HOE_Legacy2A-KM1513-LISST-Optics_2021-05-01_v1.0

This dataset comes from sampling performed on the Hawaii Ocean Experiment - Legacy 2A cruise aboard the R/V Kilo Moana (cruise KM1513) in the north Pacific subtropical gyre. All LISST data are collected with a LISST-100X Type-B instrument operated in underway mode. The angular range (median of bin) of the LISST Type-B is 0.106-17.96 degrees, and the size classes sensed are 1.44 - 231 microns (median of each size bin) albeit only particles less than 100 µm are considered here (see dataset_references). HOE-Legacy underway particle size distributions were merged with hourly mean HOE-Legacy PAR and ships position from UH Underway data files. All data have been corrected for background scattering of 0.2 micron filtered seawater sampled the first ten minutes of each hour. Data are presented as hourly means.  The volume concentration of particles (VD, in µL/L), the standard LISST output, is presented for 3 size ranges: 1.25-2 µm (VDsm), 2-20 µm (VDmed), and 20-100 µm (VDlg). Particle volume concentration is then converted to particle concentration by assuming spherical particles. The total particle concentration (nL, #/L) is calculated for particles with a diameter between 1.25 and 100 um. Larger size classes are excluded due to low detection limits. Of note is the finding that diel cycles in particle concentrations are most evident in the 2-20 µm size class; this size class drives diel variability in particle concentrations (#/L).