Sensitivity of Snowfall Characteristics to Meteorological Conditions in the Yeongdong Region of Korea

This study investigates the characteristics of cold clouds and snowfall in both the Yeongdong coastal and mountainous regions under different meteorological conditions based on the integration of numerical modeling and three-hourly rawinsonde observations with snow crystal photographs for a snowfall event that occurred on 29?30 January 2016.We found that rimed particles predominantly observed turned into dendrite particles in the latter period of the episode when the 850 hPa temperature decreased at the coastal site,whereas the snow crystal habits at the mountainous site were largely needle or rimed needle.Rawinsonde soundings showed a well-defined,two-layered cloud structure along with distinctive wind-directional shear,and an inversion in the equivalent potential temperature above the low-level cloud layer.The first experiment with a decrease in lower-layer temperature showed that the low-level cloud thickness was reduced to less than 1.5 km,and the accumulated precipitation was decreased by 87%compared with the control experiment.The difference in precipitation amount between the single-layered experiment and control experiment(two-layered)was not so significant to attribute it to the effect of the seeder?feeder mechanism.The precipitation in the last experiment by weakening winddirectional shear was increased by 1.4 times greater than the control experiment specifically at the coastal site,with graupel particles accounting for the highest proportion(~62%).The current results would improve snowfall forecasts in complicated geographical environments such as Yeongdong in terms of snow crystal habit as well as snowfall amount in both time and space domains.     

New Discovery of the Early Cretaceous Volcanic Rocks on the Barton Peninsula, King George Island,Antarctica and Its Geological Significance

Ages determined with the 40Ar/39Ar isotopic system affirms the Early Cretaceous volcanic activity in the Barton Peninsula, King George Island, Antarctica. Two specimens of basaltic andesite collected from the lowermost volcanic sequence of the peninsula were irradiated and analyzed in different experiments, yielding an identical age spectrum, and two magmatic thermal events of the Early Cretaceous (120.4± 1.6 Ma, 119± 1 Ma) and Early Tertiary (53.1± 1.5 Ma, 52± 1 Ma) are distinguished. The former is interpreted to represent the primary cooling age of basaltic andesite, whereas the latter is the thermal reset age caused by the intrusion of granitic pluton. These new ages clearly indicate that volcanism was active during the Early Cretaceous on the Barton Peninsula and that intensive hydrothermal alteration and mineralization of Mesozoic volcanic rocks resulted from Tertiary magmatism.     

Precambrian crustal evolution in Rangrim Massif , Korean Peninsula

Petrological, chronological and geotectonic geological analysis of Precambrian metamorphic rock in Korean Peninsula shows that the remnants ( > 314 Ga) of continental nuclei crust were formed in the Paleo-archean in the Rangrim Massif. In the massif, the main formation ages of continental crust range from 3.2 Ga to 2.5 Ga, its important growing period was 2.8 - 2.5 Ga. The subsequent expansion period of the Rangrim Massif was 2.4 - 2.2 Ga. The division events occurred in 1.85 Ga and in the Late Paleoproterozoic－Early Mesoproterozoic, respectively. Since then the massif was relatively stable. However, the last division of the Rangrim Massif occurred at 793 Ma.     

Effect of the Bottom Topography on Tsunami Propagation in the East （Japan） Sea

A study of tsunami events in the East （Japan） Sea using continuous Galerkin finite element model, aiming at reproducing tsunami waves generated by underwater earthquakes in 1983 and 1993 respectively has been performed focusing on the geographic extent of a topographic feature in the East （Japan） Sea. Numerical models can be the proper tools to study the combined effects of realistic topography. Subsequently, using the FEM based two-dimensional model we have simulated the smoothed and flattened topographic effects by removal of Yamato Rise and seamounts for the cases of tthe 1983 Central region earthquake tsunami and the 1993 southwestern Hokkaido earthquake tsunami. The results have shown that there will be higher tsunamis along the eastern coasts of Korea in general except some areas, like Sokcho with removal of topographic highs, thus providing complicated bottom topography of the East （Japan） Sea as effective tsunami energy scattering.     

1990年以来北京密云水库主要水环境因子时空分布特征

根据19902011年密云水库共12个监测点的月监测资料,采用聚类分析研究各监测点水环境相似性及空间分布特征,采用因子分析识别影响水质的主要因子并评价各采样点的综合水质.通过绝对主成分多元回归分析,获得汛期和非汛期各因子对各水质指标的贡献率.利用季节性Kendall检验及流量调节检验对密云水库库区水化学特征和水质状况时空分布特征进行了研究.结果表明：汛期水质主要受到农业营养物质的影响,其次为生物化学因素和有机物的影响.非汛期水质主要受到农牧业排放因素的影响,其次为人类活动和生物化学因素的影响.因子得分综合评价显示,汛期辛庄桥、内湖和大关桥综合水质较差,潮河、库西和白河综合水质较好.非汛期辛庄桥、石佛桥和大关桥综合水质较差,库东、套里和恒河综合水质较好.主要水质指标的年际变化规律不同,但最终都趋于平稳.与潮河、白河入库水质变化相比,库区水质变化趋势较小,上游入库水质和库区水质都整体趋好.除白河入库的总氮和总磷外,其他监测指标的变化趋势经流量调节前后基本一致,表明流量并不是引起水质趋势变化的主要因素,水质的变化主要是由于污染源变化而引起.     

2011年长江中下游旱涝急转成因初步分析

以2011年1~6月长江中下游"旱涝急转"事件为例,研究了长江中下游旱涝急转与大尺度环流和海温异常的关系,初步得到以下引发旱涝急转的原因:(1)中高纬度大气环流出现快速调整,迅速由强冬季风形势调整为两槽一脊环流形势所控制,进而造成长江中下游由受中高纬度系统控制转变为冷暖空气对峙之地;(2)西太平洋副热带高压位置和强度迅速调整,1~5月来自热带地区的水汽输送条件差,长江中下游地区水汽辐合较常年明显偏弱。6月,水汽输送和收支状况发生根本性转变,长江中下游表现为显著的水汽辐合中心,且明显强于常年;(3)6月青藏高原上空存在显著的气旋性异常环流,利于对流活动发展,受其底部异常西风的影响,对流活动频繁地东传至长江中下游地区,增强了梅雨锋的强度,先后引发了5次强降水过程;(4)前期持续的La Ni?a事件及其变化通过影响Walker环流、西太平洋副热带高压等大气环流系统,为旱涝急转事件的发生提供了有利的背景条件。     

中国海-西太平洋莫霍面深度分布特征及其地质意义

中国海-西太平洋位于欧亚板块、印澳板块和太平洋板块的交汇处,构造运动剧烈,地质情况复杂,是认识板块运动、洋陆相互作用、物质交换和能量传递不可多得的窗口,而莫霍面深度对于研究壳幔结构以及深部动力过程有着重要的意义.本文使用最新的覆盖全球的重力和地形数据,收集了深地震测深、多道地震测深等剖面183条,数字化得到2982个控制点,使用带控制点的三维界面反演方法来约束反演过程,得到中国海-西太平洋莫霍面深度,由莫霍面形态分析可知大洋板块的俯冲和印澳板块与欧亚板块的碰撞对西太平洋边缘海的形成演化有着重要作用.结合地热、岩石圈厚度、地震活动等地质地球物理资料,分析得知研究区内各个海域莫霍深度和地壳性质的变化是处于不同构造演化阶段的表现.并在马里亚纳沟弧盆拟合一条重力2.5维剖面,结果表明热物质上涌导致了马里亚纳海槽处地幔密度减小,马里亚纳海槽以及帕里西维拉海盆到西马里亚纳海岭的下地壳高密度异常是由残留的岩浆岩引起的.     

Influence of Tropical Cyclone Landfalls on Spatiotemporal Variations in Typhoon Season Rainfall over South China

This study examined the impact of tropical cyclone (TC) landfalls on the spatiotemporal variations in the rainfall over South China for the period 1957–2005. The target region was selected to show the noteworthy contribution of TC landfalls to the total rainfall during the typhoon season (July–October). Two prevailing spatial variations in the rainfall were obtained from an EOF analysis. The first EOF mode displays singlesign variability over South China with an explained variance of 23.4%. The associated t...     

济南市PM10中度以上污染的天气条件分析

对济南市空气污染物PM10中度以上污染日的地面、高空气象条件做统计分析,得出:沙尘造成的PM10中度以上污染主要与蒙古气旋和强冷空气活动有关,表现为风力大,相对湿度小,气温和气压变化明显等特征;非沙尘造成的PM10中度以上污染主要是天气形势稳定、污染物不断累积的结果,出现时间有相对连续性,表现为风力较小、相对湿度大、气温和气压变化不明显的特点。从地面气压场上可分为弱气压场、弱倒槽或倒槽型、均压场型三种形势。此分析为济南市中度以上污染日的预报提供了帮助,并可及时采取措施,控制或减少污染物的排放量。     

Characteristics and Nonlinear Growth of the Singular Vector Related to a Heavy Rainfall Case over the Korean Peninsula

In this study,singular vectors related to a heavy rainfall case over the Korean Peninsula were calculated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) adjoint modeling system.Tangent linear and adjoint models include moist physical processes,and a moist basic state and a moist total energy norm were used for the singular-vector calculations.The characteristics and nonlinear growth of the first singular vector were analyzed,focusing on the relationship between the basic state and the singular vector.The horizontal distribution of the initial singular vector was closely related to the baroclinicity index and the moisture availability of the basic state.The temperature-component energy at a lower level was dominant at the initial time,and the kinetic energy at upper levels became dominant at the final time in the energy profile of the singular vector.The nonlinear growth of the singular vector appropriately reflects the temporal variations in the basic state.The moisture-component energy at lower levels was dominant at earlier times,indicating continuous moisture transport in the basic state.There were a large amount of precipitation and corresponding latent heat release after that period because the continuous moisture transport created favorable conditions for both convective and nonconvective precipitation.The vertical propagation of the singular-vector energy was caused by precipitation and the corresponding latent heating in the basic state.