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.     

对“麦莎”路径及造成黄渤海域大风浪的数值模拟

2005年9号热带风暴“麦莎”8月8R凌晨开始影响大连,到10R过程完全结束,历时近两天,不仅造成了暴雨（局部大暴雨）天气,而且大连海区出现最大风力8-9级、阵风11级的大风。此时适逢天文大潮高峰期,渤海和黄海北部海域出现4m以上的浪高,形成了风暴潮。利用MM5模式和第三代浅水波浪数值预报SWAN模式,对“麦莎”的移动路径以及“麦莎”造成黄渤海域的强风场、强浪场进行模拟,结果与实况基本一致,并且通过模拟,对缺少资料的海面风场、浪高场有更全面的了解。     

Investigating Propagation of Short-Period Ocean Waves Into the Periphery of Arctic Pack Ice Using High-Resolution Upward-Looking Sonar

Springtime fetch in the Cape Bathurst Polynya System may present opportunities for winds to generate waves capable of propagating into the thick pack ice formed over the winter. A waves-in-ice event at a study site located on the Canadian Shelf in the southern Beaufort Sea that occurred 22–23 May 2011 is presented and analyzed for wave energy attenuation and dissipation characteristics. The event was monitored near the ice edge and, therefore, presents information on attenuation of waves from the ice edge into the pack. Waves of T?=?5?s, λ?=?37.5?m were observed up to approximately 143?m and approximately 77?m away from the ice edge during two separate observation periods of ice edge wave propagation. We estimated reflection coefficients of 53% and 52% and wave attenuation coefficients of α?=?2.4?×?10^?2?m^?1 and α?=?5.4?×?10^?2?m^?1, respectively, for the two periods. Estimated attenuation rates are an order of magnitude greater than in comparable studies and are inconsistent with previous findings of a “rollover” effect in attenuation rates for short-period waves.     

Simulation and Analysis of Sea Floods in the Don River Delta

Storm surges and wind waves in the Taganrog Bay (the Sea of Azov) are simulated with the ADCIRC+SWAN numerical model, and the mechanisms of the Don River delta flooding are analyzed. It is demonstrated that the most intensive flooding of the Don River delta occurs in case of southwestern wind with the speed of not less than 15 m/s. A storm surge leads to the intensification of wind waves in the whole Taganrog Bay due to the general sea level rise. As a result, the significant wave height near the Don River delta increases by 0.5–0.6 m.     

Long-term analysis of extreme wave characteristics based on the SWAN hindcasts over the Black Sea using two different wind fields

The long-term variations of wave characteristics in the Black Sea are evaluated by using a third-generation wave model (Simulating WAves Nearshore, SWAN), forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR) wind data, covering the period of 1979−2018. The model results were calibrated and validated with buoy measurements at seven stations along the Black Sea. The comparative study shows that the CFSR dataset predicted slightly greater significant wave heights than the ERA-Interim dataset. The greatest difference between two datasets in terms of wave characteristics was found in the northeastern part of the Black Sea. The long-term averages and the variations of long-term trends for wave characteristics show that southwestern part of the Black Sea was characterized by greater significant wave heights, longer mean wave periods and storm durations, and lower variability, while the northeastern part of the basin was characterized by lower significant wave heights, shorter mean wave periods and storm durations, and higher variability. The long-term trends indicate that the wave characteristics over the 40-year period are more likely to be exposed to higher variation on the eastern part of the Black Sea than the western part of the basin.     

Long-Term Variability of the Wind Field over the Indian Ocean Based on ERA-Interim Reanalysis

A detailed study of long-term variability of winds using 30 years of data from the European Centre for Medium-range Weather Forecasts global reanalysis (ERA-Interim) over the Indian Ocean has been carried out by partitioning the Indian Ocean into six zones based on local wind extrema. The trend of mean annual wind speed averaged over each zone shows a significant increase in the equatorial region, the Southern Ocean, and the southern part of the trade winds. This indicates that the Southern Ocean winds and the southeast trade winds are becoming stronger. However, the trend for the Bay of Bengal is negative, which might be caused by a weakening of the monsoon winds and northeast trade winds. Maximum interannual variability occurs in the Arabian Sea due to monsoon activity; a minimum is observed in the subtropical region because of the divergence of winds. Wind speed variations in all zones are weakly correlated with the Dipole Mode Index (DMI). However, the equatorial Indian Ocean, the southern part of the trade winds, and subtropical zones show a relatively strong positive correlation with the Southern Oscillation Index (SOI), indicating that the SOI has a zonal influence on wind speed in the Indian Ocean. Monsoon winds have a decreasing trend in the northern Indian Ocean, indicating monsoon weakening, and an increasing trend in the equatorial region because of enhancement of the westerlies. The negative trend observed during the non-monsoon period could be a result of weakening of the northeast trade winds over the past few decades. The mean flux of kinetic energy of wind (FKEW) reaches a minimum of about 100?W?m^?2 in the equatorial region and a maximum of about 1500?W?m^?2 in the Southern Ocean. The seasonal variability of FKEW is large, about 1600?W?m^?2, along the coast of Somalia in the northern Indian Ocean. The maximum monthly variability of the FKEW field averaged over each zone occurs during boreal summer. During the onset and withdrawal of monsoon, FKEW is as low as 50?W?m^?2. The Southern Ocean has a large variation of about 1280?W?m^?2 because of strong westerlies throughout the year.     

琼州海峡沿岸大风分布规律及影响系统分析

利用琼州海峡南北沿岸自动气象站2007年9月至2010年8月风向、风速资料,分析了最大风和极大风两种大风事件标准下的海峡沿岸大风分布规律,并基于大风天气影响系统分析南北沿岸大风的差异。结果表明：琼州海峡南侧沿岸大风事件多于北侧沿岸,其中最大风标准下的大风事件南侧沿岸明显多于北侧沿岸,但极大风标准下的大风事件北侧沿岸则多于南侧沿岸,且极大风风速明显偏大;北侧沿岸两种大风事件及南侧沿岸最大风事件均主要出现在秋冬季节,其中,两侧沿岸最大风事件主要由冷空气影响造成,南侧沿岸极大风事件集中出现在秋季,由冷空气影响造成较少;两岸位于海峡东侧入口沿岸的自动站点出现大风频率最高,风速偏大,两侧入口沿岸站点次之,中间沿岸各站出现大风的频率相对较低;海峡南北沿岸出现的大风风向多为北到东风;东路冷空气比西路冷空气更易造成海峡南北沿岸同步大风,琼州海峡对冷空气湍流强度的消弱作用明显。     

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.     

Simulation of the probable maximum flood in the area of the Leningrad Nuclear Power Plant with account of wind waves

At the designing of nuclear power facilities at the coastal sites the risk of their flooding caused by the combinations of adverse hydrometeorological events should be assessed with the probability of exceedance to 0.01%. According to the IAEA recommendations, the combination of statistical and deterministic methods was used to calculate the flood level of such rare occurrence. The level of flooding caused by the storm surge and reiated wind waves were computed with the probability of 0.01% for the coastal part of the Koporye Bay of the Gulf of Finland in the area of the Leningrad Nuclear Power Plant 2 (LNPP 2) construction; the results are presented. The calculations are based on the CARDINAL and SWAN software and four nested numerical models (for the Baltic Sea, the eastern part of the Gulf of Finland, the Koporye Bay, and a part of the bay in the area of LNPP). The decrease in sea-surface drag coefficient at hurricane winds is taken into account.     

南海近海面风场变化特征及其与ENSO的相关性研究

利用1979—2017年共39 a欧洲中期天气预报中心（ECMWF）海表面10 m风场资料,采用经验正交函数方法（EOF）、小波时频特征分析等方法分析了南海近海面风场变化特征及其对ENSO的响应。结果表明：南海近海面风场第一模态海表面平均风速呈减小趋势, 呈现年代际变化,且与ENSO相关,但相关性在1990年后趋于减小;第二模态中南海北部和南部平均风速呈减小趋势,中部增大;第三模态中南海中部海表面平均风速趋于减小,北部和南部增大,第二和第三模态均表现为年际变化,且均与ENSO显著相关,近年来ENSO与第三模态的相关性逐渐增强。春季南海表面平均风速从南到北逐渐增加;夏季在越南沿岸部分海域仍有一个风速极大值中心,从该海域向四周逐渐减小,整片海域风向均是西南风;秋季由南向北依次增加;冬季南海整片海域风速都较大,越南沿岸和我国东沙群岛海域存在两个极大值中心。     

渤海海效应暴雪云特征的观测分析

利用静止卫星 (GMS-5, GOES-9, MTSAT) 红外数据与CloudSat卫星云剖面雷达数据、NCEP FNL分析资料与常规观测资料,对2001—2010年发生的12次渤海海效应暴雪过程中云的演变特征、渤海热力作用与暴雪云团垂直结构及相态组成进行了观测分析。发现不同生成源地的暴雪云通常在渤海上快速发展,云中多存在水平范围可达100~300 km的密实条状或块状云团,其下对应主要降雪区域;暴雪云生成源地可分为渤海湾及莱州湾附近、渤海中部、辽东湾附近3种,暴雪云在海上移动主要受850 hPa风场影响;渤海暖海面与其上冷空气间的热量、水汽交换形成的不稳定层结条件,导致暴雪云进一步发展;暴雪云发展旺盛时期高度可达4 km,其冰水含量最大值达600 mg·m-3且主要集中在2 km高度附近,平均值可达303 mg·m-3,冰粒子有效半径最大值约为120 μm,平均值约为91 μm。     

Spatiotemporal long-term trends of extreme wind characteristics over the Black Sea

In this study, long-term change of wind characteristics on the Black Sea has been investigated using two widely used data sources, i.e., European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR), spanning 40 years between 1979 and 2018. Spatial and seasonal variability of climatic features such as the wind speed, direction, number and duration of storms, and wind power density are discussed. Wind climate is characterized by strong, durable and stable winds in the northern and western Black Sea, and relatively weak, short-lived and highly-variable winds in the eastern Black Sea. These long-term wind patterns indicate that the eastern part of the basin is likely to be subjected to the impacts of climate change. Long-term stable and strong wind conditions in the southwest part indicate reliable, persistent and sustainable wind energy potential. Long-term and seasonal variation of wind power density (WPD) at 110 m altitude over the Black Sea is investigated. There is a significant difference in WPD values between winter and summer seasons, with around 2.8 times larger WPD in winter than that in summer. In the western Black Sea, narrow confidence intervals observed in each season indicate a low level of variation during a season and ensures stable wind power conditions.     

Seasonal variations of oceanic conditions near the southeastern coast of Sakhalin Island

Seasonal variations of hydrological conditions in the area adjoining the southeastern coast of Sakhalin Island are described based on the analysis of monthly mean temperature and salinity obtained over standard oceanic sections Makarov-Cape Georgii and Cape Svobodny-the sea and from nine oceanic surveys. The Poronai River runoff that promotes the formation of a warm surface layer with low salinity largely influences the water area of Terpeniya Bay in the northern part of the area studied. In spring, these waters primarily spread southward along the coast; in summer, they flow southeastward, forming a weak vortex structure at 144° E. In the fall, major changes occur below 20 m, where waters of the cold intermediate layer are replaced by warmer waters (4–6°C) of low salinity connected with the Amur River runoff. The destruction of the CIL core near the shelf edge at depths of about 100 m resulting from the fall intensification of the East Sakhalin Current is pronounced in the southern, abyssal part of the region. The coastal area is covered by waters with salinity below 32‰ connected with the Amur River runoff. The volume of low-salinity waters coming through the Cape Svobodny-the sea section into the southern part of the Sea of Okhotsk is estimated at 3000 km³ taking into account instrumental measurements of flow rates.     

8616号(WAYNE)台风非对称研究

本文利用西沙群岛、东沙群岛、南海沿岸陆地及船舶等探空资料和航空、卫星、地面雷达等天气报告资料,对8616号台风的动力学特征进行了计算和分析。结果表明,该台风风速分布不对称,气旋性最大切向风位于台风右前象限,风速的垂直切变随台风的加强而减弱。最强的流入位于台风南半圆300hPa以下,流入最大值在700hPa附近。高层最强的反气旋流出在150—100hPa,流出主要位于台风北半圆。此外,该台风的垂直运动分布与台风的发展及所处的位置有密切的关系。      

INTERANNUAL VARIABILITY OF WINTER-TO-SPRING CIRCULATION TRANSITION OVER SOUTHERN CHINA AND ITS SURROUNDING AREAS AND MECHANISMS

The climatological features and interannual variation of winter-to-spring transition over southern China and its surrounding areas, and its possible mechanisms are examined in this study. The climatological mean winter-to-spring transition is approximately in mid-March over southern China and the northern South China Sea. During the transition stage, anomalous southwest winds prevail at low-level over southern China and its nearby regions with enhanced convergence center over southern China, bringing more moisture from the Bay of Bengal (BOB) and the South China Sea (SCS) to southern China; meanwhile, the upper level is characterized by an obvious divergence wind pattern over southern China to the southwest part of Japan and enhanced upward motion. All the change of circulation is favorable to an increase of precipitation over southern China after seasonal transition. The winter-to-spring transition is predominantly on the interannual variation over southern China and the northern SCS. Early winter-to-spring transitions may induce more precipitation over southern China in spring, especially in March, while late cases will result in less precipitation. The interannual variability of the winter-to-spring transition and the related large-scale circulation are closely associated with the decaying phase of ENSO events. The warm ENSO events contribute to early winter-to-spring transitions and more precipitation over southern China.     

The Impacts of Climate Change on the Autumn North Atlantic Wave Climate

Abstract

In this study, we investigate the impact of global warming induced by possible climate change on the autumn winds, the related storm climate, and the wave climate over the North Atlantic Ocean. These analyses are based on a third-generation wave model, WAVEWATCHIII? and dynamically downscaled winds, obtained from the Canadian Regional Climate Model driven by the third version of the Coupled Global Climate Model (T47) from the Canadian Centre for Climate Modelling and Analysis following the A1B climate change scenario of the Special Report on Emission Scenarios from the Intergovernmental Panel on Climate Change. Compared with the present wave climate, represented as 1970–1999, the significant wave heights in the northeast North Atlantic will increase, whereas in other areas, such as the mid-latitudes, they will decrease, with associated changes in winds in the future climate (2040–2069). An analysis of inverse wave ages is used to suggest that wind-driven wave regimes tend to occur more frequently in the northeast North Atlantic and decrease in the mid-latitudes in the climate change scenario. The dominant North Atlantic storm-track region is estimated to shift northward, especially over the northern Northeast Atlantic, where the frequency of occurrence of the most intense cyclones is estimated to increase. We suggest that changes in storm densities are related to changes in the upper level steering flow in the atmosphere, which are the precursor to changes in the winds and ocean waves.     

Seasonal variability of oceanological conditions in the northern part of the Tatar Strait

An average long-term distribution of temperature and salinity is analyzed for different months (May–November) computed on the basis of materials accumulated at standard oceanological sections of the northern part of the Tatar Strait. The main attention is paid to the section Korsakov Cape-Cape Syurkum crossing the water area under study practically in the middle. In early spring, the cold waters with salinity of more than 33‰ are registered at the section Korsakov Cape-Cape Syurkum. The waters with smaller salinity are revealed only in late spring, in June. In the same period, the intensification of cold intermediate layer occurs, first of all, in the western part of the section. The waters in the surface layer near the Sakhalin coast are warmed more than at the continental shelf. During the summer, this difference gradually decreases and the surface layer temperature becomes even in September. On the contrary, the spatial salinity gradients increase. In the fall, under the influence of northern and northwestern winds being typical of this period, the upwelling is formed near the Sakhalin coast and the cold dense waters emerge in the narrow coastal strip. The direction of alongshore flow changes from northern to the southern one. At the section Korsakov Cape-Cape Syurkum in November, the influence of small-salinity waters associated with the Amur River runoff is significantly revealed.     

亚洲热带气候态夏季风涌传播特征及其对中国降水的影响

基于1979—2020年逐日的NOAA向外长波辐射资料、NCEP/NCAR再分析风场资料,以及全球CMAP再分析降水资料,探讨了气候态亚洲热带夏季风涌的传播过程及与我国夏季相应的降水联系。分析结果表明,主汛期亚洲热带气候态夏季风季节内振荡(CISO)活动是亚洲夏季风活动的主要特征,随时间北传的亚洲热带夏季风CISO称为亚洲热带夏季风涌,主要有南亚夏季风涌和南海夏季风涌。亚洲热带夏季风涌的传播可分为四个阶段。在亚洲热带夏季风涌的发展阶段,印度洋区域低频气旋与对流活跃,孟加拉湾和南海热带区域被低频东风控制,我国大部分地区无降水发生,降水中心位于两广地区。当进入亚洲热带夏季风涌活跃阶段,孟加拉湾和南海热带地区低频气旋和对流活跃,东亚低频“PJ”波列显著,我国降水中心北移到长江以南的附近区域。亚洲热带夏季风涌减弱阶段,孟加拉湾与南海低频气旋消亡,对流减弱,低频西风加强,日本南部附近为低频反气旋控制,我国长江中下游低频南风活跃,降水中心也北移到长江中下游地区,而华南地区已基本无降水,此阶段的大气低频环流场与亚洲热带夏季风涌发展阶段基本相反。进入亚洲热带夏季风涌间歇阶段时,孟加拉湾和南海热带地区低...     

Regional features of long-term variability of the Black Sea surface temperature

The regional features oflong-term variability ofsea surface temperature (SST) in the Black Sea are analyzed using the satellite data for 1982-2014. It is demonstrated that the maximum intraannual and interannual variability of SST is registered on the northwestern shelf of the Black Sea. The high level of interannual variability of SST and maximum linear trends are observed in the northeastern part of the sea. The qualitative connection is revealed between the long-term variability of SST and the variations in the intensity of the Black Sea Rim Current in the long-term seasonal cycle. An increase in the level of interannual variability of SST is observed in summer, when the Black Sea Rim Current weakens. The significant negative correlation is revealed between the interannual anomalies of SST and the NAO index. The highest correlation coefficients are obtained for the eastern part of the Black Sea and near the Crimean coast.     

Generation and termination of Indian Ocean dipole events in 2003, 2006 and 2007

Evolution of Indian Ocean Dipole (IOD) events in 2003, 2006 and 2007 is investigated using observational and re-analysis data products. Efforts are made to understand various processes involved in three phases of IOD events; activation, maturation and termination. Three different triggers are found to activate the IOD events. In preceding months leading to the IOD evolution, the thermocline in southeastern Indian Ocean shoals by reflection of near equatorial upwelling Rossby waves at the East African coast into anomalous upwelling equatorial Kelvin waves. Strengthening (weakening) of northern (southern) portion of ITCZ in March/April and May/June of IOD years, leads to strengthening of alongshore winds along Sumatra/Java coasts. With the combined shallow thermocline and increased latent heat flux due to enhanced wind speeds, the SST in the southeastern Indian Ocean cools in following months. On intraseasonal time scales convection-suppressing phase of Madden-Julian oscillation (MJO) propagates from west to east in May/June of IOD year, and easterlies associated with this phase of MJO causes further shoaling of thermocline in southeastern Indian Ocean, through anomalous upwelling Kelvin wave. All these three mechanisms appear to be involved in initiating IOD event in 2006. On the other hand, except the strengthening/weakening of ITCZ, all other mechanisms are involved in activation of 2003 IOD event. Activation of 2007 IOD event was due to propagation of convection-suppressing MJO in May/June and strengthening of mean winds along Sumatra/Java coast from March to June through changes in convection. The IOD events matured into full-fledged events in the following months after activation, by surface heat fluxes, vertical and horizontal advection of cool waters supported by local along-shore upwelling favorable winds and remote equatorial easterly wind anomalies through excitation of upwelling Kelvin waves. Propagating MJO signals in the tropical Indian Ocean brings significant changes in evolution of IOD events on MJO time scales. Termination of 2003 and 2007 IOD events is achieved by strong convection-enhancing MJOs propagating from west to east in the tropical Indian Ocean which deepen the thermocline in the southeastern equatorial Indian Ocean. IOD event in 2006 was terminated by seasonal reversal of monsoon winds along Sumatra/Java coasts which stops the local coastal upwelling.