Ocean waves alter the roughness of sea surface,and sea spray droplets redistribute the momentum flux at the air-sea interface.Hence,both wave state and sea spray influence sea surface drag coefficient.Based on the new sea spray generation function which depends on sea surface wave,a wave-dependent sea spray stress is obtained.According to the relationship between sea spray stress and the total wind stress on the sea surface,a new formula of drag coefficient at high wind speed is acquired.With the analysis of the new drag coefficient,it is shown that the drag coefficient reduces at high wind speed,indicating that the sea spray droplets can limit the increase of drag coefficient.However,the value of high wind speed corresponding to the initial reduced drag coefficient is not fixed,and it depends on the wave state,which means the influence of wave cannot be ignored.Comparisons between the theoretical and measured sea surface drag coefficients in field and laboratory show that under different wave ages,the theoretical result of drag coefficient could include the measured data,and it means that the new drag coefficient can be used properly from low to high wind speeds under any wave state condition.
SHI JianZHONG ZhongLI XunqiangJIANG GuorongZENG WenhuaLI Yan
采用NCEP-FNL(Final Operational Global Analysis)再分析风场资料及WW3(WAVEWATCH Ⅲ)海浪模式对2015年连续发生的1509号台风"灿鸿"、1510号台风"莲花"和1511号台风"浪卡"进行数值模拟。通过与卫星高度计资料和浮标观测资料对比,验证了模拟结果的有效性,并分析台风浪的特征。结果表明:采用再分析风场资料驱动WW3海浪模式,较好地模拟了3个台风影响下西北太平洋海浪场的分布和演变特征;模拟波高与遥感的轨道波高资料相关性超过0.7,平均相对误差小于0.23,风速误差是造成模拟误差的主要原因;台风浪的大小不仅取决于台风强度,还受海域的影响。近海海域由于海岸与岛屿的阻碍,波浪能量频散受到抑制,易产生局地巨浪;而深海大洋开阔海域,易于台风浪能量传播。本文相关结论为台风浪的定量预报及防灾减灾提供有益参考。
