Rayleigh scattering by aqueous colloidal silica as a cause for the blue color of hydrothermal water     

Shinji Ohsawa  Takao Kawamura  Nobuki Takamatsu  Yuki Yusa 《Journal of Volcanology and Geothermal Research》2002,113(1-2)

Thermal waters in hydrothermal ponds, bathing pools and the brines of geothermal electric power plants commonly have a characteristic blue color. Although many researchers have assumed that the blue color is due to a colloidal suspension and/or absorption by dissolved ferrous iron or by water itself, there has been no specific effort to identify the physical nature of this phenomenon. We have tested, in synthetic and natural solutions, whether aqueous colloidal silica is responsible for the blue color. Aqueous colloidal silica is formed by silica polymerization in thermal waters of the neutral-chloride type which contain initially monomeric silica in concentrations up to three times above the solubilities of amorphous silica. The hue of the blue thermal waters in the pools tested agrees with that of a synthesized colloidal silica solution. Grain-size analyses of aqueous colloidal silica in the blue-colored thermal waters demonstrate that the color is caused by Rayleigh scattering from aqueous colloidal silica particles with diameters (0.1–0.45 μm) smaller than the wavelengths of visible radiation.  相似文献   

Seasonal changes in stable carbon isotopic composition of n-alkanes in the marine aerosols from the western North Pacific: Implications for the source and atmospheric transport     

James A. Bendle  Kimitaka Kawamura 《Geochimica et cosmochimica acta》2006,70(1):13-26

To constrain seasonal changes in the long-range atmospheric transport of land-derived lipid biomarker compounds, we investigated the compound-specific stable isotopic composition of marine aerosol n-alkanes collected from 1990 to 1993 at a remote island, Chichi-Jima (27°04′N, 142°13′E), in the western North Pacific. Compound-specific isotope analysis revealed, in particular, strong seasonal changes in the δ¹³C values of the C₂₉ and C₃₁n-alkanes (biomarkers for higher plants). Lighter δ¹³C values were observed in winter (typically −32 to −34‰), with a transition to heavier values in summer (typically −28 to −31‰). Using a mixing equation and typical end members for C₃ and C₄ plants, we found that this is due to relative increases in the contributions from C₄ plants in the summer season. Using backward air-mass trajectory analyses, it was shown that the Asian continent was the major source region for C₃ plant material during winter/spring, whereas Indonesia/Australia and possibly the Americas were the major source regions for C₄ material during the summer/autumn. Also observed was an enhanced atmospheric transport of n-alkanes from C₄ plants in 1991 summer/autumn during a strong El Nino event, which was associated with forest and bushfires in Indonesia and Australia. In addition to providing information on contemporary processes, this study also provides a base for future paleoclimatological work in ocean sediments.  相似文献   

Wind-driven circulation in the subarctic north Pacific using altimeter data     

Osamu Isoguchi  Hiroshi Kawamura 《Journal of Earth System Science》2002,111(3):267-279

Time-dependent wind-driven circulation in the subarctic north Pacific is investigated by using Topex/Poseidon (T/P) altimeter data and European Centre for Medium-Range Weather Forecasts (ECMWF) wind data for about 6 years. The first empirical orthogonal function (EOF) of the T/Pderived sea level anomaly (SLA) without the variation related to the steric height change (SLA1) and the first EOF of the ECMWF-based wind stress curl fields represent basin-sized south-north oscillations and their time series agree well with a correlation of 0.49. They appear to express the spin-up and spin-down of the subarctic gyre. The third EOF of SLA (SLA3) and the second EOF of the wind stress curl are also related to the variation of the subarctic gyre. Though the correlation of their time series is 0.27, drastic changes in early winter coincide well. The two EOF pairs can be considered to mean that the SLA variation followed by the latitudinal migration of the Aleutian low is separated into two standing oscillation patterns, that is, the sea level variation combined with SLA1 and SLA3 expresses seasonal variations of the wind-driven circulation of the subarctic gyre. The interannual SLAs constructed by subtracting the SLA1 and SLA3 components clearly show trans-pacific westward propagation even in the high-latitudes. The time series of SLA1 is in agreement with that ofin situ SLAs measured with the tide gauge at Petropavlovsk (53-01N, 158-38E), which implies the possibility to monitor the subarctic circulation using tide gauge data.  相似文献   

On the wave dependence of sea-surface wind stress     

Naoto Ebuchi  Yoshiaki Toba  Hiroshi Kawamura 《Journal of Oceanography》1990,46(4):177-183

Analysis is made of wind and wave data, which were obtained during the passage of Typhoon 8013 at an Ocean Data Buoy Station south of Honshu operated by the Japan Meteorological Agency, in order to investigate the wave dependence of sea-surface roughness parameter in the situation where wind waves are dominant with less significant swells. The data fit better the wave-dependent expression of the wind stress,z _{0 p}/u*=, than to Charnock's formula,gz ₀/u*²=, wherez ₀ is the roughness length, _p the angular frequency of the spectral peak of wind waves,u* the friction velocity of air,g the acceleration of gravity, and are non-dimensional constants. The results are very similar to those of our previous study using data from an oil producing platform in the Bass Strait, Australia, although the type of observation system and the synoptic situation of the winds and wind waves were totally different.  相似文献   

Relations between Sea Surface Temperature and Air-Sea Heat Flux at Periods from 1 Day to 1 Year Observed at Ocean Buoy Stations around Japan     

Hiroshi Murakami  Hiroshi Kawamura 《Journal of Oceanography》2001,57(5):565-580

Relations between sea-surface temperature (T _s) and heat flux at the sea surface (F) have been investigated using data from ocean observation buoys located off Shikoku in the Sea of Japan and in the East China Sea. Wavelet transformation decomposed F and T _s to wavelet coefficients (WLC) in the period-time domain. Assuming one-dimensional heat transfer by eddy diffusion in the upper ocean, the phase difference (δθ) defined as the difference between the phase of the temporal change rate of T _s, and the phase of F ranges statistically from 0 to +π/4 when F changes T _s, and is around −π/2 when heat convergence in the sea (Av) forces T _s. The δθ values are distributed from 0 to +π/4 at one-day and one-year periods at all buoys. WLC amplitude (WLCA) of F at periods from 16 to 32 day periods, which may be caused by the atmospheric ridge-trough systems, maintains energy longer than WLCA at periods from 2 to 16 days, which may be caused by monsoonal surges. At periods from 2 to 64 days, δθ values distribute from 0 to +π/4 or around −π/2 at each event, reflecting the surroundings of each ocean, i.e., Kuroshio recirculation in the off-Shikoku area, water-temperature front in the Sea of Japan, and water exchange in the continental shelf edge in the East China Sea. We demonstrate that the wavelet analysis can characterize the correspondence between irregular signals of F and T _s in various time scales and locations. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Merging satellite infrared and microwave SSTs: Methodology and evaluation of the new SST   总被引：3，自引：0，他引：3  

Lei?GuanEmail author  Hiroshi?Kawamura 《Journal of Oceanography》2004,60(5):905-912

The Global Ocean Data Assimilation Experiment (GODAE) requires the availability of a global analyzed SST field with high-resolution in space (at least 10 km) and time (at least 24 hours). The new generation SST products would be based on the merging of SSTs from various satellites data and in situ measurements. The merging of satellite infrared and microwave SST data is investigated in this paper. After pre-processing of the individual satellite data, objective analysis was applied to merge the SST data from NOAA AVHRR (National Oceanic and Atmospheric Administration, Advanced Very High Resolution Radiometer), GMS S-VISSR (Geostationary Meteorological Satellite, Stretched-Visible Infrared Spin Scan Radiometer), TRMM MI (Tropical Rainfall Measuring Mission, Microwave Imager: TMI) and VIRS (Visible and Infrared Scanner). The 0.05° daily cloud-free SST products were generated in three regions, viz., the Kuroshio region, the Asia-Pacific Region and the Pacific, during one-year period of October 1999 to September 2000. Comparisons of the merged SSTs with Japan Meteorological Agency (JMA) buoy SSTs show that, with considerable error sources from individual satellite data and merging procedure, an accuracy of 0.95 K is achieved. The results demonstrate the practicality and advantages of merging SST measurements from various satellite sensors.  相似文献   

Validation of Daily Amplitude of Sea Surface Temperature Evaluated with a Parametric Model Using Satellite Data     

Yoshimi Kawai  Hiroshi Kawamura 《Journal of Oceanography》2003,59(5):637-644

The authors have verified a regression model for the evaluation of the daily amplitude of sea surface temperature (ΔSST) proposed by Kawai and Kawamura (2002). The authors investigated the accuracy of satellite data used for the evaluation and showed that ΔSST error caused by satellite data error is less than ±0.7 K. The evaluated ΔSSTs were compared with in situ values. Its root-mean-square error is about 0.3 K or less, except for a coastal region, and it has a bias of more than +0.1 K in the tropics. This bias can be removed by considering latent heat flux. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Distributions of low molecular weight dicarboxylic acids in the North Pacific aerosol samples   总被引：1，自引：0，他引：1  

Kimitaka Kawamura  Kouichi Usukura 《Journal of Oceanography》1993,49(3):271-283

Marine aerosol samples collected from the North Pacific atmosphere were studied for molecular distributions of dicarboxylic acids by using a capillary gas chromatography and mass spectrometery. A homologous series of dicarboxylic acids (C₂–C₁₀) was detected in the marine aerosol samples as dibutyl esters. All the samples showed that the smallest diacid (oxalic acid: C₂) was the most abundant and comprised 41–67% of the total diacids. The second most abundant species was malonic acid (C₃) or succinic acid (C₄). The diacids with more carbon numbers were generally less abundant. Total diacid concentration range was 17–1040 ng m^–3, which accounted for up to 1.6% of total aerosol mass. This indicates that low molecular weight dicarboxylic acids are important class of organic compounds in the marine atmosphere. The concentrations were generally higher in the western North Pacific and lower in the central North Pacific. The major portion of diacids is probably derived from the Asian Continent and East Asian countries by long-range atmospheric transport and partly fromin situ photochemical production in the marine atmosphere.  相似文献   

Retrieval of Sea Surface Temperature from TRMM VIRS     

Lei Guan  Hiroshi Kawamura  Hiroshi Murakami 《Journal of Oceanography》2003,59(2):245-249

The Visible and Infrared Scanner (VIRS) aboard the Tropical Rainfall Measuring Mission (TRMM) is a five-channel radiometer with wavelength from 0.6 to 12 μm. Daily 0.125° sea surface temperature (SST) data from VIRS were first produced at the National Space Development Agency (NASDA) for comparison with SST from TRMM Microwave Imager (TMI). In order to obtain accurate high spatial resolution SST for the merging of SST from infrared and microwave measurements, new SST retrieval coefficients of the Multichannel SST (MCSST) algorithm were generated using the global matchups from VIRS brightness temperature (BT) and Global Telecommunications System (GTS) SST. Cloud detection was improved and striping noise was eliminated. One-year global VIRS level-1B data were reprocessed using the MCSST algorithm and the advanced cloud/noise treatments. The bias and standard deviation between VIRS split-window SST and in situ SST are 0.10°C and 0.63°C, and for triple-window SST, are 0.06°C and 0.48°C. The results indicate that the reprocessing algorithm is capable of retrieving high quality SST from VIRS data. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Cloning of cytochrome P450 1A (CYP1A) genes from the hermaphrodite fish Rivulus marmoratus and the Japanese medaka Oryzias latipes     

Il-Chan Kim  Young Ja Kim  Yong-Dal Yoon  Shoji Kawamura  Yong-Sung Lee  Jae-Seong Lee   《Marine environmental research》2004,58(2-5):125

To use two small fish Rivulus marmoratus (Cyprinodontiformes, Rivulidae) and the Japanese medaka Oryzias latipes (Belloniformes) as testing models in molecular ecotoxicology, we have cloned the cytochrome P450 1A (CYP1A) gene after screening of both genomic DNA libraries, and sequenced 11,863 and 7,243 bp including all the exons and introns with promoter regions, respectively. The Rivulus and the medaka CYP1A gene consisted of seven exons (including non-coding exons) with high homology to mammals. In the promoter region, Rivulus CYP1A gene has seven xenobiotic response elements (XREs) and two metal response elements (MREs), while the Japanese medaka CYP1A gene has six XREs and four MREs. Interestingly, medaka CYP1A gene has a number of MREs at the promoter, which may affect its response on metal exposure. We describe here the gene structure of both fish CYP1A genes.  相似文献