资源环境科技发展态势分析平台

Clusters of storm waves contribute disproportionately to coastal erosion hazards because the coastline has insufficient time to recover between events. Here, the change in occurrence of clustered storms and its association with atmospheric oscillation modes were investigated in New Zealand waters using 44 years (1958-2001) of wave hindcast data. First, long-term averages of cluster parameters (number of storms within the cluster, potential for coastal erosion, and cluster duration) were assessed. Then, the relationships between clustering and the El Nino-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Zonal Wavenumber-3 Pattern (ZW3), Pacific Decadal Oscillation (PDO), and Southern Annular Mode (SAM) were explored through correlation analysis over several timescales. Clusters were more frequently observed to the northeast of New Zealand and on the central eastern coast of the South Island. The most vulnerable regions to cluster-induced coastal erosion were southern New Zealand and the northwestern coast, which resulted from steady southwesterly swells, although clusters with the longest duration occurred on the east coast of the South Island. Trends suggest that clusters have incorporated more storms, have become more hazardous, and have increased in duration, particularly along the South Island coastline. Although these trends may be sensitive to the reanalysed wind fields used to force the wave hindcast, they reflect trends in the ENSO, PDO, and SAM. Stronger southwesterly winds during El Nino (negative ENSO) and El Nino-like conditions (positive IOD/PDO) generated more clustered storms mainly on the southwestern coast of New Zealand, whereas increases in clustering were observed on the north coast during La Nina and La Nina-like conditions (stronger northeasterly winds). Higher occurrence of clustering was also evident on the west coast during the strong atmospheric zonal flow associated with negative ZW3. Lastly, strengthened westerlies related to positive SAM led to increased clustering primarily to the south of New Zealand.