289 research outputs found

    Modeling Atmosphere-Ocean Radiative Transfer: A PACE Mission Perspective

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    The research frontiers of radiative transfer (RT) in coupled atmosphere-ocean systems are explored to enable new science and specifically to support the upcoming Plankton, Aerosol, Cloud ocean Ecosystem (PACE) satellite mission. Given (i) the multitude of atmospheric and oceanic constituents at any given moment that each exhibits a large variety of physical and chemical properties and (ii) the diversity of light-matter interactions (scattering, absorption, and emission), tackling all outstanding RT aspects related to interpreting and/or simulating light reflected by atmosphere-ocean systems becomes impossible. Instead, we focus on both theoretical and experimental studies of RT topics important to the science threshold and goal questions of the PACE mission and the measurement capabilities of its instruments. We differentiate between (a) forward (FWD) RT studies that focus mainly on sensitivity to influencing variables and/or simulating data sets, and (b) inverse (INV) RT studies that also involve the retrieval of atmosphere and ocean parameters. Our topics cover (1) the ocean (i.e., water body): absorption and elastic/inelastic scattering by pure water (FWD RT) and models for scattering and absorption by particulates (FWD RT and INV RT); (2) the air-water interface: variations in ocean surface refractive index (INV RT) and in whitecap reflectance (INV RT); (3) the atmosphere: polarimetric and/or hyperspectral remote sensing of aerosols (INV RT) and of gases (FWD RT); and (4) atmosphere-ocean systems: benchmark comparisons, impact of the Earth's sphericity and adjacency effects on space-borne observations, and scattering in the ultraviolet regime (FWD RT). We provide for each topic a summary of past relevant (heritage) work, followed by a discussion (for unresolved questions) and RT updates

    Modeling Atmosphere-Ocean Radiative Transfer: A PACE Mission Perspective

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    The research frontiers of radiative transfer (RT) in coupled atmosphere-ocean systems are explored to enable new science and specifically to support the upcoming Plankton, Aerosol, Cloud ocean Ecosystem (PACE) satellite mission. Given (i) the multitude of atmospheric and oceanic constituents at any given moment that each exhibits a large variety of physical and chemical properties and (ii) the diversity of light-matter interactions (scattering, absorption, and emission), tackling all outstanding RT aspects related to interpreting and/or simulating light reflected by atmosphere-ocean systems becomes impossible. Instead, we focus on both theoretical and experimental studies of RT topics important to the science threshold and goal questions of the PACE mission and the measurement capabilities of its instruments. We differentiate between (a) forward (FWD) RT studies that focus mainly on sensitivity to influencing variables and/or simulating data sets, and (b) inverse (INV) RT studies that also involve the retrieval of atmosphere and ocean parameters. Our topics cover (1) the ocean (i.e., water body): absorption and elastic/inelastic scattering by pure water (FWD RT) and models for scattering and absorption by particulates (FWD RT and INV RT); (2) the air-water interface: variations in ocean surface refractive index (INV RT) and in whitecap reflectance (INV RT); (3) the atmosphere: polarimetric and/or hyperspectral remote sensing of aerosols (INV RT) and of gases (FWD RT); and (4) atmosphere-ocean systems: benchmark comparisons, impact of the Earth’s sphericity and adjacency effects on space-borne observations, and scattering in the ultraviolet regime (FWD RT). We provide for each topic a summary of past relevant (heritage) work, followed by a discussion (for unresolved questions) and RT updates

    Factors affecting the identification of phytoplankton groups by means of remote sensing

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    A literature review was conducted on the state of the art as to whether or not information about communities and populations of phytoplankton in aquatic environments can be derived by remote sensing. In order to arrive at this goal, the spectral characteristics of various types of phytoplankton were compared to determine first, whether there are characteristic differences in pigmentation among the types and second, whether such differences can be detected remotely. In addition to the literature review, an extensive, but not exhaustive, annotated bibliography of the literature that bears on these questions is included as an appendix, since it constitutes a convenient resource for anyone wishing an overview of the field of ocean color. The review found some progress has already been made in remote sensing of assemblages such as coccolithophorid blooms, mats of cyanobacteria, and red tides. Much more information about the composition of algal groups is potentially available by remote sensing particularly in water bodies having higher phytoplankton concentrations, but it will be necessary to develop the remote sensing techniques required for working in so-called Case 2 waters. It is also clear that none of the satellite sensors presently available or soon to be launched is ideal from the point of view of what we might wish to know; it would seem wise to pursue instruments with the planned characteristics of the Moderate Resolution Imaging Spectrometer-Tilt (MODIS-T) or Medium Resolution Imaging Spectrometer (MERIS)

    Modeling atmosphere-ocean radiative transfer: A PACE mission perspective

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    The research frontiers of radiative transfer (RT) in coupled atmosphere-ocean systems are explored to enable new science and specifically to support the upcoming Plankton, Aerosol, Cloud ocean Ecosystem (PACE) satellite mission. Given (i) the multitude of atmospheric and oceanic constituents at any given moment that each exhibits a large variety of physical and chemical properties and (ii) the diversity of light-matter interactions (scattering, absorption, and emission), tackling all outstanding RT aspects related to interpreting and/or simulating light reflected by atmosphere-ocean systems becomes impossible. Instead, we focus on both theoretical and experimental studies of RT topics important to the science threshold and goal questions of the PACE mission and the measurement capabilities of its instruments. We differentiate between (a) forward (FWD) RT studies that focus mainly on sensitivity to influencing variables and/or simulating data sets, and (b) inverse (INV) RT studies that also involve the retrieval of atmosphere and ocean parameters. Our topics cover (1) the ocean (i.e., water body): absorption and elastic/inelastic scattering by pure water (FWD RT) and models for scattering and absorption by particulates (FWD RT and INV RT); (2) the air-water interface: variations in ocean surface refractive index (INV RT) and in whitecap reflectance (INV RT); (3) the atmosphere: polarimetric and/or hyperspectral remote sensing of aerosols (INV RT) and of gases (FWD RT); and (4) atmosphere-ocean systems: benchmark comparisons, impact of the Earth’s sphericity and adjacency effects on space-borne observations, and scattering in the ultraviolet regime (FWD RT). We provide for each topic a summary of past relevant (heritage) work, followed by a discussion (for unresolved questions) and RT updates

    Shipboard Lidar as a Tool for Remotely Measuring the Distribution and Bulk Characteristics of Marine Particles

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    Light detection and ranging (lidar) can provide remote estimates of the vertical distribution of optical properties in the ocean, potentially revolutionizing our ability to characterize the spatial structure of upper ocean ecosystems. However, challenges associated with quantifying the relationship between lidar measurements and biogeochemical properties of interest have prevented its adoption for routinely mapping the vertical structure of marine ecosystems. To address this, we developed a shipboard oceanographic lidar that measures attenuation (α) and linear depolarization (δ) at scales identical to those of in-water optical and biogeochemical measurements. The instrument’s ability to resolve the distribution of optical and biogeochemical properties was characterized during a series of field campaigns in the Mid-Atlantic Bight (MAB) and Gulf of Maine (GoM). α resolved vertical and horizontal gradients in absorption and chlorophyll concentration associated with the Chesapeake Bay outflow and distinct water masses in the GoM. δ was related to the particulate backscattering ratio, an optical proxy for particle size and composition, suggesting that δ could provide information on the material properties of marine particles. After initial characterizations, we conducted a 13-day deployment in the GoM and western North Atlantic to sample a mesoscale coccolithophore bloom. Bloom features were mapped at sub-kilometer scales and δ was used to distinguish coccoliths/coccolithophores from non-calcified particles. Finally, a model parameterized with in-water optical measurements from the bloom and laboratory linear depolarization measurements was used to explore the influence of multiple scattering and particle characteristics on measurements of δ. Single scattering measurements of δ exhibited a complex dependency on particle shape, size, and composition that was consistent with scattering calculations for non-spherical particles. Model results suggested that variability in δ was driven predominantly by shifts in particle concentration rather than their bulk characteristics. However, the behavior of δ when backscattering became decoupled from calcite could only be reproduced by including a separate coccolith particle class. Taken as a whole, this work provides new insights into the scattering nature of marine particles and the complex response of the lidar return signal to water column optical properties, and is an important demonstration of the sampling capabilities afforded by shipboard lidar

    Exploring Himawari-8 geostationary observations for the advanced coastal monitoring of the Great Barrier Reef

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    Larissa developed an algorithm to enable water-quality assessment within the Great Barrier Reef (GBR) using weather satellite observations collected every 10 minutes. This unprecedented temporal resolution records the dynamic nature of water quality fluctuations for the entire GBR, with applications for improved monitoring and management

    Coastal and Inland Aquatic Data Products for the Hyperspectral Infrared Imager (HyspIRI)

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    The HyspIRI Aquatic Studies Group (HASG) has developed a conceptual list of data products for the HyspIRI mission to support aquatic remote sensing of coastal and inland waters. These data products were based on mission capabilities, characteristics, and expected performance. The topic of coastal and inland water remote sensing is very broad. Thus, this report focuses on aquatic data products to keep the scope of this document manageable. The HyspIRI mission requirements already include the global production of surface reflectance and temperature. Atmospheric correction and surface temperature algorithms, which are critical to aquatic remote sensing, are covered in other mission documents. Hence, these algorithms and their products were not evaluated in this report. In addition, terrestrial products (e.g., land use land cover, dune vegetation, and beach replenishment) were not considered. It is recognized that coastal studies are inherently interdisciplinary across aquatic and terrestrial disciplines. However, products supporting the latter are expected to already be evaluated by other components of the mission. The coastal and inland water data products that were identified by the HASG, covered six major environmental and ecological areas for scientific research and applications: wetlands, shoreline processes, the water surface, the water column, bathymetry and benthic cover types. Accordingly, each candidate product was evaluated for feasibility based on the HyspIRI mission characteristics and whether it was unique and relevant to the HyspIRI science objectives

    Great Bay Estuary Water Quality Monitoring Program: Quality Assurance Project Plan 2019 - 2023

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    Is there lignin in the Ulva cell wall? A multidisciplinary structural investigation to provide new insights into cell wall evolution and macroscopic complexity in the chlorophyte green seaweeds

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    Seaweeds are not only an integral component of the marine ecosystem via their role in global carbon and sulfur cycles, but also have significant economic value as crops for food and fuel, with certain intertidal seaweeds like the green 'sea lettuce' Ulva (Chlorophyta) appearing as attractive bioenergy feedstocks due to their rapid growth rates and polysaccharide-rich cell wall that can comprise half its total biomass. Seaweeds have a distinct biochemistry to traditional land plant crops. For example, they lack the phenylpropanoid pathway, a key milestone in land plant evolution that enabled the biosynthesis of the secondary cell wall biopolymer lignin which confers structural support and facilitates water transport in vascular plants. Despite this, 'lignin-like' fractions are reported in Ulva, and lignin has been found in a coralline red seaweed (Rhodophyta). No alternative pathway for lignin biosynthesis is provided by our current metabolic knowledge, meaning we have limited understanding of how ‘lignin’ arose in seaweeds. Furthermore, the only comprehensive structural investigation into seaweed 'phycolignin' to date has been performed in the coralline reds. Consequently, the presence of an equivalent component in green seaweeds like Ulva is still debatable. As the primary aim of this thesis, I investigate the identity of the proposed lignin-like fraction of Ulva using confocal microscopy, biochemical assays, and biophysical analysis. To accomplish this, I evaluate the use of a sequential extraction protocol described for charophyte green algae (Streptophyta) to determine which cell wall polysaccharides the proposed structure associates with. No evidence for lignin-like structures in the Ulva cell wall was identified during this research. Instead, I propose that the previous attributions to lignin in Ulva were misidentifications on account of the limitations of quantification protocols used. Interestingly, a major structural protein component is identified with possible implications for how Ulva mitigates osmotic stress at low tide. The absence of 'phycolignin' in the Ulva cell wall contrary to the lignified coralline seaweeds demonstrates that seaweeds display diverse adaptations to intertidal habitats, and provides support to the current hypothesis that lignin arose convergently in the red lineage, with green seaweeds and land plants sharing a more recent evolutionary history

    Modelling of total suspended particulates in Malaysian coastal waters using remote sensing techniques

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    This study focused on environmental remote sensing with the objective of constructing a remote sensing algorithm to determine Total Suspended Particulate (TSP) concentrations in Malaysian coastal surface waters. Other objectives included coral reef mapping and production of quantitative map of [TSP] using the remote sensing algorithm at the study area which was Tanjung Rhu, located northeast of Pulau Langkawi, Peninsular Malaysia. Measured [TSP] varied from 93.92 ± 50.10 mg/L to 148.65 ± 45.39 mg/L. The biogeographic distribution of the reef in Tanjung Rhu was mapped and the hermatypic coral species was identified taxonomically. Results were compared to a control site, Teluk Datai located northwest of Pulau Langkawi. There were 37 coral species in Tanjung Rhu and 76 species in Teluk Datai. The Jaccard's score was 27% indicating that the two reefs were quite diverse in their coral compositions. The development of a remote sensing algorithm is deemed necessary to provide a synoptic view of the potential problem within the coastal waters due to the early coastal development in Tanjung Rhu. Sedimentation studies showed sediment fractions were mainly biogenic materials and lithified sediments. Sediment fallout rates in Tanjung Rhu were 1,403.48 ± 125.60 g/m2/day (dry season) and 6,550.77 ± 641.43 g/m2/day (wet season). In Teluk Datai the sediment fallout rates were 1,532.99 ± 201.81 g/m2/day (dry season) and 12,446.45 ± 237.81 g/m2/day (wet season). The remote sensing algorithm, Suspended Particulate Algorithm for Coastal Remote Sensing (SPACoRS) developed from a modified Simple Radiative Transfer Model is defined as [TSP] (mg/L) = 0.6668e4 .3892x , where x represents (Rrs-toaTM31RrstoaTM2) ratio. SPACoRS is designed to determine [TSP] of 30 - 275 mg/L with primary material of TSP having high backscattering and low absorbance values. Sensitivity of SP ACoRS to produce higher accuracies was limited to TSP ~ 15Omg/L. SP ACoRS' s accuracy using Landsat Thematic Mapper data was 66%
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