988 resultados para Canopy reflectance
Resumo:
In this study four data quality flags are presented for automated and unmanned above-water hyperspectral optical measurements collected underway in the North Sea, The Minch, Irish Sea and Celtic Sea in April/May 2009. Coincident to these optical measurements a DualDome D12 (Mobotix, Germany) camera system was used to capture sea surface and sky images. The first three flags are based on meteorological conditions, to select erroneous incoming solar irradiance (ES) taken during dusk, dawn, before significant incoming solar radiation could be detected or under rainfall. Furthermore, the relative azimuthal angle of the optical sensors to the sun is used to identify possible sunglint free sea surface zones. A total of 629 spectra remained after applying the meteorological masks (first three flags). Based on this dataset, a fourth flag for sunglint was generated by analysing and evaluating water leaving radiance (LW) and remote sensing reflectance (RRS) spectral behaviour in the presence and absence of sunglint salient in the simultaneously available sea surface images. Spectra conditions satisfying "mean LW (700-950 nm) < 2 mW/m**2/nm/Sr" or alternatively "minimum RRS (700-950 nm) < 0.010/Sr", mask the most measurements affected by sunglint, providing efficient flagging of sunglint in automated quality control. It is confirmed that valid optical measurements can be performed 0° <= theta <= 360° although 90° <= theta <= 135° is recommended.
Resumo:
Geochemical analyses of organic matter were carried out on Quaternary sediments from Sites 582 and 583 (Nankai Trough) and on Pliocene to Miocene sediments from Site 584 (Japan Trench), DSDP Leg 87, to evaluate petroleum-generating potential and to characterize the organic matter. The vitrinite-huminite reflectances of indigenous materials for these sites are less than 0.3% indicating the immature nature of the sediments. The sediments, however, contain remarkable amounts of recycled organic materials. The Quaternary sediments from Sites 582 and 583 contain small amounts of amorphous organic matter (less than 0.75 wt.% organic carbon and 66-90% amorphous debris), which is composed of predominantly recycled, oxidized, and over-matured (or matured) Type III material. The amount of hydrocarbon yield indicates that those sediments have lean-source potential for commercial hydrocarbon generation. The Pliocene to Miocene sediments from Site 584 contain organic matter (0.3-1.09 wt.% organic carbon) of predominantly amorphous debris (68-96%) that originated in two sources, an indigenous Type II material and a recycled, over-matured material. Pyrolysis shows an upward increase in the section of hydrocarbon yield and the same trend is also observed in organic-carbon content. The amount of the yield indicates that the Miocene sediments have lean-to-fair source potential and the Pliocene sediments have fair-to-good source potential.
Resumo:
During the last glacial period, the North Atlantic region experienced pronounced, millennial-scale alternations between cold, stadial conditions and milder interstadial conditions-commonly referred to as Dansgaard-Oeschger oscillations-as well as periods of massive iceberg discharge known as Heinrich events. Changes in Northern Hemisphere temperature, as recorded in Greenland, are thought to have affected the location of the Atlantic intertropical convergence zone and the strength of the Indian summer monsoon. Here we use high-resolution records of sediment colour-a measure of terrigenous versus biogenic content-from the Cariaco Basin off the coast of Venezuela and the Arabian Sea to assess teleconnections with the North Atlantic climate system during the last glacial period. The Cariaco record indicates that the intertropical convergence zone migrated seasonally over the site during mild stadial conditions, but was permanently displaced south of the basin during peak stadials and Heinrich events. In the Arabian Sea, we find evidence of a weak Indian summer monsoon during the stadial events. The tropical records show a more variable response to North Atlantic cooling than the Greenland temperature records. We therefore suggest that Greenland climate is especially sensitive to variations in the North Atlantic system-in particular sea-ice extent-whereas the intertropical convergence zone and Indian monsoon system respond primarily to variations in mean Northern Hemisphere temperature.
Resumo:
Dispersed organic matter of plant origin from three sites of the Middle America Trench transect was investigated by coal petrographic methods. Samples from the slope region are rich in lipoid and inert substances. Humic matter is predominant in the trench sediments. Reflectance measurements show that the rank of the organic matter is peat, independent of the tectonic position and age of the samples in question. A slow increase of coalification with depth is observed.
Resumo:
Deep marine successions of early Campanian age from DSDP site 516F drilled at low paleolatitudes in the South Atlantic reveal distinct sub-Milankovitch variability in addition to precession and eccentricity related variations. Elemental abundance ratios point to a similar 5 climatic origin for these variations and exclude a quadripartite structure - as observed in the Mediterranean Neogene - of the precession related cycles as an explanation for the inferred semi-precession cyclicity in MS. However, the semi-precession cycle itself is likely an artifact, reflecting the first harmonic of the precession signal. The sub-Milankovitch variability is best approximated by a ~ 7 kyr cycle as shown by 10 spectral analysis and bandpass filtering. The presence of sub-Milankovitch cycles with a period similar to that of Heinrich events of the last glacial cycle is consistent with linking the latter to low-latitude climate change caused by a non-linear response to precession induced variations in insolation between the tropics.