scholarly journals Using a two-layered sphere model to investigate the impact of gas vacuoles on the inherent optical properties of <i>M. aeruginosa</i>

2013 ◽  
Vol 10 (6) ◽  
pp. 10531-10579 ◽  
Author(s):  
M. W. Matthews ◽  
S. Bernard
Keyword(s):  
Optical Properties ◽  
Cyanobacterial Blooms ◽  
Transfer Model ◽  
Shell Layer ◽  
Sphere Model ◽  
Homogeneous Population ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Gas Vacuoles ◽  
The Impact

Abstract. A two-layered sphere model is used to investigate the impact of gas vacuoles on the inherent optical properties (IOPs) of the cyanophyte Microcystis aeruginosa. Enclosing a vacuole–like particle within a chromatoplasm shell layer significantly altered spectral scattering and increased backscattering. The two-layered sphere model reproduced features in the spectral attenuation and volume scattering function (VSF) that have previously been attributed to gas vacuoles. This suggests the model is good at least as a first approximation for investigating how gas vacuoles alter the IOPs. The central value of the real refractive index, 1+ ε, for the shell layer was determined using a radiative transfer model and measured remote sensing reflectance, Rrs, and IOP data. For a cell with 50% vacuole volume, the mean 1+ ε value for the shell layer was 1.12. The corresponding chl a specific phytoplankton backscattering coefficient, bbφ&amp;ast;, ranged between 3.9 × 10−3 and 7.2 × 10−3 m2 mg−1 at 510 nm. This agrees closely with in situ particulate backscattering measurements and values reported elsewhere. Rrs simulated for a population of vacuolate cells was greatly enlarged relative to a homogeneous population. Empirical algorithms based on Rrs were derived for estimating chl a in eutrophic/hypertrophic waters dominated by M. aeruginosa. The study confirms that gas vacuoles cause significant increase in backscattering and are responsible for the high Rrs values observed in buoyant cyanobacterial blooms. Gas vacuoles are therefore one of the most important bio-optical substructures influencing the IOPs in phytoplankton.

scholarly journals Using a two-layered sphere model to investigate the impact of gas vacuoles on the inherent optical properties of <i>Microcystis aeruginosa</i>

2013 ◽  
Vol 10 (12) ◽  
pp. 8139-8157 ◽  
Author(s):  
M. W. Matthews ◽  
S. Bernard
Keyword(s):  
Optical Properties ◽  
Microcystis Aeruginosa ◽  
Cyanobacterial Blooms ◽  
Shell Layer ◽  
Sphere Model ◽  
Homogeneous Population ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Gas Vacuoles ◽  
The Impact

Abstract. A two-layered sphere model is used to investigate the impact of gas vacuoles on the inherent optical properties (IOPs) of the cyanophyte Microcystis aeruginosa. Enclosing a vacuole-like particle within a chromatoplasm shell layer significantly altered spectral scattering and increased backscattering. The two-layered sphere model reproduced features in the spectral attenuation and volume scattering function (VSF) that have previously been attributed to gas vacuoles. This suggests the model is good at least as a first approximation for investigating how gas vacuoles alter the IOPs. Measured Rrs was used to provide a range of values for the central value of the real refractive index, 1 + ε, for the shell layer using measured IOPs and a radiative transfer model. Sufficient optical closure was obtained for 1 + ε between 1.1 and 1.14, which had corresponding Chl a-specific phytoplankton backscattering, bbφ*, between 3.9 and 7.2 × 10−3 m2 mg−1 at 510 nm. The bbφ* values are in close agreement with the literature and in situ particulate backscattering measurements. Rrs simulated for a population of vacuolate cells was greatly enlarged relative to a homogeneous population. A sensitivity analysis of empirical algorithms for estimating Chl a in eutrophic/hypertrophic waters suggests these are robust under variable constituent concentrations and likely to be species-sensitive. The study confirms that gas vacuoles cause significant increase in backscattering and are responsible for the high Rrs values observed in buoyant cyanobacterial blooms. Gas vacuoles are therefore one of the most important bio-optical substructures influencing the IOPs in phytoplankton.

scholarly journals The impact of atmospheric mineral aerosol deposition on the albedo of snow and sea ice: are snow and sea ice optical properties more important than mineral aerosol optical properties?

2015 ◽  
Vol 15 (16) ◽  
pp. 23131-23172
Author(s):  
M. L. Lamare ◽  
J. Lee-Taylor ◽  
M. D. King
Keyword(s):  
Optical Properties ◽  
Sea Ice ◽  
Atmospheric Aerosols ◽  
Aerosol Deposition ◽  
Shortwave Radiation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Polar Regions ◽  
Polar Snow ◽  
The Impact

Abstract. Knowledge of the albedo of polar regions is crucial for understanding a range of climatic processes that have an impact on a global scale. Light absorbing impurities in atmospheric aerosols deposited on snow and sea ice by aeolian transport absorb solar radiation, reducing albedo. Here, the effects of five mineral aerosol deposits reducing the albedo of polar snow and sea ice are considered. Calculations employing a coupled atmospheric and snow/sea ice radiative-transfer model (TUV-snow) show that the effects of mineral aerosol deposits is strongly dependent on the snow or sea ice type rather than the differences between the aerosol optical characteristics. The change in albedo between five different mineral aerosol deposits with refractive indices varying by a factor of 2 reaches a maximum of 0.0788, whereas the difference between cold polar snow and melting sea ice is 0.8893 for the same mineral loading. Surprisingly, the thickness of a surface layer of snow or sea ice loaded with the same mass-ratio of mineral dust has little effect on albedo. On the contrary, multiple layers of mineral aerosols deposited during episodic events evenly distributed play a similar role in the surface albedo of snow as a loading distributed throughout, even when the layers are further apart. The impact of mineral aerosol deposits is much larger on melting sea ice than on other types of snow and sea ice. Therefore, the higher input of shortwave radiation during the summer melt cycle associated with melting sea ice accelerates the melt process.

scholarly journals DERIVING INHERENT OPTICAL PROPERTIES FROM MERIS IMAGERY AND IN SITU MEASUREMENT USING QUASI-ANALYTICAL ALGORITHM

2014 ◽  
Vol 10 (1) ◽  
Author(s):  
Wiwin Ambarwulan ◽  
Widiatmaka ◽  
Syarif Budhiman
Keyword(s):  
Optical Properties ◽  
Optical Measurement ◽  
In Situ Measurements ◽  
In Situ Measurement ◽  
Coefficient Of Determination ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Inherent Optical Properties ◽  
Analytical Algorithm

The  paper  describes inherent optical properties  (IOP)  of  the  Berau  coastal  waters  derived from in  situ measurements  and Medium  Resolution  Imaging  Spectrometer  (MERIS) satellite  data. Field  measurements  of optical  water,  total  suspended  matter  (TSM), and  chlorophyll-a  (Chl-a) concentrations were carried out during the dry season of 2007. During this periode, only four MERISdata were  coincided with in  situ measurements on 31 August  2007. The MERIS  top-of-atmosphere radiances were atmospherically corrected using the MODTRAN radiative transfer model. The in situ optical  measurement  have  been  processed  into apparent optical properties  (AOP) and sub  surface irradiance. The remote sensing reflectance of in situ measurement as well as MERIS data were inverted into  the  IOP  using quasi-analytical algorithm  (QAA).  The  result  indicated  that coefficient  of determination (R 2) of backscattering coefficients of suspended particles (bbp) increased with increasing wavelength,  however  the  R2 of  absorption  spectra  of  phytoplankton  (aph)  decreased  with  increasing wavelength.

scholarly journals Water Quality Retrieval from PRISMA Hyperspectral Images: First Experience in a Turbid Lake and Comparison with Sentinel-2

2020 ◽  
Vol 12 (23) ◽  
pp. 3984
Author(s):  
Milad Niroumand-Jadidi ◽  
Francesca Bovolo ◽  
Lorenzo Bruzzone
Keyword(s):  
Water Quality ◽  
Quality Parameters ◽  
Water Quality Parameters ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Chl A ◽  
Aquatic Science ◽  
Turbid Lake ◽  
The Impact ◽  
Sentinel 2

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.

scholarly journals Significant contribution of large particles to optical backscattering in the open ocean

2009 ◽  
Vol 6 (6) ◽  
pp. 947-967 ◽  
Author(s):  
G. Dall'Olmo ◽  
T. K. Westberry ◽  
M. J. Behrenfeld ◽  
E. Boss ◽  
W. H. Slade
Keyword(s):  
Optical Properties ◽  
Phytoplankton Biomass ◽  
Field Studies ◽  
Open Ocean ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Large Particles ◽  
Similar Information ◽  
The Relationship ◽  
Beam Attenuation Coefficient

Abstract. The light scattering properties of oceanic particles have been suggested as an alternative index of phytoplankton biomass than chlorophyll-a concentration (chl-a), with the benefit of being less sensitive to physiological forcings (e.g., light and nutrients) that alter the intracellular pigment concentrations. The drawback of particulate scattering is that it is not unique to phytoplankton. Nevertheless, field studies have demonstrated that, to first order, the particulate beam-attenuation coefficient (cp) can track phytoplankton biomass. The relationship between cp and the particulate backscattering coefficient (bbp), a property retrievable from space, has not been fully evaluated, largely due to a lack of open-ocean field observations. Here, we present extensive data on inherent optical properties from the Equatorial Pacific surface waters and demonstrate a remarkable coherence in bbp and cp. Coincident measurements of particle size distributions (PSDs) and optical properties of size-fractionated samples indicate that this covariance is due to both the conserved nature of the PSD and a greater contribution of phytoplankton-sized particles to bbp than theoretically predicted. These findings suggest that satellite-derived bbpcould provide similar information on phytoplankton biomass in the open ocean as cp.

scholarly journals On the Improvement of COAMPS Weather Forecasts Using an Advanced Radiative Transfer Model

2009 ◽  
Vol 24 (1) ◽  
pp. 286-306 ◽  
Author(s):  
Ming Liu ◽  
Jason E. Nachamkin ◽  
Douglas L. Westphal
Keyword(s):  
Optical Properties ◽  
Radiative Transfer ◽  
Liquid Water ◽  
Atmospheric Stability ◽  
Sensitivity Study ◽  
Radiative Heating ◽  
Radiative Transfer Model ◽  
Surface Model ◽  
Transfer Model ◽  
The Impact

Abstract Fu–Liou’s delta-four-stream (with a two-stream option) radiative transfer model has been implemented in the U.S. Navy’s Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS)1 to calculate solar and thermal infrared fluxes in 6 shortwave and 12 longwave bands. The model performance is evaluated at high resolution for clear-sky and overcast conditions against the observations from the Southern Great Plains of the Atmospheric Radiation Measurement Program. In both cases, use of the Fu–Liou model provides significant improvement over the operational implementation of the standard Harshvardhan radiation parameterization in both shortwave and longwave fluxes. A sensitivity study of radiative flux on clouds reveals that the choices of cloud effective radius schemes for ice and liquid water are critical to the flux calculation due to the effects on cloud optical properties. The sensitivity study guides the selection of optimal cloud optical properties for use in the Fu–Liou parameterization as implemented in COAMPS. The new model is then used to produce 3-day forecasts over the continental United States for a winter and a summer month. The verifications of parallel runs using the standard and new parameterizations show that Fu–Liou dramatically reduces the model’s systematic warm bias in the upper troposphere in both winter and summer. The resultant cooling modifies the atmospheric stability and moisture transport, resulting in a significant reduction in the upper-tropospheric wet bias. Overall ice and liquid water paths are also reduced. At the surface, Fu–Liou reduces the negative temperature and sea level pressure biases by providing more accurate radiative heating rates to the land surface model. The error reductions increase with forecast length as the impact of improved radiative fluxes accumulates over time. A combination of the two- and four-stream options results in major computational efficiency gains with minimal loss in accuracy.

scholarly journals The impact of atmospheric mineral aerosol deposition on the albedo of snow & sea ice: are snow and sea ice optical properties more important than mineral aerosol optical properties?

2016 ◽  
Vol 16 (2) ◽  
pp. 843-860 ◽  
Author(s):  
M. L. Lamare ◽  
J. Lee-Taylor ◽  
M. D. King
Keyword(s):  
Optical Properties ◽  
Sea Ice ◽  
Atmospheric Aerosols ◽  
Shortwave Radiation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Polar Regions ◽  
Mass Ratio ◽  
Polar Snow ◽  
The Impact

Abstract. Knowledge of the albedo of polar regions is crucial for understanding a range of climatic processes that have an impact on a global scale. Light-absorbing impurities in atmospheric aerosols deposited on snow and sea ice by aeolian transport absorb solar radiation, reducing albedo. Here, the effects of five mineral aerosol deposits reducing the albedo of polar snow and sea ice are considered. Calculations employing a coupled atmospheric and snow/sea ice radiative-transfer model (TUV-snow) show that the effects of mineral aerosol deposits are strongly dependent on the snow or sea ice type rather than the differences between the aerosol optical characteristics. The change in albedo between five different mineral aerosol deposits with refractive indices varying by a factor of 2 reaches a maximum of 0.0788, whereas the difference between cold polar snow and melting sea ice is 0.8893 for the same mineral loading. Surprisingly, the thickness of a surface layer of snow or sea ice loaded with the same mass ratio of mineral dust has little effect on albedo. On the contrary, the surface albedo of two snowpacks of equal depth, containing the same mineral aerosol mass ratio, is similar, whether the loading is uniformly distributed or concentrated in multiple layers, regardless of their position or spacing. The impact of mineral aerosol deposits is much larger on melting sea ice than on other types of snow and sea ice. Therefore, the higher input of shortwave radiation during the summer melt cycle associated with melting sea ice accelerates the melt process.

scholarly journals Direct contribution of phytoplankton-sized particles to optical backscattering in the open ocean

2009 ◽  
Vol 6 (1) ◽  
pp. 291-340 ◽  
Author(s):  
G. Dall'Olmo ◽  
T. K. Westberry ◽  
M. J. Behrenfeld ◽  
E. Boss ◽  
W. H. Slade
Keyword(s):  
Optical Properties ◽  
Surface Waters ◽  
Phytoplankton Biomass ◽  
Field Studies ◽  
Open Ocean ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Similar Information ◽  
The Relationship ◽  
Beam Attenuation Coefficient

Abstract. Light scattering properties of oceanic particles have been suggested as an alternative index of phytoplankton biomass than chlorophyll-a concentration (chl-a), with the benefit of being less sensitive to physiological forcings (e.g., light and nutrients) that alter the intracellular pigment concentrations. The drawback of particulate scattering is that it is not unique to phytoplankton. Nevertheless, field studies have demonstrated that, to first order, the particulate beam-attenuation coefficient (cp) can track phytoplankton abundance. The relationship between cp and the particulate backscattering coefficient (bbp), a property retrievable from space, has not been fully evaluated, largely due to a lack of open-ocean field observations. Here, we present extensive data on inherent optical properties from the Equatorial Pacific surface waters and demonstrate a remarkable coherence in bbp and cp. Coincident measurements of particle size distributions (PSDs) and optical properties of size-fractionated samples indicate that this covariance is due to both the conserved nature of the PSD and a greater contribution of phytoplankton-sized particles to bbp than theoretically predicted. These findings suggest that satellite-derived bbp could provide similar information on phytoplankton biomass in the open ocean as cp.

scholarly journals The Impact of Smoke on the Ultraviolet and Visible Radiative Forcing Under Different Fire Regimes

2018 ◽  
Vol 11 ◽  
pp. 117862211877480 ◽  
Author(s):  
Yun H Park ◽  
Irina N Sokolik ◽  
Samuel R Hall
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Environmental Changes ◽  
Spectral Response ◽  
Fire Regimes ◽  
Transfer Model ◽  
Aerosol Composition ◽  
Actinic Flux ◽  
Smoke Aerosol ◽  
The Impact

The quantification of the UV characteristics of smoke aerosols is valuable to UV Index forecasting, air quality studies, air chemistry studies, and assessments of the impacts on regional and global environmental changes. The wavelength dependence of the light absorption by smoke aerosol has been researched throughout the UV and visible spectral region and varies with fire type and aerosol composition. An objective of this study is to investigate the spectral optical properties (eg, extinction coefficient, single-scattering albedo, and asymmetry parameter), UV actinic fluxes, and radiative forcing of smoke of different fire regimes. The smoke aerosol information (eg, simulated smoke fields from biomass burning emission and vertical distribution of the mass concentration of smoke components) from WRF-Chem is used to distinguish 2 smoke types: flaming and smoldering. To compute the spectral optical properties for the fire regimes, the representative size distribution and spectral refractive index have been implemented into the Mie code, and the optical properties are used to run the tropospheric ultraviolet and visible radiative transfer model. We make comparisons between simulated model and measured actinic flux in the UV and visible spectra under smoke aerosol laden conditions. The WRF-Chem-SMOKE model simulates the smoke plume matched with fire locations and comparable aerosol optical depth (AOD) with satellite measurements. However, the correlation between the simulated and observed AOD is small, which implies that adjusting the fire size for the emission inputs and improving meteorological fields are required for further research. The smoke at selected locations reduces the UV actinic flux and increases the visible actinic flux above the plume at small solar zenith angles. The specific spectral response is dependent on the smoke type. Overall, the results of this investigation show that this approach is valuable to estimate the impact of smoke on UV and visible radiative fluxes.

scholarly journals A Semi-Empirical Chlorophyll-a Retrieval Algorithm Considering the Effects of Sun Glint, Bottom Reflectance, and Non-Algal Particles in the Optically Shallow Water Zones of Sanya Bay Using SPOT6 Data

2020 ◽  
Vol 12 (17) ◽  
pp. 2765
Author(s):  
Yan Yu ◽  
Shengbo Chen ◽  
Wenhan Qin ◽  
Tianqi Lu ◽  
Jian Li ◽  
...  
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Chlorophyll A ◽  
Coastal Waters ◽  
Green Band ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Sanya Bay ◽  
Semi Empirical ◽  
Empirical Algorithms

Chlorophyll-a (Chl-a) concentration retrieval is essential for water quality monitoring, aquaculture, and guiding coastline infrastructure construction. Compared with common ocean color satellites, land observation satellites have the advantage of a higher resolution and more data sources for retrieving the concentration of Chl-a from optically shallow waters. However, the sun glint (Rsg), bottom reflectance (Rb), and non-algal particle (NAP) derived from terrigenous matter affect the accuracy of Chl-a concentration retrieval using land observation satellite image data. In this paper, we propose a semi-empirical algorithm based on the remote sensing reflectance (Rrs) of SPOT6 to retrieve the Chl-a concentration in Sanya Bay (SYB), considering the effect of Rsg, Rb, and NAP. In this semi-empirical algorithm, the Cox–Munk anisotropic model and radiative transfer model (RTM) were used to reduce the effects of Rsg and Rb on Rrs, and the Chl-a concentration was retrieved by the Chl-a absorption coefficient at 490 nm (aphy(490)) to remove the effect of NAP. The semi-empirical algorithm was in the form of Chl-a = 43.3[aphy(490)]1.454, where aphy (490) was calculated by the total absorption coefficient and the absorption coefficients of each component by empirical algorithms. The results of the Chl-a concentration retrieval show the following: (1) SPOT6 data are available for Chl-a retrieval using this semi-empirical algorithm in oligotrophic or mesotrophic coastal waters, and the accuracy of the algorithm can be improved by removing the effects of Rsg, Rb, and NAP (R2 from 0.71 to 0.93 and root mean square error (RMSE) from 0.23 to 0.11 ug/L); (2) empirical algorithms based on the blue-green band are suitable for oligotrophic or mesotrophic coastal waters, and the algorithm based on the blue-green band difference Chl-a index (DCI) has stronger anti-interference in terms of the effects of sun glint and bottom reflectance than the algorithm based on the blue-green ratio (BGr); (3) in the case of ignoring Rsg unrelated to inherent optical properties (IOPs), NAP is the biggest interference factor when >9.5 mg/L and the effect of bottom reflectance should be considered when the water depth (H) <5 m in SYB; and (4) the inherent optical properties of the waters in SYB are dominated by NAP (Chl-a = 0.2–2.6 ug/L and NAP = 2.2–30.1 mg/L), and the nutrients are concentrated by enclosed terrain and southeast current. This semi-empirical algorithm for Chl-a concentration retrieval has the potential to monitor Chl-a in oligotrophic and mesotrophic coastal waters using other land observation satellites (e.g., Landsat8 OLI, ASTER, and GaoFen2).

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