The local SLP gradient and its squared value

(a proxy of the geostrophic wind energy) click here are used to account for the local wave generation. This study illustrates that the local predictors (P   and G  ) alone (Setting 1), as used in Wang et al. (2010), are not sufficient to properly model HsHs in near shore areas where the coastline orientation seems to enhance the role of swell waves. Similar to the findings by Wang et al. (2012), a large improvement is achieved in this study by adding the leading PCs of SLP gradient fields (in this study including magnitudes and directions) to account for swell waves (Settings 2 and 3) and adding the lagged HsHs to account for the temporal dependence (Setting 4). Since this study aims to improve

the performance in modeling HsHs in the near shore areas, where good representation of the swell component is particularly important, special focus has been given to the swell term. The proposed SP600125 method (Setting 5) uses the PCs derived from the squared SLP gradient vectors (including magnitudes and directions). By retaining the geostrophic wind direction information and separating between its positive and negative phase, this approach enables the detection of swell wave trains affecting each wave grid location. The time lag between the wave generation area and the propagated swell at the point of interest is also considered. Based on the directional/frequency dispersion of

waves, each swell train is finally weighted as a function of the considered frequency bin and the deviation of the swell wave train propagation from the forcing wind direction at the origin. Results show that, in the study area (especially in the near shore areas), the model performs better with this swell representation approach. The improvement is not very pronounced though, which might be attributable to the short fetches of the study area. More pronounced improvement can be expected if this method is used to model HsHs in near shore areas with larger fetches (and therefore swell waves travelling longer distances). Meanwhile, the proposed PCs sign decomposition and swell train detection approach could be adapted to model wave direction together with HsHs in a future study. To overcome the problem of having non-Gaussian (non-negative) variables (whereas linear Tideglusib regression assumes normal residuals), we have tried a couple of methods to transform the non-negative predictors. The results show that transformation of the predictand (HsHs) alone (Setting 6) worsens the model skill, because it distorts the relationship between HsHs and the squared SLP gradient fields (as discussed in the Auxiliary Material of Wang et al., 2012). The log-transformation (Setting 7) improves the results for low-to-medium waves, and the Box–Cox transformation (Setting 8), for medium-to-high waves, especially at offshore locations.