Abstract
Abstract. The use of ground sampled water quality information for global studies is limited due to practical and financial constraints. Remote sensing is a valuable means to overcome such limitations and to provide synoptic views of ambient water quality at appropriate spatio-temporal scales. In past years several large data processing efforts were initiated to provide corresponding data sources. The Diversity II water quality dataset consists of several monthly, yearly and 9-year averaged water quality parameters for 340 lakes worldwide and is based on data from the full ENVISAT MERIS operation period (2002–2012). Existing retrieval methods and datasets were selected after an extensive algorithm intercomparison exercise using in situ reference measurements for more than 40 lakes representing a wide range of bio-optical conditions. Chlorophyll-a, total suspended matter, turbidity, coloured dissolved organic matter, lake surface water temperature, cyanobacteria and floating vegetation maps, as well as several auxiliary data layers, provide a generically specified data basis that can be used for assessing a variety of locally relevant ecosystem properties and environmental problems. We demonstrate the use of the products by illustrating and discussing remotely sensed evidence of lake-specific processes and prominent regime shifts documented in literature. The Diversity II data are available from https://doi.pangaea.de/10.1594/PANGAEA.871462, and Python scripts for their analysis and visualization are provided at https://github.com/odermatt/diversity/.
Highlights
The first globally representative lake water quality dataset from remote sensing provided a snapshot of chlorophyll-a concentrations in 80 000 lakes worldwide based on Medium Resolution Imaging Spectrometer (MERIS) full-resolution (FR) data acquired in 2011 (Sayers et al, 2015)
MERIS was operated in 2002–2012 on-board the near-polar orbiting ENVISAT satellite by the European Space Agency (ESA; Rast et al, 1999)
Each lake’s perimeter was defined in a shapefile that resulted from vectorized outlines of the Synthetic Aperture Radar Water Bodies (SAR-WB) map created by Santoro and Wegmüller (2014)
Summary
Freshwater ecosystems have undergone more dramatic changes than any other type of ecosystem (Sectretariat of the Convention on Biological Diversity, 2010). Sensed products for water availability and quality are complementary to in situ data in terms of spatial and temporal coverage. They provide synoptic views of spatial distribution unachievable by other means and are ideally suited to covering the broad range of space scales and timescales associated with inland water applications. The first globally representative lake water quality dataset from remote sensing provided a snapshot of chlorophyll-a (chl-a) concentrations in 80 000 lakes worldwide based on MERIS full-resolution (FR) data acquired in 2011 (Sayers et al, 2015). Several case studies are available that demonstrate such assessments with lake-specific foci (Odermatt et al, 2015b), but the larger part of the dataset is yet to be exploited
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