Iranian National Institute for Oceanography and Atmospheric Sciences (INIOAS)
In this study, the evolution and dependency of infragravity waves (IGWs) on wind waves for breaking and nonbreaking conditions is separately investigated. The efficiency of two constant cutoff frequencies (0.125 and 0.14 Hz) is compared for wave data measured in the sandy beaches of Nowshahr at the Southern Caspian Sea. It is found that the frequency of 0.125 Hz results higher correlation coefficients between IGWs energy content and two wind wave groups. Two pair different correlation patterns between IGWs in one side and wind waves higher and lower than 0.125 Hz in another side were recognized for breaking and nonbreaking conditions. In can be concluded that the IGWs excitation is controlled by the frequency distribution of wind wave energy.
According to 0.125 Hz as more successful option, the correlation of IGWs with swell waves is generally more significant than sea waves. In the nonbreaking wave condition, the IGWs are well correlated with sea waves, whereas no considerable correlation between IGWs and sea waves is found in the breaking condition. It is resulted that IGWs energy is approximately linearly proportional of both swell and sea waves in nonbreaking condition. In the high and moderate energy incident wave conditions, the IGWs energy grows shoreward, while energy attenuation can be detected for IGWs in very low energy waves.