Satellite remote sensing is a powerful tool for lake water quality monitoring. Validation of remote sensing products requires ground reference measurements, which are time-consuming and costly to obtain. With the recent advances in sensor technology, automated hyperspectral radiometric systems are increasingly used to acquire frequent near-real-time data. Such datasets do not only drastically increase the number of matchups, but also ensure a more balanced seasonal sampling compared to traditional field campaigns. In this study, we present optical properties (including remote sensing reflectance) and biogeochemical data from three research platforms in Lake Geneva (Switzerland/France), Lake Garda (Italy), and Greifensee (Switzerland). Remote sensing reflectance data were obtained through automated hyperspectral radiometers below (Wetlabs Thetis), at (JB Hyperspectral RoX), or above the water surface (WaterInsight WISPstation, Hypstar, and PML So-Rad). The cross-validated measurements were used to evaluate the performance of selected atmospheric correction algorithms, namely POLYMER, C2RCC, and Acolite applied to Sentinel-2/-3 products. We also performed an optical closure exercise to further assess the uncertainty of optical measurements in Lake Geneva, where simultaneous inherent optical property measurements were available. Our results suggest that automated spectroradiometers are becoming a reliable data source for validating satellite products and associated uncertainties at regional and global scales, with the added value of simultaneous biogeochemical measurements.

Primary Presenter: Abolfazl Irani Rahaghi, Eawag, Swiss Federal Institute of Aquatic Science & Technology (abolfazl.irani@eawag.ch)

Authors:

Abolfazl Irani Rahaghi, Eawag, Swiss Federal Institute of Aquatic Science & Technology, Dübendorf, Switzerland  (abolfazl.irani@eawag.ch)

Mortimer Werther, Eawag, Swiss Federal Institute of Aquatic Science & Technology, Dübendorf, Switzerland  (Mortimer.Werther@eawag.ch)

Camille Minaudo, Department of Ecology, University of Barcelona, Barcelona, Spain   (camille.minaudo@ub.edu)

Mariano Bresciani, IREA-CNR, Milan, Italy  (bresciani.m@irea.cnr.it)

Marina Amadori, University of Trento, Trento, Italy & IREA-CNR, Milan, Italy  (marina.amadori@unitn.it)

Claudia Giardino, IREA-CNR, Milan, Italy  (giardino.c@irea.cnr.it)

Alexander Damm, Department of Geography, University of Zurich, Zurich, Switzerland  (alexander.damm@geo.uzh.ch)

Vittorio Brando, ISMAR-CNR, Rome, Italy  (vittorio.brando@cnr.it)

Daniel Odermatt, Eawag, Swiss Federal Institute of Aquatic Science & Technology, Dübendorf, Switzerland  (Daniel.Odermatt@eawag.ch)