*2.2. Ocean Data*

Theoretically, the frequencies of ocean waves that generate DF microseisms should be half of the frequencies of DF peaks. Therefore, daily WWIII hindcast of *E*(*F*/2) (log10(m<sup>2</sup> /Hz)) distributions within the half frequency bands of corresponding DF peaks are used in this study in order to explore the association between the ocean wave climates in Northern Atlantic Ocean and DF microseisms.

Additionally, a total of 19 ocean buoys in Atlantic Ocean (see Figure 1 for locations) were selected to retrieve recordings of the ocean climate parameters including dominant wave period and significant wave height (detailed descriptions of which can be found at National Data Buoy Center website). In order to clearly display the locations of the buoys on the figure and to facilitate discussion of the observations, these buoys were renumbered and divided into four groups according to their locations (Figure 1): (1) deep ocean (DO) buoys (9, 10, and 11); (2) the continental slope and deep ocean side (SlDO) buoys (2, 5, 17, and 25); (3) the continental slope and shelf side (SlSh) buoys (3, 6, 7, 19, 21, and 23); and (4) the continental shelf (Sh) buoys (the remaining ones).

In order for a direct comparison of frequency compositions of the ocean wave and DF microseisms, the dominant ocean wave frequency of ocean waves at each buoy was simply doubled to determine the double ocean wave frequency (DWF).
