International Monitoring System infrasound data products for atmospheric studies and civilian applications

Abstract

Abstract. The International Monitoring System (IMS) was established in the late 1990s for verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Upon completion, 60 infrasound stations distributed over the globe will monitor the Earth's atmosphere for low-frequency pressure waves. In this study, we present advanced infrasound data products of the 53 currently certified IMS infrasound stations for atmospheric studies and civilian applications. For this purpose, 18 years of raw IMS infrasound waveform data (2003–2020) were reprocessed using the Progressive Multi-Channel Correlation (PMCC) method. A one-third octave frequency band configuration between 0.01 and 4 Hz was chosen to run this array-processing algorithm which detects coherent infrasound waves within the background noise. From the comprehensive detection lists, four products were derived for each of the certified 53 IMS infrasound stations. The four products cover different frequency ranges and are provided at the following different temporal resolutions: a very low-frequency set (0.02–0.07 Hz, 30 min; https://doi.org/10.25928/bgrseis_bblf-ifsd, Hupe et al., 2021a), two so-called microbarom frequency sets – covering both the lower (0.15–0.35 Hz, 15 min; https://doi.org/10.25928/bgrseis_mblf-ifsd, Hupe et al., 2021b) and a higher (0.45–0.65 Hz, 15 min; https://doi.org/10.25928/bgrseis_mbhf-ifsd, Hupe et al., 2021c) part – named after the dominant ambient noise of interacting ocean waves that are quasi-continuously detected at IMS stations, and observations with center frequencies of 1 to 3 Hz (5 min), called the high-frequency product (https://doi.org/10.25928/bgrseis_bbhf-ifsd, Hupe et al., 2021d). Within these frequency ranges and time windows, the dominant repetitive signal directions are summarized. Along with several detection parameters, calculated quantities for assessing the relative quality of the products are provided. The validity of the data products is demonstrated through example case studies of recent events that produced infrasound detected at IMS infrasound stations and through a global assessment and summary of the products. The four infrasound data products cover globally repeating infrasound sources such as ocean ambient noise or persistently active volcanoes, which have previously been suggested as sources for probing the winds in the middle atmosphere. Therefore, our infrasound data products open up the IMS observations also to user groups who do not have unconstrained access to IMS data or who are unfamiliar with infrasound data processing using the PMCC method. These types of data products could potentially serve as a basis for volcanic eruption early warning systems in the future.