Enrichment of alkanes within a phytoplankton bloom during an in situ iron enrichment experiment in the western subarctic Pacific     

Sohiko Kameyama  Urumu Tsunogai  Fumiko Nakagawa  Motoki Sasakawa  Daisuke D. Komatsu  Akira Ijiri  Junko Yamaguchi  Takeo Horiguchi  Hiroshi Kawamura  Aika Yamaguchi  Atsushi Tsuda 《Marine Chemistry》2009,115(1-2):92-101

During the Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study ΙΙ (SEEDS-II), we monitored variations in the concentrations of non-methane hydrocarbons (NMHCs), CH₃Cl, N₂O, and CH₄ within a phytoplankton bloom. Stable isotopic compositions were also determined to evaluate the sources of the variations. Although there was little variation in either the concentrations or the stable isotopic compositions of alkenes, CH₃Cl, N₂O, and CH₄ during the 23-day observation period, alkane concentrations increased substantially as the phytoplankton bloomed. The column-integrated quantities of alkanes increased to 3 times pre-bloom levels for C₂H₆, 5 times for C₃H₈, and 20 times for n-C₄H₁₀. The δ¹³C values of both C₂H₆ and C₃H₈ remained almost constant while concentrations increased, whereas that of n-C₄H₁₀ increased by about 12‰. To evaluate the sources of the alkanes produced during the bloom, we compared their δ¹³C values with those of alkanes produced in axenic phytoplankton cultures in our laboratory. We concluded that during the SEEDS-ΙΙ experiment the major portions of C₂H₆ and C₃H₈ were produced during the autolysis of diatoms cells, whereas n-C₄H₁₀ was produced during autolysis of other phytoplankton cells such as cryptophytes and dinoflagellates.  相似文献   

Hourly sea surface temperature retrieval using the Japanese Geostationary Satellite,Multi-Functional Transport Satellite (MTSAT)     

Hiroshi Kawamura  Huiling Qin  Futoki Sakaida  Riza Yuliratno Setiawan 《Journal of Oceanography》2010,66(1):61-70

An algorithm has been developed for retrieving sea surface temperature (SST) from hourly data transmitted from the Japanese Advanced Meteorological Imager (JAMI) aboard a Japanese geostationary satellite, Multi-functional Transport Satellite (MTSAT)-1R. Threshold tests screening cloudy pixels are empirically adjusted to cases of daytime with/without sun glitter, and nighttime. The Non-Linear SST (NLSST) equation, including several new additional terms, is used to calculate MTSAT SST. The estimated SST is compared with drifting and moored buoy measurements, with the result that the bias of the MTSAT SST is nearly 0.0°K. The root mean square (rms) error is about 0.8°K, and it is 0.7°K under the condition that the satellite zenith angle is less than 50°. It is demonstrated that the hourly MTSAT SST produced by the algorithm developed here captures diurnal SST variations in the equatorial sea in mid-November 2006.  相似文献   

Retrieval of surface wave parameters from sar images and their validation in the coastal seas around Japan   总被引：2，自引：0，他引：2  

Jian Sun  Hiroshi Kawamura 《Journal of Oceanography》2009,65(4):567-577

We have developed a scheme to retrieve surface wave parameters (wave height and wave propagation direction) from European Remote-Sensing Satellite (ERS) Synthetic Aperture Radar (SAR) image mode data in coastal seas around Japanese coastlines. SAR spectra are converted to surface wave spectra of swell-dominated or wind-wave dominated cases. The SAR spectrum and SAR-derived wind speed are used to derive the surface wave spectrum. The wind-wave dominated case and swell-dominated case are differentiated by a wind speed of 6 m/s, and processed in different ways because of their different degree of nonlinearity. It is indicated that the cutoff wavelength for retrieval of the wind-wave dominated spectrum is proportional to the root of significant wave height, which is consistent with the results of previous studies. We generated 66 match-ups using the SAR sub-images and the in-situ surface wave parameters, which were measured by wave gauges installed in near-shore seas. Among them, there are 57 swell-dominated cases, and 9 wind-wave dominated cases. The significant wave heights derived from SAR and from in-situ observation agree with the bias of 0.09 m, the standard deviation of 0.61 m and the correlation coefficient of 0.78. The averaged absolute deviation of wave propagation directions is 18.4°, and the trend of the agreement does not depend on the wave height. These results demonstrate that the SAR surface wave spectrum retrieved by the present system can be used to observe the surface wave field in the coastal seas around Japan.  相似文献   

A redetermination of the isotopic abundances of atmospheric Ar   总被引：5，自引：0，他引：5  

Jee-Yon Lee  Kurt Marti  Kenji Kawamura  Hee-Soo Yoo  Jin Seog Kim 《Geochimica et cosmochimica acta》2006,70(17):4507-4512

Atmospheric argon measured on a dynamically operated mass spectrometer with an ion source magnet, indicated systematically larger ⁴⁰Ar/³⁶Ar ratios compared to the generally accepted value of Nier [Nier A.O., 1950. A redetermination of the relative abundances of the isotopes of carbon, nitrogen, oxygen, argon, and potassium. Phys. Rev. 77, 789-793], 295.5 ± 0.5, which has served as the standard for all isotopic measurements in geochemistry and cosmochemistry. Gravimetrically prepared mixtures of highly enriched ³⁶Ar and ⁴⁰Ar were utilized to redetermine the isotopic abundances of atmospheric Ar, using a dynamically operated isotope ratio mass spectrometer with minor modifications and special gas handling techniques to avoid fractionation. A new ratio ⁴⁰Ar/³⁶Ar = 298.56 ± 0.31 was obtained with a precision of 0.1%, approximately 1% higher than the previously accepted value. Combined with the ³⁸Ar/³⁶Ar (0.1885 ± 0.0003) measured with a VG5400 noble gas mass spectrometer in static operation, the percent abundances of ³⁶Ar, ³⁸Ar, and ⁴⁰Ar were determined to be 0.3336 ± 0.0004, 0.0629 ± 0.0001, and 99.6035 ± 0.0004, respectively. We calculate an atomic mass of Ar of 39.9478 ± 0.0002. Accurate Ar isotopic abundances are relevant in numerous applications, as the calibration of the mass spectrometer discrimination.  相似文献   

Transport phenomena in kaolinite clay: Molecular simulation,homogenization analysis and similitude law     

Jung Hae Choi  A. H. M. Faisal Anwar  Katsuyuki Kawamura  Yasuaki Ichikawa 《国际地质力学数值与分析法杂志》2009,33(5):687-707

Kaolinite is a common clay mineral. It is a nanomaterial with a platelet crystalline structure. In order to analyze the behavior of kaolinite, its microscopic structure and material properties must be specified correctly. A molecular dynamics (MD) simulation is used for determining the microscale properties of hydrated kaolinite, and these properties are introduced into a multiscale homogenization analysis (HA). We previously developed such an MD/HA technique to investigate seepage, diffusion, sorption and consolidation in bentonite clay (Proceedings of the Science Basis for Nuclear Waste Management, Davos, Switzerland, vol. XXI. Material Research Society: Warrendale, PA, 1997; 359–366; Eng. Geol. 1999; 54 :21–31; Eng. Geol. 2001; 60 :127–138; Coupled Thermo‐Hydro‐Mechanical‐Chemical Processes in Geo‐systems. Elsevier: Amsterdam, 2005; 457–464). We here apply the method to kaolinite clay to investigate the permeability, diffusion and related similitude law. The obtained results are supported by existing experimental data. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Study on SST front disappearance in the subtropical North Pacific using microwave SSTs     

Chunhua Qiu  Hiroshi Kawamura 《Journal of Oceanography》2012,68(3):417-426

We investigated the processes relating to the weakening of the SST front in the subtropical front (STF) zone using the Advanced Microwave Scanning Radiometer for the Earth Observing System SSTs for 7?years with temporal/spatial resolutions of 1?day/12.5?km. In April, the SST front is strong with a high gradient magnitude (GM) and Jensen–Shannon divergence (JSD) band; in August, SSTs become uniform (28–30?°C), together with small GMs (<0.8?°C/100?km) and JSDs (<0.75). Since the SST front features become invisible in GM/JSD snapshots and weekly–monthly averaged images, we call this phenomenon ‘SST front disappearance (SFD)’. The SFD occurs in August, but the number of high SSTs (>30?°C) in August is smaller than that in July, which indicates that the SFD results from not only the increase in lower SSTs but also the decrease in higher SSTs. In June and July, the GM distributions have quite large standard deviations compared to those in May and August. We also investigated the vertical profile of STF using in situ temperature/salinity profiles. It was revealed that the SFD influence extends to 50?m depth. The area of high integrated heat flux and shallow mixed layer depth were found to correspond to the area where the GM decreases from 0.9 to 0.6?°C/100?km during June–August. Quantitative analyses confirmed that the SFD mechanism may be attributable to the establishment of the shallow mixed layer by the high integrated heat flux from May to July. From July to August, the SST heating/cooling in the north/south of the SST front may accelerate the SFD.  相似文献   

Parameterization of rain cell properties using an advection-diffusion model and rain gage data     

Akira Kawamura  Kenji Jinno  Ronny Berndtsson  Takashi Furukawa 《Atmospheric Research》1996,42(1-4)

To reduce flooding risks and improve urban drainage management, there is a need to increase the forecasting accuracy for rainfall models on small typical urban time and space scales. Increased rainfall forecasting accuracy will in turn improve runoff prediction and thus, prevent flooding hazards, decrease pollution discharge through combined sewers, increase waste water treatment efficiency, etc. For this purpose, we analyzed the parameters of a two-dimensional stochastic advection-diffusion model including a Fourier domain method and an extended Kalman filter algorithm for investigation of motion, shape, size, and intensity distribution of convective rainfall. The resulting set of model parameters (advective velocity, apparent turbulent diffusion, and development/decay of rainfall rate) is used to study convective rainfall variability. It appears that the speed at which the rainfall cell is advected is not dependent on the cell development stage or apparent diffusion. Instead, there is a dependence between the source/sink term and apparent diffusion. This can be explained by the turbulent updraft of warm air which results in large rainfall intensity increase. This strong turbulence results in larger diffusion (and vice versa). The behavior of the model parameters is therefore physically explainable and relevant. The results can be used as first choice of parameter values when modeling convective rainfall over ungaged areas.  相似文献   

Long-chain carboxylic acids in pyrolysates of Green River kerogen     

Kimitaka Kawamura  Eu Tannenbaum  B.J. Huizinga  I.R. Kaplan 《Organic Geochemistry》1986,10(4-6)

Long-chain fatty acids (C₁₀-C₃₂), as well as C₁₄-C21 isoprenoid acids (except for C₁₈), have been identified in anhydrous and hydrous pyrolyses products of Green River kerogen (200–400°C, 2–1000 hr). These kerogen-released fatty acids are characterized by a strong even/odd predominance (CPI: 4.8-10.2) with a maximum at C₁₆ followed by lesser amounts of C₁₈ and C₂₂ acids. This distribution is different from that of unbound and bound geolipids extracted from Green River shale. The unbound fatty acids show a weak even/odd predominance (CPI: 1.64) with a maximum at C₁₄, and bound fatty acids display an even/odd predominance (CPI: 2.8) with maxima at C₁₈ and C₃₀. These results suggest that fatty acids were incorporated into kerogen during sedimentation and early diagenesis and were protected from microbial and chemical changes over geological periods of time. Total quantities of fatty acids produced during heating of the kerogen ranged from 0.71 to 3.2 mg/g kerogen. Highest concentrations were obtained when kerogen was heated with water for 100 hr at 300°C. Generally, their amounts did not decrease under hydrous conditions with increase in temperature or heating time, suggesting that significant decarboxylation did not occur under the pyrolysis conditions used, although hydrocarbons were extensively generated.  相似文献   

Tightly bound aliphatic acids in Lake Biwa sediments: Their origin and stability     

Kimitaka Kawamura  Ryoshi Ishiwatari 《Organic Geochemistry》1984,7(2):121-126

Tightly bound geolipids were separated from a 200 m sediment core of Lake Biwa by a second saponification of sediments from which unbound and bound lipids had been extracted. Tightly bound fatty acids, β-hydroxy acids, ω-hydroxy acids and α,ω-dicarboxylic acids were released; their concentrations ranged from 4.7–31.5, 5.6–60.5, 3.4–9.5 and 0.2–5.4 μg/g dry sediment, respectively. These geolipids were considered to be incorporated in humic substances.Tightly bound fatty acids showed a unimodal distriution with a peak at C₁₆, suggesting that they originate from algae and bacteria and that they are more stable than unbound and bound fatty acids in the sediments. Most of the total β-hydroxy acids, which probably originate from bacteria, were found in the tightly bound fraction. This suggests that a large portion of tightly bound geolipids are formed in the water column and in surface sediments as a result of microbial alteration dead algae. Each class of tightly bound lipids showed higher concentrations between depths of 3 and 15 m in the sediments, where primary production was thought to be enhanced in the past.  相似文献   

Water-Soluble dicarboxylic acids, ketoacids and dicarbonyls in the atmospheric aerosols over the southern ocean and western pacific ocean   总被引：2，自引：0，他引：2  

Haobo Wang  Kimitaka Kawamura  Koji Yamazaki 《Journal of Atmospheric Chemistry》2006,53(1):43-61

Water-soluble dicarboxylic acids (DCAs), ketoacids, and α-dicarbonyls in the marine aerosol samples collected over the Southern Ocean and western Pacific Ocean were determined. Oxalic acid was the most abundant species, followed by malonic acid and then succinic acid. It is suggested that aerosol concentrations of the organics over the Southern Ocean in this work represent their global background levels. Over the Southern Ocean, total concentrations of DCAs ranged from 2.9 to 7.2 ng m⁻³ (average: 4.5 ng m⁻³), ketoacids from 0.14 to 0.40 ng m⁻³ (av.: 0.28 ng m⁻³), and dicarbonyls from 0.06 to 0.29 ng m⁻³ (av.: 0.11 ng m⁻³). Over the western Pacific, total concentrations of DCAs ranged from 1.7 to 170 ng m⁻³ (av.: 60 ng m⁻³), ketoacids from 0.08 to 5.3 ng m⁻³ (av.: 1.8 ng m⁻³), and dicarbonyls from 0.03 to 4.6 ng m⁻³ (av.: 0.95 ng m⁻³). DCAs over the western Pacific have constituted a large fraction of organic aerosols with a mean DCAs-C/TC (total carbon) of 7.0% (range: 0.59–14%). Such a high value was in contrast to the low DCAs-C/TC (av.: 1.8%; range: 0.89–4.0%) for the Southern Ocean aerosols. Based on the relative abundances and latitudinal distributions of these organics, we propose that long-range atmospheric transport is more important over the western Pacific Ocean, in contrast, in situ photochemical production is more significant over the Southern Ocean although absolute concentrations of the organics are much lower.  相似文献