On The Wave-induced Effect To Circulation Transport And The Characteristics Of Swell Propagation And Dissipation

The persistency and extensiveness of small scale ocean waves makes themimportant to large scale ocean phenomena. In this dissertation, the wave-inducedCoriolis-Stokes effect in upper ocean water transport is analyzed, placing emphasis onocean swells. The large ocean swell transport and dissipation characteristics are alsodiscussed, together with model performance assessment of the newly publishedWavewatchIII v3.14on ocean swells.Ocean swells are important to wave-induced Stokes transport, especially in theMean Wave Direction calculation. The global Ekman transports are band-likedistributed with maximums at Trade wind areas. The W-E components of the Ekmantransport tilt with longitudinal wind. The Stokes transports are also in band withmaximums at westerlies. The W-E components are large in the eastern parts of theoceans where swell are more dominant. The Stokes transport contributes to the Ekmantransport in50%at large; both of the integrated transports across three latitudesat27.5N,30Nand32.5Nare stronger in summer and autumn and weaker inwinter and spring. The Stokes transports are similar in seasonal variations withSverdrup transports along the three latitudes and occupy5to10%in magnitude, withcontributions from October to April and cancellations from May to September.Compared with SODA Kuroshio transport, a5%contribution of the Stokes transportis also found. By introducing the wave-driven surface stress into the modified Ekmanequation, the wave-driven pumping effect is discussed. The wave-driven pumpingvelocities are large in middle and high latitudes with magnitude of about5cm/day.The large scale part of ocean waves are often called swells. The source areas inthe westerlies where most swells arose are approximately round and can be regardedas ‘points’4km away from the original areas. Swells disperse and travel along greatcircles in group velocities, and longer ones move faster. The energy signals are wellcarried by Mean Wave Period in propagation after large storms. Swells keep similardispersing velocities in transverse direction but the correlations to the sourcesdecrease with distance. The continuity of wave crest is often broken by land and islands. At local areas with large winds, the swells also interact with winds and windwaves. The dissipation rate of swell energy in space is approximately-4⁵×10^-7m^-1.The swell energy is disperse within6000km from the source and tends to contractbetween6000km and12000km but increases a little away from12000km. Dissipationincreases with wave steepness. Swell-turbulent stress interaction in marineatmosphere boundary layer （MABL） and swell-turbulence interaction in ocean mixedlayer （OML） are the main sources of dissipation, and the wave steepness and theinverse wave age are the main index in assessing the dissipation rate. Observedinverse wave age increases with wave steepness and distance to source whiledecreases with wave period. The wave steepness δ=0.01is a dividing line forinverse wave age: whenδ <0.01the inverse wave age is between-1and1withalmost the same positive and negative values, indicating the existence of bothfollowing and against wind waves; but whenδ>0.01, inverse wave age tends to bepositive, indicating that following waves are dominant and short swells remain to beinfluenced by local winds.Dissipation parameterizations related to ocean swells are included in WW3model ACC350package; comprehensive model assessments show that it can reflectthe wave height very well within8m. Biases are largest in April and smallest inDecember. The wave model errors mainly come from the errors in swell componentsmodeling, especially in wave period. ACC350package is better in performance thanthe default WAM4BAJ package, but still shows room to get progress relying on moreobservations and research on physical processes.