Multiplafform sampling (ship, aircraft, and satellite) of a Gulf Stream warm core ring.

The purpose of this paper is to demonstrate the ability to meet the need to measure distributions of physical and biological properties of the ocean over large areas synoptically and over long time periods by means of remote sensing utilizing contemporaneous buoy, ship, aircraft, and satellite (i.e., multiplatform) sampling strategies. A mapping of sea surface temperature and chlorophyll fields in a Gulf Stream warm core ring using the multiplatform approach is described. Sampling capabilities of each sensing system are discussed as background for the data collected by means of these three dissimilar methods. Commensurate space/time sample sets from each sensing system are compared, and their relative accuracies in space and time are determined. The three-dimensional composite maps derived from the data set provide a synoptic perspective unobtainable from single platforms alone.

Phytoplankton blooming off the u.s. East coast: a satellite description.

A "bloom" of near-surface phytoplankton occurs in the Atlantic Slope region of the western Atlantic Ocean off the U.S. East Coast in the spring. Satellite time series of sea-surface temperature and phytoplankton pigment concentration, derived from measurements of the National Oceanic and Atmospheric Administration NOAA-7 Advanced Very-High-Resolution Radiometer and the National Aeronautics and Space Administration Nimbus-7 Coastal Zone Color Scanner, respectively, give information on the spatial extent and temporal development of such a bloom for a 28-day period in April through May 1982. The phytoplankton concentration of the slope area is comparable to that of the Atlantic Shelf. Total primary productivity of the slope during this period is equivalent to that of the shelf. The primary productivity within a warm-core ring and in the Gulf Stream system is less by a factor of 2.

Phytoplankton pigment concentrations in the Middle Atlantic Bight: comparison of ship determinations and CZCS estimates.

The processing algorithms used for relating the apparent color of the ocean observed with the Coastal-Zone Color Scanner on Nimbus-7 to the concentration of phytoplankton pigments (principally the pigment responsible for photosynthesis, chlorophyll a) are developed and discussed in detail. These algorithms are applied to the shelf and slope waters of the Middle Atlantic Bight and also to Sargasso Sea waters. In all, four images are examined, and the resulting pigment concentrations are compared to continuous measurements made along ship tracks. The results suggest that over the 0.08-1.5-mg/m3 range the error in the retrieved pigment concentration is of the order of 30-40% for a variety of atmospheric turbidities. In three direct comparisons between ship-measured and satellite-retrieved values of the water-leaving radiance the atmospheric correction algorithm retrieved the water-leaving radiance with an average error of approximately 10%. This atmospheric correction algorithm does not require any surface measurements for its application.

Evolution of sea surface temperature in the somali basin during the southwest monsoon of 1979.

Satellite and research vessel observations of sea surface temperature during the southwest monsoon of 1979 show the development of large wedge-shaped areas of cold water along the Somali coast at both 5 degrees and 10 degrees N during June and July. The cold water associated with the large northern and southern Somali eddy systems could be traced several hundred kilometers offshore. By late August the cold wedge at 5 degrees N translated northeastward as far as 10 degrees N at speeds of 15 to 30 centimeters per second, indicating a coalescence of the systems.

Computed relationships between the inherent and apparent optical properties of a flat homogeneous ocean.

Monte Carlo simulations of the transfer of radiation in the ocean are used to compute the apparent optical properties of a flat homogeneous ocean as a function of the inherent optical properties. The data are used to find general relationships between the inherent and apparent optical properties for optical depths tau

Diffuse reflectance of the ocean: some effects of vertical structure.

Monte Carlo computations of the diffuse reflectance of an ocean consisting of two homogeneous layers with differing optical properties are presented, along with a simplified method of computation that uses results of previous Monte Carlo simulations. It is demonstrated that it is impossible to distinguish between thin layers of strong scattering and thick layers of weak scattering through measurement of the diffuse reflectance. Analyzing the two-layer reflectance under the assumption of a homogeneous ocean yields an optical property that is shown to be nearly the average of the associated property over the penetration depth of the medium, i.e., the depth over which the downwelling irradiance falls to l/e of its value at the surface.

Influence of bottom depth and albedo on the diffuse reflectance of a flat homogeneous ocean.

The influence of the bottom albedo on the diffuse reflectance of a flat, homogeneous ocean is computed as a function of bottom depth and albedo for three oceanic scattering phase functions and several values of omega(0). The results show that the bottom can have a large effect on the reflectivity, especially for small optical depths. When combined with the observed optical properties of clear natural water, the calculations are shown to be in good agreement with the observed dependence of in-water nadir radiance spectra, with depth. The apparent independence of the reflectance on the mode of illumination observed earlier for the infinitely deep ocean is found to be invalid for a shallow ocean. The effect of departures of the bottom law of diffuse reflectance from Lambertian is investigated and shown to be considerable in some cases.

Size-refractive index distribution of clear coastal water particulates from light scattering.

Simultaneous measurements of the size distribution and volume scattering function of particles in clear coastal water are used to estimate a particle size-refractive index distribution. Various possibilities of the refractive index distribution and the observed particle distribution are studied systematically using Mie theory. The resulting model has minerals in mid-sizes and organic material in large and small sizes, but does not yield the correct dependence of scattering on wavelength. By assuming the existence of minerals or organics in sizes too small to be measured by the particle counter, two other models are developed, both of which yield acceptable wavelength dependence of scattering. The results of the three models are combined to provide limits on the size-refractive index distribution of the particles. Within these limits, volume scattering functions computed for the particles show good agreement with the measurements.

Irradiance reflectivity of a flat ocean as a function of its optical properties.

The radiative transfer equation has been solved by a Monte Carlo technique for a flat homogeneous ocean with two different incident radiance distributions. The irradiance reflectivity R for photons that penetrate the ocean is presented as a function of the single scattering albedo omega(0), and the scattering phase function P(theta) of the medium. The P(theta)'s used are based on experimental observations. The results clearly show that R depends strongly on both omega(0) and P(theta) but apparently not on the form of the incident radiance distribution. Arguments are presented to show that in clearest ocean water the upwelling field above the surface can provide information only about the upper 25 m of the medium.

Two component mie scattering models of sargasso sea particles.

The volume scattering function is calculated for particle suspensions consisting of two components systematically distributed in a manner consistent with Coulter Counter observations in the Sargasso Sea. The components are assigned refractive indices 1.01-0.01i and 1.15 to represent organic and inorganic particles, respectively. The only models found that reproduce observed scattering functions require a considerable fraction of the suspended particle volume to be organic in nature. This fraction, however, contributes less than 10% to the total scattering function. The model finally chosen indicates that the inorganic particles smaller than 2.5 micro do not occur in large enough concentrations to have a significant effect on the volume scattering function.