摘要
南海北部内孤立波异常活跃,具有极强的非线性、极高的强度和极大的能量,其传播特性和精细结构在背景过程影响下更加复杂,加剧了内孤立波预报和海上石油平台作业的难度.基于南海北部陆丰海域 295 m水深处一套潜标连续 79d的观测资料,分析了秋季内孤立波的波动特征和统计规律.典型内孤立波表现为波列的形式,头波振幅达 86.7 m,在海洋上层导致局地增温超过 8.0℃,并诱发最大达0.83 m/s的西向流和 0.60 m/s的北向流,在波前产生最大达 0.25 m/s的下降流.对观测期间捕捉到的 91个内孤立波统计分析表明,内孤立波主要沿WNW方向传播,平均振幅为 59.9 m,在海洋上层诱发的最强西向流速平均值为 0.79 m/s;在天文大潮时期,内孤立波在 04:00至 06:00和 16:00至 19:00频繁出现,且农历初二至初五和十六至十八期间经过陆丰海域的内孤立波具有更大的强度.此外,全日内潮与半日内潮共同作用下压了温跃层,导致典型内孤立波中形成了 1个上凸波动,其在近底层导致局地降温达1.3℃,并诱发超过 0.30 m/s的西向流和 0.20 m/s的北向流;该上凸波动陡峭的波前汇聚了强剪切,极易触发剪切不稳定.本研究结果可为陆丰海域海上石油平台施工、勘探船作业等提供重要参考.
Abstract
Internal solitary waves(ISWs)in northern South China Sea are very active,featured by strong nonlinearity,high intensity,and concentrated energy.Their propagation characteristics and fine-scale structures are complicated under the influence of background processes,increasing the difficulties in predicting ISWs and conducting offshore operations of oil platforms.Based on a mooring deployed at a water depth of 295 m in the Lufeng Area in northern South China Sea for 79 days,the property and temporal variation of the ISWs were carefully analyzed.The typical ISW appeared as wave trains with a leading wave amplitude of up to 86.7 m,and induced local warming of more than 8.0℃ and the maximum westward and northward currents of up to 0.83 m/s and 0.60 m/s in upper layer,respectively.The statistical results showed that 91 ISWs captured during observation period mainly propagated northwestward with an average amplitude of 59.9 m and a mean value of up to 0.79 m/s in upper layer.Moreover,the ISWs occurred more frequently and stronger during 04:00-06:00 and 16:00-19:00 and on the 2-5 and 16-18 lunar days.In addition,thermocline depressed by the diurnal and semi-internal tides formed an elevation soliton in the typical ISWs,which caused local cooling of 1.3℃ and westward and northward currents of more than 0.3 m/s and 0.2 m/s near sea bottom,respectively.The steep front of the elevation soliton converge enhanced shear,making it prone to trigger shear instability.This study provides important references for offshore construction of oil platforms and survey operations in the Lufeng Area.
基金项目
中海石油(中国)有限公司科技项目(YXKY-ZX102021)
中国海洋石油集团总公司"十四五"重大科技项目(KJGG2022-0202)
三亚崖州湾科技城科技计划项目(SKJC-2022-01-001)
海南省"南海新星"科技创新人才平台项目(NHXXRCXM202364)
维普
万方数据