Modeling Atmosphere-Ocean Radiative Transfer: A PACE Mission Perspective

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

SeaWiFS technical report series. Volume 5: Ocean optics protocols for SeaWiFS validation

Protocols are presented for measuring optical properties, and other environmental variables, to validate the radiometric performance of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), and to develop and validate bio-optical algorithms for use with SeaWiFS data. The protocols are intended to establish foundations for a measurement strategy to verify the challenging SeaWiFS accuracy goals of 5 percent in water-leaving radiances and 35 percent in chlorophyll alpha concentration. The protocols first specify the variables which must be measured, and briefly review rationale. Subsequent chapters cover detailed protocols for instrument performance specifications, characterizing and calibration instruments, methods of making measurements in the field, and methods of data analysis. These protocols were developed at a workshop sponsored by the SeaWiFS Project Office (SPO) and held at the Naval Postgraduate School in Monterey, California (9-12 April, 1991). This report is the proceedings of that workshop, as interpreted and expanded by the authors and reviewed by workshop participants and other members of the bio-optical research community. The protocols are a first prescription to approach unprecedented measurement accuracies implied by the SeaWiFS goals, and research and development are needed to improve the state-of-the-art in specific areas. The protocols should be periodically revised to reflect technical advances during the SeaWiFS Project cycle

Modeling Atmosphere-Ocean Radiative Transfer: A PACE Mission Perspective

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

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

Consistent space-based retrievals of chlorophyll fluorescence and atmospheric CO2 and CH4 for improved estimates of carbon fluxes

Understanding the natural carbon cycle and its feedback to climate change requires atmospheric carbon observations to constrain carbon surface fluxes. The retrieval method RemoTeC uses satellite measurements to retrieve atmospheric CO2 and CH4. This work improves the retrieval such that it accounts for chlorophyll fluorescence. Furthermore, this work shows that the CO2 retrieval accounting for chlorophyll fluorescence provides observational constraints on carbon surface flux estimates

Polarimetric imaging microscopy for advanced inspection of vegetal tissues

Optical microscopy techniques for plant inspection benefit from the fact that at least one of the multiple properties of light (intensity, phase, wavelength, polarization) may be modified by vegetal tissues. Paradoxically, polarimetric microscopy although being a mature technique in biophotonics, is not so commonly used in botany. Importantly, only specific polarimetric observables, as birefringence or dichroism, have some presence in botany studies, and other relevant metrics, as those based on depolarization, are underused. We present a versatile method, based on a representative selection of polarimetric observables, to obtain and to analyse images of plants which bring significant information about their structure and/or the spatial organization of their constituents (cells, organelles, among other structures). We provide a thorough analysis of polarimetric microscopy images of sections of plant leaves which are compared with those obtained by other commonly used microscopy techniques in plant biology. Our results show the interest of polarimetric microscopy for plant inspection, as it is non-destructive technique, highly competitive in economical and time consumption, and providing advantages compared to standard non-polarizing techniques

Aspects of in situ angular scattering measurements in contrasting waters

Rapid changes are observed in oceanic and coastal environments around the world due to global temperatures increases, ocean acidification and changing weather patterns - anthropogenic climate change. These changes have large effects on the ecosystems of the ocean. In order to understand the effects and possibly mitigate their consequences, it is necessary to increase and improve the environmental monitoring of the ocean. Optical properties of natural waters within the visible spectrum is closely linked to properties of phytoplankton, the foundation of oceanic ecosystems, as well as other particles on the micrometer and sub-micrometer scale in the water mass. Optical measurements can thus give us valuable information about the particle content of the water and the state of the ecosystem. The volume scattering function (VSF) is a fundamental optical property describing how much light is scattered by a medium and in what direction the light is scattered. In natural waters, by far most of the light is scattered in the very forward direction, which makes it technically challenging to measure the VSF. The LISST-VSF is the first commercially available instrument for field measurements of the VSF over a large angular domain. To trust the measurements, it is important to validate the performance of instrument and identify any error sources, in particular the valid range of the instrument, given that scattering coefficients of natural waters can span three orders of magnitude. In this thesis, I have characterised LISST-VSF measurements using both in situ measurements of highly contrasting water types, controlled laboratory measurements, and Monte Carlo simulations of instrument geometry. Similar aspects have been investigated for the LISST-200X, which measures the VSF at angles 0.04-13˚ at 670 nm. In Paper I, these two instruments are calibrated and validated using polymer beads and in situ measurements spanning from clear waters on the North Pole to highly turbid glacial meltwater. The measurements demonstrated that due to instrument design, the LISST-200X only gives valid scattering measurements in moderate-to-turbid waters. The LISST-VSF gives valid measurements also in clear waters (however with a loss in precision), but is limited by multiple scattering errors in more turbid waters. Multiple scattering effects on LISST-VSF measurements are investigated in detail in in Paper II and III. For this purpose, a Monte Carlo simulation was developed and validated with experimental data, and subsequently used to simulate LISST-VSF measurements with Fournier-Forand and Henyey-Greenstein phase functions. We demonstrated that the multiple scattering can yield uncertainties of 10% when the scattering coefficient is 1 m-1, which significantly restricts the accurate measurement range of LISST-VSF. LISST-200X is less affected by this error due to its shorter path length. Scattering can be an error source for other optical measurements as well. In Paper IV, we attempt to correct in situ depth profiles of absorption coefficients measured with the ac-s instrument using VSF measurements collected with the LISST-VSF in coastal waters. We show that this method does not show a clear and consistent improvement over existing methods, which are simpler to use but make strong assumptions about absorption and scattering properties. The discrepancies in the VSF correction can be attributed to several different confounding factors, such as spatial variability and multiple scattering, which are exceedingly propagated to the corrected absorption values. Nevertheless, VSF measurements are found useful to analyze the scattering error. We show that the VSF between 5-90˚ can contribute significantly to the scattering error, depending on the phase function and the reflectance efficiency of the reflective tube. Moreover, by simulating the VSF wavelength-dependency using Mie theory, we show that particle sub-populations with diameters close to the wavelength can explain why scaling the scattering error with the scattering coefficient sometimes fails.Doktorgradsavhandlin

Remote sensing of optically active marine components

Merged with duplicate record 10026.1/649 on 20.12.2016 by CS (TIS). Merged with duplicate record 10026.1/2083 on 07.02.2017 by CS (TIS)This is a digitised version of a thesis that was deposited in the University Library. If you are the author please contact PEARL Admin ([email protected]) to discuss options.Remote sensing is an efficient tool to monitor the aquatic ecology. The optical signature in coastal marine environment is a reflection of the complex distribution of optically active marine components. It is essential to understand the relationship between the remote sensing signal and marine constituent material to take advantage of high resolution remote sensing data available from spaceborne and airborne platforms. The objective of this research was to develop a semi-analytical forward model to predict the remote sensing optical signature in coastal waters dominated by non-planktonic material. Laboratory and in situ measurements collected over a5 year period (1998-2003) were used to compile a biogeooptical database for coastal waters. The database is exploited to realise various biogeophysical relationships. A major advancement proposed in the thesis towards the modelling of backscattering probability was the synthesis of knowledge from Mie theory and particulate composition from geochemical analysis. This approach was used to derive particulate backscattering from in situ absorption and attenuation measurements. Results show that this model can produce backscattering values in a realistic way than with a constant value as proposed by Petzold. Absorption and backscattering values derived from ac-9 measurements were used to calculate radiance reflectance and remote sensing reflectance. The biogeophysical relationships developed were incorporated into the forward optics model to successfully simulate the inherent optical property ratio. Further development of the model and applications through inversion were discussed and outlined.Plymouth Marine Laborator