A double-peaked spectrum for the northern parts of the Gulf of Oman: Revisiting extensive field measurement data by new calibration methods

Calibration of double-peaked spectra based on partitioning of frequency spectra sometimes starts by assuming that relations existing between two observed peaks are valid through the calibration procedure. Here, often two facts are overlooked: each system (i.e., swell and wind-sea systems) in a typical double-peaked spectrum contributes to the other one, and swell system in its peak zone is highly asymmetric. Actually peak spectral densities and corresponding peak frequencies of partitioned systems are different from those observed in an integrated double-peaked spectrum. Besides, those observed as peak values are not good candidates of the peak due to the asymmetry of swell system. To highlight these issues, we examine 2 different methods to fit 2 JONSWAP spectra to double-peaked spectra observed in 2 series of measurement in the northern part of the Gulf of Oman (i.e., 2006-2007 and 2016); one which directly uses observed values, and the other which adjusts them. Discussing such, we introduce two modifications, one dependent and one independent of measurements. Here, we address how data gathered from integrated double-peaked spectra can be modified to maximize accuracy of results. This is what less addressed by studies focusing on calibration of spectra, while it is of great importance in practice.