The relationship of tropical Pacific sea surface temperature and sea level to tropical cyclones on varying time scales

Abstract

This study examined the relationship between sea surface height (SSH), sea surface temperature (SST), El Niño Southern Oscillation (ENSO), and tropical cyclones (TC) on high-frequency (monthly to yearly) and low-frequency (decadal to multidecadal) timescales in the Western Tropical Pacific. We verified the relationship between SST and TCs on short timescales, found a minimum SSH for anomalously intense tropical cyclones (SSHm), and discovered a long-term relationship between SSH and TC counts. Our research produced a SSHm of 70 cm, an anomaly indicative of the minimum upper ocean heat content with the potential intensity for an anomalous TC. We analyzed the size of areas of the sea surface that had SST or SSH greater than or equal to the lower limit for anomalously intense tropical cyclones. On yearly to decadal timescales, SSH and TC counts show an interesting likeness, where TC count fluctuations are mirrored in SSH patterns. We focused on the heat content of the upper ocean as an important driver of TC intensity, and as the factor that unites SST, SSH, and TC count. SST is directly indicative of surface heat content, SSH represents the integrated upper ocean heat content, and TC formation is driven by heat. We conclude that the multidecadal and high-frequency variability patterns of SST are more closely tied to the activity of tropical cyclones than those of SSH. The relationship between SSH and tropical cyclone counts on low-frequency timescales merits further investigation to establish a new understanding of shifts in TC count and extended occurrence patterns.