Satellite and in situ measurements for coastal water quality assessmentand monitoring: a comparison between MODIS Ocean Color and SSTproducts with Wave Glider observations in the Southern Tyrrhenian Sea(Gulf of Naples, Italy).

A wave-propelled autonomous vehicle (Wave Glider, WG) carrying a variety of oceanographic and meteorological sensors was launched from Gulf of Naples on the 12th September 2012 for a three-week mission in the Southern Tyrrhenian Sea. The main objective of the mission was the opportunity to evaluate the usefulness of combined satellite and autonomous platform observations in providing reliable and concurrent information about sea wa-ter parameters about the Southern Tyrrhenian Sea surface layer. The Wave Glider was equipped with sensors tomeasure temperature, salinity, currents, as well as CDOM, turbidity and refined fuels fluorescence. Wave Glider oceanographic data were also compared to satellite measurements. In particular, MODIS Ocean Color (OC) prod-ucts concerning sea water properties collected during the Wave Glider mission were used. The EOS constellation allowed us to have about two daily diurnal imagery providing information about ocean color products. Concerning SST, both diurnal and night-time data were available. The first study we performed was focused on the analysis ofSST information coming from both WG and MODIS. A good coefficient of correlation was achieved consideringtogether both day-time and night-time acquisitions, with a discrepancy not higher than 0,7◦C. The correlation increases considering only day-time values, when more samples respect to the night-time ones were available. The results confirm the capability of MODIS products to reproduce over large area the SST variability, with agood level of accuracy. A similar analysis has been carried out to compare the turbidity WG data with the kd-490MODIS product, which provide information about the diffuse attenuation coefficient in water at 490 nm and it isdirectly related to the presence of scattering particles, either organic or inorganic, in the water column and thus itis an indication of water clarity or of the water column turbidity. The absence of correlation seems to indicate, forsuch a specific parameter, that the two sensors are looking at not similar objects. A different depth of investigation or a small scale variability, that MODIS is not able to capture, could be a few of the explanations of these results.It should be also stressed that, by its design, the WG is propelled at the surface like a surfboard and bubbles ofall sizes will roll along the bottom of the float. Microbubbles are of particular concern since they will not rapidly ascend and are likely to represent a source noise for the turbidity WG parameter. Finally, the refined fuels WG datahave been compared with a statistical indicator of oil spill presence named RST-OIL and the correlation was quitepoor. Such a results is quite expected since for its construction, values of RETIRAbox within +/-2σ, like those achieved along WG path, have a probability of occurrence of 97,75% representing the normal fluctuation of thesignal, hence randomly varying.