Bridging the gap between weather forecasting and tsunami forecasting: a background model of the open ocean in the tsunami spectrum

Abstract. A reference power law of ω ^-2, where ω is angular frequency, has been traditionally used to characterize the background open ocean tsunami spectrum (BOOTS) slope from a period of 10 mins to 120 mins and that its noise profile can be assumed to be normally distributed. However, this characterization is based on data from temporary deployments of bottom pressure sensors that lasted from several weeks to 11 months and only in scattered areas of the Pacific. Here we measure the BOOTS noise profile using 1–15 years of bottom pressure recorder data sampled at 15 s from the Deep-ocean Assessment and Reporting of Tsunamis (DART) stations. We utilize probabilistic power spectral density plots to create background noise models for 34 DART stations across the Pacific basin. We find that often a simple normal probability distribution does not correctly characterize the observed background noise spectrum at periods of 120 s, 250 s, 800 s, and 2700 s. We find deviations from the expected behavior follow a strong seasonality signal due to infragravity waves. We calculate infragravity wave heights and their mean values for December, January, and February and June, July, and August. We found that meteorologically induced infragravity wave events are the largest factors in seasonal variations of the BOOTS slope and intercept, especially in the east Pacific. We show the typical meteorological systems that drive these events, and we connected tropical systems from off the coast of Mexico to infragravity wave events in the east and central Pacific. And that these infragravity wave generating events potentially affect the probability distributions of the BOOTS. Finally, we convert plot the spatial distributions of the probability distribution functions.