ECO-VSF3 data used for characterization of the bucket for backscattering observation in the flow-through CoCa system

This dataset was used to assess the quality of the optical backscattering coefficient measurements taken during the BIOOPT2019 cruise in the Black Sea. The reference work by the same team, is "Single dual mode (Continuous and Cast) instrumentation package for IOP measurements: characterisation of the bucket for backscattering observation". The dataset consists of two parts, which were used to estimate the underway system inertia and the system uncertainty, respectively. The former aimed at assessing the b4bbo (bucket for backscattering observations) renewal water time and consists only of data collected underway (16 data files), while the latter is made of measurements acquired both continuously (56 data files) and during station (56 data files), profiling the water column.

Volume Scattering Function (VSF) data were acquired with a WetLab Inc. ECO-VSF3 sensor, from which the spectral backscattering coefficients can be derived, also included into the dataset. ECO-VSF3 samples the water at three wavelengths (470, 532, 660 nm) in three angles (111, 138, 154 degrees). This is presented as a comma-separated file also including time, location and the water flow through the system. File naming convention is: {instrument}-{context}-{two digits of progressive number}.csv. {context} can be as follows:

•  co, for continuous measurements (example file name ecovsf3-co-01.csv);
•  ca, for cast measurements (example file name ecovsf3-ca-01.csv):
•  si, for continuous measurements used to derive the system inertia (example file name ecovsf3-si-01.csv).

Each data file includes a two line header with variable names and units. The fields included into each data file are:

• YYYY: four digits for year of measurement
• MM: two digits for month of measurement
• DD: two digits for day of measurement
• HH: two digits for hour of measurement (UTC time)
• MI: two digits for minute of measurement
• SS: two digits for second of measurement
• Lon: degrees East
• Lat: degrees North
• VSF_111_470: Volume Scattering Function at 111 degrees for the 470 nm band (m-1 sr-1)
• VSF_138_470: Volume Scattering Function at 138 degrees for the 470 nm band (m-1 sr-1)
• VSF_154_470: Volume Scattering Function at 154 degrees for the 470 nm band (m-1 sr-1)
• VSF_111_532: Volume Scattering Function at 111 degrees for the 532 nm band (m-1 sr-1)
• VSF_138_532: Volume Scattering Function at 138 degrees for the 532 nm band (m-1 sr-1)
• VSF_154_532: Volume Scattering Function at 154 degrees for the 532 nm band (m-1 sr-1)
• VSF_111_660: Volume Scattering Function at 111 degrees for the 660 nm band (m-1 sr-1)
• VSF_138_660: Volume Scattering Function at 138 degrees for the 660 nm band (m-1 sr-1)
• VSF_154_660: Volume Scattering Function at 154 degrees for the 660 nm band (m-1 sr-1)
• bb_470: backscattering coefficient at 470 nm (m-1)
• bb_532: backscattering coefficient at 532 nm (m-1)
• bb_660: backscattering coefficient at 660 nm (m-1)

CTD measurements from Sea-Bird Scientific, Inc., MicroCAT SBE-37-SI were also include in cast data files:

• Depth: depth (m)
• Temp: sea water temperature (degrees Celsius)
• Sal: sea water salinity (psu)

Apart from the manufacturer calibration, no post processing was performed to any of these data. For each independent system inertia experiment, an automatic electro valve was activated twice. The first time, after 122 seconds from measurement acquisition start, to redirect the water through a 0.2 µm filter before entiring b4bbo for non-particulate bb measurement. The second, after 602 seconds from acquisition start, to let the water directly into b4bbo for total bb measurement.