Validation of MERIS bio-optical products with in situ data in the turbid Lithuanian Baltic Sea coastal waters

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A Case Study of Alpine Lakes in the Mount Everest Region

Abstract This study presents satellite data and in situ measurements to estimate the concentration of suspended solids in high-altitude and remote lakes of the Himalayas. Suspended particulate matter (SPM) concentrations measured in 13 lakes to the south of Mount Everest (Nepal) in October 2008 and reflectance values of the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) onboard ALOS, acquired a few days after the fieldwork activities concluded, were combined to build a relationship (R2  =  0.921) for mapping SPM concentrations in lakes of the Mount Everest region. The satellite-derived SPM concentrations were compared with in situ data (R2  =  0.924) collected in the same period in 4 additional lakes, located to the north of Mount Everest (Tibet, China). The 13 water samples collected in lakes in Nepal were also used to investigate the absorption coefficients of particles ap(λ) and colored, dissolved organic matter aCDOM(λ), with the aim of parameterizing a bio-optical model. An accurate m..

remote sensing supports the definition of the water quality status of lake omodeo italy

AbstractLake Omodeo is the largest artificial reservoir of Sardinia and its waters are a valuable resource for irrigation, domestic and industrial purposes. Lake Omodeo has serious problems of eutrophication. Since 2007 the local water authority has been undertaken a monitoring program designed to test an integrated methodology based on field measurements and remote sensing. This study illustrates the production of multitemporal spatialised maps of chlorophyll-a concentrations from satellite data acquired from Medium Resolution Imaging Spectrometer (MERIS). The analysis confirmed the eutrophic status of Omodeo. especially between spring and summer (mainly due to cyanobacteria bloom) assessing their dependency on weather conditions and river inputs

Osservazione delle zone marine costiere da dati ottici multi-sensore: il caso studio della foce del Volturno

Questo lavoro s’inserisce nell’ambito del progetto bandiera RITMARE (Ricerca ITaliana per il MARE, 2012-2016, MIUR-CNR) che ha lo scopo di studiare, monitorare, gestire e valorizzare la risorsa marina in Italia. A tale fine il telerilevamento è parte integrante al progetto che, in questo studio, viene applicato alla fascia costiera della foce del Volturno. Lo studio si avvale dell’utilizzo di immagini satellitari (RapidEye (2013) e Landsat-8 OLI (2014)) e aviotrasportate (MIVIS (2011)). A supporto dell’analisi delle immagini sono state acquisite misure in-situ di riflettanza e di concentrazione dei seguenti parametri: clorofilla-a (Chl-a), sedimenti totali sospesi (TSM) e sostanza organica colorata disciolta (CDOM) durante una campagna svoltasi in agosto 2014. I dati telerilevati, geocodificati e co-registrati, sono stati pre-elaborati per correggere gli effetti radiometrici ed atmosferici. Le immagini sono state successivamente elaborate per classificare le acque marino-costiere secondo diversi gradi di complessità ottica e per produrre mappe di concentrazione di Chl-a, TSM e CDOM. In particolare, per la generazione delle mappe è stato applicato un approccio semi-empirico basato su analisi di correlazione dei dati in-situ; in particolare tra valori spettrali di riflettanza (es. rapporti di banda) e le corrispondenti misure di concentrazione di Chl-a, TSM e CDOM. I risultati mostrano un gradiente crescente di complessità ottica delle acque spostandosi dalle zone pelagiche verso le aree costiere. In queste aree l’analisi del dato OLI ha mostrato una variabilità spaziale di Chl-a, TSM e CDOM imputabile ai regimi idrologici del fiume Volturno

Optical remote sensing of lakes: an overview on Lake Maggiore

Optical satellite remote sensing represents an opportunity to integrate traditional methods for assessing water quality of lakes: strengths of remote sensing methods are the good spatial and temporal coverage, the possibility to monitor many lakes simultaneously and the reduced costs. In this work we present an overview of optical remote sensing techniques applied to lake water monitoring. Then, examples of applications focused on lake Maggiore, the second largest lake in Italy are discussed by presenting the temporal trend of chlorophyll-a (chl-a), suspended particulate matter (SPM), coloured dissolved organic matter (CDOM) and the z90 signal depth (the latter indicating the water depth from which 90% of the reflected light comes from) as estimated from the images acquired by the Medium Resolution Imaging Spectrometer (MERIS) in the pelagic area of the lake from 2003 to 2011. Concerning the chl-a trend, the results are in agreement with the concentration values measured during field surveys, confirming the good status of lake Maggiore, although occasional events of water deterioration were observed (e.g., an average increase of chl-a concentration, with a decrease of transparency, as a consequence of an anomalous phytoplankton occurred in summer 2011). A series of MERIS-derived maps (summer period 2011) of the z90 signal are also analysed in order to show the spatial variability of lake waters, which on average were clearer in the central pelagic zones. We expect that the recently launched (e.g., Landsat-8) and the future satellite missions (e.g., Sentinel-3) carrying sensors with improved spectral and spatial resolution are going to lead to a larger use of remote sensing for the assessment and monitoring of water quality parameters, by also allowing further applications (e.g., classification of phytoplankton functional types) to be developed

Evidence from field measurements and satellite imaging of impact of Earth rotation on Lake Iseo chemistry

During an initial field survey in 2012, we observed an unexpected asymmetry of dissolved oxygen distribution between the western and eastern side in northern Lake Iseo. Motivated by this apparent anomaly, we conducted a detailed field investigation, and we used a physical model of the northern part of the lake to understand the in- fluences that might affect the distribution of material in the northern section of the lake. These investigations sug- gested that the Earth's rotation has significant influence on the inflow of the lake's two main tributaries. In order to further crosscheck the validity of these results, we conducted a careful analysis at a synoptic scale using images acquired during thermally unstratified periods by Landsat-8 and Sentinel-2 satellites. We retrieved and post- processed a large set of images, providing conclusive evidence of the role exerted by the Earth's rotation on pol- lutant transport in Lake Iseo and of the greater environmental vulnerability of the north-west shore of this lake, where important settlements are located. Our study confirms the necessity for three-dimensional hydrodynamic models including Coriolis effect in order to effectively predict local impacts of inflows on nearshore water quality of medium-sized elongated lakes of similar scale to Lake Iseo

Synergy of multispectral and multisensors satellite observations to evaluate desert aerosol transport and impact of dust deposition on inland waters: study case of Lake Garda

The capabilities of different Earth Observation multispectral satellites are employed for detecting and tracking of desert dust coming from North Africa toward the Northern Italy area and for evaluating the impact of Saharan dust deposition in inland waters, such as those of Lake Garda. Absorbing and scattering spectral optical properties of desert aerosol in the atmospheric windows in the ultraviolet, visible-near-infrared, and infrared spectral ranges are exploited in the dust retrieval performed by OMI/Aura, MODIS/Terra-Aqua, and SEVIRI/MSG satellite sensors. Therefore, the direct link between dust deposition and increase in phytoplankton abundance has been assessed retrieving MERIS-based chlorophyll-a (chl-a) concentration for the desert dust events. Estimates of the increased chl-a in the lake have been derived with values in concentration from 30% to 170%. AERONET sun-photometer measurements, gravimetric particulate matter samplings

Aquatic biomonitoring: Lessons from the past, challenges for the future

This special issue stems from an increasing awareness on the key contribution made by biometrics and biological indices in the quality classification of aquatic ecosystems. This theme has been the subject of passionate debate during the 13th European Ecological Federation (EEF) and 25th Italian Society of Ecology's (S.It.E.) joined congresses held in Rome in September 2015. In this frame, on the margins of the special symposium named "Biomonitoring: Lessons from the past, challenges for the future", it was launched the idea of a special issue of the Journal of Limnology on the "aquatic" contributions presented at the conference. The present volume mainly reports these studies, enriched by few invited papers. Among the other things, the main message is the need of a better integration between sector knowledges and legislative instruments. This is even truer given the on-going climate change, and the necessity to record rapid changes in ecosystems and to elaborate effective/adaptive responses to them. </p

multitemporal analysis of algal blooms with meris images in a deep meromictic lake

MERIS images (2003-2011) were used to detect algal bloom events in Lake Idro (Northern Italy) applying a semi-empirical algorithm. From the study of an intense phenomenon occurred in late summer 2010, a retrospective analysis of similar events during late summer/ early autumn period was performed. High intra- and inter-annual variability was observed and three additional bloom events were identified on 2003, 2005 and 2008. Hydrological and weather parameters were examined at different temporal intervals (August-October, September-October and monthly from August to October) to investigate the regulating factors of bloom incidence. Rather low temperatures and the persistence of clouds seem t

An Introduction to the Project BLASCO - Blending LAboratory and Satellite techniques for detecting CyanObacteria

Algal blooms can have an impact on health care costs, on the costs associated with the treatment of water intended for human consumption and on the tourism industry. The implementation of early warning systems would reduce these costs and the efforts needed to face and control the harmful effects of an algal bloom. A system for monitoring the quality of the waters, which operates on a large scale and at high frequency, would allow to keep under control the evolution of a bloom. The observation by satellite allows such a monitoring: in particular, the project is focused on the development of techniques for the analysis of satellite images, in order to detect the specific phytoplankton species potentially responsible for bloom formation in lakes. To reach this goal, it is necessary to analyse the spectral response characteristic of cyanobacteria and to develop algorithms to be applied to the analysis of satellite images. New calibration algorithms for the interpretation of satellite images will be obtained in lab experiments, using algal cultures. The developed algorithms will be tested through the analysis of remote sensing images, with particular attention to the bloom events occurring in the lakes of Lombardy and Piedmont. Field data on water optical properties and phytoplankton samples will be also collected. Moreover, different approaches will be applied and compared to quantify the amount of cyanobacteria (HPLC, counting, in vivo fluorimetry, spectroradiometry). Among the main results there will be the creation of a dataset of spectral signatures of some cyanobacteria taxa, as well as the development of calibration curves for the qualitative and quantitative estimation of the blooms. In general, we expect that it will be possible to distinguish, in natural conditions, the spectral signatures of cyanobacteria, even at low concentrations and within mixed populations of phytoplankton