Airborne plumes of desert dust from North Africa are observable all year on satellite images over the Tropical Atlantic. In addition to its radiative impact, it has been suggested that this mineral ...dust has a substantial influence on the marine productivity. This effect is however difficult to gauge because present atmospheric correction algorithms for ocean color sensors are not capable of handling absorbing mineral dust. We apply a new approach to atmospheric correction in which the atmosphere is removed and the case 1 water properties are derived simultaneously. Analysis of SeaWiFS images acquired off Western Africa during a dust storm demonstrates the efficacy of this approach in terms of increased coverage and more reliable pigment retrievals.
Eros: Shape, Topography, and Slope Processes Thomas, P.C.; Joseph, J.; Carcich, B. ...
Icarus (New York, N.Y. 1962),
January 2002, 2002-01-00, 20020101, Letnik:
155, Številka:
1
Journal Article
Recenzirano
Stereogrammetric measurement of the shape of Eros using images obtained by NEAR's Multispectral Imager provides a survey of the major topographic features and slope processes on this asteroid. This ...curved asteroid has radii ranging from 3.1 to 17.7 km and a volume of 2535±20 km3. The center of figure is within 52 m of the center of mass provided by the Navigation team; this minimal difference suggests that there are only modest variations in density or porosity within the asteroid. Three large depressions 10, 8, and 5.3 km across represent different stages of degradation of large impact craters. Slopes on horizontal scales of ∼300 m are nearly all less than 35°, although locally scarps are much steeper. The area distribution of slopes is similar to those on Ida, Phobos, and Deimos. Regions that have slopes greater than 25° have distinct brighter markings and have fewer large ejecta blocks than do flatter areas. The albedo patterns that suggest downslope transport of regolith have sharper boundaries than those on Phobos, Deimos, and Gaspra. The morphology of the albedo patterns, their lack of discrete sources, and their concentration on steeper slopes suggest transport mechanisms different from those on the previously well-observed small bodies, perhaps due to a reduced relative effectiveness of impact gardening on Eros. Regolith is also transported in talus cones and in connected, sinuous paths extending as much as 2 km, with some evident as relatively darker material. Talus material in at least one area is a discrete superposed unit, a feature not resolved on other small bodies. Flat-floored craters that apparently contain ponded material also suggest discrete units that are not well mixed by impacts.
We report application and validation of a spectral optimization algorithm for processing SeaWiFS data in Case 1 waters. The algorithm couples a simplified aerosol model with a sophisticated ...water-reflectance model to simultaneously retrieve both atmospheric and ocean parameters. Two of the retrieved ocean properties—the absorption coefficient of colored detrital material and the chlorophyll
a concentration—are validated by comparison with “surface” truth obtained with airborne and space-borne sensors. We show that employing a more complete water reflectance model significantly improves the decoupling between the oceanic and atmospheric optical signals. Methodologies for applying the algorithm to Case 2 waters and for delineating terrestrial vs. marine chromophoric dissolved organic matter (CDOM) are suggested.
Perpendicular recording may be the most viable, near future, replacement for the longitudinal core technology in ultrahigh-density magnetic disk storage. Central to this mode of recording is a soft ...underlayer (SUL) which facilitates flux flow between writer poles, and is responsible for an effective increase in recording field. However, there are controversies concerning the effectiveness and limitations of using soft underlayers; among which are readback noise and inadequate switching torque. Patterned SUL is proposed as a new and viable approach to SUL limitations in perpendicular media, with improved system performance. Numerical models have been developed using commercially available FEM and BEM software suites (ANSYS and Ampere) to demonstrate key advantages of patterned SUL in perpendicular media
Micromagnetics of a soft underlayer Litvinov, D.; Chomko, R.M.; Abelmann, L. ...
IEEE transactions on magnetics,
09/2000, Letnik:
36, Številka:
5
Journal Article, Conference Proceeding
Odprti dostop
The micromagnetic properties of a soft underlayer in perpendicular media are studied. It is shown that stray fields from a recording layer can substantially modify magnetic properties of soft ...underlayer material. The degree of modification is determined by the characteristic bit size in the recording layer and by the soft underlayer material magnetic characteristics. It is found that there exists a thin layer within a soft underlayer with reduced permeability. The effects of the presence of such a reduced permeability region within a soft underlayer on both reading and writing processes are discussed.
Dynamics of perpendicular recording heads Litvinov, D.; Chomko, R.; Wolfson, J. ...
IEEE transactions on magnetics,
07/2001, Letnik:
37, Številka:
4
Journal Article, Conference Proceeding
Odprti dostop
3D modeling and inductance measurements were used to design an ultra-high frequency perpendicular system. Kerr microscopy and spin-stand experiments with focused ion beam (FIB) trimmed perpendicular ...heads and perpendicular media directly verified the high frequency concepts.
During the southwest monsoon (SWM) in the northern Arabian Sea, the phytoplankton bloom associated with upwelling has remained incompletely characterized by satellite ocean-color observations. This ...is due to the prevalence of dust storms in the region from May to September that prevents good satellite-derived chlorophyll retrievals. To ameliorate this problem, SeaWiFS data from May to September 2000 were processed with the spectral-matching algorithm (SMA) using a suite of Saharan dust models. The use of SMA significantly increased chlorophyll data recovery in areas otherwise completely masked by standard SeaWiFS processing, and permitted a description of the bloom over the SWM period. Maps of the frequency and spatial distribution of TOMS-absorbing aerosol index indicate that Africa and Arabia are the most probable dust sources, and that the nearshore area parallel to the Arabian coast was the most affected by dust events during the SWM, which is also where chlorophyll retrievals are also poorest. Weekly averages of the SeaWiFS images produced using the SMA show that at the onset of upwelling in June, the bloom along the Omani coast has limited offshore extent except for a few small thin filaments. From July to September, the high-chlorophyll features evolve into more complex structures that extend offshore into the Arabian Sea interior. In October, when the SWM has ended, the filaments appear to merge, forming a high-chlorophyll band off the Omani coast. Quikscat wind data suggest that the widespread filament formation occurs only when the SWM winds begin to weaken, which results in greater spatial variability in the zone of maximum wind stress (the Findlater Jet). Although the bloom is generally restricted to the cold-water upwelling area (as indicated by TMI sea-surface temperatures) that lies northwest of the Findlater Jet axis, the high-chlorophyll structures do not occur solely in association with coldest upwelling features. This suggests that thermal satellite imagery cannot be used to infer chlorophyll distributions for periods in which no ocean-color data are available, e.g., the earlier JGOFS cruises.
This paper will present an unconventional way to answer the above questions. In contrast to the conventional flat geometry of SUL, it is proposed to use a patterned SUL. FEM-based simulations will be ...performed to illustrate many key benefits of the use of a patterned SUL.
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