About
77
Publications
15,579
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
2,540
Citations
Introduction
Current institution
Additional affiliations
January 2011 - January 2017
Publications
Publications (77)
Species Distribution Models (SDMs) are frequently applied in ecological research, but geographic transferability of SDMs holds major uncertainties. Here, we assess the cross-realm (sea to lake) geographic transferability of four SDM methods: Generalized Linear Models (GLMs), Generalized Additive Models (GAMs), Boosted Regression Trees (BRTs), and B...
We estimated chlorophyll-a (Chl-a) concentration using various combinations of routine sampling, automatic station measurements, and MERIS satellite images. Our study site was the northern part of the large, shallow, mesotrophic Lake Pyhäjärvi located in southwestern Finland. Various combinations of measurements were interpolated spatiotemporally u...
Seasonal lake ice is sensitive to temperature fluctuations and long-term temperature trends. It is therefore a good indicator of climate warming, which will likely have dramatic impacts on lake ice phenology in northern latitudes. Beside the climate change aspect, lake ice data are important regarding transport and safety issues. In addition, chang...
Colored dissolved organic matter (CDOM) in marine environments impacts primary production due to its absorption effect on the photosynthetically active radiation. In coastal seas, CDOM originates from terrestrial sources predominantly and causes spatial and temporal changing patterns of light absorption which should be considered in marine biogeoch...
The coloured dissolved organic matter (CDOM) concentration is the standard measure of humic substance in natural waters. CDOM measurements by remote sensing is calculated using the absorption coefficient (a) at a certain wavelength (e.g. 440nm). This paper presents a comparison of four machine learning methods for the retrieval of CDOM from remote...
Colored dissolved organic matter (CDOM) in marine environments impacts primary production due to its absorption effect on the photosynthetically active radiation. In coastal seas, CDOM originates from terrestrial sources predominantly and causes spatial and temporal changing patterns of light absorption which should be considered in marine biogeoch...
Executive summary and recommendations The EU Water Framework Directive 1 (WFD) is an ambitious legislation framework to achieve good ecological and chemical status for all surface waters and good quantitative and chemical status for groundwater by 2027. A total of 111,062 surface waterbodies are presently reported on under the Directive, 46% of whi...
We aim a better understanding of the effect of spring-time snow melt on the remotely sensed scene reflectance by using an extensive amount of optical spectral data obtained from an airborne hyperspectral campaign in Northern Finland. We investigate the behaviour of thin snow reflectance for different land cover types, such as open areas, boreal for...
Monitoring temporal changes in phytoplankton dynamics in high latitude lakes is particularly timely for understanding the impacts of warming on aquatic ecosystems. In this study, we analyzed 33-years of high resolution (30 m) Landsat (LT) data for reconstructing seasonal patterns of chlorophyll a (chl a) concentration in four lakes across Finland,...
Triggered by decreases in photoperiod and temperature, evergreen needle-leaved trees in the boreal region downregulate photosynthetic activity and enter dormancy in autumn. Accompanying changes in canopy structure and chlorophyll content are small and precede the cessation of photosynthetic activity. Low solar elevation and cloud cover during this...
This paper describes the methodology for deriving yearly pixel-wise snow melt-off day maps from optical data-based FSC (Fractional Snow Cover) without conducting any interpolation for cloud-obscured pixels or otherwise missing data. The Copernicus CryoLand Pan-European FSC time series for 2001–2016 re-gridded to 0.1° serves as input for the product...
Earth Observation (EO) offers spatially and temporally unique data for generating information required under various environmental regulations for assessing the status of surface waters. These requirements, which are laid down in, for example, European Union directives and the Clean Water Act in the United States, share two core elements with respe...
The colored dissolved organic matter (CDOM) variable is the standard measure of humic substance in waters optics. CDOM is optically characterized by its spectral absorption coefficient, aCDOM at at reference wavelength (e.g., ≈ 440 nm). Retrieval of CDOM is traditionally done using bio-optical models. As an alternative, this paper presents a compar...
The remote-sensing reflectance (Rrs) is in someway an artificial unit, that is constructed in order to contain the spectral colour information of the water body, but to be hardly influenced by the atmosphere above. In ocean colour remotesensing it is the measure to define the optical properties of the water/water constituents. Rrs is the ratio of w...
Recent studies indicate that inland waters play a very important role in the global carbon cycle. Inland water bodies are the main source of drinking water in many parts of the world and important resource for aquaculture and tourism. Neither determining the true role of lakes in the global carbon cycle nor monitoring lake water quality in real tim...
Cyanobacteria form spectacular mass occurrences almost annually in the Baltic Sea. These harmful algal blooms are the most visible consequences of marine eutrophication, driven by a surplus of nutrients from anthropogenic sources and internal processes of the ecosystem. We present a novel Cyanobacterial Bloom Indicator (CyaBI) targeted for the ecos...
Remote sensing studies published up to now show that the performance of empirical (band-ratio type) algorithms in different parts of the Baltic Sea is highly variable. Best performing algorithms are different in the different regions of the Baltic Sea. Moreover, there is indication that the algorithms have to be seasonal as the optical properties o...
The objective of this document is to analyse the usability of GLaSS products for the monitoring and reporting required for the Water Framework Directive. The document starts with an introduction to the directive. The directive monitoring and reporting activities of six member states (Finland, Estonia, Sweden, Germany, The Netherlands and Italy) are...
Boreal lakes often contain high concentrations of colored dissolved organic matter (CDOM). This leads to strong absorption of light especially in the blue and green parts of the spectrum and complicates the use of EO methods. Standard algorithms often fail in these waters and new methods are needed. This document describes the results of five studi...
Citizen observations, environmental data gathered by volunteers without professional observation capabilities, have been extensively used for Finnish water quality monitoring tasks. Recently, mobile smartphones and their digital cameras have enabled more direct measurements of transparency related water quality variables with inexpensive technology...
The European collaborative project GLaSS aims to prepare for the use of the data streams from Sentinel 2 and Sentinel 3. Its focus is on inland waters, since these are considered to be sentinels for land-use- and climate change and need to be monitored closely. One of the objectives of the project is to compare existing water quality algorithms and...
To analyze the applicability of direct insertion of total suspended matter (TSM) concentration field based on turbidity derived from satellite data to numerical simulation, dispersion studies of suspended matter in Lake Säkylän Pyhäjärvi (lake area 154 km(2); mean depth 5.4 m) were conducted using the 3D COHERENS simulation model. To evaluate the p...
We evaluated MERIS spectral inversion processors in the estimation of chlorophyll a (Chl-a), total suspended matter (TSM), absorption of colored dissolved organic matter (aCDOM at 443 nm) and Secchi disk transparency (ZSD) in four lakes located in southern Finland. The lakes represent oligotrophic, mesotrophic and humic (high aCDOM, low TSM) lake t...
The GlaSS consortium has an excellent working knowledge on how to apply MERIS RR and The GlaSS consortium has an excellent working knowledge on how to apply MERIS RR and The GlaSS consortium has an excellent working knowledge on how to apply MERIS RR and The GlaSS consortium has an excellent working knowledge on how to apply MERIS RR and The GlaSS...
Turbidity is an essential parameter for describing water quality by direct and indirect impacts on fish, invertebrates and aquatic plants. Currently, environmental monitoring measurements are carried out with appropriate quality by accredited testing laboratories, but there is also a need for employing the third sector, i.e. citizens and voluntarie...
The scope of this document is to list the technical details of the initial test datasets that have been prepared for further work within the GLaSS project. The initial test data was generated by partners EOMAP and SYKE with input from the other consortium partners, and is available to the GLaSS consortium for further use in WP2, WP3 and WP4. This r...
Water transparency is one indicator of water quality. High water transparency is an indication of clean water. A common method for measuring water transparency is Secchi depth. In this paper, we present an approach to water quality (Secchi depth and turbidity) monitoring using mobile phones and a small device designed for water quality measurements...
Three MERIS Case II water processors included in the BEAM software package were studied for estimating the water quality in the coastal waters of the northern Baltic Sea. The processors, named Case II Regional (C2R), boreal (BOR), and eutrophic (EUT), for the associated lake types, have been developed for different types of coastal or inland (Case...
Finland has over 56 000 lakes (size > 1 ha) many of which are small and have an irregular shape. The Finnish coast line is scattered and contains many bays and peninsulas. The coastal waters are characterized by thousands of small islands. Thus, the water quality of Finnish lakes and coastal waters with moderate resolution satellite sensors such as...
New tools, such as intensive measurements, together with advanced mathematical models, are increasingly needed in water management and environmental research. The new approaches are being developed at Pyhäjärvi, a large (155 km2) lake in southwest Finland. Pyhäjärvi is highly valuable in terms of water supply, fisheries and recreational use. The ec...
The objective of the ESA funded project “Development of MERIS Lake Water Algorithms” (January 2007 – June 2008) was to develop and validate a plug-in module for the BEAM toolbox that allows the retrieval of water quality parameters in lake waters from MERIS imagery. For this purpose, new algorithms were developed, based on the optical properties of...
Remote sensing can provide an alternative to field data sampling in many species-habitat studies. However, its usefulness may depend on the species, habitat studied, spatial resolution and extent. We used a high spatial and spectral remote-sensing image to locate and delineate small amphibian breeding sites in a Mediterranean ecosystem (Doñana Nati...
We investigated the use of Landsat ETM+ images in the monitoring of turbidity, colored dissolved organic matter (CDOM), and Secchi disk transparency (Z(SD)) in lakes of two river basins located in southern Finland. The ETM+ images were acquired in May, June, and September 2002 and were corrected for atmospheric disturbance using the simplified meth...
The effects of an atmospheric correction method for water quality estimation have been studied and validated for Airborne Imaging Spectrometer for Applications (AISA) data. This novel approach uses atmospheric input parameters from a numerical weather prediction model: HIRLAM (High
Resolution Limited Area Model). The atmospheric correction method d...
The concentrations of chlorophyll-a (chl-a), total suspended solids (TSS) and the absorption coefficient of colored dissolved organic matter (aCDOM(400)) are estimated in Case II waters using medium resolution imaging spectrometer (MERIS) satellite (full resolution [FR] level 1b, 300 m resolution) and AISA airborne spectrometer data acquired during...
We present results obtained with data collected during two water quality measurement campaigns: Gulf of Finland (Baltic Sea) on 27 April 2004 and Finnish Lake Lohjanjärvi on 5 August 2004. The concentrations of chlorophyll-a, total suspended solids and the absorption coefficient of colored dissolved organic matter are retrieved using MERIS and airb...
Examples on results obtained in the mapping of water quality related parameters of the Baltic Sea and Finnish lakes using MERIS and other satellite data sources are presented. The results demonstrate that the MERIS instrument is well applicable to be used for operational water quality monitoring in the study region.
The traditional method used in the water quality classification of Finnish lakes includes the collection of water samples from lakes and their analysis in laboratory conditions. The classification is based on statistical analysis of water quality parameter values and on expert opinion. It is possible to acquire similar information by using radiance...
In: Ocean Optics XVII [Conference]. Fremantle, Australia October 25-29, 2004. Program & abstracts. [Fremantle], Office of Naval Research. 19 p. [CD-ROM]. A water quality measurement campaign using multiple sensors was conducted at the coast of Finland (ca-se 2 water), near the city of Helsinki on April 27, 2004. The campaign took place during the s...
In: Ocean Optics XVII [Conference]. Fremantle, Australia October 25-29, 2004. Program & abstracts. [Fremantle], Office of Naval Research. 16 p. [CD-ROM]. Satellite detection of water quality is based on visible and near infrared light intensity measurements. Satellite instruments providing operational near real time optical data usable for this pur...
The spatial distribution of the sum of chlorophyll a and phaeophytin a concentrations (chl-a) under light wind (0-2 m s−1) conditions was studied in two lakes with an AISA airborne imaging spectrometer. Chl-a was interpreted from AISA radiance data using an algorithm based on the near-infrared (700-710 nm) to red (660-665 nm) ratio. The results of...
In this paper empirical algorithms for determining the Secchi disk depth (SDD) are developed and employed using optical (e.g., Landsat TM) and microwave (e.g., ERS-2 SAR) remote sensing data from the Gulf of Finland and the Archipelago Sea. The SDD is an important optical measure of water quality in the study area, where the coastal water considera...
This paper presents chlorophyll-a estimation in coastal waters off the Gulf of Finland using remote optosensors. Concurrent remote optosensor data and in situ measurements of water quality were obtained in the study area. Significant correlations were observed between digital values and chlorophyll-a measurements. The results as a case study show t...
This paper presents the applicability of combined Landsat Thematic Mapper and European Remote Sensing 2 synthetic aperture radar (SAR) data to turbidity, Secchi disk depth, and suspended sediment concentration retrievals in the Gulf of Finland. The results show that the estimated accuracy of these water quality variables using a neural network is m...
This paper presents the detection of sea surface temperature (SST) in the Gulf of Finland using infrared band data of Advanced Very High Resolution Radiometer (AVHRR). AVHRR imagery is evaluated as a main data source for monitoring SST as a measure of upwelling's dynamic. Sea surface effects (SSE), however, cause a temperature difference between th...
Two major water quality parameters can be estimated from optical, thermal infrared (IR), and microwave remotely sensed data. The results show that these data combined can result in better estimated accuracy than the optical retrieval of water quality observations. However, the technique still needs to be refined in future studies. © 2002 Wiley Peri...
Since neural networks have been widely applied to the nonlinear transfer function approximation, we present an empirical neural network algorithm to estimate major parameters in surface waters from combined optical data and microwave data in the Gulf of Finland. Concurrent in situ surface water quality measurements, optical (Landsat TM) data and mi...
Presents the detection of sea surface temperature (SST) in the Gulf of Finland using AVHRR data. AVHRR imagery is evaluated as a main data source for monitoring SST as a measure of upwelling dynamics. Sea surface effects (SSE), however, cause a temperature difference between the sea surface skin and water below the surface. Therefore, SSE are taken...
We study the use of airborne and simulated satellite remote sensing data for classification of three water quality variables: Secchi depth, turbidity, and chlorophyll a. An extensive airborne spectrometer and ground truth data set obtained in four lake water quality measurement campaigns in southern Finland during 1996–1998 was used in the analysis...
This paper presents the application of neural networks to chlorophyll-a and turbidity estimation using AVHRR data over the Gulf of Finland. Chlorophyll-a and turbidity are two major parameters in surface waters used for monitoring coastal water quality in the study. Since the Gulf of Finland is highly affected by the input from the rivers where hav...
Abstract—This study employed water transparent characteristics from the Gulf and archipelago of Finland and the corresponding data sets of optical sensors at the green wavelength band to estimate Secchi disk depth (SDD). The SDD is one major optical measurement of water transparency in the study area,where the coastal waters are dominated by absorp...
—This paper presents the applicability of combined microwave (ERS-2 SAR) and optical (Landsat TM) data for surface water quality retrievals. Three surface water quality parameters such as turbidity, Secchi disk depth (SDD), and suspended sediment concentration (SSC) in the Gulf of Finland are estimated using multivariate approach. The results indic...
INTRODUCTION The spatial and temporal variation of water quality in Finnish lakes and coastal regions is high compared with typical conditions in open sea areas or in large lakes. Both the lake regions and the coastal archipelago consist of small basins or sub-basins isolated from each other by islands and peninsulas. Moreover, Finnish lakes as wel...
The aim of the study was to test the feasibility of the band combination of the TERRA MODIS and ENVISAT MERIS instruments for operational monitoring of lakes and coastal waters in Finland. Also simulated LANDSAT TM data were tested. Satellite bands were simulated using airborne measurements with AISA imaging spectrometer. Semi-empirical algorithms...
The suitability of the AISA airborne imaging spectrometer for monitoring lake water quality was tested in four surveys carried out in southern Finland in 1996-1998. Altogether, 11 lakes were surveyed and the total number of stations with concurrent remote sensing and limnological measurements was 127. The ranges of the water quality variables were:...
A semi-operative approach to retrieve chlorophyll-a concentration from airborne/spaceborne spectrometer observations has been developed and tested using the airborne imaging spectrometer (AISA) data from 11 lakes located in southern Finland. The retrieval approach is empirical and requires nearly simultaneous in situ training data on water quality...
Chlorophyll-a (chl-a) concentration of lake water can be measured with airborne (or spaceborne) optical remote sensing instruments. The rmse obtained here with empirical algorithms and 122 measurement points was 8.9 microg/l (all points used for training and testing). Airborne Imaging Spectrometer for Applications (AISA) was used in four lake water...
The state of surface waters is affected by the quantity and
quality of various suspended and dissolved substances. Loading from
sources such as agriculture, fish farming, industry and municipalities
can cause eutrophication and have other adverse effects on water
quality. In Finland the quality of lake water is traditionally
determined by collectin...
Abstract—This paper,presents the,applicability of combined microwave (ERS-2 SAR) and optical (Landsat TM) data for surface water quality retrievals. Three surface water quality parameters such as turbidity,Secchi disk depth (SDD),and suspended sediment concentration (SSC) in the Gulf of Finland are estimated using multivariate approach. The results...
Remote sensing methods for water quality assessment are discussed.
Secchi depth, turbidity and chlorophyll-a concentration are important
variables. Remote sensing offers some advantages such as good spatial
and temporal coverage and the possibility of measuring many lakes
simultaneously. With remote sensing some variables of lake water quality
coul...
An approach to monitor water quality in lake and coastal regions was described using simulated ENVISAT MERIS data. The feasibility of ENVISAT MERIS observations of water quality was studied by applying an experimental water reflectance data set together with atmospheric modeling. The data enable the simulation of ENVISAT MERIS observations and asse...
Stein, Tammy, I. (ed.). IGARSS '98, Sensing and Managing the Environment. 1998 IEEE International Geoscience and Remote Sensing Symposium Proceedings: Volume V. Seattle, 6-10 July 1998. Sheraton Seattle, Seattle WA, USA. Piscataway, IEEE Publications.P. 2597-2599. IGARSS '98, Sensing and Managing the Environment. 1998 IEEE International Geoscience...
Sea ice is one of the most important components of the Earth's
cryosphere. It modifies the sea-air heat and momentum exchanges, Earth's
radiation budget and affects the global heat and freshwater circulation.
None of the existing satellite instruments can provide detailed
measurements of the sea ice topography and elevation, that is necessary
for t...
Monitoring of environment requires several sources of information to be combined: "General knowledge" of the monitored area, measurement information on it and naturally previously made assessments of the same area. To use earth observation in monitoring of for example lake water quality, traditional images have limited value: How could they be used...
Two field campaigns were used to demonstrate the usefulness of an atmospheric correction method specifically developed for Case 2 waters. The correction method utilizes bio-optical reflectance modeling and principal component analysis. The MODTRAN radiative transfer code simulations were conducted to obtain a statistical database for varying atmosp...
Novel methods are developed to directly assimilate remote sensing data to (a) discrete in situ monitoring data and (b) environmental models. The objective is to investigate the feasibility of the devel-oped methods as they are applied to the operative and semi-operative systems employed in Finland by the Finnish Environment Institute. The developme...
A user survey was conducted among Finnish professional users on their requirements on water quality information, which could be produced with remote sensing. The purpose of the survey was to direct the related research and development to the most interesting applications from the user perspective. The results additionally highlight the requirements...
In this thesis empirical remote sensing methods for estimating water quality in Finnish lakes and coastal areas are developed and tested. The remote sensing instruments used here are Airborne Imaging Spectrometer for Applications (AISA), Medium Resolution Imaging Spectrometer (MERIS) onboard the Envisat-satellite and Moderate Resolution Imaging Spe...
Proceedings of the Fifth International Conference Remote Sensing for Marine and Coastal Environments, 5-7 October, San Diego, California, USA. Volume II. Ann Arbor, ERIM International, Inc. P. II-306-313., 1066-3711 The aim of the present work is to test the suitability of optical remote sensing in quantitative monitoring of coastal waters. An Airb...
Brebbia, C.A.(ed.). Environmental coastal regions. Computational Mechnics Publicatios/WITpress. P. 123-134. Environmental Studies ; 1., 1462-6098 The aim of the present work is to test what parameters of coastal waters could be quantitatively and operatively monotored with passive optical senors from airborne and/or satellite measurements. Airborne...
