Robert A. Arnone

Effect of suspended particulate and dissolved organic matter on remote sensing of coastal and riverine waters

We use remote sensing reflectance (RSR) together with the inherent optical properties of suspended particulates to determine the backscattering ratio b(b)/b for coastal waters. We examine the wavelength dependence of b(b)(lambda) and f(lambda)/Q(lambda) and establish the conditions when C(lambda) in RSR(lambda) approximately or = C(lambda)b(b)(lambda)/a(lambda) can be treated as a constant. We found that for case 2 waters, RSR was insensitive to the natural fluctuations in particle-size distributions. The cross-sectional area of the suspended particulate per unit volume, x(g), showed an excellent correlation with the volume scattering coefficient.

Uniqueness in remote sensing of the inherent optical properties of ocean water

We examine the problem of uniqueness in the relationship between the remote-sensing reflectance (Rrs) and the inherent optical properties (IOPs) of ocean water. The results point to the fact that diffuse reflectance of plane irradiance from ocean water is inherently ambiguous. Furthermore, in the 400 < lambda < 750 nm region of the spectrum, Rrs(lambda) also suffers from ambiguity caused by the similarity in wavelength dependence of the coefficients of absorption by particulate matter and of absorption by colored dissolved organic matter. The absorption coefficients have overlapping exponential responses, which lead to the fact that more than one combination of IOPs can produce nearly the same Rrs spectrum. This ambiguity in absorption parameters demands that we identify the regions of the Rrs spectrum where we can isolate the effects that are due only to scattering by particulates and to absorption by pure water. The results indicate that the spectral shape of the absorption coefficient of phytoplankton, a(ph)(lambda), cannot be derived from a multiparameter fit to Rrs(lambda). However, the magnitude and the spectral dependence of the absorption coefficient can be estimated from the difference between the measured Rrs(lambda) and the best fit to Rrs(lambda) in terms of IOPs that exclude a(ph)(lambda).

Remote-sensing technique for determination of the volume absorption coefficient of turbid water

We use remote-sensing reflectance from particulate R(rs) to determine the volume absorption coefficient a of turbid water in the 400 < lambda < 700-nm spectral region. The calculated and measured values of a(lambda) show good agreement for 0.5 < a < 10 (m(-1)). To determine R(rs) from a particulate, we needed to make corrections for remote-sensing reflectance owing to surface roughness S(rs). We determined the average spectral distribution of S(rs) from the difference in total remote-sensing reflectance measured with and without polarization. The spectral shape of S(rs) showed an excellent fit to theoretical formulas for glare based on Rayleigh and aerosol scattering from the atmosphere.

Seasonal trends of biophysical ocean properties and anomalies across the Mississippi Shelf

The seasonal cycle in surface biological, optical and physical properties across the river dominated Mississippi (MS) Shelf changed during years 2015 to 2017 at different locations across the shelf. VIIRS satellite and ocean model products were used to monitor cycles for different properties of both the nowcast and anomalous water properties. MS Shelf water properties vary spatially between offshore waters and coastal MS Sound waters, as well as temporally throughout the year. Ten selected regions spanning east to west from the MS Sound to the shelf break characterized the cross shelf seasonal fluctuations in satellite-derived chlorophyll-a, backscattering, euphotic depth, sea surface temperature, and modeled salinity currents. The seasonal relationships between physical and bio-optical properties were determined for different regions across the shelf and the seasonal eastward movement of the MS river plume across the shelf was identified in June. Yearly MS Sound seasonal cycles of coastal bio-physical properties are different from the shelf regions’ offshore seasonal cycles and indicate a time-lag between the bio-optical responses to the physical properties. Bio-optical and physical results on the shelf indicated seasonal movements of the MS River plume locations. Results show the seasonal bio-physical response of the shelf waters which can be used to address and understand the timing of data collection and how ocean events are influenced by the natural seasonal cycle interactions between biological and physical properties. The seasonal cycle study will enable the ability to monitor the shelf water quality and to identify non-typical conditions and the impact of an event on the cycle. Correlations between the monthly seasonal cycle of bio-optical and physical properties such as salinity, ocean color, chlorophyll-a and particle scattering were not consistent over the shelf. Seasonal cycles of salinity and chlorophyll-a show improved correlation if chlorophyll-a is delayed one month from the salinity at offshore locations on the shelf. Results of the seasonal trends support how data collected at a single image location on the shelf during a certain month can be different from other seasons. The seasonal cycle of the dynamic anomaly properties (DAP) of bio-physical properties were determined to show how seasonal abnormal changes and trends at locations across the shelf can provide a method for seasonal adaptive sampling. The yearly differences in monthly cycles from 2015 to 2017 at shelf locations, identified elevated chlorophyll-a in several months of 2016 and yearly temperature differences in multiple areas. The seasonal cycle of Euphotic depth, solar UV light penetration, showed a maximum peak (deeper Euphotic depth) at certain shelf locations during the months of September and October and minimal penetration in Aug of 20152016,2017. This information could be useful to understand months for maximum oil UV degradation in case of an oil spill

Comparison of aerosol models from the Ocean Color satellite sensors and AERONET-OC and their impact on reflectance spectra in coastal waters

The choice of aerosol model in the atmospheric correction is critical in the process of the derivation of the water leaving radiances from the Ocean Color (OC) imagery for ocean monitoring. For the current sensors like MODIS, VIIRS and now OLCI atmospheric correction procedures include assumptions about the characteristics of atmospheric aerosols based on relative humidity and particle size distributions. At the sea level, SeaPRISM radiometric instruments which are part of the Aerosol Robotic Network (AERONET) make direct measurements of the water leaving radiances from the ocean, as well as observations of sky radiances from which aerosol parameters such as aerosol optical depth (AOD), fraction of fine and coarse aerosols and others are determined. The discrepancies between satellite and AERONET data are usually significant in coastal areas which are primarily due to the more complex atmospheres near the coast than in the open ocean. Using NASA SeaDAS software, characteristics of aerosols in atmospheric correction models for VIIRS and MODIS sensors are retrieved and compared with the ones from AERONET-OC data in terms of AOD, and remote sensing reflectance (Rrs) at the several AERONET-OC sites. The impact of the solar angles, scattering angles determined by the Sun-sensor geometry and wind speed on the differences in aerosols parameters are evaluated and correlated with the accuracies in the retrieval of the remote sensing reflectance spectra from ocean waters. Significant dependence of AOD on the wind speed is demonstrated which is most likely related to the modeling of the state of the ocean surface.

Coastal Features and River Plumes as Seen with the Hyperspectral Imager for the Coastal Ocean (HICO)

The Hyperspectral Imager for the Coastal Ocean (HICO) is now operating on the International Space Station. Here we review the processing of HICO data and its application to study coastal features and river plumes.