白冠破碎空间分布模式的统计推断方法

白冠空间分布模式分析是海浪破碎统计研究的前提。本文提出利用空间点过程统计分析工具研究白冠空间分布模式,并结合实际白冠破碎观测录像资料,计算观测数据的L-函数和K-函数,与Markov chain Monte Carlo(MCMC)方法生成的模拟包迹进行比较,推断得出其白冠空间分布模式类型为空间齐次Poisson过程。研究表明空间点过程统计分析工具适用于白冠破碎研究。     

海洋环境因素对白冠覆盖率的影响及其数值估算

波浪破碎是一个强非线性过程,破碎时产生的大量气泡在海面上表现为白冠,白冠覆盖率是刻画波浪破碎一个重要参数。研究表明,白冠覆盖率与海上风速、海浪状态和大气稳定度等多种海洋环境因素有关。综合前人的观测数据,本文给出了更为可靠的依赖风速的白冠覆盖率公式,发现海水温度越高,白冠覆盖率越大。提出了以波浪破碎耗散函数为参数的白冠覆盖率公式,同时发现波龄小于某个临界值时,白冠覆盖率随波龄增大,波龄大于临界值时,白冠覆盖率保持不变,该临界值随风速增大而减小。     

细胞破碎方法对Bacillus sp.DL-2胞内蛋白酶拆分乙酸苏合香酯的影响

(R)-1-苯乙醇是手性药物合成的关键手性砌块, 在多种手性化合物的合成及医药、香料的工业生产中具有重要的作用。对筛选自西太平洋深海沉积物的Bacillus sp. DL-2进行破碎, 获取的胞内蛋白酶能有效拆分(±)-乙酸苏合香酯, 制备高光学纯的(R)-1-苯乙醇。为使拆分效果最优化, 本试验对比了表面活性剂、溶菌酶和超声法3种不同的破碎细胞方式, 并对表面活性剂和溶菌酶破碎法进行了单因素条件优化。最优方法及优化的反应条件为: 使用体积分数0.5%的表面活性剂曲拉通X-100在35℃和pH7.0条件下破碎细胞2h。经过优化后, (R)-1-苯乙醇的对映体过量值为96%, 转化率为23%, 为利用胞内蛋白酶生产手性化学品提供了参考。     

基于破碎临界区的新型拍岸浪统计计算模型研究

When waves propagate from deep water to shallow water, wave heights and steepness increase and then waves roll back and break. This phenomenon is called surf. Currently, the present statistical calcula...     

东海中南部鱼类群聚结构的空间特征

依据1997～2000年东海中南部(25°30'～29°00'N,120°30'～127°00'E)四个季节的底拖网调查资料,运用聚类分析和非度量多维标度(NMDS)的方法分析了东海中南部鱼类群聚结构的空间特征,结果显示,东海中南部鱼类群聚大致可分为近海群聚和外海群聚.在不同季节两个群聚的种类组成保持了相对的稳定,并且具有一定的持续性.近海群聚的特征种类为带鱼、发光鲷等.外海群聚的特征种类主要为黄鳍马面鲀、短尾大眼鲷、黄鲷等.鱼类群聚与环境因子水深有较好的相关关系.     

The BCI criterion for the initiation of breaking process in Boussinesq-type equations wave models

The Breaking Celerity Index (BCI) is proposed as a new wave breaking criterion for Boussinesq-type equations wave propagation models (BTE).The BCI effectiveness in determining the breaking initiation location has been verified against data from different experimental investigations conducted with incident regular and irregular waves propagating along uniform slope [Utku, M. (1999). “The Relative Trough Froude Number. A New Criteria for Wave Breaking”. Ph.D. Dissertation, Dept. of Civil and Enviromental Engineering, Old Dominion University, Norfolk, VA; Gonsalves Veloso dos Reis, M.T.L. (1992). “Characteristics of waves in the surf zone”. MS Thesis, Department of Civil Engineering, University of Liverpool., Liverpool; Lara, J.L., Losada, I.J., and Liu, P.L.-F. (2006). “Breaking waves over a mild gravel slope: experimental and numerical analysis”. Journal of Geophysical Research, VOL 111, C11019] and barred beaches [Tomasicchio, G.R., and Sancho, F. (2002). “On wave induced undertow at a barred beach”. Proceedings of 28th International Conference on Coastal Engineering, ASCE, New York, 557–569]. The considered experiments were carried out in small-scale and large-scale facilities. In addition, one set of data has been obtained by the use of the COBRAS model based upon the Reynolds Averaged Navier Stokes (RANS) equations [Liu, P.L.-F., Lin, P., Hsu, T., Chang, K., Losada, I.J., Vidal, C., and Sakakiyama, T. (2000). “A Reynolds averaged Navier–Stokes equation model for nonlinear water wave and structure interactions”. Proceedings of Coastal Structures ‘99, Balkema, Rotterdam, 169–174; Losada, I.J., Lara, J.L., and Liu, P.L.-F. (2005). “Numerical simulation based on a RANS model of wave groups on an impermeable slope”. Proceedings of Fifth International Symposium WAVES 2005, Madrid].Numerical simulations have been performed with the 1D-FUNWAVE model [Kirby, J.T., Wei, G., Chen, Q., Kennedy, A.B., and Dalrymple, R.A. (1998). “FUNWAVE 1.0 Fully Nonlinear Boussinesq Wave Model Documentation and User's Manual”. Research Report No CACR-98-06, Center for Applied Coastal Research, University of Delaware, Newark]. With regard to the adopted experimental conditions, the breaking location has been calculated for different trigger mechanisms [Zelt, J.A. (1991). “The run-up of nonbreaking and breaking solitary waves”. Coastal Engineering, 15, 205–246; Kennedy, A.B., Chen, Q., Kirby, J.T., and Dalrymple, R.A. (2000). “Boussinesq modeling of wave transformation, breaking and run-up. I: 1D”. Journal of Waterway, Port, Coastal and Ocean Engineering, 126, 39–47; Utku, M., and Basco, D.R. (2002). “A new criteria for wave breaking based on the Relative Trough Froude Number”. Proceedings of 28th International Conference on Coastal Engineering, ASCE, New York, 258–268] including the proposed BCI.The calculations have shown that BCI gives a better agreement with the physical data with respect to the other trigger criteria, both for spilling and plunging breaking events, with a not negligible reduction of the calculation time.     

Determining the onset and strength of unforced wave breaking in a numerical wave tank

A numerical wave tank is used to investigate the onset and strength of unforced wave breaking, and the waves have three types of initial spectra： constant amplitude spectrum, constant steepness spectrum and Pierson-Moscowitz spectrum. Numerical tests are performed to validate the model results. Then, the onset of wave breaking is discussed with geometric, kinematic, and dynamic breaking criteria. The strength of wave breaking, which is always characterized by the fractional energy loss and breaking strength coefficient, is studied for different spectra. The results show how the energy growth rate is better than the initial wave steepness on estimating the fractional energy losses as well as breaking strength coefficient.     

30多年来盐城市围填海空间格局变化特征

为探究盐城市围填海空间格局的变化特征,选取1984~2015年Landsat 4/5/7/8影像数据,利用景观指数计算方法,对盐城市新增围填海的面积、强度、聚集度和质心等4个方面变化特征进行分析。结果如下:(1)1984~2015年,盐城市新增和侵蚀破坏围填海面积分别为95 182.71 ha和1 970.45 ha,且随时间变化围填海侵蚀破坏区不断向南扩张。1984~2015年,围填海利用类型经历了从已围待利用地为主到盐养用地为主的演变过程。(2)1984~2015年的3个时间段内港池蓄水围填海强度指数均较小,最大围填海强度指数仅为0.19 ha/km。建设填海造地、已围待利用地和盐养用地的围填海强度指数呈现不断上升的变化趋势,最大围填海强度指数分别为2.15,27.53和77.33 ha/km。农业填海造地的围填海强度指数呈现先上升后下降的变化趋势,最大围填海强度指数为18.51 ha/km;(3)1984~2015年,盐城市围填海各类型的聚集度指数均较高,平均聚集度指数高达96.98。盐城市围填海质心不断向东南方向迁移,说明盐城市围填海开发的重点区域逐渐向南迁移。     

Simulation of the ocean surface mixed layer under the wave breaking

A one-dimensional mixed-layer model, including a Mellor-Yamada level 2.5 turbulence closure scheme, was implemented to investigate the dynamical and thermal structures of the ocean surface mixed layer in the northern South China Sea. The turbulent kinetic energy released through wave breaking was incorporated into the model as a source of energy at the ocean surface, and the influence of the breaking waves on the mixed layer was studied. The numerical simulations show that the simulated SST is overestimated in summer without the breaking waves. However, the cooler SST is simulated when the effect of the breaking waves is considered, the corresponding discrepancy with the observed data decreases up to 20% and the MLD calculated averagely deepens 3.8 m. Owing to the wave-enhanced turbulence mixing in the summertime, the stratification at the bottom of the mixed layer was modified and the temperature gradient spread throughout the whole thermocline compared with the concentrated distribution without wave breaking.     

海浪破碎对北太平洋海表面温度模拟的影响

基于海浪模式WAVEWATCH Ⅲ模拟北太平洋海浪要素,结合NDBC浮标资料进行验证,发现模拟出的有效波高与浮标测量值具有很好的一致性。基于改进型白冠覆盖率耗散模型,利用海浪模式模拟出的有效波高、有效波周期和摩擦速度等海浪要素计算出单位面积水柱内因海浪破碎产生的湍动能通量。通过改变环流模式sbPOM湍动能方程的上边界条件,引入海浪破碎产生的湍动能通量,并探究海浪破碎对北太平洋海表面温度模拟的影响。研究表明,由于海浪破碎的引入,环流模式sbPOM对北太平洋海表面温度模拟的准确程度得到提升,这为大气模式提供一个准确的北太平洋下边界条件具有重要意义。     

Investigating the impact of surface wave breaking on modeling the trajectories of drifters in the northern Adriatic Sea during a wind-storm event

An accurate numerical prediction of the oceanic upper layer velocity is a demanding requirement for many applications at sea and is a function of several near-surface processes that need to be incorporated in a numerical model. Among them, we assess the effects of vertical resolution, different vertical mixing parameterization (the so-called Generic Length Scale –GLS– set of k–ε, k–ω, gen, and the Mellor–Yamada), and surface roughness values on turbulent kinetic energy (k) injection from breaking waves.First, we modified the GLS turbulence closure formulation in the Regional Ocean Modeling System (ROMS) to incorporate the surface flux of turbulent kinetic energy due to wave breaking. Then, we applied the model to idealized test cases, exploring the sensitivity to the above mentioned factors. Last, the model was applied to a realistic situation in the Adriatic Sea driven by numerical meteorological forcings and river discharges. In this case, numerical drifters were released during an intense episode of Bora winds that occurred in mid-February 2003, and their trajectories compared to the displacement of satellite-tracked drifters deployed during the ADRIA02-03 sea-truth campaign.Results indicted that the inclusion of the wave breaking process helps improve the accuracy of the numerical simulations, subject to an increase in the typical value of the surface roughness z₀. Specifically, the best performance was obtained using α_CH = 56,000 in the Charnok formula, the wave breaking parameterization activated, k–ε as the turbulence closure model. With these options, the relative error with respect to the average distance of the drifter was about 25% (5.5 km/day). The most sensitive factors in the model were found to be the value of α_CH enhanced with respect to a standard value, followed by the adoption of wave breaking parameterization and the particular turbulence closure model selected.     

不同采样设计对估计鱼类空间格局指数的影响

查明渔业种群空间格局可为渔业资源的合理利用和管理提供参考依据。在渔业资源调查中,采样设计会影响调查分析结果的准确性和适用性。为查明采样设计对分析种群空间格局的影响,本文根据2016年10月、2017年2月、5月、8月在山东南部近海调查获得的数据,以星康吉鳗(Conger myriaster)、方氏云鳚(Enedrias fangi)为目标鱼种,应用计算机模拟重抽样方法,研究了4种样本量下简单随机抽样、系统抽样、分层随机抽样、分层系统抽样对估计目标种群的平均拥挤度和聚块指数的影响。应用相对估计误差和相对偏差衡量不同采样设计的表现。结果表明,系统抽样、分层系统抽样的模拟结果较接近空间格局指数“真值”,简单随机抽样和分层随机抽样表现较差;样本量对空间格局指数估计的影响较大,随着样本量增大,目标鱼种两个空间格局指数的相对估计误差均呈降低趋势。种群原始空间分布对空间格局指数估计具有一定影响,聚块指数估计的精确度随目标种群聚块指数真值的增加而减小,整体出现偏高的估计偏差。不同采样设计影响鱼类种群空间格局分析,种群聚集程度也对分析结果有所影响,因此,在渔业资源调查设计时可以纳入目标种群空间格局指标以完善多目标渔业资源调查方案。