Thinking Outside of the Blue Marble: Novel Ocean Applications Using the VIIRS Sensor

While planning for future space-borne sensors will increase the quality, quantity, and duration of ocean observations in the years to come, efforts to extend the limits of sensors currently in orbit can help shed light on future scientific gains as well as associated uncertainties. Here, we present several applications that are unique to the polar orbiting Visual Infrared Imaging Radiometer Suite (VIIRS), each of which challenge the threshold capabilities of the sensor and provide lessons for future missions. For instance, while moderate resolution polar orbiters typically have a one day revisit time, we are able to obtain multiple looks of the same area by focusing on the extreme zenith angles where orbital views overlap, and pair these observations with those from other sensors to create pseudo-geostationary data sets. Or, by exploiting high spatial resolution (imaging) channels and analyzing patterns of synoptic covariance across the visible spectrum, we can obtain higher spatial resolution bio-optical products. Alternatively, non-traditional products can illuminate important biological interactions in the ocean, such as the use of the Day-Night-Band to provide some quantification of phototactic behavior of marine life along light polluted beaches, as well as track the location of marine fishing vessel fleets along ocean fronts. In this talk, we explore ways to take full advantage of the capabilities of existing sensors in order to maximize insights for future missions

QWIP: A Quantitative Metric for Quality Control of Aquatic Reflectance Spectral Shape Using the Apparent Visible Wavelength

The colors of the ocean and inland waters span clear blue to turbid brown, and the corresponding spectral shapes of the water-leaving signal are diverse depending on the various types and concentrations of phytoplankton, sediment, detritus and colored dissolved organic matter. Here we present a simple metric developed from a global dataset spanning blue, green and brown water types to assess the quality of a measured or derived aquatic spectrum. The Quality Water Index Polynomial (QWIP) is founded on the Apparent Visible Wavelength (AVW), a one-dimensional geophysical metric of color that is inherently correlated to spectral shape calculated as a weighted harmonic mean across visible wavelengths. The QWIP represents a polynomial relationship between the hyperspectral AVW and a Normalized Difference Index (NDI) using red and green wavelengths. The QWIP score represents the difference between a spectrum’s AVW and NDI and the QWIP polynomial. The approach is tested extensively with both raw and quality controlled field data to identify spectra that fall outside the general trends observed in aquatic optics. For example, QWIP scores less than or greater than 0.2 would fail an initial screening and be subject to additional quality control. Common outliers tend to have spectral features related to: 1) incorrect removal of surface reflected skylight or 2) optically shallow water. The approach was applied to hyperspectral imagery from the Hyperspectral Imager for the Coastal Ocean (HICO), as well as to multispectral imagery from the Visual Infrared Imaging Radiometer Suite (VIIRS) using sensor-specific extrapolations to approximate AVW. This simple approach can be rapidly implemented in ocean color processing chains to provide a level of uncertainty about a measured or retrieved spectrum and flag questionable or unusual spectra for further analysis

Consensus on Aquatic Primary Productivity Field Protocols for Satellite Validation and Model Synthesis

The NASA PACE project, in conjunction with the IOCCG, EUMETSAT, and JAXA, have initiated an Aquatic Primary Productivity working group, with the aim to develop community consensus on multiple methods for measuring aquatic primary productivity used for satellite validation and model synthesis. A workshop to commence the working group efforts was held December 05-07, 2018 at the University Space Research Association headquarters in Columbia, MD U.S.A., bringing together 26 active researchers from 16 institutions. The group discussed the primary differences, nuances, scales, uncertainties, definitions, and best practices for measurements of primary productivity derived from in situ/on-deck/laboratory radio/stable isotope incubations, dissolved oxygen concentrations (from incubations or autonomous platforms such as floats or gliders), oxygen-argon ratios, triple oxygen isotope, natural fluorescence, and FRRF/ETR/kinetic analysis. These discussions highlighted the necessity to move the community forward towards the establishment of climate-quality primary productivity measurements that follow uniform protocols, which is imperative to ensure that existing and future measurements can be compared, assimilated, and their uncertainties determined for model development and validation. The specific deliverable resulting from of this activity will be a protocol document, published in coordination with the IOCCG. This presentation will discuss the findings of the meeting, and address future activities of the working group

Phytoplankton composition from sPACE: Requirements, opportunities, and challenges

Ocean color satellites have provided a synoptic view of global phytoplankton for over 25 years through near surface measurements of the concentration of chlorophyll a. While remote sensing of ocean color has revolutionized our understanding of phytoplankton and their role in the oceanic and freshwater ecosystems, it is important to consider both total phytoplankton biomass and changes in phytoplankton community composition in order to fully understand the dynamics of the aquatic ecosystems. With the upcoming launch of NASA\u27s Plankton, Aerosol, Clouds, ocean Ecosystem (PACE) mission, we will be entering into a new era of global hyperspectral data, and with it, increased capabilities to monitor phytoplankton diversity from space. In this paper, we analyze the needs of the user community, review existing approaches for detecting phytoplankton community composition in situ and from space, and highlight the benefits that the PACE mission will bring. Using this three-pronged approach, we highlight the challenges and gaps to be addressed by the community going forward, while offering a vision of what global phytoplankton community composition will look like through the “eyes” of PACE

PEG−peptide conjugates

The remarkable diversity of the self-assembly behavior of PEG−peptides is reviewed, including self-assemblies formed by PEG−peptides with β-sheet and α-helical (coiled-coil) peptide sequences. The modes of self-assembly in solution and in the solid state are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized

Enhanced Satellite Remote Sensing of Coastal Waters Using Spatially Improved Bio-Optical Products From SNPP-VIIRS

The spatial dynamics of coastal and inland regions are highly variable and monitoring these waters with ocean color remote sensors requires increased spatial resolution capabilities. A procedure for the spatial enhancement of ocean color products, including chlorophyll and inherent optical properties (IOPs), is developed using a sharpened visible water-leaving radiance spectrum for the visible infrared imaging radiometer suite (VIIRS). A new approach for spectral sharpening is developed by utilizing the spatial covariance of the spectral bands for sharpening the M bands (412, 443, 486, 551, 671. nm; 750-m resolution) with the I-1 band (645. nm; 375-m resolution). The spectral shape remains consistent by the use of a dynamic, wavelength-specific spatial resolution ratio that is weighted as a function of the relationship between proximate I- and M-band variance at each pixel. A comparison of bio-optical satellite products at 375-m and 750-m spatial resolution with in situ measurements of water leaving radiance and bio-optical properties show an improved capability of the VIIRS 375-m products in turbid and optically complex waters, such as the Chesapeake Bay and Mississippi River Plume. We demonstrate that the increased spatial resolution improves the ability for VIIRS to characterize bio-optical properties in coastal waters

Comparison of VIIRS SST fields obtained from differing SST equations applied to a region covering the northern Gulf of Mexico and western North Atlantic

Several groups produce Sea Surface Temperature (SST) retrievals derived from data acquired by the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on-board the S-NPP satellite. Because of varying requirements or history, the groups often use differing SST equations to make their SST retrievals. Here we compare and discuss the equations through an examination of the SST fields. In most cases, the fields are created using the same program but differing equations, while in other cases, such as for the Interface Data Processing Segment (IDPS) Environmental Data Records (EDR), the SST fields are directly produced by other groups. Also discussed is the effect of the equation coefficients because independent groups may use the same equation but with different coefficients The focus of this study is on a region covering the Northern Gulf of Mexico and part of the Western North Atlantic. The comparison to buoys tries to minimize the effect of data contamination such as clouds on the results by matching the best satellite derived SST value in a neighborhood to the value from drifting or moored buoys. Finally we look at the overlap between consecutive passes to evaluate how the various equations perform at higher satellite zenith angles. © 2014 SPIE

Improved Monitoring of Bio-Optical Processes In Coastal and Inland Waters Using High Spatial Resolution Channels On SNPP-VIIRS Sensor

The dynamic and small-scale spatial variability of bio-optical processes that occurs in coastal regions and inland waters requires high resolution satellite ocean color feature detection. The Visual Infrared Imaging Radiometer Suite (VIIRS) currently utilizes five ocean color M-bands (410,443,486,551,671 nm) and two atmospheric correction M-bands in the cnear infrared (NIR; 745,862 nm) to produce ocean color products at a resolution of 750-m. VIIRS also has several high resolution (375-m) Imaging (I)-bands, including two bands centered at 640 nm and 865 nm. In this study, a spatially improved ocean color product is demonstrated by combining the 750-meter (M- channels) with the 375-m (I1-channel) to produce an image at a pseudo-resolution of 375-m. The new approach applies a dynamic wavelength-specific spatial ratio that is weighted as a function of the relationship between proximate I- and M-band variance at each pixel. This technique reduces sharpening artifacts by incorporating the native variability of the M-bands. In addition, this work examines the viability of replacing the M7-band (862 nm) with the I2-band (865 nm) to determine the atmospheric correction and aerosol optical depth at a higher resolution. These true (I-band) and pseudo (M-band) high resolution radiance values can subsequently be utilized as input parameters into various algorithms to yield high resolution optical products. The results show new capability for the VIIRS sensor for monitoring bio-optical processes in coastal waters. © 2013 SPIE

Comparison of VIIRS SST Fields Obtained From Differing SST Equations Applied To a Region Covering the Northern Gulf of Mexico and Western North Atlantic

Several groups produce Sea Surface Temperature (SST) retrievals derived from data acquired by the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on-board the S-NPP satellite. Because of varying requirements or history, the groups often use differing SST equations to make their SST retrievals. Here we compare and discuss the equations through an examination of the SST fields. In most cases, the fields are created using the same program but differing equations, while in other cases, such as for the Interface Data Processing Segment (IDPS) Environmental Data Records (EDR), the SST fields are directly produced by other groups. Also discussed is the effect of the equation coefficients because independent groups may use the same equation but with different coefficients The focus of this study is on a region covering the Northern Gulf of Mexico and part of the Western North Atlantic. The comparison to buoys tries to minimize the effect of data contamination such as clouds on the results by matching the best satellite derived SST value in a neighborhood to the value from drifting or moored buoys. Finally we look at the overlap between consecutive passes to evaluate how the various equations perform at higher satellite zenith angles. © 2014 SPIE

Estimating Sea Surface Salinity In Coastal Waters of the Gulf of Mexico Using Visible Channels On SNPP-VIIRS

Sea surface salinity is determined using the visible channels from the Visual Infrared Imaging Radiometer Suite (VIIRS) to derive regional algorithms for the Gulf of Mexico by normalizing to seasonal river discharge. The dilution of river discharge with open ocean waters and the surface salinity is estimated by tracking the surface spectral signature. The water leaving radiances derived from atmospherically-corrected and calibrated 750-m resolution visible M-bands (410, 443, 486, 551, 671 nm) are applied to bio-optical algorithms and subsequent multivariate statistical methods to derive regional empirical relationships between satellite radiances and surface salinity measurements. Although radiance to salinity is linked to CDOM dilution, we explored alternative statistical relationships to account for starting conditions. In situ measurements are obtained from several moorings spread across the Mississippi Sound and Mobile Bay, with a salinity range of 0.1-33. Data were collected over all seasons in the year 2013 in order to assess inter-Annual variability. The seasonal spectral signatures at the river mouth were used to track the fresh water end members and used to develop a seasonal slope and bias between salinity and radiance. Results show an increased spatial resolution for remote detection of coastal sea surface salinity from space, compared to the Aquarius Microwave salinity. Characterizing the coastal surface salinity has a significant impact on the physical circulation which affects the coastal ecosystems. Results identify locations and dissipation of the river plumes and can provide direct data for assimilation into physical circulation models. © 2014 SPIE