Simulation of stratospheric ozone in global forecast model using linear photochemistry parameterization

The two types of ozone, the simulation with interactive (prognostic) ozone using linear photochemistry parameterization (LPP) (INTR) and the simulation with non-interactive ozone using ozone climatology (CLIM), were used in the global forecast model. These two types of ozone were compared with ozone observations from the Aura Microwave Lim Sounder (MLS) and ozonesondes from 16-30 September 2008. The INTR is sensitive to LPP schemes while less sensitive to the time average of initial ozone data. Among three LPP schemes, CARIOLLE, COPCAT, and LINOZ, the COPCAT produces ozone profiles with least differences from MLS and ozonesondes. CLIM overestimates MLS at 200-20 hPa while INTR with COPCAT scheme underestimates MLS ozone above 5 hPa. Over the Antarctic in the lower stratosphere CLIM overestimates MLS and ozonesondes whereas INTR underestimates MLS but overestimates the ozonesonde data. Thus, COPCAT agrees better with ozonesonde data than any other LPP schemes and CLIM. Changing the ozone distribution from CLIM to INTR affects temperature profiles mainly through the modification of differential radiative fluxes. The correlations between ozone, differential radiative fluxes, and temperature are distinguished by altitude (or pressure levels). The correlations are strong or moderate between 3-1000 hPa (lower atmosphere) and weak above 3 hPa (upper atmosphere). This study demonstrates that the simulation of ozone using an appropriate LPP scheme is excellent in overcoming the drawbacks of using climatological ozone profiles that poorly agree with observations in extreme ozone hole events.     

Contribution of baseflow during dry spells in irregular channel cross section

The discharge and water level of a gaining stream are known to be maintained during dry spells by baseflow, which is defined as discharge from underground storage. However, the effect of baseflow on a real river is not well known because direct measurements of baseflow in field are difficult to conduct. Therefore, this study attempts to clarify the contribution of baseflow to streamflow and the extent to which the water level is maintained even during dry spells. A digital filter technique is applied to the records of daily mean streamflow in order to estimate the amount of baseflow, and the lateral distribution method is applied to irregular cross sections at observational sites to obtain the stage–discharge rate curve. Through a comparison of the observed data and calculation results, the amount of baseflow is estimated across the channel, in addition to the maximum water level retained during dry spells in relation to the baseflow. Finally, based on the results of an energy conservation model, this study proposes that the source of the amount of baseflow estimated across a channel section may be different from that of the water level maintained during dry spells.     

An SMP critical state model for methane hydrate‐bearing sands

Mechanical properties of methane hydrate‐bearing soils are complex. Their behavior undergoes a significant change when hydrates dissociate and become methane gas. On the other hand, methane hydrates are ice‐like compounds and, depending on the hydrate accumulation habits and the degree of hydrate saturation, may cement soil particles into stronger and stiffer soils. A new constitutive model is proposed that is capable of capturing essential characteristics of hydrate‐bearing soils. The core of the model includes the spatial mobilized plane concept; a transformed stress, t_ij; the critical state; and the subloading framework. The proposed model gives soil responses due to stress changes or hydrate saturation changes or both. The performance of the model has been found satisfactory, over a range of hydrate saturation and confining pressures, using triaxial test data from laboratory‐synthesized samples and from field samples extracted from Nankai Trough, Japan. Copyright © 2015 John Wiley & Sons, Ltd.     

SWAT application to estimate design runoff curve number for South Korean conditions

Runoff estimations based on the standard USDA–NRCS curve number (CN) table without calibration have a tendency to give inaccurate results when the CN values are applied in South Korea which has many high slope watersheds and that has a continental monsoon climate. Particularly for the design flood estimation, accurately calibrated CN values are required because the estimated peak flow is very sensitive to the selection of CN. However, the lack of flood data makes it difficult to calibrate and assign runoff CNs to Korean watersheds. Even if sufficient data are available to estimate CN values, it is also difficult to obtain the direct flows by separating base flows from total runoff hydrographs due to the temporal irregularity of rainfall events and the resulting complex pattern of runoff. Therefore, an alternative method for estimating CNs needs to be developed to overcome these issues. The purpose of this study is to present a method for estimating runoff CNs using the soil and water assessment tool (SWAT) model which can take into account watershed heterogeneities such as climate conditions, land use and soil types. The proposed CN estimation method uses the simulated flow data by SWAT instead of using measured flow data. This method has advantages in estimating CN values spatially for each subbasin division considering watershed characteristics. The use of daily data can reduce the sensitivity to the abnormality that is commonly involved in flow data with a small time scale. The SWAT‐based CN estimation method, combined with the asymptotic CN method, was applied to the Chungju dam watershed in South Korea. A regression equation was then developed from this approach, which was used to estimate CN values that decrease exponentially as rainfall amounts increase and that converge to 60·6 and 79·4 without and with considering subsurface lateral flow, respectively. Furthermore, the CN values for the antecedent moisture conditions were determined using the probabilistic approach. The CN associated with the 50% probability for the Chungju dam watershed is 87·8 which can be taken to be representative of antecedent moisture condition (AMC) II. The CN_I and CN_III associated with 90% and 10% probabilities are 78·9 and 94·1, respectively. The estimated CN_II = 87·8 differs markedly from the geographic information system (GIS)‐based CN 65·0, which implies that the standard USDA–NRCS CN method should be calibrated to the studied area of interest. Copyright © 2010 John Wiley & Sons, Ltd.     

Ecological effects of soil antimony on the crop plant growth and earthworm activity

High levels of antimony have been frequently detected in some industrial sites. This study evaluated the adverse effects of antimony (Sb) on the surface-casting activity of earthworm and the early growths of some important crop plants. Asian earthworm (Perionyx excavates) and four crop plant species (Chinese cabbage, Brassica campestris; wheat, Triticum aestivum; cucumber, Cucumis sativus; and mung bean, Phaseolus radiatus) were exposed to soil antimony in laboratory. Survival, abnormality and the surface-casting activity of earthworm were monitored. Negative effects of the survival and the morphological abnormalities were observed in the P. excavates exposed to Sb. The earthworm activity, expressed as surface cast production, was significantly inhibited with elevated Sb levels. In terms of plant assay, the growth of all test plants was adversely affected in Sb-contaminated soils, and the content of Sb in plant tissues increased with increasing Sb concentration in soil. The results demonstrate that elevated Sb concentrations in soil would inhibit the early growth of crop plants, and the earthworm casting activity that is a key function of earthworm to increase soil fertility. This is the first report on the negative effect of Sb on the casting activity of earthworm as well as the growth of test plant species selected.     

吉林珲春三叠纪高镁闪长岩的发现及地质意义

吉林珲春地区首次发现的高镁闪长岩对于讨论东北地区岩石圈演化历史具有重要意义。该类岩石的锆石LAICPMSU-Pb年龄为241～240Ma,SiO_2和MgO的含量分别介于51.93%～55.85%和3.97%～10.38%之间,具有较高的Mg~#(0.45～0.70),属于钠质钙碱性系列。轻稀土略微富集,但稀土配分曲线近于平坦型,富集Rb,亏损Ba、Nb、Ta、P和Ti等元素。该类岩石的锆石~(176)Hf/~(177)Hf值和ε_(Hf)(t)值分别变化于0.282672～0.283085和1.78～15.95之间,显示地幔来源的特征,最小单阶段模式年龄(t_(DMI)=246Ma)与其侵入年龄(t=240～241Ma)相一致,表明该区乃至延边地区在240Ma左右的中三叠世存在一次重要的地壳增生事件。Sr/Y(3.19～12.48)-Y(19.3×10~(-6)～81.1×10~(-6))和(La/Yb)_N(1.00～3.51)-Yb_N(4.15～14.62)判别图解显示其形成可能与赞岐岩有相似的岩浆过程,即形成于消减带之上的地幔楔环境,由地幔橄榄岩与消减洋壳板片部分熔融产生的富Si质熔体平衡反应形成。综合研究表明,延边地区早三叠世之前为活动陆缘环境,古亚洲洋板块向华北板块之下俯冲。     

Radiocesium reaction with illite and organic matter in marine sediment

The mineralogical effect on the (137)Cs reaction with marine sediment has not been systematically studied yet, even though illite has been known to adsorb Cs preferentially on its frayed edge sites in a low Cs concentration. Ninety-three marine sediment samples were collected near Yangnam, Korea for quantitative X-ray-diffraction (XRD), gamma-ray, and total organic carbon (TOC) analysis. Illite content was in the range of 0-23 wt.% and those of (137)Cs and TOC were minimum detectable activity (MDA) approximately 7.19 Bq/kg-dry and approximately 3.32%, respectively. The illite content in the marine sediment showed a good relationship with the (137)Cs content (R(2)=0.69), but with an increase in the illite content, the relationship became less linear. This trend can be clearly shown in two groups of samples with different size fractions (< and >5Mdvarphi). For the samples of larger particle sizes (low contents of illite), the relationship is linear, but for the samples of the smaller particle sizes (high illite content) it is less linear with a decreased slope, indicating that increase in illite content does not significantly contribute to the fixation of (137)Cs in marine sediment. Rather, the TOC has a more linear relationship with (137)Cs content with no slope change in all particle size ranges. This may indicate that humic materials in marine sediment block the access of (137)Cs to the frayed edge site and reduces the adsorption of (137)Cs on illite and that the organic materials in marine sediment play more important roles in adsorbing Cs than illite.     

Why did the copepod Calanus sinicus increase during the 1990s in the Yellow Sea?

Recent field and retrospective data were combined to investigate variations from 1984 to 1998 in the spring abundance of dominant copepods in the Yellow Sea. A calanoid copepod, Calanus sinicus, was chosen to assess the long-term changes in abundance associated with temperature, salinity, chlorophyll-a and predator abundance. Average anomalies of sea surface temperature (SST), salinity, and the abundance of C. sinicus were positive in the 1990s and negative in the 1980s. The average abundances of C. sinicus in the study area in the 1990s were also significantly higher than those in the 1980s (p<0.01). Catches of the anchovy Engraulis japonicus, a predator of C. sinicus, showed a decreasing trend during the study period. The higher abundances of C. sinicus in the 1990s may have been affected by an increase in water temperature and a decrease in predators, without distinctive changes in chlorophyll-a concentrations during the study period.     

Long-runout pyroclastic surge on a Cretaceous alluvial plain, Republic of Korea

Pyroclastic surge is a dilute and turbulent flow of volcanic gas and tephra that is commonly generated during explosive volcanic eruptions and can threaten lives along its flow paths. Assessing its travel distance and delineating future volcanic hazards have therefore been major concerns of volcanologists. Historical eruptions show that most pyroclastic surges travel a few tens of kilometres or less from their sources. Aeolian or aquagene processes have therefore been evoked for the emplacement of supposed surge deposits much beyond this distance. Here we show that a Cretaceous tuff bed in Korea was emplaced by an exceptionally powerful pyroclastic surge that flowed as far as the most powerful pyroclastic flows that formed the low-aspect-ratio ignimbrites (LARI). This has significant implications for interpreting ancient volcanic eruptions and delineating volcanic hazards by pyroclastic surges, and casts intriguing questions on the eruption dynamics and physics of long-runout pyroclastic surges and their distinction from LARI-forming pyroclastic flows.