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(Color online) Monthly spectral probability percentiles of omni-directional data between February 2019 and January 2021 showing year to year changes. Lower and upper whiskers represent 10th and 90th percentiles, while boxes represent 25th, 50th, and 75th percentiles. Lower levels from February through June of 2020 relative to 2019 are consistent with reduced shipping caused by COVID-19.
