THE STUDY OF THE YELLOW SEA WARM CURRENT AND ITS SEASONAL VARIABILITY

The Yellow Sea Warm Current (YSWC) penetrates northward along the Yellow Sea Trough, and brings warm and saline water towards the Bohai Sea. The YSWC becomes much less intrusive in summer and is limited mostly in the southern trough, contrasting with a deep winter penetration well into the trough. The seasonal variability of the YSWC has prompted a debate regarding which controls the YSWC and its seasonal variability. In this article, the annual mean and seasonal variability of the YSWC was examined by using a 3-D ocean model together with several experiments. The results show that in the annual mean the YSWC is a compensating current firstly for the southward Korea Coastal Current (KCC), which is mainly caused by the Kuroshio Current (KC). The local wind-stress forcing plays an important but secondary role. However, the local monsoonal forcing plays a prominent role in modulating the seasonal variability. A deep northwestward intrusion of the YSWC in winter, for instance, is mainly due to a robustly developed China Coastal Current (CCC) which draws water along the Yellow Sea trough to feed a southward flow all the way from the Bohai Sea to the Taiwan Strait.     

Seasonal variability of circulation and air-sea interaction in the Caspian Sea based on a high resolution circulation model

The Caspian Sea is the largest closed basin on Earth, with unique physical characteristics and complex bathymetry. Sparse measurements and coarse resolution models have not yet provided a full picture of its dynamics. In this study, a high resolution (～3.3 km) Regional Ocean Modeling System (ROMS) was used to study its annual and seasonal circulation patterns, and distributions of salinity and temperature. Temperature and salinity nudging were implemented which forced the model to follow in situ observations. This approach effectively limited the model error in predicting the temperature and salinity. The model successfully reproduced sea surface temperature and salinity over the entire basin. The simulated sea surface salinity showed three salinity fronts over the Caspian Sea. The salinity profile was vertically uniform in deep waters of the Caspian Sea. In contrast, the vertical thermal structure formed the seasonal thermocline at a depth of 15–40 m which was intensified in summer. In general, the seasonal variability of water temperature or salinity was confined to the upper 100 m of the water column. Simulations revealed an impermanent weak northward current along the eastern coasts of the Middle Caspian Sea, a persistent strong southward current along its western coasts and a permanent deep anticyclonic gyre over the Southern Caspian Sea. Using a high resolution model, this study also reports several mesoscale and small scale structures in the Caspian Sea which have not been reported before.     

SEASONAL VARIATIONS OF CIRCULATION AND SUSPENDED MATTER TRANSPORT IN THE YELLOW AND EAST CHINA SEAS

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THE EFFECTS OF MONSOONS AND CONNECTIVITY OF SOUTH CHINA SEA ON THE SEASONAL VARIATIONS OF WATER EXCHANGE IN THE LUZON STRAIT

Seasonal variations of water exchange in the Luzon Strait are studied numerically using the improved Princeton Ocean Model (POM) with a consideration of the effects of connectivity of South China Sea (SCS) and monsoons. The numerical simulations are carried out with the strategy of variable grids, coarse grids for the Pacific basin and fine grids for the SCS. It is shown that the Mindoro Strait plays an important role in adjusting the water balance between the Pacific and the SCS. The SCS monsoon in summer seasons hinders the entrance of the Pacific water into the SCS through the Luzon Strait while the SCS monsoon in winter seasons promotes the entrance of Pacific water into the SCS through the Luzon Strait. However, the SCS monsoon does not affect the annual mean Luzon Strait transport, as is mainly determined by the Pacific basin wind.     

冬、夏季北黄海悬浮物分布特征

利用国家908专项ST02区块(北黄海)水体专项调查2007年夏、冬资料,应用浊度观测资料对悬浮物质量浓度进行线性拟合,得到较好的反演结果。在北黄海海域选取了具有代表性的9个断面,利用反演的悬浮物质量浓度,综合温度、盐度等水文要素,辅以冬、夏季山东半岛沿岸流、北黄海冷水团和黄海暖流的季节变化特征,着重分析了冬、夏季北黄海悬浮物分布特征、形成原因以及季节变化。研究结果表明,冬、夏山东半岛北部沿岸、成山头海域和老铁山水道以及旅顺湾附近海域始终为高悬浮物浓度区,呈现出近岸高,离岸低,底层高,表层低的态势。夏季,水体垂向层结显著,受北黄海冷水团以及沿岸流的作用,老铁山水道附近及山东半岛北部沿岸的高悬浮物浓度值区基本不能进入北黄海,只能沿岸分布,并且由于海底底质为粘土质以及沿岸流的共同作用,成山头附近海域悬浮物浓度值很高,但基本为局地再悬浮,没有向外输送的趋势。冬季受强劲东北风的影响,水体垂向混合均匀,悬浮物浓度值比夏季高得多,悬浮物的分布受黄海暖流、沿岸流以及地形的影响,特别是成山头附近海域,存在一个显著的高悬浮物浓度值区,并具有向南输送的特征。     

Seasonal and interannual variabilities of mean velocity of Kuroshio based on satellite data

Combining sea level anomalies with the mean dynamic topography derived from the geoid of the EGM08 global gravity field model and the CLS01 mean sea surface height, this study examined the characteristics of global geostrophic surface currents and the seasonal and interannual variabilities of the mean velocity of the Kuroshio (the Kuroshio source and Kuroshio extension).The patterns of global geostrophic surface currents we derived and the actual ocean circulation are basically the same. The mean velocity of the Kuroshio source is high in winter and low in fall, and its seasonal variability accounts for 18% of its total change. The mean velocity of the Kuroshio extension is high in summer and low in winter, and its seasonal variability accounts for 25% of its total change. The interannual variabilities of the mean velocity of the Kuroshio source and Kuroshio extension are significant. The mean velocity of the Kuroshio source and ENSO index are inversely correlated. However, the relationship between the mean velocity of the Kuroshio extension and the ENSO index is not clear. Overall, the velocity of the Kuroshio increases when La Ni a occurs and decreases when El Ni o occurs.     

海平面上升背景下辐射沙脊风暴潮增水研究

海平面上升将对沿海环境构成严重威胁,风暴潮灾害频发和加剧是其中的重要表现。相关研究揭示水深和潮波变化是引起风暴潮增水与海平面上升之间非线性关系的两大主要因素。在地形和潮波系统较为复杂的苏北辐射沙脊海域这种非线性关系尤为明显。总结了该海域潮波、风暴潮特征和海平面变化趋势,利用WRF模式和Delft 3D风暴潮模式相结合,建立了东中国海和南黄海二维天文潮-风暴潮耦合数学模型。分析研究了海平面上升以后,相同路径和强度的两种典型台风作用下,辐射沙脊海域风暴增水极值和高潮位变化。分析结果表明:海平面上升后,辐射沙脊海域增水作用普遍减弱,近岸较外海明显;而在辐射沙脊中、南部,海平面上升对天文潮高潮位的增强作用要强于对风暴增水的减弱作用。     

黄海冷水团的季节变化特征及其形成机制研究

在普林斯顿海洋模式(POM)的基础上,利用高精度卫星遥感得到的风和海表温度(SST)数据并考虑M2分潮的作用,模拟了黄、渤海海域三维热结构和环流的时、空变化;在此基础上,系统描述了黄海冷水团水文现象;并对黄海冷水团形成机制进行了探讨。研究结果表明:温跃层、潮混合、暖流和地形对黄海冷水团起着重要作用。     

中国河口海岸风暴潮及海洋动力三维数值预报模型(CHINACOAST)研究Ⅱ:模型验证与应用

简述了在我国珠江口应用实测潮位过程、海表温度以及冬、夏季盐度分布资料对模型的验证与参数率定。在此基础上应用中国河口海岸风暴潮及海洋动力三维数值预报模型(CHINACOAST),对我国沿海冬季东北季风作用下的环流进行了模拟计算,并对环流特征进行了分析。模型被进一步用来模拟在9316号台风影响下珠江口的风暴潮位、海流过程及分布结构的变化。     

Statistical Analysis of Long Term Trends of Rainfall During 1901–2002 at Assam,India

Rainfall is a principal element of the hydrological cycle and its variability is important from both the scientific as well as socio-economic point of view. This study presents an analysis based on the precipitation variation in Assam, India over 102 years from 1901 to 2002. Precipitation data from 21 stations have been collected. These data have been analyzed for both annual and seasonal variation. For trend analysis, Mann-Kendell and Sen’s slope estimator test were used. To compare seasonal variations, three seasons of winter, summer and monsoon have been considered. Mean annual precipitation varied from 2,074 mm (at Tinsukia) to 3,538 mm (at North Chahar Hills). The most probable year of change was 1959 in annual precipitation. Time series of the Standardized Precipitation Index (SPI) depict that near normal occurs in about 68 years out 102 years, and in 2.48 years out of 102 years there was an extreme wet. All these findings can help provide rational regulatory and policy in relation to water resources to maintain the health of the various ecosystems that make up Assam, India.     

黄河三角洲地区降水时序变化特征研究

基于黄河三角洲内5个气象站1961—2007年逐日降水资料,采用Mann Kendal非参数检验、小波分析等方法,对近50年来黄河三角洲地区降水量时序变化特征进行研究。结果表明,黄河三角洲地区近50年来,年际和年内不同季节降水量均呈逐步下降趋势,并在1976年左右发生突变,之后降水量下降显著。年际降水存在约8~9年的主变化周期,而春夏秋冬四季降水存在约16~17年的主变化周期。根据周期变化特征,预测2012—2014年黄河三角洲地区将处于多水期,其中秋季和冬季降水较多,而春季和夏季降水较少。     

念青唐古拉山南坡夏季降水梯度观测

利用在念青唐古拉山脉西段南坡沿海拔架设的10个翻斗式自记雨量计2006年至2008年的夏季风降水记录,分析了不同海拔降水的年际年内和日变化特征.结果表明该地区夏季降水的海拔梯度效应明显,高海拔降水日过程和低海拔差异显著,最大降水高度位于山坡上部的5 100 m附近.     

1961- 2013 年贵州省地面温度时空变化特征

利用贵州省1961-2013年逐日0cm地面温度观测资料,采用ArcGIS空间分析、线性趋势分析、小波分析、Mann-kendall非参数统计检验法等对贵州省地温的空间分布、变化趋势、突变特点、周期变化等进行研究。结果表明:平均地温、平均最低地温年际、季节空间分布大致从黔西北向黔东南随经度增加、海拔和纬度的降低而逐渐升高;平均最高地温年际与秋、冬季空间分布大致从黔东北向黔西南随着经度、纬度的降低和海拔的升高而逐渐升高。平均地温与平均最低地温年际、季节变化均呈增温趋势,尤以平均最低地温年际、季节增温趋势最显著;平均最高地温年际与春、夏、秋季均呈增温趋势,冬季呈缓慢下降趋势。平均地温、平均最高地温、平均最低地温年际、季节突变集中于20世纪90年代以来;且均以春、秋季突变十分显著。平均地温、平均最高地温、平均最低地温年际、季节周期变化主要以长周期为主周期。年平均地温、年平均最低地温与海拔呈显著的负相关,与经度呈显著的正相关,而年平均最高地温则与纬度呈显著的负相关。     

武汉市大气降水δD和δ~(18)O变化特征及水汽来源

为了确定长江流域中游大气降水特征和水汽来源,以全球大气降水观测网(GNIP)武汉站点多年大气降水稳定同位素数据为基础,探讨了长江中游武汉地区大气降水稳定同位素随季节变化特征。通过建立当地大气降水方程,结合气象因素和降水氘盈余变化,揭示了武汉地区不同季节大气降水水汽来源。结果表明:大气降水在降落地面之前经历了非平衡分馏过程,且平衡程度接近于东部季风沿海地区;大气降水稳定同位素表现出明显的季节性特征,且冬季和夏季降水δD和δ~(18)O值与雨量之间负相关,表现出明显的"雨量效应";大气降水水汽来源主要受季风活动的控制,冬季水汽主要来自北方大陆冷湿气流,而春季降水表现出局地蒸发来源,夏季和秋季降水来源受西南季风和东南季风的双重影响。     

STUDY OF NON-BOUSSINESQ EFFCET ON SEA SURFACE HEIGHT

A set of equations was derived for a nonBoussinesq ocean model in this paper. A new time-splitting scheme was introduced which incorporates the 4th-order Runge-Kutta explicit scheme of low-frequency mode and an implicit scheme of high-frequency mode. With this model, potential temperature, salinity fields and sea surface height were calculated simultaneously such that the numerical error of extrapolation of density field from the current time level to the next one could be reduced while using the equation of mass conservation to determine sea surface height. The non-Boussinesq effect on the density field and sea surface height was estimated by numerical experiments in the final part of this paper.     

NUMERICAL SIMULATION OF SUMMER CIRCULATION IN THE EAST CHINA SEA AND ITS APPLICATION IN ESTIMATING THE SOURCES OF RED TIDES IN THE YANGTZE RIVER ESTUARY AND ADJACENT SEA AREAS

Based on the COHERENS (a Coupled Hydrodynamical Ecological model for Regional Shelf seas), a three-dimensional baroclinic model for the summer of East China Sea (ECS) was established with the sigma-coordinate in the vertical direction and spherical coordinate in the horizontal direction. The circulation patterns of the Kuroshio Current, the Taiwan Warm Current (TWC), the Tsushima Current and the Yangtze Diluted Water (YDW) were successfully simulated with this model. The calculated results are fairly consistent with previous observations and studies. Based on this baroclinic current field, the Lagranian particles tracking was simulated to estimate the possible origins of the red tides frequently occurring in the Yangtze River estuary and its adjacent sea areas. If there are “seeds” (cysts) of the red tide algae at the seabed of the Taiwan Strait, the offshore of Fujian and Zhejiang Provinces and the northeast Taiwan Island, those are extremely possible sources of the red tides in the Yangtze River estuary and its adjacent sea areas. Field data are needed to confirm it. Numerical simulation to estimate the source of the red tides is a new application of the Lagrangian transport in the marine ecology.     

灌河潮流界位置确定与港口防淤探讨

盐城市位于江苏省中部,地处黄海之滨,承接里下河腹部区的排水,区内入海河流众多,在这些入海河流上大多建有挡潮闸坝。但由于盐城市近海为淤积型海岸,闸坝的建设改变了河口的自然状态,造成港口下游淤积严重,排水不畅。灌河作为江苏省沿海唯一下游没有建挡潮闸的重要入海河流,仍为自然状态,下游港口未淤积。本文通过对灌河水体涨、落潮中氯离子含量的监测,找出海水上溯的最大距离,确定其影响范围,为其它入海流河流的防淤提供借鉴。     

1956-2016年黄河流域河川径流演变规律

黄河流域水资源短缺问题突出,深入分析河川径流的演变规律对于流域水资源管理具有重要的指导意义。基于黄河干流上、中、下游不同位置的代表性水文站实测径流,利用Mann-Kendall非参数趋势检验方法分析了1956-2016年期间黄河流域年、月径流的历史演变规律。结果表明:1956-2016年,除源头区年径流变化不显著以外,黄河流域径流呈现出显著的下降趋势,达到了1%的显著性水平。从上游到下游,河川径流下降幅度越来越大,趋势越来越显著。1980-2000和2001-2016年的多年平均入海径流比1956-1979年分别减少了50. 07%和59. 67%。径流演变呈现出3阶段特征,20世纪50、60年代属于丰水期;随后在70至90年代径流持续下降;在2000年以后径流有所回升。除源头区以外,黄河流域的月径流总体呈现减少趋势;上游和中游地区的月径流占年径流的比例枯增丰减;下游地区月径流占年径流的比例在冬季、夏季增大,春季、秋季减小。     

海堤设计中的若干问题探讨

结合新颁布的海堤设计规范和工程实例,对海堤工程设计中海堤的界定、海堤防潮（洪）标准、设计波浪要素计算、复式斜坡堤波浪爬高计算及按控制越浪量确定堤顶高程等几个问题进行了探讨,提出海堤应以波高来界定、修建消浪平台的最佳位置为静水位附近、最佳宽度为入射波长的1/4及海堤设计应该直接以控制越浪量确定堤顶高程。     

Numerical analysis of impacts of 2011 Japan Tohoku tsunami on China Coast

On the 11th of March, 2011, a subduction earthquake of magnitude Mw9.0 happened at the northeast of Japan, generating a tsunami which resulted in huge damage in Japan. Okada’s elastic fault model is used to generate the deformation of the sea bottom based on USGS sources and UCSB sources respectively. The shallow water equations are solved by the adaptively refined finite volume methods so that it can compute the propagation of tsunami in the Pacific Ocean efficiently. The computed time series of the surface elevation are compared with the measured data from NOAA real-time tsunami monitoring systems for model validation, and UCSB sources derive better results than USGS sources. Furthermore, one nested domain with fine grid and higher topography resolution is combined to compute numerically this tsunami spreading in the Bohai Sea, Yellow Sea, East China Sea, and North of South China Sea. The impacts on China Coast and seas are analyzed and discussed. The results show that the tsunami has almost no impact in the Bohai Sea and Yellow Sea. It has some kind impact on the East China Sea and South China Sea. However, maximum wave height on China Coast is smaller than 0.5 m. It is thus concluded that the 2011 Tohoku tsunami did not generate a significant influence on China Coast.