A Novel Near-Real-Time Quality-Control Procedure for Radiometric Profiles Measured by Bio-Argo Floats: Protocols and Performances

Abstract

An array of Bio-Argo floats equipped with radiometric sensors has been recently deployed in various open ocean areas representative of the diversity of trophic and bio-optical conditions prevailing in the so-called case 1 waters. Around solar noon and almost every day, each float acquires 0-250-m vertical profiles of photosynthetically available radiation and downward irradiance at three wavelengths (380, 412, and 490 nm). Up until now, more than 6500 profiles for each radiometric channel have been acquired. As these radiometric data are collected out of an operator's control and regardless of meteorological conditions, specific and automatic data processing protocols have to be developed. This paper presents a data quality-control procedure aimed at verifying profile shapes and providing near-real-time data distribution. This procedure is specifically developed to 1) identify main issues of measurements (i.e., dark signal, atmospheric clouds, spikes, and wavefocusing occurrences) and 2) validate the final data with a hierarchy of tests to ensure a scientific utilization. The procedure, adapted to each of the four radiometric channels, is designed to flag each profile in a way compliant with the data management procedure used by the Argo program. Main perturbations in the light field are identified by the new protocols with good performances over the whole dataset. This highlights its potential applicability at the global scale. Finally, the comparison with modeled surface irradiances allows for assessing the accuracy of quality-controlled measured irradiance values and identifying any possible evolution over the float lifetime due to biofouling and instrumental drift.

Two databases derived from BGC-Argo float measurements for marine biogeochemical and bio-optical applications

“…Designed in the context of the Remotely-Sensed Biogeochemical Cycles in the Ocean (remOcean) and Novel Argo Ocean Observing System (NAOS) projects, this profiling float has also been adopted by several international collaborators and research programs. A full technical description of the platform and instrument arrangements can be found in Leymarie et al (2013) and Organelli et al (2016a). All PROVOR CTS4 profiling floats were programmed to acquire 0-1000 m vertical profiles every 1 to 10 days while operating (every 4 ± 2 days on average; see Appendix A), depending on the mission and scientific objectives.…”

“…Vertical profiles of PAR and E d (λ) were quality controlled following the procedures detailed in Organelli et al (2016a). This protocol accepts measurements acquired both under clear and cloudy sky conditions as good as soon as these re- main stable during the cast (Organelli et al, 2016a).…”

“…This protocol accepts measurements acquired both under clear and cloudy sky conditions as good as soon as these re- main stable during the cast (Organelli et al, 2016a). A first step of the quality control consisted of identifying and discarding each profile acquired under very unstable sky and sea conditions (see quantitative metrics in Organelli et al, 2016a).…”

“…In 2012, an array of BGC-Argo floats started to be deployed in several oceanic areas encompassing a wide range of biogeochemical and trophic conditions, from subpolar to tropical and from eutrophic systems to oligotrophic midocean gyres (Organelli et al, 2016a. This array of floats was devoted to the acquisition of profiles of key biogeochemical quantities via their optical properties (i.e., chlorophyll a and colored dissolved organic matter, CDOM) and of hydrological variables (i.e., temperature and salinity).…”

“…The geographic and temporal distribution of each parameter is described and discussed. A second database is specifically devoted to field and remote ocean color applications (Organelli et al, 2016b). It is focused on observations and derived products within the first optical depth Z pd (also known as the penetration depth, i.e., the layer of interest for satellite remote sensing; Gordon and McCluney, 1975; units of m) and includes the "Biogeochemical and OPtical Argo Database -surface" (BOPAD-surf) Chl, FDOM, and b bp (700) quantities derived from the qualitycontrolled vertical profiles in addition to the diffuse attenuation coefficients for downward irradiance (K d (λ), m −1 ) and PAR (K d (PAR), m −1 ).…”