NUMERICAL SIMULATION OF SOUTH CHINA SEA MONSOON ONSET BASED ON GRAPES MODEL AND EXPERIMENTS ON INITIAL MODEL FIELDS

The Global and Regional Assimilation and Prediction System (GRAPES), a limited-area regional model, was used to simulate the onset of South China Sea summer monsoon. In view of the relatively insufficient information about the initial field in simulation predictions, the Advanced Microwave Sounding Unit-B (AMSU-B) data from a NOAA satellite were introduced to improve the initial values. By directly using the 3-dimensional variational data assimilation system of GRAPES, two schemes for assimilation tests were designed. In the design, Test 1 (T1) assimilates both sounding and AMSU-B data, and Test 2 (T2) assimilates only the conventional sounding data, before applying the model in simulation forecasts. Comparative experiments showed that the model was very sensitive to initial fields and successful in reproducing the monsoon onset, allocation of high- and low-level wind fields during the pentad of onset, and the northward advancement of the monsoon and monsoon rain bands. The scheme, however, simulated rainfall and the location of the subtropical high with deviations from observations. The simulated location of the subtropical high was more westward and northward and the simulated rainfall for the South China Sea was larger and covered a broader area.

THREE-DIMENSIONAL BAROCLINIC NUMERICAL SIMULATION OF THE SOUTH CHINA SEA CIRCULATION'S SEASONAL CHARACTERISTICS II. MIDDLE AND DEEP CIRCULATION

A three-dimensional baroclinic shelf sea model’s numerical simulation of the South China Sea (SCS) middle and deep layer circulation structure showed that: 1. In the SCS middle and deep layer, a southward boundary current exists along the east shore of the Indo-China Peninsula all year long. A cyclonic eddy (gyre) is formed by the current in the above sea areas except in the middle layer in spring, when an anticyclonic eddy exists on the eastern side of the current. In the deep layer, a large-scale anticyclonic eddy often exists in the sea areas between the Zhongsha Islands and west shore of southern Luzon Island. 2. In the middle layer in summer and autumn, and in the deep layer in autumn and winter, there is an anticyclonic eddy (gyre) in the northeastern SCS, while in the middle layer in winter and spring, and in the deep layer in spring and summer, there is a cyclonic one. 3. In the middle layer, there is a weak northeastward current in the Nansha Trough in spring and summer, while in autumn and winter it evolves into an anticyclonic eddy (gyre), which then spreads westward to the whole western Nansha Islands sea areas.

3-D BAROCLINIC NUMERICAL SIMULATION OF THE SOUTH CHINA SEA I. UPPER CIRCULATION

A three dimensional baroclinic shelf sea model was employed to simulate the seasonal characteristics of the South China Sea (SCS) upper circulation. The results showed that: in summer, an anticyclonic eddy, after its formation between the Bashi Channel and Dongsha Islands in the northeastern SCS, moves southwestward until it disperses slowly. There exists a northward western boundary current along the east shore of the Indo China Peninsula in the western SCS and an anticyclonic gyre in the southern SCS. But at the end of summer and beginning of autumn, a weak local cyclonic eddy forms in the Nansha Trough, then grows slowly and moves westward till it becomes a cyclonic gyre in the southern SCS in autumn. At the beginning of winter, there exists a cyclonic gyre in the northern and southern SCS, and there is a southward western boundary current along the east shore of the Indo China Peninsula. But at the end of winter, an anticyclonic eddy grows and moves toward the western boundary after forming in the Nansha Trough. The eddy’s movement induces a new opposite sign eddy on its eastern side, while the strength of the southward western boundary current gets weakened. This phenomenon continues till spring and causes eddies in the southern SCS.

Evaluation of numerical wave model for typhoon wave simulation in South China Sea

The simulating waves nearshore(SWAN) model has typically been designed for wave simulations in near-shore regions. In this study, the model's applicability to the simulation of typhoon waves in the South China Sea(SCS) was evaluated. A blended wind field, consisting of an interior domain based on Fujita's model and an exterior domain based on Takahashi's model, was used as the driving wind field. The waves driven by Typhoon Kai-tak over the SCS that occurred in 2012 were selected for the numerical simulation research. Sensitivity analyses of time step, grid resolution, and angle resolution were performed in order to obtain optimal model settings. Through sensitivity analyses, it can be found that the time step has a large influence on the results, while grid resolution and angle resolution have a little effect on the results.

SIMULATION OF SUMMER CLIMATE IN CHINA DURING 1997 AND 1998 USING A REGIONAL AIR-SEA COUPLED MODEL

Using the regional air-sea coupled climate model RegCM3-POM,a series of numerical experiments are performed to simulate the summer climate in 1997 and 1998 with different coupling time steps.The results show that the coupled model has good performance on the simulation of the summer sea surface temperature(SST) in 1997 and 1998,and the simulation results of CPL1(with the coupling time step at 1 hour) are similar to those of CPL6(with the coupling time step at 6 hours).The coupled model can well simulate SST differences between 1997 and 1998.As for the simulation of the drought in 1997 and the flood in 1998,the results of CPL6 are more accurate.The coupled model can well simulate the drought in 1997 over North China,and compared with the results of the atmosphere model RegCM3,the simulation ability of the coupled model is improved.The coupling model has better ability in the simulation of the circulation in the middle and low levels,and the water vapor transportation in the coupling model is reasonable in both 1997 and 1998.RegCM3(an uncoupled model) cannot correctly simulate the transportation path differences between 1997 and 1998,but the coupled model can simulate the differences well.

A modified discrete element model for sea ice dynamics

Considering the discontinuous characteristics of sea ice on various scales,a modified discrete element model（DEM） for sea ice dynamics is developed based on the granular material rheology.In this modified DEM,a soft sea ice particle element is introduced as a self-adjustive particle size function.Each ice particle can be treated as an assembly of ice floes,with its concentration and thickness changing to variable sizes under the conservation of mass.In this model,the contact forces among ice particles are calculated using a viscous-elastic-plastic model,while the maximum shear forces are described with the Mohr-Coulomb friction law.With this modified DEM,the ice flow dynamics is simulated under the drags of wind and current in a channel of various widths.The thicknesses,concentrations and velocities of ice particles are obtained,and then reasonable dynamic process is analyzed.The sea ice dynamic process is also simulated in a vortex wind field.Taking the influence of thermodynamics into account,this modified DEM will be improved in the future work.

Fine-resolution simulation of surface current and sea ice in the Arctic Mediterranean Seas

A free-resolution model is developed for ocean circulation simulation in the National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）, Chinese Academy of Sciences, and is applied to simulate surface current and sea ice variations in the Arctic Mediterranean Seas. A dynamic sea ice model in elastic-viscous-plastic rheology and a thermodynamic sea ice model are employed. A 200-year simulation is performed and a dimatological average of a 10-year period （14lst-150th） is presented with focus on sea ice concentration and surface current variations in the Arctic Mediterranean Seas. The model is able to simulate well the East Greenland Current, Beaufort Gyre and the Transpolar Drift, but the simulated West Spitsbergen Current is small and weak. In the March climatology, the sea ice coverage can be simulated well except for a bit more ice in east of Spitsbergen Island. The result is also good for the September scenario except for less ice concentration east of Greenland and greater ice concentration near the ice margin. The extra ice east of Spitsbergen Island is caused by sea ice current convergence forced by atmospheric wind stress.

渤海氮磷营养盐和叶绿素浓度时空分布数值模拟与富营养化评估

当前渤海富营养化风险仍居高不下,严重制约了环渤海社会经济可持续发展。开展近海富营养化评估与趋势分析是国家生态安全保障的需求,其难点在于富营养化评价要素长期演变进程高质量数据的获取。基于HAMSOM海洋生态模型,通过修正溶解有机氮(dissolved organic nitrogen,DON)的难/易降解组分降解动力学形式,构建了适用于富营养化评估与趋势分析的渤海三维水动力/生物地球化学耦合模型。利用2019年渤海春、夏、秋、冬四个季节DON、溶解无机氮(dissolved inorganic nitrogen,DIN)、溶解无机磷(dissolved inorganicphosphorus,DIP)和叶绿素a(chlorophyll a,chl a)调查结果,对模型进行了校正,并利用1980年至2020年的长期调查结果进行了验证,模拟结果与调查结果相比较,在数值大小和变化趋势上均吻合较好,相对标准偏差、相似性系数和Kappa系数分别为24%、0.77和0.60。利用模型模拟计算的DIN、DIP、DON和chl a长期演变进程数据,计算了营养状态质量指数(nutritional quality index,NQI)。结果表明,当前渤海富营养化状态整体上处于贫营养状态,但在渤海湾、辽东湾和莱州湾湾底近岸海域处于富营养状态,季节上5~10月份处于中等富营养化状态,从长期变化趋势看,渤海整体上富营养化状态趋于改善。与复合富营养化指数(compound eutrophication index,CEI)对比表明,渤海富营养化评估按NQI计算结果与按CEI计算结果相当吻合,相似性系数为0.83。文章建立的渤海富营养化评估方法具有较高可靠性,可用于渤海富营养化评估。

履齿结构对深海沉积物扰动分析

为探究集矿车在行进过程中履带运动对深海沉积物的扰动机理,并建立适用于机械结构与沉积物作用的仿真模型,结合水槽实验和模拟分析,设定对照试验,研究机械结构运动对沉积物的扰动作用和羽状流扩散现象。实验与仿真结果表明:偏置一字形履齿低扰动性能较好,扰动最大速度在1.5 m/s以下;扰动源的下陷深度和转速对水槽中的浊度变化有显著影响,浊度计最大和最小测量值为4 381.3 mg/L和3 073.3 mg/L,相差29.9%,峰值时间相差超过50%。搭建欧拉多相流模型,设定参数和边界条件,仿真与试验结果接近,可用于后续开展小范围内的机械扰动研究。

SIMULATION ON CLIMATIC VARIATION OF ARCTIC SEA ICE THROUGH AN ICE-OCEAN COUPLED MODEL

An ocean model developed by the Institute of Marine Research and the University of Bergen in Norway (BOM) and a state-of-the-art sea ice model developed by NCAR (CSIM4) are coupled, Considering influences of 9 major rivers,forced by the NCEP reanalysis atmospheric fields and the Levitus surface salinity,the Arctic sea ice climatic variation from January 1949 to December.1999 was simulated through the coupled model.The comparison of simulated results and observations shows that:(1)the long-term ice concentration variation tendencies are in consistent with the observations in the divisional ocean regions;(2)simulated ice thickness horizontal distribution is reasonable.Simulated ice thickness has a decreasing tendency in the central Arctic,which agrees with the submarine observations.Simulated annually maximum ice thickness is highly related to observed fast-ice thickness off the Russian coast;and (3)sea ice area/volume fluxes through the Fram Strait are in accord with the satellite-derived data.Generally,the coupled model successfully simulated the Arctic Ocean sea ice climatic variation.

裂缝填充型天然气水合物识别及饱和度预测

天然气水合物通常以孔隙和裂缝两种充填形态存在于自然界中,不同赋存形态的水合物具有不同的岩石物理性质,判别天然气水合物赋存形态对资源评价和开发具有重要意义。速度、密度和电阻率是反映水合物物理特征最常用的三个参数,本文基于岩石物理模型构建了含天然气水合物沉积物纵横波速度、密度、电阻率随水合物体积分数变化的数值模型,发现在相同水合物含量的背景下,含裂隙填充型水合物沉积层的纵波速度比孔隙型的稍低,密度明显小于孔隙型,但其电阻率却高得多。由此构建了水合物赋存类型的判别图版,并以南海典型水合物为例进行了验证,实际数据与理论图版吻合良好,成功识别了天然气水合物赋存形态并计算了裂缝填充型水合物的饱和度,证明此方法可以用于南海裂缝填充型天然气水合物的判别及资源量计算。

基于外加电流保护法的在役平台快速修复方案设计

全寿命周期中,在役平台长期遭受恶劣海况影响,牺牲阳极保护系统难以维持预期防护效果,对在役平台提出快速修复方案十分必要。针对南海海域某试验平台,建立了1/8缩比模型。通过控制缩比模型与裸钢板之间的电连接进行涂层破损模拟。基于外加电流阴极保护法设计了一种快速修复装置。采用数值模拟计算方法确立了装置的最佳布放方案。在小平岛海域进行了实海试验验证。结果表明:快速修复装置可有效针对在役平台涂层破损问题进行快速修复,数值模拟计算方法在快速修复方案设计中具有可靠性及准确性。

深远海大兆瓦级半潜式风机基础运动特性数值模拟及试验研究

针对水深百米以上的深远海浮式风电开发需求,本文面向可搭载大兆瓦级(15 MW)风机的新型半潜式风机基础的运动特性展开研究。利用AQWA软件建立了该基础与系泊系统的数值模型,基于南海实际海况确定了风机塔筒的载荷,并开展了缩尺比为1∶64的水池模型试验,验证了数值模型计算的准确性;基于验证的数值模型分析了新型风机基础在南海恶劣海况下的运动特性及系泊张力,发现该新型风机基础的运动极值和系泊张力均满足规范要求。相同海况下,新型风机基础与经典半潜式风机基础OC4-DeepCwind(三浮筒平台)的运动性能及系泊缆张力对比结果表明:发电工况下,新型风机基础的垂荡和倾角的极值较三浮筒平台的分别下降62.8%和81.3%;停机工况下,垂荡和倾角的极值则分别下降46.1%和41.4%,充分说明该新型风机基础具有优越的运动性能;而在停机工况下1、2号缆系泊张力最大值分别下降17.4%和9.6%,大大降低了系泊系统的设计难度。研究结果为中国深远海浮式风电开发船型的选择提供了借鉴。

京唐港海域溢油漂移扩散模拟分析

为分析京唐港海域发生溢油漂移扩散产生的影响,基于三向不可压缩和Reynolds值均布的Navier-Stokes方程,并服从Boussinesq假定和静水压力的假定,对整个渤海海域建立二维潮流场数值模型。以水动力为基础,根据Lagrangian“油粒子”理论对粒子进行追踪,建立溢油漂移扩散预测模型,模拟不同工况下油膜在海水中的漂移扩散过程。结果表明,溢油污染对附近自然保护区、旅游休闲娱乐区、渔业养殖捕捞区及岸线均存在一定的影响,其大清河口附近渔业捕捞区的影响最大;72 h内油膜最大扩散面积出现在冬季强风涨潮时溢油,其面积为213.373 km 2。通过对油膜的运动轨迹和敏感区目标的影响进行分析预测,对在京唐港附近海域发生溢油事故采取应急措施、海洋环境影响评价等提供一定的依据和技术支持。

黄海、东海夏季环流的数值模拟

基于ECOM -si,建立了一个垂向取σ坐标、水平取球面坐标的三维高分辨率湍流闭合的黄海、东海海洋环流数值模式 .考虑实际岸线和水深、边界通量、密度梯度力和风应力 ,应用该模式较成功地模拟出了夏季黄海、东海环流 (黑潮、台湾暖流、对马暖流、黄海冷水团环流和沿岸流 ) ,摸拟结果与以往实际观测和研究结果较为一致 。

黄海浒苔漂移输运模式的建立与应用

本文利用NCEPGFS预报风场和中国近海高分辨率三维MASNUM海浪-潮流-环流耦合海洋数值预报系统的预报数据,建立黄海浒苔漂移输运模式,用于黄海浒苔溯源和漂移输运数值模拟研究。使用2009年5月份黄海表层漂流浮标数据和2012年MODIS卫星遥感浒苔漂移分布资料对所建立的漂移输运模式进行验证,结果表明所建立的模式能够有效的模拟出浒苔暴发区漂流浮标运动状况,并能够有效地模拟出2012年浒苔漂移输运过程。最后运用所建立的模式开展2008年和2010年浒苔漂移输运过程,模拟结果与文献报道的卫星观测结果一致。模拟结果表明,受海洋表层流影响两年浒苔特征显著不同:2010年浒苔影响海域明显小于2008年,且2010年浒苔主体没有大规模在青岛近岸堆积。

中尺度海-气相互作用对台风暴雨过程的影响

利用中尺度海-气耦合模式MCM对两个典型台风过程进行了数值模拟试验,定量地分析了海-气相互作用对台风暴雨的影响,并探讨了这一影响的物理机制.结果表明,模式MCM能成功模拟台风的路径、强度以及台风暴雨的落时、落区.考虑海-气相互作用能使台风中心气压48和72 h分别回升9.9和3.5 hPa,使后续时段的台风对流性降水减小40～100 mm,还明显改变了非对流性降水分布.耦合与非耦合试验对比分析初步表明,海-气相互作用影响台风暴雨的机制是一种通过台风大风区附近海平面温度(SST)下降来调节的负反馈机制.

印度尼西亚近海潮汐潮流的数值模拟

利用FVCOM海洋数值模式计算了印尼近海的M2,S2,K1,O1分潮的分布,计算范围从20°S～20°N,90°～150°E,计算网格分辨率在印尼海域岛屿平均为1/12度,在大陆边界平均为1/5度,在开边界平均为1/2度。计算结果与104个TOPEX/Poseidon卫星高度计交叉点数据和79个验潮站数据进行比较,符合良好;与高度计交叉点比较,M2分潮振幅的均方根差为6cm,迟角为7°;S2分潮的振幅偏差为3cm,迟角偏差为8°;K1分潮振幅的偏差为6cm,迟角偏差为10°;O1分潮振幅偏差为3cm,迟角偏差为10°。根据计算结果给出了4个分潮的潮汐、潮流、潮余流和潮能通量密度分布图。

一个海冰气耦合模式中格陵兰海海冰年际变异及其成因的个例分析

利用一个全球海冰气耦合模式模拟结果,选取冬季年际变率最大的海冰区———格陵兰海海冰区中的一个4年海冰剧烈变化过程展开分析,试图探讨此个例过程中海冰剧烈变化的原因。结果表明,在此个例中,该区域海冰年际变异主要是由大气环流异常驱动的,海表面温度和海冰密集度变化主要是对大气环流变化的响应。海表面温度变化决定着海冰范围及海冰密集度的变化,但海冰变化时通过相变潜热的释放或吸收反过来对海表面温度变化有一定影响。

台湾海峡海陆风数值模式与数值模拟试验

研制了一个包括水平及垂直扩散、牛顿冷却的二维 46层非弹性运动方程组的台湾海峡海陆风数值模式 ,并用此模式来模拟及研究台湾海峡两岸海陆风的生成与变化特征。模式中考虑了太阳辐射、长波辐射及其日变化、地表向大气的感热与潜热输送以及向土壤层的热传导等。数值计算中采用了分解算法及隐式时间差分方案。用此模式得出的模拟结果与闽东南及台湾海陆风的观测事实比较吻合 ,表明了此模式能够较好地描述海峡两岸的海陆风变化规律。