Wave interpretation of major Baltic inflows

The water dynamics in the straits between the North and Baltic seas during two major Baltic inflows that took place in the January of 1993 and 2003 is investigated using satellite altimetry data. It is found that the water mass surge to the eastern coast of the North Sea occurs before the beginning of the major Baltic inflow, and the sea level difference between the two seas is ~60 cm. Low-frequency fluctuations in the sea level and its wave parameters are studied. The wavelet analysis and the frequency-directed spectral analysis reveal the wave nature of the mechanisms leading to major Baltic inflows. The empirical characteristics of the obtained low-frequency waves are compared with the theoretical dispersion relations for the gradient-vorticity waves. Sea level variations during major Baltic inflows in the Danish Straits are identified as baroclinic Rossby waves. The analysis of cyclonic activity in the Northern Hemisphere demonstrated that stationary cyclones were observed during the inflows; this proves the feasibility of the resonance mechanism of the generation of major Baltic inflows.     

On the resonance-wave mechanism of major Baltic inflows

The features of the spatiotemporal variability of the sea level in the North and Baltic seas during the periods of formation of major Baltic inflows are investigated using the analysis of satellite altimetry data. It is demonstrated that dramatic drops in the sea level between the Baltic and North seas are observed during a few weeks before major inflows. A process of intensive inflows of the North Sea water to the Baltic Sea is accompanied not only by horizontal motions but also by vertical ones manifested in the increase in convergent flows in the North Sea and divergent flows in the Baltic Sea. A pronounced feature of the low-frequency dynamics of water of the North and Baltic seas is its wave structure. In both seas, low-frequency waves with the periods of 14–36 days propagate with the eastern component of the phase velocity along the isobaths and are identified as barotropic topographic Rossby waves. Phase velocities and lengths of low-frequency waves in the Baltic Sea are smaller by several times than those in the North Sea. Using the data of the analysis of meteorological information, a resonance-wave mechanism of generation of major Baltic inflows is studied.     

Wave Climate in the Caspian Sea Based on Wave Hindcast

The results of wind wave hindcast for the Caspian Sea for the period of 1979–2017 are presented. The WAVEWATCHIII wave model and wind forcing from the NCEP/CFSR reanalysis are used. The modeling is performed on the unstructured grid with the spacing to 1 km in the coastal zone. Mean and extreme values of wave height, length, and period are provided. It is shown that the maximum height of waves of 3% probability of exceedance is 11.7 m. The interannual variability of wave parameters is analyzed. No unambiguous trend towards increase or decrease in the storm activity was revealed over the hindcasting period.     

Wind Waves in the Northwestern Black Sea

The study presents the results of long-term monitoring of wind waves was carried out on the offshore fixed gas production platform in the northwestern part of the Black Sea in 1995–2011. The analysis of more than 31000 wave records provided reliable statistical characteristics of wind waves in the analyzed region. It was found that the maximum wave height reached 4.8 m in summer and 8.76 m in winter. The maximum hourly wave height exceeds significant wave height by 1.9 times in the vast majority of cases. The method of annual maxima revealed that in the Karkinit Bay the maximum wave height with the return period of 50 years is equal to 9.2 m.     

1961-2010年环渤海地区寒潮时空分布及变化特征

利用1961-2010年环渤海地区58个站的逐日平均气温、日最低气温资料,按照寒潮国家标准统计寒潮次数和寒潮强度,分析环渤海地区单站寒潮和区域寒潮的气候变化特征。结果表明：环渤海地区单站寒潮出现频次的地域差异很大,大体上呈现自北至南递减态势,年平均次数最多的为张北21次,最少的京津地区不足2次。近50 a来环渤海地区共有233次区域性寒潮,出现在当年9月至次年4月,其中11月最多。区域寒潮呈显著减少趋势。20世纪60-70年代区域性寒潮事件频发,80年代开始明显减少并在1983年出现了突变。区域特强寒潮不多,20世纪60年代出现了2次,自70年开始特强寒潮平均每个年代出现1次。在气候变暖背景下,环渤海地区区域寒潮次数明显减少,但特强寒潮亦极端寒潮事件并未减少。     

WAVEWATCHIII模式在渤海海浪预报的应用与检验

大连黄海、渤海海浪数值预报系统采用WAVEWATCHIII模式进行海浪预报,预报产品包括48 h内浪高、周期、浪向的逐3 h预报,并对其进行检验。结果表明：WAVEWATCHIII模式对渤海中部浪高模拟较好,浪高预报TS为71.7 %,对近岸海区浪高模拟相对差些。个例的检验表明,浪高最大值模拟较好,模拟浪高最大值出现的时间与实况基本吻合,浪高变化趋势预报也较好。AVEWATCHIII模式对两个周期个例进行检验,预报误差最低可达到0.17 s,预报效果较好。     

Numerical simulation of storm waves near the northeastern coast of the Black Sea

The results ofnumerical simulation of storm waves near the northeastern coast ofthe Black Sea using different wind forcing (CFSR reanalysis, GFS forecast, and WRF reanalysis and forecast) are presented. The wave modeling is based on the SWAN spectral wave model and the high-resolution unstructured grid for the Tsemes Bay. The quality estimates of wave simulation results for various wind forcing are provided by comparing the model results with the instrumental data on wind waves in the Tsemes Bay. It is shown that the forecast of the maximum wave height for some storms using the WRF wind forcing is more accurate than that based on the GFS forcing.     

Studying the variability of the wind wave period

Analyzed are the experimental data on the range of the sea wind waves obtained using a laser meter of hydrospheric pressure variations in 2007, 2010, 2011, and 2012 at different points of the shelf of the Sea of Japan. It is demonstrated that the variations of wind wave periods at their leaving the zone of cyclonic action can be associated not only with the dispersion but also with the Doppler effect and variations of the wind speed and wind direction in the zone of cyclonic action. Carried out was the analysis of the results of the processing of experimental data of the laser meter of hydrospheric pressure variations and the mobile laser meter of hydrospheric pressure variations; this analysis revealed that the transformation of wind waves with the decrease in the period and energy takes place in the case of their movement along the shelf of the decreasing depth.     

The Secondary Sea Level Maximum during Floods in Saint Petersburg and Its Simulation with Numerical Models

The study considered two- and three-dimensional models used to compute the Baltic Sea level. It is demonstrated for three floods that the BALT-P three-dimensional hydrodynamic model and the INMOM three-dimensional hydrothermodynamics model successfully simulate extreme sea level fluctuations during the floods in Saint Petersburg. To simulate extreme sea level fluctuations in the Baltic Sea, it is appropriate to use the BALT-P model which requires less input information. The analysis of simulation data for the considered cases reveals that the reason for the occurrence of the second flood maximum is the excitation of the wind-induced fundamental single-node seiche of the Baltic Sea.     

海冰覆盖度变化下北冰洋海浪研究进展

北冰洋地区海浪的生成和发展会受到海冰范围变化的显著影响.本文介绍了近年来基于浮标、潜标和走航观测,以及卫星遥感和数值模拟等方法开展的不同海冰覆盖度下北冰洋海浪的研究进展,包括海冰覆盖区海浪的传播机制等.北冰洋夏季开阔海域的平均有效波高可达3 m,在风暴期间,波弗特海有效波高可达5 m.除大西洋一侧,夏季北冰洋大部分海域...     

北印度洋-南海季风区热带海洋极端波候变化特征

利用1979—2016年ERA-Interim有效波高（SWH）和海表风场数据,分析了南海-北印度洋极端海浪场分布和变化.结果表明：南海-北印度洋极端SWH分布和极端风速分布形态以及年际变化趋势高度一致,说明了涌浪为主的北印度洋和风浪为主的南海一样,极端SWH都由局地的极端风速控制;强极端SWH主要分布在阿拉伯海以及南海北部,阿拉伯海北部增长与该区域气旋强度增强有着密切关系,而南海的极端SWH主要受东北季风控制;东非沿岸极端SWH线性增长趋势则与索马里急流的年代际尺度上有逐渐增强的线性趋势有关.北印度洋及南海海域极端SWH距平场的EOF分析结果表明,南海极端SWH与北印度洋表现出反相变化的特征.北印度洋（南海海域）极端SWH多出现在西南季风（东北季风）期间,因为在西南季风（东北季风）期间,极端风速也相对增强.     

On the contribution of Rossby waves driven by surface buoyancy fluxes to low-frequency North Atlantic steric sea surface height variations

Previous studies have shown that wind-forced baroclinic Rossby waves can capture a large portion of low-frequency steric sea surface height (SSH) variations in the North Atlantic. In this paper, the classical wind-driven Rossby wave model derived in a 1.5-layer ocean is extended to include surface buoyancy forcing, and the new model is then used to assess the contribution from buoyancy-forced Rossby waves to low-frequency North Atlantic steric SSH variations. Buoyancy forcing is determined from surface heating as freshwater fluxes are negligible. It is found that buoyancy-forced Rossby waves are important in only a few regions belonging to the subtropical-to-midlatitude and eastern subpolar North Atlantic. In these regions, the new Rossby wave model accounts for 25%–70% of low-frequency steric SSH variations. Furthermore, as part of the analysis it is also shown that a simple static model driven by local surface heat fluxes captures 60%–75% of low-frequency steric SSH variations in the Labrador Sea, which is a region where Rossby waves are found to have no influence on the steric SSH.     

寒潮过程中风浪对黄海海气热量通量和动量通量影响研究

采用2009—2013年CFSR(Climate Forecast System Reanalysis)大气和海洋再分析资料对黄海海气间热量通量和动量通量的特征进行统计分析,并通过FVCOMSWAVE浪流耦合模式对典型寒潮过程中风浪的影响效果进行模拟研究与对比分析。统计结果显示,通量受海表大风、海气温差及海洋环流等因子影响,秋冬季节强烈,春夏季节相对较弱,在寒潮活跃的冷季该海域的海流处于弱流期,风浪对海面通量的作用明显增强。海温特征也显示冷季的不稳定性显著强于暖季,因此该海域冷季具有更强的海气热量通量。沿岸站点的比较显示,南部吕泗站面向更开阔的东海海域,其平均波高高出北部20%左右。这与沿海南部通量强于北部特征对应。数值模拟显示,在寒潮过程中,海气界面热量通量和动量通量输送比多年月平均状态显著增强,动量通量增大1~5倍,热量通量增大1~6倍。寒潮过程入海冷锋走向、强度、移动方向显著影响海面热量通量和动量通量大值区的分布。偏北路寒潮纬向型冷锋入海,其强度东部大于西部,造成通量大值区形成在黄海东北部,而偏西路寒潮经向型冷锋入海,其强度南部大于北部,造成通量大值区形成在黄海南部。同时偏北路径寒潮强度大于偏西路径,海气动量通量响应较偏西路径强约25%,热量通量强约50%。耦合风浪作用的模拟显示,海气间热量通量和动量通量明显增大,对不同强度风浪,浪高增加1.5倍,动量通量最大值增大约2倍,热量通量增大10~160 W/m2;浪高减弱至0.5倍,动量通量最大值则减弱约40%,热量通量减小10~55 W/m2。冷锋及其驱动的风浪强烈影响区域海气通量时空特征。     

Seasonal characteristics of waves in the southeastern part of the Baltic Sea in 2008–2009

Presented are the characteristics of waves in the southeastern part of the Baltic Sea obtained from the results of continuous instrumental observations in 2008–2009 on the offshore oil-and-gas platform. Discussed are the conditions and prerequisites for the formation of extreme waves.     

Estimation of the effect of protective piers on wind wave parameters in the Sevastopol Bay

An effectiveness of the storm wave attenuation by protective piers in the Sevastopol Bay of the Black Sea is studied on the basis of numerical simulation using the SWAN spectral model. Analyzed are the parameters of waves generated by winds of four main directions as well as by the southern cyclone during the storm on November 11, 2007. It is obtained that waves from the northwest part of the Black Sea penetrate most intensively into the Sevastopol Bay in case of western wind and, to a lesser degree, in case of northern and southern winds. A protective effect of the piers is observed in the west part of the bay only and the wave attenuation near the southern coast is more significant than near the northern one. The area of the southern coast directly behind the southern pier is completely protected from the storm waves and, as moving away from the pier, the danger of intensive wave effect on the coast is kept.     

黄海西部海洋工程风、浪设计参数的分析和计算

使用黄海西部站点观测、船舶记录及海洋调查资料，建立计算海面风速的转换关系式。综合转换风速、台风报告或台风风场计算风速，分七个区块建立年最大风速序列；藉助极值Ⅰ型概率分布，推导了各区不同重现期的大风极值。开发使用美国SOWM波浪谱模式产品，推导了二个格点上不同重现期的波高极值，该值与近海波浪计算值一起组成合理的极端波高分布。     

Effect of wind shear on atmospheric wave instabilities revealed by FM/CW radar observations

An FM/CW radar sounding system designed and built by one of us (Richter, 1969) reveals atmospheric wave structure in unparalleled detail.The most outstanding features evident in the record are; internal gravity waves; features resembling Kelvin/Helmholtz instability structures; and multiple layering, often with lamina only a few meters thick.This paper shows a variety of atmospheric structural patterns and compares them with several hypothetical models of internal waves to obtain more insight into the atmospheric processes at work. Special attention is given to the distribution of the Richardson number in trapped and untrapped gravity waves. It is proposed that the multiple layers result from untrapped internal gravity waves whose propagation vector is directed nearly vertically within very stable height regions. It is argued that the layers are caused by dynamic instability resulting from reduction in the Richardson number due to wave induced shear and to some background wind shear when the amplitude-to-wavelength ratio grows during propagation into thermally stable height regions of the atmosphere.     

Pseudo-global warming projections of extreme wave storms in complex coastal regions: the case of the Adriatic Sea

This numerical work aims to better understand the behavior of extreme Adriatic Sea wave storms under projected climate change. In this spirit, 36 characteristic events—22 bora and 14 sirocco storms occurring between 1979 and 2019, were selected and ran in evaluation mode in order to estimate the skill of the kilometer-scale Adriatic Sea and Coast (AdriSC) modelling suite used in this study and to provide baseline conditions for the climate change impact. The pseudo-global warming (PGW) methodology—which imposes an additional climatological change to the forcing used in the evaluation simulations, was implemented, for the very first time, for a coupled ocean–wave–atmosphere model and used to assess the behavior of the selected storms under Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 greenhouse gas projections. The findings of this experiment are that, on the one hand, the AdriSC model is found capable of reproducing both the Adriatic waves associated with the 36 storms and the northern Adriatic surges occurring during the sirocco events and, on the other hand, the significant wave heights and peak periods are likely to decrease during all future extreme events but most particularly during bora storms. The northern Adriatic storm surges are in consequence also likely to decrease during sirocco events. As it was previously demonstrated that the Adriatic extreme wind-wave events are likely to be less intense in a future warmer climate, this study also proved the validity of applying the PGW methodology to coupled ocean–wave–atmosphere models at the coastal and nearshore scales.

     

有关沿岸山地俘获波的研究

在采用线性化的浅水方程组并假设地形坡度沿山脉走向不变的情况下,本文对具有底面地形坡度的沿岸山地俘获波作了研究,结果表明,当底面地形缓变时,可用摄动法得到沿岸山地俘获波的结构,此时零级近似为经典Kelvin波解,一级近似体现了Rossby变形半径内的底面地形对经典Kelvin波解的修正;直至一级近似,沿岸山地俘获波仍是非频散的。在沿岸处当底面地形坡度平缓时,沿岸山地俘获波表现为Kelvin波结构,此时扰动位势高度最大值出现在沿岸;而当底面地形坡度陡峭时,其表现为修正Kelvin波结构,此时扰动位势高度最大值偏离沿岸,在沿岸则扰动位势高度相对为低值,而在沿岸外侧则有位势高度的高值。在沿岸底面地形高度越高,地形坡度越大,扰动位势高度廓线的变化就越剧烈。     

Summer heat waves over western Turkey between 1965 and 2006

Global warming is one of the greatest environmental, economic, and social threats in the world. There are many assessments to estimate climate variability over many regions. A change in the Earth’s surface temperature leads to increase in extreme temperature events, which are harmful to the ecosystem, and moreover, they create danger on human health. In this study, we have selected the western part of Turkey as the study area, since climate change projections for Turkey point out that the highest temperature change can be expected on this region during summer, and the Turkish population is very dense here to be affected by extreme events. We have used apparent temperatures to define the heat waves which we have determined their frequencies for the summer months (June–August) of 1965–2006. Since the regional comparisons of station results are intended, we selected the 90th percentile value for each station as a threshold value to be used in the delineation of heat waves. Then, the number of heat waves is determined by imposing the constraint that apparent temperatures stay above the threshold value at least for three consecutive days. Then, the changes in the number of hot days and heat waves and also their durations are analyzed by using the linear least square method. We have found that the number of hot days, heat waves, and heat wave durations is increased between 1965 and 2006 on the western part of Turkey. Additionally, their rate of change is larger within the last decade and extremes are frequently observed after 1998. Regional distributions show that the tendency of the number of heat wave events increases towards the southern latitudes of the domain. Moreover, we investigated the relationship between the number of hot days and the sea surface temperatures of the Mediterranean Sea and Black Sea. Correlation analyses are carried out by the number of hot days and averaged sea surface temperatures on the regions of the western, central, and eastern Mediterranean Sea and the Black Sea. It is found that the number of hot days of west Turkey is better correlated with the sea surface temperatures averaged over eastern Mediterranean and Black Seas. The number of heat waves is found significantly correlated with the fire occurrences for most of the stations.