Abstract
A new era of spaceborne hyperspectral imaging has just begun with the recent availability of data from PRISMA (PRecursore IperSpettrale della Missione Applicativa) launched by the Italian space agency (ASI). There has been pre-launch optimism that the wealth of spectral information offered by PRISMA can contribute to a variety of aquatic science and management applications. Here, we examine the potential of PRISMA level 2D images in retrieving standard water quality parameters, including total suspended matter (TSM), chlorophyll-a (Chl-a), and colored dissolved organic matter (CDOM) in a turbid lake (Lake Trasimeno, Italy). We perform consistency analyses among the aquatic products (remote sensing reflectance (Rrs) and constituents) derived from PRISMA and those from Sentinel-2. The consistency analyses are expanded to synthesized Sentinel-2 data as well. By spectral downsampling of the PRISMA images, we better isolate the impact of spectral resolution in retrieving the constituents. The retrieval of constituents from both PRISMA and Sentinel-2 images is built upon inverting the radiative transfer model implemented in the Water Color Simulator (WASI) processor. The inversion involves a parameter (gdd) to compensate for atmospheric and sun-glint artifacts. A strong agreement is indicated for the cross-sensor comparison of Rrs products at different wavelengths (average R ≈ 0.87). However, the Rrs of PRISMA at shorter wavelengths (<500 nm) is slightly overestimated with respect to Sentinel-2. This is in line with the estimates of gdd through the inversion that suggests an underestimated atmospheric path radiance of PRISMA level 2D products compared to the atmospherically corrected Sentinel-2 data. The results indicate the high potential of PRISMA level 2D imagery in mapping water quality parameters in Lake Trasimeno. The PRISMA-based retrievals agree well with those of Sentinel-2, particularly for TSM.
Highlights
The applications of Earth observation data are becoming more and more widespread in the monitoring and management of aquatic systems [1,2]
We examined a physics-based approach for inversion of water quality parameters from the newly available hyperspectral PRecursore IperSpettrale della Missione Applicativa (PRISMA) imagery at a turbid lake
We conducted preliminary analyses on the quality and consistency of Rrs and water quality products derived from PRISMA level 2D compared to those derived from Sentinel-2 images
Summary
The applications of Earth observation data are becoming more and more widespread in the monitoring and management of aquatic systems [1,2]. Having accurate and timely information on biophysical parameters such as water quality and habitat indicators is crucial for sustainable management of a variety of aquatic ecosystem services, such as urban and agricultural water supply, fisheries, tourism, and recreation activities [4,5]. This kind of information contributes to a better understanding of processes such as eutrophication and harmful algal blooms, carbon cycle, as well as climate change impacts [6,7,8]. Spatiotemporal monitoring of CDOM can contribute to studies of carbon cycle, aquatic ecology, climate change, and water treatment projects [14,15,16]
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