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Journal ArticleDOI

New aerosol models for the retrieval of aerosol optical thickness and normalized water-leaving radiances from the SeaWiFS and MODIS sensors over coastal regions and open oceans

10 Oct 2010-Applied Optics (Optical Society of America)-Vol. 49, Iss: 29, pp 5545-5560
TL;DR: The development of a new suite of aerosol models for the retrieval of atmospheric and oceanic optical properties from the SeaWiFS and MODIS sensors, including aerosol optical thickness, angstrom coefficient, and water-leaving radiance are described.
Abstract: We describe the development of a new suite of aerosol models for the retrieval of atmospheric and oceanic optical properties from the SeaWiFs and MODIS sensors, including aerosol optical thickness (tau), angstrom coefficient (alpha), and water-leaving radiance (L(sub w)). The new aerosol models are derived from Aerosol Robotic Network (AERONET) observations and have bimodal lognormal distributions that are narrower than previous models used by the Ocean Biology Processing Group. We analyzed AERONET data over open ocean and coastal regions and found that the seasonal variability in the modal radii, particularly in the coastal region, was related to the relative humidity, These findings were incorporated into the models by making the modal radii, as well as the refractive indices, explicitly dependent on relative humidity, From those findings, we constructed a new suite of aerosol models. We considered eight relative humidity values (30%, 50%, 70%, 75%, 80%, 85%, 90%. and 95%) and, for each relative humidity value, we constructed ten distributions by varying the fine-mode fraction from zero to 1. In all. 80 distributions (8Rh x 10 fine-mode fractions) were created to process the satellite data. We. also assumed that the coarse-mode particles were nonabsorbing (sea salt) and that all observed absorptions were entirely due to fine-mode particles. The composition of fine mode was varied to ensure that the new models exhibited the same spectral dependence of single scattering albedo as observed in the AERONET data,

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Citations
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Journal ArticleDOI
TL;DR: In this paper, a color index (CI) was proposed to estimate surface chlorophyll-a concentrations (Chl) in the global ocean for Chl less than or equal to 0.25 milligrams per cubic meters.
Abstract: A new empirical algorithm is proposed to estimate surface chlorophyll-a concentrations (Chl) in the global ocean for Chl less than or equal to 0.25 milligrams per cubic meters (approximately 77% of the global ocean area). The algorithm is based on a color index (CI), defined as the difference between remote sensing reflectance (R(sub rs), sr(sup -1) in the green and a reference formed linearly between R(sub rs) in the blue and red. For low Chl waters, in situ data showed a tighter (and therefore better) relationship between CI and Chl than between traditional band-ratios and Chl, which was further validated using global data collected concurrently by ship-borne and SeaWiFS satellite instruments. Model simulations showed that for low Chl waters, compared with the band-ratio algorithm, the CI-based algorithm (CIA) was more tolerant to changes in chlorophyll-specific backscattering coefficient, and performed similarly for different relative contributions of non-phytoplankton absorption. Simulations using existing atmospheric correction approaches further demonstrated that the CIA was much less sensitive than band-ratio algorithms to various errors induced by instrument noise and imperfect atmospheric correction (including sun glint and whitecap corrections). Image and time-series analyses of SeaWiFS and MODIS/Aqua data also showed improved performance in terms of reduced image noise, more coherent spatial and temporal patterns, and consistency between the two sensors. The reduction in noise and other errors is particularly useful to improve the detection of various ocean features such as eddies. Preliminary tests over MERIS and CZCS data indicate that the new approach should be generally applicable to all existing and future ocean color instruments.

684 citations

Journal ArticleDOI
TL;DR: An overview of the state of the art in atmospheric correction algorithms is provided, recent advances are highlighted and the possible potential for hyperspectral data to address the current challenges is discussed.
Abstract: Accurate correction of the corrupting effects of the atmosphere and the water’s surface are essential in order to obtain the optical, biological and biogeochemical properties of the water from satellite-based multi- and hyper-spectral sensors. The major challenges now for atmospheric correction are the conditions of turbid coastal and inland waters and areas in which there are strongly-absorbing aerosols. Here, we outline how these issues can be addressed, with a focus on the potential of new sensor technologies and the opportunities for the development of novel algorithms and aerosol models. We review hardware developments, which will provide qualitative and quantitative increases in spectral, spatial, radiometric and temporal data of the Earth, as well as measurements from other sources, such as the Aerosol Robotic Network for Ocean Color (AERONET-OC) stations, bio-optical sensors on Argo (Bio–Argo) floats and polarimeters. We provide an overview of the state of the art in atmospheric correction algorithms, highlight recent advances and discuss the possible potential for hyperspectral data to address the current challenges.

490 citations


Cites background or methods from "New aerosol models for the retrieva..."

  • ...The model takes into account eight variations of relative humidity (95%, 90%, 85%, 80%, 75%, 70%, 50% and 30%), as well as 10 variations on how fine or coarse the particles are, resulting in a total of 80 variants [159]....

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  • ...The availability of data from AERONET has paved the way for the creation of aerosol models [159,162]....

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  • ...[159] developed a model for the ocean colour sensors, SeaWiFS and MODIS....

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  • ...The optical properties of atmospheric aerosols can be classified in terms of their aerosol optical depth, Angstrom exponent, single scattering albedo, phase function and size distribution [27,30,159]....

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Journal ArticleDOI
TL;DR: In this paper, a semi-analytical bio-optical algorithm is used to help interpret regional to global SeaWiFS chlorophyll observations from using three independent, well-validated ocean color data products; the chilophyll a concentration, absorption by CDM and particulate backscattering.

241 citations

Journal ArticleDOI
TL;DR: Several large-scale climate patterns influenced climate conditions and weather patterns across the globe during 2010 as mentioned in this paper, ranging from record wetness across much of Australia to historically low Eastern Pacific basin and near-record high North Atlantic basin hurricane activity.
Abstract: Several large-scale climate patterns influenced climate conditions and weather patterns across the globe during 2010. The transition from a warm El Nino phase at the beginning of the year to a cool La Nina phase by July contributed to many notable events, ranging from record wetness across much of Australia to historically low Eastern Pacific basin and near-record high North Atlantic basin hurricane activity. The remaining five main hurricane basins experienced below- to well-below-normal tropical cyclone activity. The negative phase of the Arctic Oscillation was a major driver of Northern Hemisphere temperature patterns during 2009/10 winter and again in late 2010. It contributed to record snowfall and unusually low temperatures over much of northern Eurasia and parts of the United States, while bringing above-normal temperatures to the high northern latitudes. The February Arctic Oscillation Index value was the most negative since records began in 1950. The 2010 average global land and ocean surface tem...

209 citations


Cites background from "New aerosol models for the retrieva..."

  • ...…(lunar views and intense ground efforts) to set sensor gains and offsets, and advanced algorithms to correct satellite signals for the atmospheric path radiance and establish the relationships between ocean ref lectance spectra and ocean properties (McClain 2009; Ahmad et al. 2010; NRC 2011)....

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Journal ArticleDOI
TL;DR: The European Space Agency's Sentinel-2A mission with the MultiSpectral Instrument (MSI) onboard was launched in 2015, initiating a new era in high-to-moderate-resolution (i.e., 10 to 60m) imaging of Earth's resources as discussed by the authors.

202 citations


Cites background from "New aerosol models for the retrieva..."

  • ...It is, thus, necessary to augment/ update the existing aerosol models (Ahmad et al., 2010) to reduce the associated noise when retrieving Rrs over inland waters, in particular, those with high loads of dissolved organic matters....

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  • ...Pahlevan et al. (2017a) showed that if the ambient aerosol properties are not represented in the aerosol models (Ahmad et al., 2010), high uncertainties in Rrs(443) are expected....

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  • ...(2017a) showed that if the ambient aerosol properties are not represented in the aerosol models (Ahmad et al., 2010), high uncertainties in Rrs(443) are expected....

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References
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Journal ArticleDOI
TL;DR: The operation and philosophy of the monitoring system, the precision and accuracy of the measuring radiometers, a brief description of the processing system, and access to the database are discussed.

6,535 citations


"New aerosol models for the retrieva..." refers background in this paper

  • ...[16,17], Dubovik and King [18], Dubovik et al....

    [...]

Journal ArticleDOI
TL;DR: In this paper, a review of scattering theory required for analysis of light reflected by planetary atmospheres is presented, which demonstrates the dependence of single-scattered radiation on the physical properties of the scatterers.
Abstract: This paper reviews scattering theory required for analysis of light reflected by planetary atmospheres. Section 1 defines the radiative quantities which are observed. Section 2 demonstrates the dependence of single-scattered radiation on the physical properties of the scatterers. Section 3 describes several methods to compute the effects of multiple scattering on the reflected light.

2,691 citations


"New aerosol models for the retrieva..." refers background in this paper

  • ...(1) takes the form dNðrÞ d ln r ¼ X2 i¼1 Noiffiffiffiffiffi 2π p σi exp − ln r − ln rnoiffiffiffi 2 p σi 2 ; ð2Þ where Noi is the number of particles, and rnoi is the mean geometric radius of the ith distribution, and the radius rnoi and Noi are, respectively, related to rvoi and Voi as ln rnoi ¼ ln rvoi − 3σ2i ; ð3aÞ Noi ¼ Voi½0:75=ðπr3noiÞ expð−4:5σ2i Þ: ð3bÞ Two other quantities of interest are effective radius (reff ) and effective variance (veff ), which are defined as reff ¼ Zrmax rmin πr3nðrÞdr= Zrmax rmin πr2nðrÞdr; ð4aÞ veff ¼ Zrmax rmin ðr − reff Þ2πr2nðrÞdr=r2eff Zrmax rmin πr2nðrÞdr; ð4bÞ where nðrÞ ¼ dN=dr: Hansen and Travis [24] have shown that all distributions (for example, modified gamma, power law, and various lognormal distributions) that have the same values of reff and veff have very similar scattering properties....

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  • ...Hansen and Travis [24] have shown that all distributions (for example, modified gamma, power law, and various lognormal distributions) that have the same values of reff and veff have very similar scattering properties....

    [...]

Journal ArticleDOI
TL;DR: In this paper, the AERONET network of ground-based radiometers were used to remotely sense the aerosol absorption and other optical properties in several key locations, and the results showed robust differentiation in both the magnitude and spectral dependence of the absorption, a property driving aerosol climate forcing.
Abstract: Aerosol radiative forcing is a critical, though variable and uncertain, component of the global climate. Yet climate models rely on sparse information of the aerosol optical properties. In situ measurements, though important in many respects, seldom provide measurements of the undisturbed aerosol in the entire atmospheric column. Here, 8 yr of worldwide distributed data from the AERONET network of ground-based radiometers were used to remotely sense the aerosol absorption and other optical properties in several key locations. Established procedures for maintaining and calibrating the global network of radiometers, cloud screening, and inversion techniques allow for a consistent retrieval of the optical properties of aerosol in locations with varying emission sources and conditions. The multiyear, multi-instrument observations show robust differentiation in both the magnitude and spectral dependence of the absorption—a property driving aerosol climate forcing, for desert dust, biomass burning, urban‐industrial, and marine aerosols. Moreover, significant variability of the absorption for the same aerosol type appearing due to different meteorological and source characteristics as well as different emission characteristics are observed. It is expected that this aerosol characterization will help refine aerosol optical models and reduce uncertainties in satellite observations of the global aerosol and in modeling aerosol impacts on climate.

2,653 citations

Journal ArticleDOI
TL;DR: The developed algorithm is adapted for the retrieval of aerosol properties from measurements made by ground-based Sun-sky scanning radiometers used in the Aerosol Robotic Network (AERONET) and allows a choice of normal or lognormal noise assumptions.
Abstract: The problem of deriving a complete set of aerosol optical properties from Sun and sky radiance measurements is discussed. Algorithm development is focused on improving aerosol retrievals by means of including a detailed statistical optimization of the influence of noise in the inversion procedure. The methodological aspects of such an optimization are discussed in detail and revised according to both modern findings in inversion theory and practical experience in remote sensing. Accordingly, the proposed inversion algorithm is built on the principles of statistical estimation: the spectral radiances and various a priori constraints on aerosol characteristics are considered as multisource data that are known with predetermined accuracy. The inversion is designed as a search for the best fit of all input data by a theoretical model that takes into account the different levels of accuracy of the fitted data. The algorithm allows a choice of normal or lognormal noise assumptions. The multivariable fitting is implemented by a stable numerical procedure combining matrix inversion and univariant relaxation. The theoretical inversion scheme has been realized in the advanced algorithm retrieving aerosol size distribution together with complex refractive index from the spectral measurements of direct and diffuse radiation. The aerosol particles are modeled as homogeneous spheres. The atmospheric radiative transfer modeling is implemented with well-established publicly available radiative transfer codes. The retrieved refractive indices can be wavelength dependent; however, the extended smoothness constraints are applied to its spectral dependence (and indirectly through smoothness constraints on retrieved size distributions). The positive effects of statistical optimization on the retrieval results as well as the importance of applying a priori constraints are discussed in detail for the retrieval of both aerosol size distribution and complex refractive index. The developed algorithm is adapted for the retrieval of aerosol properties from measurements made by ground-based Sun-sky scanning radiometers used in the Aerosol Robotic Network (AERONET). The results of numerical tests together with examples of experimental data inversions are presented.

2,122 citations


"New aerosol models for the retrieva..." refers background in this paper

  • ...The details of AERONET network and measurements are described in many papers, including Holben et al. [16,17], Dubovik and King [18], Dubovik et al. [19–22] and Sinyuk et al. [23]....

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  • ...[16,17], Dubovik and King [18], Dubovik et al....

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Journal ArticleDOI
TL;DR: In this paper, the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into a spectral optical properties climatology.
Abstract: Long-term measurements by the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into an aerosol optical properties climatology. Quality assured monthly means are presented and described for 9 primary sites and 21 additional multiyear sites with distinct aerosol regimes representing tropical biomass burning, boreal forests, midlatitude humid climates, midlatitude dry climates, oceanic sites, desert sites, and background sites. Seasonal trends for each of these nine sites are discussed and climatic averages presented.

1,891 citations