WAVEWATCH和SWAN嵌套模拟台风浪场的结果分析

利用WAVEWATCH和SWAN嵌套模拟2007年8月墨西哥湾飓风迪安的波浪场.将QSCAT/NCEP混合风场与台风模型风场合成为背景风场.修改WAVEWATCH和SWAN嵌套接口以使WAVEWATCH和SWAN2种海浪预报模式能够有效地嵌套运行.利用WAVEWATCH和SWAN嵌套模拟飓风迪安的波浪场,采用浮标资料检验模拟结果,以验证WAVEWATCH和SWAN模拟的准确性及修改后嵌套接口的可用性.结果表明,修改嵌套接口之后模式运行平稳,2种模式的结果与浮标及高度计观测数据均基本吻合.嵌套模拟结果好于单纯使用WAVEWATCH模拟的结果,体现了利用2种模式嵌套模拟台风浪场的科学性.     

Numerical simulation of scatterometer assimilated wind and ocean wave in eastern China seas and adjacent waters

Using the latest version of Mesoscale Modeling System (MM5v3), we assimilated wind data from the scatterometer and built a model to assimilate the wind field over eastern China seas and adjacent waters and applied the wave model WAVEWATCH-Ⅲ to test the sea area with assimilative wind and blended wind of QSCAT and NCEP as driving forces. High precision and resolution numerical wave results were obtained. Analysis indicated that if we replace the model wind result with the blended wind, better sea surface wind results and wave results could be obtained.     

An efficient algorithm for generating a spherical multiple-cell grid

This paper presents an efficient algorithm for generating a spherical multiple-cell(SMC) grid. The algorithm adopts a recursive loop structure and provides two refinement methods:(1) an arbitrary area refinement method and(2) a nearshore refinement method. Numerical experiments are carried out, and the results show that compared with the existing grid generation algorithm, this algorithm is more flexible and operable.     

WAVEWATCHIII 同化模块的建立和检验

将基于最优插值 (OI) 的同化并行模块植入全谱空间的第三代海浪模式WAVEWATCH III version3.14,建立数据同化的海浪模式预报系统, 并通过实际的预报个例对同化系统进行检验。个例实验是以5°S 以北的印度洋海域为目标计算区域, 海面风场强迫采用业务单位的中尺度天气预报模式WRF(weather research and forecast) 提供的逐时海面风场预报产品。模式积分过程中连续同化2010 年12 月15 日、16 日和17 日过境北印度洋的Jason-2 卫星高度计沿轨有效波高 (SWH) 数据 (需要指出的是, 每次同化得到新的SWH 分析场后需重构相应的二维海浪谱用于谱模式)。SWH 同化分析值和无同化的对照组分别与高度计沿轨观测数据比较发现, 就日平均统计来看, 同化较无同化使SWH分析值的均方根误差减小约25%～50%。以SWH 同化分析场作为初始场的预报表明, 同化对预报影响的时效性可延长至48～60 h。本研究目的是通过将高度计测量的SWH 数据同化到海浪模式进一步提升海浪数值预报的准确度。     

数据同化的南海台风浪后报模式

将基于最优插值(OI)的同化并行模块植入第三代海浪模式WAVEWATCH III version3.14, 建立数据同化的台风海浪模式预报系统。该系统的强迫风场采用模型台风风场与台风来前海区背景风场混成的风场。以模式后报2010 年7 月严重影响南海北部的“康森”和“灿都”台风引起的海浪场为例, 首先对所构造的混合风场的台风海面风场结构进行定性检验, 并用高度计沿轨风速对混合风场精度进行定量验证。在此基础上, 海浪模式在混合风场强迫下边积分边同化。同化数据采用上述台风过境南海期间Jason-2 卫星高度计沿轨有效波高 (SWH)。值得指出的是, 同化时只取SWH 沿轨数据的一部分用于同化计算, 而另一部分沿轨数据则用于对同化分析结果进行检验。先后同化了4 条轨道上的SWH数据。将SWH 的同化分析与无同化的对照组结果分别与高度计测量SWH 比较, 发现同化较无同化可使均方根误差获得50%以上的明显改进。以同化分析场作为初始场, 同化影响预报(这里是后报)的时效性约在48 h 以内。本研究目的是通过同化高度计SWH 数据进一步提升台风海浪模式预报的准确度。     

风能输入参数对珠江口波浪模拟的影响

珠江口是粤港澳大湾区的核心区域,台风、风暴潮和巨浪等海洋灾害频发,对沿岸人民的生命财产安全构成严重威胁。准确的高分辨率波浪模拟/预报对区域经济建设和防灾减灾具有重要意义。波浪预报/模拟的质量很大程度上取决于风能输入的误差。本研究基于WAVEWATCH Ⅲ（WW3）的南海-珠江口双重嵌套精细化海浪模式,探讨不同的风场产品与风能输入参数方案组合对珠江口波浪动力过程模拟的影响,确定最优的风场和参数方案组合。ERA5风场更适合珠江口海域的风浪模拟,其模式结果略优于采用CFSR风场的模式结果。ERA5风场+T500方案的组合对珠江口波高变化过程的模拟效果最好,ERA5风场+T471方案的组合次之,ERA5风场+ST6方案再次之。CFSR风场与T471f参数方案最为适配,其结果稍差于ERA5风场+ST6参数方案。T500方案调整高风速下的风能输入和涌浪对风能输入的反馈作用,并考虑水深引起的波浪破碎效应,更适合水深限制的珠江口浅水区域。另外,WW3模式开关ST4的参数方案的表现优于开关ST6的参数方案。      

0801号台风风浪场和涌浪场的数值模拟

利用美国国家海洋大气总局/美国国家环境预报中心（NOAA/NCEP）发布的最新版WAV-EWATCHⅢ（version3.14）海浪模式对0801号台风＂浣熊＂进行数值模拟,并在此基础上对台风浪的发展过程和台风影响下的海面有效波高、风浪场及涌浪场的分布特征进行分析。结果表明：海面有效波高的分布和演变受台风系统强度和移动的影响;台风过程中所产生的大浪主要为风浪;涌浪场的分布与风浪场的分布几乎相反,涌浪场基本分布在远离台风中心的外围海域;涌浪场波高比风浪场波高要小。     

Numerical simulation and preliminary analysis on ocean waves during Typhoon Nesat in South China Sea and adjacent areas

Using the wave model WAVEWATCH III(WW3), we simulated the generation and propagation of typhoon waves in the South China Sea and adjacent areas during the passage of typhoon Nesat(2011). In the domain 100°–145°E and 0°–35°N, the model was forced by the cross-calibrated multi-platform(CCMP) wind fi elds of September 15 to October 5, 2011. We then validated the simulation results against wave radar data observed from an oil platform and altimeter data from the Jason-2 satellite. The simulated waves were characterized by fi ve points along track using the Spectrum Integration Method(SIM) and the Spectrum Partitioning Method(SPM), by which wind sea and swell components of the 1D and 2D wave spectra are separated. There was reasonable agreement between the model results and observations, although the WW3 wave model may underestimate swell wave height. Signifi cant wave heights are large along the typhoon track and are noticeably greater on the right of the track than on the left. Swells from the east are largely unable to enter the South China Sea because of the obstruction due to the Philippine Islands. During the initial stage and later period of the typhoon, swells at the fi ve points were generated by the propagation of waves that were created by typhoons Haitang and Nalgae. Of the two methods, the 2D SPM method is more accurate than the 1D SIM which overestimates the separation frequency under low winds, but the SIM method is more convenient because it does not require wind speed and wave direction. When the typhoon left the area, the wind sea fractions decreased rapidly. Under similar wind conditions, the points located in the South China Sea are affected less than those points situated in the open sea because of the infl uence of the complex internal topography of the South China Sea. The results reveal the characteristic wind sea and swell features of the South China Sea and adjacent areas in response to typhoon Nesat, and provide a reference for swell forecasting and offshore structural designs.     

利用WAVEWATCH和SWAN嵌套计算珠江口附近海域的风浪场*

基于CCMP(Cross Calibrated Multi-platform)卫星遥感海面风场数据,通过将WAVEWATCH和SWAN (Simulating WAves Nearshore)模型嵌套的方法,数值模拟了珠江口附近海域的风浪场。将总计10个月的数值模拟的有效波高、波周期和波向分别与相应的观测值进行了定量比较。结果说明,有效波高的平均绝对误差为15.4cm,分散系数SI为0.240,相关系数为0.925;波周期的平均绝对误差为1.9s,分散系数SI为0.433,相关系数为0.636;波向的平均绝对误差为23.9°。计算的波高和波向与观测结果的变化趋势相吻合。由于第三代海浪模式本身的缺陷,导致所计算的波周期偏小。总体说来,本文所采用的数值模式能较好地模拟珠江口附近海域的风浪场。另外,还设计了6个算例以探讨采用不同的计算方法和风场对计算结果精度的影响。结果表明使用本文的数值方法和高精度的CCMP风场确实可以提高计算结果的精度。     

Stokes漂流近似公式对海洋表层流场估算的影响

本文采用波浪订正的Ekman模型,研究分析了三种Stokes漂流近似公式(单波公式、e指数公式、Phillips谱近似公式)对海洋表层流场估算的影响。海表总流场由海表面高度(SSH)数据计算的地转流和海浪模式WAVEWATCH Ⅲ输出结果计算的非地转流组成,并采用拉格朗日浮标观测数据对计算结果进行了验证。研究表明,随着Stokes漂流近似公式精度的提高,其计算的拉格朗日流速更接近于谱积分公式的计算结果,更贴近拉格朗日浮标观测数据。与谱积分公式计算的海表拉格朗日流速相比,单波公式的平均相对偏差为0.0834,e指数公式的平均相对偏差为0.0392,Phillips谱近似公式的平均相对偏差为0.0101,说明Phillips谱近似公式在不同风速下均能对谱积分公式有良好的近似效果。在低风速条件下,由Stokes漂流近似公式精度引起的海洋表层流场估算误差可以忽略不计,但随着风速增加,由近似公式精度引起的偏差逐渐变大,此时应该选择Phillips谱近似公式计算Stokes漂流,来减小误差。