东亚地区春季二氧化硫的输送与转化过程研究I.模式及其验证

结合新近评估的东亚地区污染源资料,作者利用一个耦合的区域化学输送模式系统以探讨东亚地区春季期间气象过程、气相与液相化学过程、非均相化学过程、气溶胶过程和干湿沉降过程对二氧化硫输送及转化过程的影响,并研究二氧化硫和硫酸盐气溶胶的空间分布及变化特征.模拟的二氧化硫和硫酸盐气溶胶的浓度值与2001年春季飞机和地面获取的观测值进行了比较.比较结果显示,模拟值与观测值具有很好的一致性,模式系统很好地反映了二氧化硫和硫酸盐气溶胶的分布特征和变化规律,再现了许多观测到的重要特征,为进一步分析模拟结果奠定了基础.     

Bed morphology and grain size characteristics around a spur dyke

This paper presents an experimental study on the local bed morphology and grain size characteristics around an impermeable spur dyke.A series of experiments are conducted with different types of sedime...     

Size fraction and class composition of phytoplankton in the Antarctic marginal ice zone along the 140°E meridian during February–March 2003

We investigated the size fraction and pigment-derived class compositions of phytoplankton within the euphotic zone of the Antarctic marginal ice zone between 63.3°S and 66.5°S along the 140°E meridian on two consecutive cruises in the late austral summer and early austral autumn of 2003. We observed significant temporal and spatial variations in phytoplankton size and taxonomic composition, although chlorophyll a concentrations were generally below 1 μg l⁻¹ during both periods. Microphytoplankton (>20 μm), mainly diatoms, were prominent in the euphotic zone in the southernmost area around 66.5°S during late summer. In the rest of the study area during both cruises, the phytoplankton community was dominated by pico- and nano-sized populations (<20 μm) throughout the euphotic zone. The small-size populations mostly consisted of diatoms and haptophytes, although chlorophytes were dominant in extremely cold water (−1.5°C) below the overlying warm water around 65.5°S during late summer. From late summer to early autumn, chlorophytes declined in abundance, probably due to increasing temperature within the euphotic zone (−1 to 0°C). These pico- and nano-phytoplankton-dominated populations were often accompanied by relatively high concentrations of ammonium, suggesting the active regeneration of nutrients within the small-size plankton community.     

Detailed measurements of thickness and grain size of a widespread onshore tsunami deposit in Phang‐nga Province,southwestern Thailand

Measurements of thickness and grain size along flow‐parallel transects across onshore deposits of the 2004 Indian Ocean tsunami revealed macroscopic horizontal variations and provided new insights into tsunami sedimentation. The tsunami caused severe erosion of beaches, river mouths, and the shallow seafloor along the coast of southwestern Thailand and supplied sufficient sediment to deposit a kilometer‐wide blanket of sand on the land surface. The tsunami deposits generally fine landward with some fluctuations caused by local entrainment and settlement of sediments. Sediments of medium and fine sand are restricted to a few hundreds of meters inland from their source, whereas finer grained sediments were suspended longer and deposited 1 km or more inland. Although the thickness of the tsunami deposits is strongly influenced by local topography, they generally thin landward. In areas of low‐relief topography, the rate of landward thinning is exponential and reflects the dominance of sediment supply to nearshore areas over that to areas farther inland.     

Investigation of ULF Seismo-Magnetic Phenomena in Kanto, Japan During 2000–2010: Case Studies and Statistical Studies

In order to clarify the ultra low frequency (ULF) seismo-magnetic phenomena, a sensitive geomagnetic network has been installed in Kanto, Japan. In this study, we have analyzed geomagnetic data observed during the past decade in Izu and Boso Peninsulas. Energy of ULF geomagnetic signals at the frequency around 0.01 Hz has been investigated by wavelet transform analysis. To identify anomalous changes in ionospheric disturbances, the station Memabutsu has been chosen as a reference station. Case studies of magnitude 6 class earthquakes have demonstrated that there are unusual geomagnetic energy enhancements in the vertical component before the main shocks. Statistical studies by superposed epoch analysis have indicated that, before a sizeable earthquake, there are clearly higher probabilities of ULF anomalies than after the earthquake: statistical results of daily counts were found significant at about 3–4 weeks before, 1 week before, few days before, and 1 day after the event for Seikoshi station in Izu and around 2 weeks before, few days before, and 1 day after the event for Kiyosumi station in Boso, respectively.     

Observed response of marine boundary layer cloud to the interannual variations of summertime Oyashio extension SST front

Active roles of both sea surface temperature (SST) and its frontal characteristics to the atmosphere in the mid-latitudes have been investigated around the western boundary current regions, and most studies have focused on winter season. The present study investigated the influence of the variation of the summertime Oyashio extension SST front (SSTF) in modulating low-level cloud properties (i.e., low-level cloud cover [LCC], cloud optical thickness [COT], and shortwave cloud radiative effect [SWCRE]) on inter-annual timescales, based on available satellite and Argo float datasets during 2003–2016. First, we examined the mechanism of summertime SSTF variability itself. The strength of the SSTF (S_SSTF), defined as the maximum horizontal gradient of SST, has clear inter-annual variations. Frontogenesis equation analysis and regression analysis for subsurface temperature indicated that the inter-annual variations of the summertime S_SSTF in the western North Pacific are closely related to the variations of not surface heat flux, but western boundary currents, particularly the Oyashio Extensions. The response of low-level cloud to intensified S_SSTF is that negative SWCRE with positive COT anomaly in the northern flank of the SSTF can be induced by cold SST anomalies. The spatial scale of the low-level cloud response was larger than the SST frontal scale, and the spatial distribution of the response was mainly constrained by the pathways of Kuroshio and Oyashio Extensions. Multi-linear regression analysis revealed that the local SST anomaly played largest role in modulating the SWCRE and COT anomalies among the cloud controlling factors (e.g., estimated inversion strength, air-temperature advection) accounting for more than 50% of the variation. This study provides an observational evidence of the active role of local SST anomalies in summertime associated with the western boundary currents to the oceanic low-level cloud.

     

Driftwood deposition from debris flows at slit-check dams and fans

Experience shows that debris flows containing large woody debris (driftwood) can be more damaging than debris flows without driftwood. In this study, the deposition process of debris flows carrying driftwood was investigated using numerical simulations and flume experiments. Debris-flow trapping due to driftwood jamming in a slit-check dam was also investigated. A numerical model was developed with an interacting combination of Eulerian expression of the debris flow and Lagrangian expression of the driftwood, in which the fluctuating coordinates and rotation of the driftwood were treated stochastically. The calculated shapes and thicknesses of a debris-flow fan and the positions and orientations of the deposited driftwood on a debris-flow fan were consistent with experimental flume results. The jamming of driftwood in a slit-check dam was evaluated based on geometry and probability. The simulated results of outflow discharge and the proportion of driftwood passed through the slit-check dam also agreed with the experimental results.     

Detection and isolation of p-nitrophenol-lowering bacteria from intestine of marine fishes caught in Japanese waters

To determine the existence of p-nitrophenol (PNP)-lowering bacteria in intestine of Japanese coastal fish, the gastro-intestinal contents were incubated in Brain Heart Infusion (BHI) broth and minimal medium (MM) broths containing 1 mmol/L PNP at 30 °C for 7 days. Among 26 samples of 19 fish species, 17 samples showed a decrease in PNP of 0.5-0.8 mmol/L in BHI broth, but no decrease was shown in MM broth. Eighteen PNP-lowering bacterial strains were isolated from four fishes. All of the strains were identified as Lactococcus lactis subsp. lactis. Three L. lactis strains JS1-3 isolated from Japanese seabass Lateolabrax japonicus showed the highest PNP-lowering activity (0.44 mmol/L). Optimum temperature and pH for the growth and PNP decreasing corresponded with the marine environment. These results suggested that marine fishes have PNP decreasing bacteria in their intestine. These bacteria might protect host fish from toxicities of PNP and PNP related compounds.     

Empirical ocean-color algorithms to retrieve chlorophyll-a, total suspended matter, and colored dissolved organic matter absorption coefficient in the Yellow and East China Seas

A bio-optical dataset collected during the 1998?C2007 period in the Yellow and East China Seas (YECS) was used to provide alternative empirical ocean-color algorithms in the retrieval of chlorophyll-a (Chl-a), total suspended matter (TSM), and colored dissolved organic matter (CDOM) absorption coefficients at 440 nm (ag₄₄₀). Assuming that remote-sensing reflectance (Rrs) could be retrieved accurately, empirical algorithms for T_Chl (regionally tuned Tassan??s Chl-a algorithm) in case-1 waters (T_Chl2i in case-2 waters), T_TSM (regionally tuned Tassan??s TSM algorithm), and T_ag440 or C_ag440 (regionally tuned Tassan??s or Carder??s ag₄₄₀ algorithm) were able to retrieve Chl-a, TSM, and ag₄₄₀ with uncertainties as high as 35, 46, and 35%, respectively. Applying the standard SeaWiFS Rrs, T_Chl was not viable in the eastern part of the YECS, which was associated with an inaccurate SeaWiFS Rrs retrieval because of improper atmospheric correction. T_Chl behaved better than other algorithms in the turbid case-2 waters, although overestimation was still observed. To retrieve more reliable Chl-a estimates with standard SeaWiFS Rrs in turbid water (a proxy for case-2 waters), we modified T_Chl for data with SeaWiFS normalized water-leaving radiance at 555 nm (nLw₅₅₅) > 2 mW cm^?2 ??m^?1 sr^?1 (T_Chl2s). Finally, with standard SeaWiFS Rrs, we recommend switching algorithms from T_Chl2s (for case-2 waters) to MOC_Chl (SeaWiFS-modified NASA OC4v4 standard algorithm for case-1 waters) for retrieving Chl-a, which resulted in uncertainties as high as 49%. To retrieve TSM and ag₄₄₀ using SeaWiFS Rrs, we recommend empirical algorithms for T_TSM (pre-SeaWiFS-modified form) and MT_ag440 or MC_ag440 (SeaWiFS Rrs-modified forms of T_ag440 or C_ag440). These could retrieve with uncertainties as high as 82 and 52%, respectively.