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11.
Toru Hirawake Hiroo Satoh Takashi Ishimaru Yukuya Yamaguchi Motoaki Kishino 《Journal of Oceanography》2000,56(3):245-260
Both historic and currently operational chlorophyll algorithms of the satellite-borne ocean color sensors, such as SeaWiFS, were evaluated for in situ spectral radiation and chlorophyll data in some Case I waters, including the waters in the Indian Ocean sector of the Southern Ocean. Chlorophyll a concentration of the data set (n = 73) ranged from 0.04 to 1.01 mg m–3. The algorithms had higher accuracy for the low- and mid-latitude waters (RMSE: 0.163–0.253), specifically the most recently developed algorithms of OCTS and Sea WiFS showed 0.163 and 0.170 of Root Mean Square Errors, respectively. However, these algorithms had large errors (0.422–0.621) for the Southern Ocean data set and underestimated the surface chlorophyll by more than a factor of 2.6. The absorption coefficients in the blue spectral region retrieved from remote sensing reflectance varied in a nonlinear manner with chlorophyll a concentration, and the value in the Southern Ocean was significantly lower than that in the low- and mid-latitude waters for each chlorophyll a concentration. The underestimation of chlorophyll a concentration in the Southern Ocean with these algorithms was caused by the lower specific absorption coefficient in the region compared with the low- and mid-latitude waters under the same chlorophyll a concentration. 相似文献
12.
A seismic coda wave from local earthquakes is an indication of heterogeneity in the crust and upper mantle, and codaQ (Q
c
) is the parameter defining the temporal decay of the coda wave. ButQ
c
estimates obtained with the conventional least-square method are not based on any solid statistical background, assuming the Gaussian distributiona priori. In this study, we propose a statistically reliable estimation method of estimatingQ
c
using the maximum likelihood method, and show its validity and usefulness with the data from the 1986 Joint Seismological Research in the western Nagano Prefecture. We found first that theQ
c
estimation with the maximum likelihood method is statistically valid and its reliability can be checked with the -square test. Next,Q
c
around Ohtaki village, within the studied area, is estimated using the maximum likelihood method. The averageQ
c
value at low frequencies (up to 2 Hz) is one of the lowest in the world, which is in harmony with the geological setting of the site condition directly above an active fault. 相似文献
13.
Nobumitsu Tsunematsu Hironori Iwai Shoken Ishii Motoaki Yasui Yasuhiro Murayama Kohei Mizutani 《Boundary-Layer Meteorology》2009,131(2):263-275
The relationship between local meteorological fields and the behaviour of airborne Asian dust that arrived in the Tokyo metropolitan
area on 1 April 2007 with the passage of a synoptic-scale cold front has been investigated through Doppler lidar observations,
experiments using a regional atmospheric numerical model, and analyses of surface and upper-air meteorological observations.
Results of the Doppler lidar observations showed that the Asian dust passed above the metropolitan area with strong south-westerly
winds with speeds of 15–26 m s−1. Meteorological fields reproduced by the numerical experiments showed the development of a surface-based stable layer in
the metropolitan area caused by nocturnal radiational cooling near the ground surface and south-westerly warm air advection
at upper levels. The blocking effect of the mountainous region located to the west of the metropolitan area induced an area
of stagnant air inside the metropolitan area and promoted the stable layer development. Although strong downdrafts prevailed
in the upper air, the airborne Asian dust did not spread to the ground when the stable layer was formed. These results strongly
indicate that the developed stable layer prevented strong downdrafts from spreading to the ground, acting as an obstacle to
the transport of the Asian dust particles from the upper air towards the ground. This is considered to be one of the main
causes of the low appearance frequency of Asian dust phenomena near the ground in the Tokyo metropolitan area and eastern
Japan. 相似文献
14.
J. Ishizaka H. Fukushima M. Kishino T. Saino M. Takahashi 《Journal of Oceanography》1992,48(3):305-327
Phytoplankton pigment (chlorophylla+pheopigments) distributions in a regional upwelling around the Izu Peninsula obtained by the Coastal Zone Color Scanner (CZCS) on May 23, 1982, were compared with ship-observed pigment and satellite sea-surface-temperature distributions. Pigment concentrations detected by the CZCS were positively correlated with the ship-observed pigment concentrations. However, they were about factor of 5 smaller when atmospheric correction parameters known for typical oceanic and land aerosol were used and when the parameters were estimated with the clear water algorithm. When the atmospheric correction parameters were adjusted so that a pigment concentration derived by CZCS was equivalent to a concentration obtained by the ship at a coincide location, the pattern and magnitudes of the CZCS-derived pigment distributions showed remarkable agreement with ship-observed pigment distributions. Thus, the normal atmospheric correction algorithm may not be suitable for waters around Japan, and the development of better atmospheric correction methods combined with more verification programs is required. The pigment distributions showed patterns that were similar to those observed in sea-surface-temperature distributions. Cold water showed higher pigment concentrations, and warm water showed lower pigment concentrations. The Kuroshio, which can be identified by generally warm, low pigment water, showed a large meander which flowed offshore at Shiono-misaki, looped back onshore from Hachijo Island to Omaezaki and then flowed northeast along the Izu and Boso Peninsulas. Locally upwelled water along the Izu Peninsula was seen clearly in the sea-surface-temperature and CZCS pigment distributions as a region of cold water and high pigment concentrations. Cold upwelled waters were also found at the eastern side of the Izu Islands, but pigment concentrations in these waters was not always high. This difference in the two upwelling regions may be caused by different physical and biological interactions. 相似文献
15.
Measurements of underwater irradiance revealed that the vertical attenuance in upward irradiance for wavelengths above 520
nm decreased with increasing depth, while the attenuance in the remaining wavelength region and also the attenuance in the
downward irradiance in the whole wavelength range kept almost constant values. In this paper, it is suggested that the decrease
in the attenuance for the upward irradiance above 520 nm can be ascribed to the Raman scattering of water molecules excited
by the intense blue-green light in the downward irradiance.
The pure water Raman scattering function at a scattering angle of 90° is measured and the results are used for the theoretical
computation of upward irradiance generated by Raman scattering. Then, the difference between observed upward irradiance and
the upward irradiance obtained by extrapolation from that in the shallow layers is computed under the assumption of constant
irradiance attenuance. Since this difference is expected to represent the upward irradiance generated by Raman scattering,
its value is compared with the upward irradiance due to Raman scattering obtained by theoretical computation. The similarity
between the two upward irradiances so evaluated supports the view that Raman scattering makes a significant contribution to
upward irradiance in the longer wavelength region. 相似文献
16.
In order to evaluate near-surface water quality parameters from spectral irradiance reflectance observed just below the surface, models of both radiative transfer and optical properties of sea water are used. The computed water quality parameters are compared with those determined directly from concurrent surface water samples. In this comparison, efforts have been made to minimize the number of spectral irradiance reflectance used in the computation while ensuring that the computed water quality parameters fit well to the observed ones.The observed water quality parameters were found to be closely represented by those computed from the irradiance reflectance at wavelengths of 400 nm, 440 nm, 510 nm and 600 nm, and the fit is as good as the fit of observed water quality parameters to those computed from the irradiance reflectances at 151 wavelengths located between 400 nm and 700 nm at intervals of 2 nm. This implies that the water quality parameters can be evaluated from at least four radiances observed at high altitude, if the effects of the atmosphere and the sea surface can be correctly removed. 相似文献
17.
Intrinsic oxygen-fugacity (fO2) measurements were made on five ordinary chondrites, a carbonaceous chondrite, an enstatite chondrite, a pallasite, and a tektite. Results are of the form of linear log plots. Except for the enstatite chondrite, measured results agree well with calculated estimates by others.The tektite produced fO2 values well below the range measured for terrestrial and lunar rocks. The lowpressure atmospheric regime that is reported to follow large terrestrial explosions, coupled with a very high temperature, could produce glass with fO2 in the range measured.The meteorite Salta (pallasite) has low fO2 and lies close to Hvittis (E6). Unlike the other samples, results for Salta do not parallel the iron-wüstite buffer, but are close to the fayalite-quartz-iron buffer in slope.Minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites. fO2 values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of fO2 conditions. The samples equilibrated with respect to fO2 in relatively short time on heating. Equilibration with respect to fO2 in ordinary chondrites takes place between grades 3 and 4 of metamorphism. Application of P ? T ? fO2 relations in the system C-CO-CO2 indicates that the ordinary chondrites were metamorphosed at pressures of 3–20 bars, as it appears that they lay on the graphite surface.A steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior, an oxidized near-surface layer, and an interior that is increasingly reduced with depth; a shallow thermal gradient will produce the reverse. A body heated by accretion on the outside will have a reduced exterior and oxidized interior. Meteorites from the same parent body clearly are not required to have similar redox states. 相似文献
18.
Chlorophyll a concentrations (chla) and the absorption coefficients of total particulate matter [a
p()], phytoplankton [a
ph()], detritus [a
d()], and colored dissolved organic matter: CDOM [a
CDOM()] were measured in seawater samples collected in the subarctic North Pacific and the southern Bering Sea during the summer of 1997. We examined the specific spectral properties of absorption for each material, and compared the light fields in the Western subarctic Gyre (area WSG) with those in the Alaskan Gyre (area AG), and the southern Bering Sea (area SB). In the area WSG, the irradiance in the surface layer decreased markedly, indicating high absorption. In the area AG, the radiant energy penetrated deeply, and the chl a and absorption values were low throughout the water column. In the area SB, light absorption was high in the surface layer on the shelf edge and decreased with increasing depth; on the other hand, light absorption was low in the surface layer in the shelf area and increased with increasing depth. 相似文献
19.
Noboru Okami Motoaki Kishino Shigehiko Sugihara Noburu Takematsu Sanae Unoki 《Journal of Oceanography》1983,38(6):362-372
The spectral measurements of the attenuation coefficient of sea water and the absorption coefficient of suspended particles and of yellow substance were made with a spectrophotometer for the sea waters sampled in Tokyo Bay. These parameters can be used to compute the expected spectral irradiance reflectance. Some relationships between the optical properties of sea water and the concentration of dissolved organic carbon, the dry weight of suspended matter and chlorophyll-a concentration are presented. On the basis of these results, the possibility of modelling the relationship between optical and material properties is discussed. 相似文献
20.
Motoaki Kishino Takashi Ishimaru Ken Furuya Tomohiko Oishi Kiyoshi Kawasaki 《Journal of Oceanography》1998,54(5):431-436
In-water algorithms for OCTS standard products were developed using in situ data and installed for operationally processing
at NASDA/EOC. This paper describes the in-water algorithms Version 1.0 for chlorophylla concentration, pigment concentration, and attenuation coefficient at a wavelength of 490 nm. The selected OCTS standard algorithms
(Ver. 1.0) are as follows:
相似文献