Relationship between Bering Sea Ice Cover and East Asian Winter Monsoon Year-to-Year Variations

In this study, the relationship between year-to-year variations in the Bering Sea ice cover （BSIC） and the East Asian winter monsoon （EAWM） for the period 1969-2001 was documented. The time series of total ice cover in the eastern Bering Sea correlated with the EAWM index at -0.49, indicating that they are two tightly related components. Our results show that the BSIC was closely associated with the simultaneous local and large-scale atmosphere over the Asian-northern Pacific region. Heavy BSIC corresponded to weaker EAWM circulations and light BSIC corresponded to stronger EAWM circulations. Thus, the BSIC should be considered as one of the possible factors affecting the EAWM variation.

The Interdecadal Variation Characteristics of Arctic Sea Ice Cover-ENSO-East Asian Monsoon and Their Interrelationshipat Quasi-Four Years Time Scale

Interdecadal and quasi-four years variation characterstics of Arctic sea for cover, ENSO and East Asian monsoon index(EAMI) are analyzed based on Singular Spectrum Analys. (SSA), lead-lag correlation and EOF for the past four decades. Results show that the Arctic sea for cover decreased in the early 1970s, several years earlier than that of global SSTA increase in the mid 1970s, which indicates that recent warming over the Northern Hemisphere firstly begins in the Arctic region in the 1970s. Great change of the East Asian monsoon intensity from stronger to weaker in summer (from weaker to stronger in winter) took place in the mid 1970s response to the abrupt modulation of SSTA particularly in the tropical eastern Pacific.Focus on the quasi-four years oscillation,close relationship is found among the sea ice cover, ENSO and EAMI based on lead-lag correlation. In which, the correlation coefficient reaches its maximum when the index of NINO3 SSTA variation takes 6 and 9 months lead of the western Pacific subtropical high and sea for cover index in Section-Ⅲ. Their interaction can be explained in the framework of asymmetric Walker circulation anomaly and Western Pacific Northern Pole (WPN) teleconnection pattern in the context of quasi-four years oscillation.

Contribution of a pathway through the Arctic Ocean to the recent reduction in the ice cover

The sea ice cover in the Arctic Ocean has been reducing and hit the low record in the summer of 2007. The anomaly was extremely large in the Pacific sector. The sea level height in the Bering Sea vs. the Greenland Sea has been analyzed and compared with the current meter data through the Bering Strait. A recent peak existed as a consequence of atmospheric circulation and is considered to contribute to inflow of the Pacific Water into the Arctic Basin. The timing of the Pacific Water inflow matched with the sea ice reduction in the Pacific sector and suggests a significant increase in heat flux. This component should be included in the model prediction for answering the question when the Arctic sea ice becomes a seasonal ice cover.

Conditions of spatiotemporal variability of the thickness of the ice cover on lakes in the Tatra Mountains

This research aimed to identify the impact of local climatic and topographic conditions on the formation and development of the ice cover in highmountain lakes and the representativeness assessment of periodic point measurements of the ice cover thickness by taking into consideration the role of the avalanches on the icing of the lakes.Field works included measurement of the ice and snow cover thickness of seven lakes situated in the Tatra Mountains(UNESCO biosphere reserve)at the beginning and the end of the 2017/2018 winter season.In addition,morphometric,topographic and daily meteorological data of lakes from local IMGW(Polish Institute of Meteorology and Water Management)stations and satellite images were used.The obtained results enabled us to quantify the impact of the winter eolian snow accumulation on the variation in ice thickness.This variation was ranging from several centimetres up to about 2 meters and had a tendency to increase during the winter season.The thickest ice covers occurred in the most shaded places in the direct vicinity of rock walls.The obtained results confirm a dominating role of the snow cover in the variation of the ice thickness within individual lakes.

A Numerical Study of the Mechanism for the Effect of Northern Winter Arctic Ice Cover on the Global Short-Range Climate Evolution

By using a nine-layer global spectral model involving fuller parameterization of physical processes, with a rhomboidal truncation at wavenumber 15, experiments are performed in terms of two numerical schemes, one with long-term mean coverage of Arctic ice (Exp.1), the other without the ice (Exp.2). Results indicate that the Arctic region is a heat source in Exp.2 relative to the case in Exp.1. Under the influence of the polar heat source simulated, there still exist stationary wavetrains that produce WA-EUP and weak PNA patterns in Northern winter. That either the Arctic or the tropical heat source can cause identical climatic effects is due to the fact that the anomaly of the Arctic ice cover will directly induce a south-propagating wavetrain, and bring about the redistribution of the tropical heat source / sink. The redistribution is responsible for new wavetrains that will exert impact on the global climate. The simulation results bear out further that the polar region in Exp.2 as a heat source, can produce, by local forcing, a pair of positive and negative difference centers, which circle the Arctic moving eastwards. Observed in the Northern Hemisphere extratropics is a 40-50 day oscillation in relation to the moving pair, both having the same period.

Detecting Arctic snow and ice cover with FY-1D global data

Chinese meteorological satellite FY-1D can obtain global data from four spectral channels which include visible channel(0.58-0.68 μm) and infrared channels(0.84-0.89 μm,10.3-11.3 μm,11.5-12.5 μm).2366 snow and ice samples,2024 cloud samples,1602 land samples and 1648 water samples were selected randomly from Arctic imageries.Land and water can be detected by spectral features.Snow-ice and cloud can be classified by textural features.The classifier is Bayes classifier.By synthesizing five d ays classifying result of Arctic snow and ice cover area,complete Arctic snow and ice cover area can be obtained.The result agrees with NOAA/NESDIS IMS products up to 70%.

Flow structure and shear stress in the presence of both ice cover on water surface and leafless vegetation in channel bed

This study aimed to investigate the previously unexplored effects of ice cover and submerged vegetation on flow structure.Experiments were undertaken under both open channel and ice-covered flow conditions.The bed material consisted of three non-uniform sands.The findings revealed that when vegetation patches were present on the bed and an ice cover was present,the velocity profiles exhibited a distinctive pattern with two peak values.Turbulent kinetic energy(TKE)also exhibited two peaks,one above the vegetation bending height and another at the sheath section,with a decreasing trend towards the ice cover.Furthermore,quadrant analysis showed that when the flow surface is covered by an ice cover,the contributions of inward and outward events increased compared with those observed in an open channel flow.In most cases,these contributions surpassed the sweep and ejection events.The findings enhance our understanding of vegetation’s response to diverse surface conditions and have practical implications for river management and environmental engineering.

INCIPIENT MOTION OF NON-COHESIVE SEDIMENT UNDER ICE COVER-AN EXPERIMENTAL STUDY

Based on a series of experiments under both ice-covered and free surface conditions, the present article discusses the role of flow velocity and critical shear Reynolds number for incipient motion of bed material. The influence of the resistance coefficients of both the underside of the ice cover and the channel bed on the location of the maximum velocity has been discussed. In addition, the impacts of ice and composite resistance coefficients on flow velocity for incipient motion of bed material have been assessed. The diagram describing the critical shear Reynolds number and the dimensionless shear stress for the incipient motion of sediment under ice covered conditions with different under cover resistance coefficient has been established. The effects of grain size on densimetric Froude number for incipient motion of bed material have been investigated. A relationship between the densimetric Froude number for incipient motion of bed material and the median grain size of bed material as well as the roughness coefficient of channel bed and roughness coefficient of ice cover has been established.

Impacts of ice cover on local scour around semi-circular bridge abutment

The presence of ice cover in winter can significantly change the flow field around bridge abutments, which can also cause a different local scour pattern. To investigate the impacts of ice cover, results from a recent flume experiments were presented. Smooth and rough ice covers were created to investigate the impacts of ice cover roughness on the scour geometry around the semi-circular abutment. Three bed materials were used, with 50D s of 0.58 mm, 0.50 mm, 0.47 mm respectively. Scour volume and scour area were calculated. It was found that the maximum scour depth was located 75o inclined to the flume wall. Under rough ice cover, the scour area and scour depth were the largest. An empirical equation on the maximum scour depth was also developed.

NUMERICAL EXPERIMENTS FOR THE IMPACT OF ANTARCTIC ICE COVER AND SEA SURFACE TEMPERATURE ON CLIMATE VARIABILITY

By using a three-level atmospheric general circulation model (AGCM),we have completed several numerical experiments to study the impacts of sea surface temperature anomaly (SSTA) and antarctic ice cover anomaly (AICA) during 1981—1983 on climate variability.The results show that during the El Nino period of 1982—1983 the impact of SSTA overrides that of AICA.SSTA mainly affects equatorial zonal circulation and produces PNA wave train,and SE-NW wave train in East Asia to influence the weather of China.AICA produces west-east anomalous vortex streets in the middle latitudes of both hemispheres and affects the intensity of the polar vortex of Southern Hemisphere.

Revisit submergence of ice blocks in front of ice cover–an experimental study

The present paper studies the stabilities of ice blocks in front of an ice cover based on experiments carried out in laboratory by using four types of ice blocks with different dimensions. The forces acting on the ice blocks in front of the ice cover are analyzed. The critical criteria for the entrainment of ice blocks in front of the ice cover are established by considering the drag force caused by the flowing water, the collision force, and the hydraulic pressure force. Formula for determining whether or not an ice block will be entrained under the ice cover is derived. All three dimensions of the ice block are considered in the proposed formula. The velocities calculated by using the developed formula are compared with those of calculated by other formulas proposed by other researchers, as well as the measured flow velocities for the entrainment of ice blocks in laboratory. The fitting values obtained by using the derived formula agree well with the experimental results.

NUMERICAL EXPERIMENTS FOR CLIMATE VARIABILITY OF MONSOON UNDER THE UNITED EFFECTS OF ANTARCTIC ICE COVER AND SEA SURFACE TEMPERATURE

In order to study the mechanisms of climate natural variability under the united effects of antarc- tic ice cover(AIC)and sea surface temperature(SST),we have done a series of numerical experi- ments for the climate variability of the period from January 1981 to December 1983 by using a three- level atmospheric general circulation model(AGCM).Firstly we conduct climate integration for six years,then 3 years'control integration from January 16 of the seventh year.Moreover,we do three sensitivity experiments,which are the sensitivity experiments forced by observed SST and AIC.ob- served SST and climatic AIC,observed AIC and climatic SST respectively,to study the climate vari- ability and its mechanisms affected by SST and AIC.We put emphasis on the variability of East Asia monsoon and the Southern Hemisphere(SH)circulation.In this paper,introduction is made to the results of control test and the sensitivity experiment forced by observed SST and AIC,and the pre- dictability of the monsoon climate variability is discussed.

A New Prediction Model for Grain Yield in Northeast China Based on Spring North Atlantic Oscillation and Late-Winter Bering Sea Ice Cover

Accurate estimations of grain output in the agriculturally important region of Northeast China are of great strategic significance for guaranteeing food security.New prediction models for maize and rice yields are built in this paper based on the spring North Atlantic Oscillation index and the Bering Sea ice cover index.The year-to-year increment is first forecasted and then the original yield value is obtained by adding the historical yield of the previous year.The multivariate linear prediction model of maize shows good predictive ability,with a low normalized root-mean-square error（NRMSE）of 13.9%,and the simulated yield accounts for 81%of the total variance of the observation.To improve the performance of the multivariate linear model,a combined forecasting model of rice is built by considering the weight of the predictors.The NRMSE of the model is 12.9%and the predicted rice yield explains 71%of the total variance.The corresponding cross-validation test and independent samples test further demonstrate the efficiency of the models.It is inferred that the statistical models established here by applying year-to-year increment approach could make rational prediction for the maize and rice yield in Northeast China before harvest.The present study may shed new light on yield prediction in advance by use of antecedent large-scale climate signals adequately.

Oblique Wave Scattering by An Undulating Porous Bottom in A Two-Layer Ice-Covered Fluid

The present study analyzes the reflection and transmission phenomenon of water-waves in a two-layer ice-covered system. The upper layer is covered by an ice-sheet, whereas the bottom of the lower layer is undulated and permeable. By using regular perturbation analysis and Fourier transform technique, the problem is solved and the first order reflection and transmission coefficients are determined. It is found that these coefficients depend on the shape as well as the permeability of the undulating bottom. Therefore, from the practical viewpoint, an undulating bottom topography is considered to determine all the aforesaid coefficients. The role of various system parameters, such as porosity, angle of incidence and ice parameters, are discussed to analyze the transformation of incident water wave energy from one layer to another layer. The outcomes are demonstrated in graphical forms.

EFFECT OF ARCTIC ICE COVER ON THE MONTHLY TEMPERATURE AND PRECIPITATION IN CHINA

Filtering technique, extended empirical orthogonal function (EEOF), spectrum distribution function and correla- tion analysis have been employed to study the relationship between arctic ice cover (AIC) and monthly mean tempera- ture and precipitation in China. The function of power spectrum density shows that not only a semi-annual and an an- nual oscillation but also a quasi-biennial oscillation can be found in AIC area index series, especially in June, September and November. During the period of analysis, it can also be found that there exists a good correlation between the El Nino events and the AIC area index. An analysis on the EEOF of AIC and the temperature over China exhibits some significant temporal-spatial patterns and a better time-lag interrelationship between them. The results from the correla- tion analysis indicate that the variation of AIC area has a significant influence on the temperature and precipitation in subsequent months over China. In addition, it experiences a quasi-biennial low-frequency oscillation and displays to certain extent some features of propagation.

Scattering of water waves by thick rectangular barriers in presence of ice cover

Assuming linear theory,the two dimensional problem of water wave scattering past thick rectangular barrier in presence of thin ice cover,is investigated here.Mainly four types of thick barriers are considered here and also the ice cover is taken as a thin elastic plate.May be the barrier is partially immersed or bottom standing or fully submerged in water or in the form of thick rectangular wall with a submerged gap presence in water.The problem is formulated in terms of a first kind integral equation by considering the symmetric and antisymmetric parts of velocity potential function.The integral equation is solved by using multi term Galerkin approximation method involving ultraspherical Gegenbauer polynomials as its basis function.The numerical solutions of reflection and transmission coefficients are obtained for different parametric values and these are seen to satisfy the energy identity.These coefficients are depicted graphically against the wave number in a number of figures.Some figures available in the literature drawn by using different mathematical methods as well as laboratory experiments are also recovered following the present analysis without the presence of ice cover,thereby confirming the correctness of the results presented here.It is also observed that the reflection and transmission coefficients depend significantly on the width of the barriers.

Analysis of VIV for Barrel-Shaped Mast with Covering Ice by HPD-S Method

The vortex-induced vibrations （VIV） of barrel-shaped mast are calculated by three numerical metods, i.e. New- mark- β, HPD-L （High Precision Direct integration scheme-Linear form）, and HPD-S （High Precision Direct integration scheme-Sinusoidal form）. According to the measured value, the accuracy curves are given to show the advantages of HPD-S method over others. Based on the comparison above, HPD-S method is used to calculate the influence of ice covering on the mast to VIV responses. It has been proved that the vortex-induced responses of barrel-shaped mast are changed along with ice thicknesses and types.

覆冰绝缘子串闪络前的泄漏电流特性(英文)

Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspension insulator string,measuring method and analysis of the leakage current are developed for ice-covered XWP_2-160 porcelain suspension insulator string in this paper.The waveform of the leakage current is perfectly recorded from the occurrence of micro-discharge to flashover,in which the process can be divided into four periods according to the evolution of the leakage current.There are different rising rates of the leakage current and various phenomena of arc discharge in different periods with the increase of the applied voltage,and the distortion on the leakage current waveform is detected because of the effect of arc discharge.A characteristic current(I_w)and a critical current(I_(FT))of flashover,two important parameters of the leakage current before ice-covered insulator string flashover,are defined for analysis of the leakage current characteristics of pre-flashover along the polluted insulator string covered with ice.Statistical experimental results show that the average values of I_w and I_(FT) are within the major distribution zones,and both currents can be used for predicting the icing flashover.The values of two important leakage currents are approximately constant at different contamination degrees,while the direct relationships between the critical currents and the contamination degrees are not found in this paper.

Numerical simulation of mechanical breakup of river ice-cover

Ice jams and ice dams in rivers will cause significant rises of water levels. Under extreme conditions, the ice flooding during winter or early spring may occur. In this paper, by considering the fluid-solid coupling effect caused by the water and the ice cover, the mechanisms of the mechanical breakup of the river ice cover are studied. A formula is obtained for determining whether or not the mechanical breakup process would happen under the hydraulic pressure of the flow. Combined with the hydraulic model under the ice covered flow, a numerical model is built and the interaction between the discharge, the hydraulic pressure under the ice cover and the date for the mechanical breakup of the river ice cover is simulated. The simulated results of the dates for the mecha- nical breakup of the river ice cover agree very well with the field observations of the breakups of the river ice cover in the Hequ Reach of the Yellow River. Therefore, the numerical model might serve as a good preliminary step in studying the breakup of the river ice-cover, evidencing many important parameters that affect the ice-cover process,

Correlation between sea surface temperature and wind speed in Greenland Sea and their relationships with NAO variability

The North Atlantic Oscillation （NAO） is one of the major causes of many recent changes in the Arctic Ocean. Generally, it is related to wind speed, sea surface temperature （SST）, and sea ice cover. In this study, we analyzed the distributions of and correlations between SST, wind speed, NAO, and sea ice cover from 2003 to 2009 in the Greenland Sea at 10°W to 10°E, 65°N to 80°N. SST reached its peak in July, while wind speed reached its minimum in July. Seasonal variability of SST and wind speed was different for different regions. SST and wind speed mainly had negative correlations. Detailed correlation research was focused on the 75~N to 80~N band. Regression analysis shows that in this band, the variation of SST lagged three months behind that of wind speed Ice cover and NAO had a positive correlation, and the correlation coefficient between ice cover and NAO in the year 2007 was 0.61 SST and NAO also had a positive correlation, and SST influenced NAO one month in advance. The correlation coefficients between SST and NAO reached 0.944 for the year 2005, 0.7 for the year 2008, and 0.74 for the year 2009 after shifting SST one month later. NAO also had a positive correlation with wind speed, and it also influenced wind speed one month in advance. The correlation coefficients between NAO and wind speed reached 0.783, 0.813, and 0.818 for the years 2004, 2005, and 2008, respectively, after shifting wind speed one month earlier.