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Particulate backscattering coefficient (bbp) Backscattering voltage was converted to beta at 140° by subtracting dark voltages (median in-situ dark voltage, 0.078 V) and multiplying by factory calibration scale factors, modified based on measurements and calculations of Sullivan et al. (subm.). The calibration factor did not change between pre-cruise and post-cruise factory calibration. at 140° was converted to bbp (m-1 or reciprocal meter) at 700 nm by subtracting of seawater (Zhang et al., 2009) and multiplying by 2pi beta(where beta = 1.132).

Particulate backscattering coefficient bbp (700nm); Acquired with WET Labs MCOMS Scattering Meter with 700-nm wavelength and in-water centroid angle of 150 deg. See Table 3 in paper.

The particulate volume scattering coefficient ?p was calculated as

?p(150 deg,700 nm) [m-1 sr-1] = Scale Factor * (Output - Dark Counts)

using a factory-determined scale factor and a dark offset, computed separately for each sensor as the mean of the deep-water minima measured during all profiles between July and September 2013 at BATS (https://www.bco-dmo.org/dataset/728371). Particulate backscattering coefficient, bbp(?) [m-1], is estimated as

bbp = 2???p(150 deg)

? = 1.13 for 150 deg (from Boss and Pegau 2001).