Sampsa Koponen - Academia.edu (original) (raw)
Papers by Sampsa Koponen
Water Science & Technology, 2015
To analyze the applicability of direct insertion of total suspended matter (TSM) concentration fi... more 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 practicality of direct insertion, five cases with different initialization frequencies were conducted: (1) every time, when satellite data were available; (2) every 10 days; (3) 20 days; (4) 30 days; and (5) control run without repeated initialization. To determine the effectiveness of initialization frequency, three methods of comparison were used: simple spatial differences of TSM concentration without biomass in the lake surface layer; averaged spatial differences between initialization data and the forecasts; and time series of TSM concentration and observation data at 1 m depth at the deepest point of the lake. Results showed that direct insertion improves the forecast significantly, even if it is applied less often.
Accreditation and Quality Assurance, 2014
ABSTRACT Turbidity is an essential parameter for describing water quality by direct and indirect ... more ABSTRACT 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 voluntaries in environmental monitoring. A device called “Secchi3000” was developed as a low-cost and simple-to-operate tool so that water quality measurements can also be carried out by non-experts and citizens. The measurement using the new device is simple: The user fills the container with water and places the measurement structure in the container. The user takes a photograph with the camera on a mobile phone through a hole in the lid. The software sends the photograph to a server, which analyses the photographs automatically. Finally, the results are returned to the user’s mobile phone and stored on a database for further analysis. In this study, the measuring system for turbidity measurements in natural waters was validated. Validation included an estimation of the limit of quantification, investigations of the influence of water colour and illumination conditions on turbidity measurement values and the estimation of measurement uncertainty. A comparison of turbidity results obtained with the new device and laboratory instrument in natural water samples was carried out, and turbidity values obtained with different mobile phones were compared. According to the validation results, the new device was appropriate for the measurement of turbidity lower than 7 FNU (Formazine Nephelometric Unit). An algorithm applied for present turbidity calculations is not fully suitable for higher turbidities. For potential routine use, this is not a major problem, since most Finnish natural waters have turbidities lower than 7 FNU. For official monitoring purposes, the limit of the quantification needs to be lower than presently achieved (1.7 FNU). Although the present configuration of the Secchi3000 device is not yet fully suitable for official environmental monitoring, it will already enable the involvement of the third sector in water quality monitoring, and in this way, citizens’ observations could then serve at least as supplementary information for reporting and surveys.
2nd MERIS/AATSR …, 2008
The objective of the ESA funded project "Development of MERIS Lake Water Algorithms" (January 200... more 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 lakes and atmospheric aerosols from different areas of Europe.
Science of the Total Environment, Mar 14, 2001
A semi-operative approach to retrieve chlorophyll-a concentration from airborne/spaceborne spectr... more 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 for the determination of regression coefficients. However, the training data does not have to be collected from every lake under investigation. Instead, the results obtained indicate that reliable estimates on the level of chlorophyll-a (chl-a) for an individual lake can be achieved without employing in situ data representing this specific lake. This enables the estimation of water quality from remotely sensed data for numerous lakes with the aid of reference data only for a few selected lakes representing the region under investigation. In addition, it is shown that the remotely sensed spectrum shape characteristics are highly affected by the trophic and humic state of the lake water.
IGARSS'97. 1997 IEEE International Geoscience and Remote Sensing Symposium Proceedings. Remote Sensing - A Scientific Vision for Sustainable Development, 1997
Sea ice is one of the most important components of the Earth's cryosphere. It modifies the sea-ai... more 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 the study of the sea ice mass balance.
Boreal Environment Research
Zhang, Y., Pulliainen, J., Koponen, S. & Hallikainen, M. 2003: Empirical algorithms for Secchi di... more Zhang, Y., Pulliainen, J., Koponen, S. & Hallikainen, M. 2003: Empirical algorithms for Secchi disk depth using optical and microwave remote sensing data from the Gulf of Finland and the Archipelago Sea. Boreal Env. Res. 8: 251-261. ISSN 1239-6095 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 considerably attenuates light because of the presence of phytoplankton, suspended matter and yellow substance. The results show that the accuracy of SDD estimation using a neural network-based method is much higher than that of a semiempirical or multivariate approach. On the other hand, the additional use of SAR data only slightly improved SDD estimation when compared with the use of TM data only. Although the improvement is marginal, the results suggest that there may be some SAR backscattering signatures correlated to SDD measurements in the area. However, such a small improvement is not very helpful for the practical estimation of SDD. In the future, the technique of using combined optical and microwave data still needs to be refi ned using, e.g., MERIS and ASAR data.
... Fig.8. Correlation between measured and estimated concentrations of total phosphorus. ... An ... more ... Fig.8. Correlation between measured and estimated concentrations of total phosphorus. ... An idea also rises that the turbidity measurements are complicated in case of waters where turbidity is higher than 10 ... Seasonal differences in remote sensing algorithms are also seen in Fig ...
IGARSS '98. Sensing and Managing the Environment. 1998 IEEE International Geoscience and Remote Sensing. Symposium Proceedings. (Cat. No.98CH36174), 1998
... Fig.8. Correlation between measured and estimated concentrations of total phosphorus. ... An ... more ... Fig.8. Correlation between measured and estimated concentrations of total phosphorus. ... An idea also rises that the turbidity measurements are complicated in case of waters where turbidity is higher than 10 ... Seasonal differences in remote sensing algorithms are also seen in Fig ...
In: Ocean Optics XVII [Conference]. Fremantle, Australia October 25-29, 2004. Program & abstracts... more 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 spring bloom dominated by dinoflagellates and diatoms; hence the spatial variations of water quality parameters were large within the measurement area. The data collected during the campaign consist of ground truth data, and airborne and spaceborne remote sensing data. The ground truth data include a 28 km long transect measured with a flow-through measurement system installed on a boat (5103 data points), ten water sam-ples analysed in a laboratory, and five Secchi depth measurements (range 0.6-3.5 m). The flow-through system measures temperature, conductivity, and total absorption and scattering coefficients at 9 wave-lengths (between 412...
Novel methods are developed to directly assimilate remote sensing data to (a) discrete in situ mo... more 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 development work is focused on (a) water quality monitoring and pre-diction and (b) hydrological monitoring and forecasting. The investigated applications include the monitor-ing and prediction of snowmelt, runoff and the level of soil moisture/evapotranspiration. The developed as-similation procedures take into account the accuracy characteristics of physical models (or those of in situ data), the accuracy of remote sensing data and models, and additionally, the propagation of errors with time. The first test results of satellite data assimilation to dynamical environmental models were obtained in snowmelt monitoring/discharge forecasting. These r...
Two field campaigns were used to demonstrate the usefulness of an atmospheric correction method s... more 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 atmospheric situations. Bio-optical reflectance model takes into account the water quality and it's influence on the detected reflectance. Both field campaigns represent high concentrations of optically active substances such as chlorophyll-a, total suspended sediment and humus. The first field campaign was held at a coastal site of Finland, on the Gulf of Finland, while the other field campaign represents a Finnish lake water area. On both campaigns MERIS satellite instrument and airborne spectrometer data were available.
Remote Sensing of Environment, 2002
Since neural networks have been widely applied to the nonlinear transfer function approximation, ... more 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 microwave (ERS-2 SAR) data were obtained in selected locations in August 1997. The TM and ERS-2 SAR data from locations of water samples were extracted and digital data were examined in numerous transformations. Although significant correlations were observed between digital data and chlorophyll-a (Chl-a), suspended sediment concentration (SSC), turbidity (Turb), and Secchi disk depth (SDD), application of neural networks appears to yield a superior performance in modeling transfer functions in this study area. Here, an empirical neural network algorithm is applied to estimate the transfer functions between the major characteristics of surface waters and the satellite optical and microwave data. The results show that the estimation accuracy for major characteristics of surface waters using the neural network is much better than those from regression analysis. The results also indicate that microwave data can assist to improve the estimation of these characteristics. Therefore, it may be possible to develop surface water quality algorithms in which microwave data are used as supplementary data to optical observations. However, this improvement of optical data retrieval algorithm is limited in this case study. The technique still needs to be refined in detail in order to detect differences within the typical range of these water quality parameters found in the area under study. D 2002 Elsevier Science Inc. All rights reserved. 0034-4257/02/$ -see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 3 4 -4 2 5 7 ( 0 2 ) 0 0 0 0 9 -3
Ocean Optics: Remote Sensing and Underwater Imaging, 2002
ABSTRACT
Water Science & Technology, 2015
To analyze the applicability of direct insertion of total suspended matter (TSM) concentration fi... more 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 practicality of direct insertion, five cases with different initialization frequencies were conducted: (1) every time, when satellite data were available; (2) every 10 days; (3) 20 days; (4) 30 days; and (5) control run without repeated initialization. To determine the effectiveness of initialization frequency, three methods of comparison were used: simple spatial differences of TSM concentration without biomass in the lake surface layer; averaged spatial differences between initialization data and the forecasts; and time series of TSM concentration and observation data at 1 m depth at the deepest point of the lake. Results showed that direct insertion improves the forecast significantly, even if it is applied less often.
Accreditation and Quality Assurance, 2014
ABSTRACT Turbidity is an essential parameter for describing water quality by direct and indirect ... more ABSTRACT 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 voluntaries in environmental monitoring. A device called “Secchi3000” was developed as a low-cost and simple-to-operate tool so that water quality measurements can also be carried out by non-experts and citizens. The measurement using the new device is simple: The user fills the container with water and places the measurement structure in the container. The user takes a photograph with the camera on a mobile phone through a hole in the lid. The software sends the photograph to a server, which analyses the photographs automatically. Finally, the results are returned to the user’s mobile phone and stored on a database for further analysis. In this study, the measuring system for turbidity measurements in natural waters was validated. Validation included an estimation of the limit of quantification, investigations of the influence of water colour and illumination conditions on turbidity measurement values and the estimation of measurement uncertainty. A comparison of turbidity results obtained with the new device and laboratory instrument in natural water samples was carried out, and turbidity values obtained with different mobile phones were compared. According to the validation results, the new device was appropriate for the measurement of turbidity lower than 7 FNU (Formazine Nephelometric Unit). An algorithm applied for present turbidity calculations is not fully suitable for higher turbidities. For potential routine use, this is not a major problem, since most Finnish natural waters have turbidities lower than 7 FNU. For official monitoring purposes, the limit of the quantification needs to be lower than presently achieved (1.7 FNU). Although the present configuration of the Secchi3000 device is not yet fully suitable for official environmental monitoring, it will already enable the involvement of the third sector in water quality monitoring, and in this way, citizens’ observations could then serve at least as supplementary information for reporting and surveys.
Water Science & Technology, 2015
To analyze the applicability of direct insertion of total suspended matter (TSM) concentration fi... more 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 practicality of direct insertion, five cases with different initialization frequencies were conducted: (1) every time, when satellite data were available; (2) every 10 days; (3) 20 days; (4) 30 days; and (5) control run without repeated initialization. To determine the effectiveness of initialization frequency, three methods of comparison were used: simple spatial differences of TSM concentration without biomass in the lake surface layer; averaged spatial differences between initialization data and the forecasts; and time series of TSM concentration and observation data at 1 m depth at the deepest point of the lake. Results showed that direct insertion improves the forecast significantly, even if it is applied less often.
Accreditation and Quality Assurance, 2014
ABSTRACT Turbidity is an essential parameter for describing water quality by direct and indirect ... more ABSTRACT 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 voluntaries in environmental monitoring. A device called “Secchi3000” was developed as a low-cost and simple-to-operate tool so that water quality measurements can also be carried out by non-experts and citizens. The measurement using the new device is simple: The user fills the container with water and places the measurement structure in the container. The user takes a photograph with the camera on a mobile phone through a hole in the lid. The software sends the photograph to a server, which analyses the photographs automatically. Finally, the results are returned to the user’s mobile phone and stored on a database for further analysis. In this study, the measuring system for turbidity measurements in natural waters was validated. Validation included an estimation of the limit of quantification, investigations of the influence of water colour and illumination conditions on turbidity measurement values and the estimation of measurement uncertainty. A comparison of turbidity results obtained with the new device and laboratory instrument in natural water samples was carried out, and turbidity values obtained with different mobile phones were compared. According to the validation results, the new device was appropriate for the measurement of turbidity lower than 7 FNU (Formazine Nephelometric Unit). An algorithm applied for present turbidity calculations is not fully suitable for higher turbidities. For potential routine use, this is not a major problem, since most Finnish natural waters have turbidities lower than 7 FNU. For official monitoring purposes, the limit of the quantification needs to be lower than presently achieved (1.7 FNU). Although the present configuration of the Secchi3000 device is not yet fully suitable for official environmental monitoring, it will already enable the involvement of the third sector in water quality monitoring, and in this way, citizens’ observations could then serve at least as supplementary information for reporting and surveys.
2nd MERIS/AATSR …, 2008
The objective of the ESA funded project "Development of MERIS Lake Water Algorithms" (January 200... more 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 lakes and atmospheric aerosols from different areas of Europe.
Science of the Total Environment, Mar 14, 2001
A semi-operative approach to retrieve chlorophyll-a concentration from airborne/spaceborne spectr... more 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 for the determination of regression coefficients. However, the training data does not have to be collected from every lake under investigation. Instead, the results obtained indicate that reliable estimates on the level of chlorophyll-a (chl-a) for an individual lake can be achieved without employing in situ data representing this specific lake. This enables the estimation of water quality from remotely sensed data for numerous lakes with the aid of reference data only for a few selected lakes representing the region under investigation. In addition, it is shown that the remotely sensed spectrum shape characteristics are highly affected by the trophic and humic state of the lake water.
IGARSS'97. 1997 IEEE International Geoscience and Remote Sensing Symposium Proceedings. Remote Sensing - A Scientific Vision for Sustainable Development, 1997
Sea ice is one of the most important components of the Earth's cryosphere. It modifies the sea-ai... more 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 the study of the sea ice mass balance.
Boreal Environment Research
Zhang, Y., Pulliainen, J., Koponen, S. & Hallikainen, M. 2003: Empirical algorithms for Secchi di... more Zhang, Y., Pulliainen, J., Koponen, S. & Hallikainen, M. 2003: Empirical algorithms for Secchi disk depth using optical and microwave remote sensing data from the Gulf of Finland and the Archipelago Sea. Boreal Env. Res. 8: 251-261. ISSN 1239-6095 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 considerably attenuates light because of the presence of phytoplankton, suspended matter and yellow substance. The results show that the accuracy of SDD estimation using a neural network-based method is much higher than that of a semiempirical or multivariate approach. On the other hand, the additional use of SAR data only slightly improved SDD estimation when compared with the use of TM data only. Although the improvement is marginal, the results suggest that there may be some SAR backscattering signatures correlated to SDD measurements in the area. However, such a small improvement is not very helpful for the practical estimation of SDD. In the future, the technique of using combined optical and microwave data still needs to be refi ned using, e.g., MERIS and ASAR data.
... Fig.8. Correlation between measured and estimated concentrations of total phosphorus. ... An ... more ... Fig.8. Correlation between measured and estimated concentrations of total phosphorus. ... An idea also rises that the turbidity measurements are complicated in case of waters where turbidity is higher than 10 ... Seasonal differences in remote sensing algorithms are also seen in Fig ...
IGARSS '98. Sensing and Managing the Environment. 1998 IEEE International Geoscience and Remote Sensing. Symposium Proceedings. (Cat. No.98CH36174), 1998
... Fig.8. Correlation between measured and estimated concentrations of total phosphorus. ... An ... more ... Fig.8. Correlation between measured and estimated concentrations of total phosphorus. ... An idea also rises that the turbidity measurements are complicated in case of waters where turbidity is higher than 10 ... Seasonal differences in remote sensing algorithms are also seen in Fig ...
In: Ocean Optics XVII [Conference]. Fremantle, Australia October 25-29, 2004. Program & abstracts... more 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 spring bloom dominated by dinoflagellates and diatoms; hence the spatial variations of water quality parameters were large within the measurement area. The data collected during the campaign consist of ground truth data, and airborne and spaceborne remote sensing data. The ground truth data include a 28 km long transect measured with a flow-through measurement system installed on a boat (5103 data points), ten water sam-ples analysed in a laboratory, and five Secchi depth measurements (range 0.6-3.5 m). The flow-through system measures temperature, conductivity, and total absorption and scattering coefficients at 9 wave-lengths (between 412...
Novel methods are developed to directly assimilate remote sensing data to (a) discrete in situ mo... more 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 development work is focused on (a) water quality monitoring and pre-diction and (b) hydrological monitoring and forecasting. The investigated applications include the monitor-ing and prediction of snowmelt, runoff and the level of soil moisture/evapotranspiration. The developed as-similation procedures take into account the accuracy characteristics of physical models (or those of in situ data), the accuracy of remote sensing data and models, and additionally, the propagation of errors with time. The first test results of satellite data assimilation to dynamical environmental models were obtained in snowmelt monitoring/discharge forecasting. These r...
Two field campaigns were used to demonstrate the usefulness of an atmospheric correction method s... more 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 atmospheric situations. Bio-optical reflectance model takes into account the water quality and it's influence on the detected reflectance. Both field campaigns represent high concentrations of optically active substances such as chlorophyll-a, total suspended sediment and humus. The first field campaign was held at a coastal site of Finland, on the Gulf of Finland, while the other field campaign represents a Finnish lake water area. On both campaigns MERIS satellite instrument and airborne spectrometer data were available.
Remote Sensing of Environment, 2002
Since neural networks have been widely applied to the nonlinear transfer function approximation, ... more 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 microwave (ERS-2 SAR) data were obtained in selected locations in August 1997. The TM and ERS-2 SAR data from locations of water samples were extracted and digital data were examined in numerous transformations. Although significant correlations were observed between digital data and chlorophyll-a (Chl-a), suspended sediment concentration (SSC), turbidity (Turb), and Secchi disk depth (SDD), application of neural networks appears to yield a superior performance in modeling transfer functions in this study area. Here, an empirical neural network algorithm is applied to estimate the transfer functions between the major characteristics of surface waters and the satellite optical and microwave data. The results show that the estimation accuracy for major characteristics of surface waters using the neural network is much better than those from regression analysis. The results also indicate that microwave data can assist to improve the estimation of these characteristics. Therefore, it may be possible to develop surface water quality algorithms in which microwave data are used as supplementary data to optical observations. However, this improvement of optical data retrieval algorithm is limited in this case study. The technique still needs to be refined in detail in order to detect differences within the typical range of these water quality parameters found in the area under study. D 2002 Elsevier Science Inc. All rights reserved. 0034-4257/02/$ -see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 3 4 -4 2 5 7 ( 0 2 ) 0 0 0 0 9 -3
Ocean Optics: Remote Sensing and Underwater Imaging, 2002
ABSTRACT
Water Science & Technology, 2015
To analyze the applicability of direct insertion of total suspended matter (TSM) concentration fi... more 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 practicality of direct insertion, five cases with different initialization frequencies were conducted: (1) every time, when satellite data were available; (2) every 10 days; (3) 20 days; (4) 30 days; and (5) control run without repeated initialization. To determine the effectiveness of initialization frequency, three methods of comparison were used: simple spatial differences of TSM concentration without biomass in the lake surface layer; averaged spatial differences between initialization data and the forecasts; and time series of TSM concentration and observation data at 1 m depth at the deepest point of the lake. Results showed that direct insertion improves the forecast significantly, even if it is applied less often.
Accreditation and Quality Assurance, 2014
ABSTRACT Turbidity is an essential parameter for describing water quality by direct and indirect ... more ABSTRACT 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 voluntaries in environmental monitoring. A device called “Secchi3000” was developed as a low-cost and simple-to-operate tool so that water quality measurements can also be carried out by non-experts and citizens. The measurement using the new device is simple: The user fills the container with water and places the measurement structure in the container. The user takes a photograph with the camera on a mobile phone through a hole in the lid. The software sends the photograph to a server, which analyses the photographs automatically. Finally, the results are returned to the user’s mobile phone and stored on a database for further analysis. In this study, the measuring system for turbidity measurements in natural waters was validated. Validation included an estimation of the limit of quantification, investigations of the influence of water colour and illumination conditions on turbidity measurement values and the estimation of measurement uncertainty. A comparison of turbidity results obtained with the new device and laboratory instrument in natural water samples was carried out, and turbidity values obtained with different mobile phones were compared. According to the validation results, the new device was appropriate for the measurement of turbidity lower than 7 FNU (Formazine Nephelometric Unit). An algorithm applied for present turbidity calculations is not fully suitable for higher turbidities. For potential routine use, this is not a major problem, since most Finnish natural waters have turbidities lower than 7 FNU. For official monitoring purposes, the limit of the quantification needs to be lower than presently achieved (1.7 FNU). Although the present configuration of the Secchi3000 device is not yet fully suitable for official environmental monitoring, it will already enable the involvement of the third sector in water quality monitoring, and in this way, citizens’ observations could then serve at least as supplementary information for reporting and surveys.