Introduction
Continuous, flow-through measurements of temperature and salinity have been collected with thermo-salinographs for decades (e.g. Henin and Grelet, 1996), which has led to well-established protocols for quality control, archiving and distribution of such underway data (e.g. Gosud, Surface (Underway) Temperature/Salinity Data). Chlorophyll fluorescence has also been integrated to such systems, with the first underway flow-through fluorometry dating back to the late 60’s (Lorenzen, 1966).
More recently, several research groups have begun collecting detailed optical data in a similar manner. These “in-line” data (measured onboard while underway) have been successfully collected on both research vessels and vessels of opportunity and can provide data at spatial resolutions of 10-100 m. These measurement scales are not accessible with standard hydrographic surveys and enable characterization of sub-pixel variability in satellite Ocean Color data. Thus, data collected using this approach are useful for targeted science questions, but also for large-scale calibration/validation of satellite ocean color products.
As the number of research groups making these measurements has grown, we have recognized a need for coordinated exchange of data collection and processing protocols to standardize methodology and data quality. In 2015, a workshop was organized to share such knowledge and to create shared processing software (Fig. 1). Here, we discuss the essential issues associated with in-line data collection, provide recommendations on best practices and a progress report on common software development. Feedback from the broader community is welcome and will help ensure that the developments that we are making are widely useful.
This sit is organized as follows. First, we address the instruments and hardware associated with deploying an in-line system and discuss a number of considerations that can affect data Quality Assurance/Quality Control (QA/QC). Then, we address characteristics of a software package developed specifically to process data generated with in-line systems, particularly those employing absorption-attenuation meters and a flow switched to measure total and dissolved optical properties (and by difference the optical properties of particles).