changes are applied strictly to the stratosphere only. The improved ozone field results in an improved simulation of the stepwise temperature transitions observed in the lower stratosphere in the aftermath of the two major recent volcanic eruptions. The contribution of the solar cycle signal in the ozone field to this improved representation of the stepwise cooling is discussed. The improved ozone field and also the QBO result in an improved simulation of observed trends, both globally and at tropical latitudes. The Eulerian upwelling in the lower stratosphere in the equatorial region is enhanced by the improved ozone field and is affected by the QBO relaxation, yet neither induces a significant change in the upwelling trend.