Interdecadal changes in interannual variability of the global monsoon precipitation and interrelationships among its subcomponents     

Eun-Jeong Lee  Kyung-Ja Ha  Jong-Ghap Jhun 《Climate Dynamics》2014,42(9-10):2585-2601

The interdecadal and the interannual variability of the global monsoon (GM) precipitation over the area which is chosen by the definition of Wang and Ding (Geophys Res Lett 33: L06711, 2006) are investigated. The recent increase of the GM precipitation shown in previous studies is in fact dominant during local summer. It is evident that the GM monsoon precipitation has been increasing associated with the positive phase of the interdecadal Pacific oscillation in recent decades. Against the increasing trend of the GM summer precipitation in the Northern Hemisphere, its interannual variability has been weakened. The significant change-point for the weakening is detected around 1993. The recent weakening of the interannual variability is related to the interdecadal changes in interrelationship among the GM subcomponents around 1993. During P1 (1979–1993) there is no significant interrelationship among GM subcomponents. On the other hand, there are significant interrelationships among the Asian, North American, and North African summer monsoon precipitations during P2 (1994–2009). It is noted that the action center of the interdecadal changes is the Asian summer (AS) monsoon system. It is found that during P2 the Western North Pacific summer monsoon (WNPSM)-related variability is dominant but during P1 the ENSO-related variability is dominant over the AS monsoon region. The WNPSM-related variability is rather related to central-Pacific (CP) type ENSO rather than the eastern-Pacific (EP) type ENSO. Model experiments confirm that the CP type ENSO forcing is related to the dominant WNPSM-related variability and can be responsible for the significant interrelationship among GM subcomponents.  相似文献   

Discharge prediction using hydraulic characteristics of mean velocity equation     

Tai Ho Choo  Soo Kwon Chae  Hyeon Cheol Yoon  Yeon Moon Choo 《Environmental Earth Sciences》2014,71(2):675-683

Discharge is an important factor in river design for water utilization, water control and hydraulic structures; therefore, an accurate estimation of the discharge is required. At present, a rating curve depicting the relationship between a stage and discharge is used to calculate the discharge from river systems. Although the rating curve has an advantage in that it can predict and use the discharge during the flood season in which the measurement is difficult, there is room for improvement as it does not reflect the hydraulic characteristics of rivers. Therefore, in this study, discharge was predicted using the convenient calculation method with empirical mediating variables of the Manning and Chezy equations which were proposed by the author’s previous research as a new methodology for estimating discharge in an open channel. This was proven, based on the data measured in a meandering open channel system in a lab at the Mississippi River in the US and at the Columbia Del Dique Canal, and an accuracy level at a coefficient of 0.8 was demonstrated. Thus, this method, which reflects the hydraulic characteristics and predicts the discharge in a simple manner, is expected to be convenient in practice.  相似文献   

Double injection events of mafic magma into supersolidus Yucheon granites to produce two types of mafic enclaves in the Cretaceous Gyeongsang Basin,SE Korea     

Jong-Sun Kim  Moon Son  Byoung-Hoon Hwang  Ki-Cheol Shin  Hyeongseong Cho  Young Kwan Sohn 《Mineralogy and Petrology》2014,108(2):207-229

Petrographic and geochemical features of the Cretaceous Yucheon granites and their mafic microgranular/magmatic enclaves (MMEs), SE Korea, reveal that the MMEs originated from magma mixing. Mesoscopic and microscopic features indicate that mechanical mixing operated heterogeneously to produce the MMEs with a wide range of sizes and textures. Chemical compositions of amphibole, biotite, and plagioclase rims of both the MMEs and host granites are almost identical, indicating that chemical homogenization took place to some extent after the mechanical mixing. Plagioclase cores, however, have various compositions depending on the host rocks and/or sampling locations, suggesting their sluggish re-equilibration. The MMEs are divided into Type A (low TiO₂, very fine-grained, chilled margins) and Type B (high TiO₂, fine- to medium-grained, no chilled margins). The lower TiO₂ MMEs cooled more rapidly and interacted with granitic magma for a shorter period of time than the higher TiO₂ MMEs. Additionally, the former are less enriched in HREEs than the latter. Zoned plagioclase has two zones of increased An content. These features are indicative of double injection events of mafic magma. A previous model explains the magma mixing as resulting from the generation of a slab window due to Kula-Pacific ridge subduction. The model cannot, however, explain the eastward younging of the granites in Korea, necessitating a new, more elaborate model of Cretaceous geodynamics and magmatism in East Asia.  相似文献   

Holocene migration of oceanic front systems over the Conrad Rise in the Indian Sector of the Southern Ocean     

Kota Katsuki  Minoru Ikehara  Yusuke Yokoyama  Masako Yamane  Boo‐Keun Khim 《第四纪科学杂志》2012,27(2):203-210

There has been limited previous research about Holocene climate variability in the Indian Sector of the Southern Ocean. Here we examine centennial‐scale changes in diatom assemblages and stable isotopic ratios since 10 000 cal a BP in a high‐accumulation‐rate sediment core from the Conrad Rise. Although abundances of dominant diatom taxa (Fragilariopsis kerguelensis and Thalassiothrix antarctica) are comparatively constant, relative abundances of secondary taxa fluctuate. Before c. 9900 cal a BP, winter sea‐ice and cold water covered the Conrad Rise. Following deglaciation the sea‐ice retreated from the Conrad Rise, lagging that of the Atlantic and eastern Indian Sectors by about 1500 a. The Polar Front moved southward during the early Holocene optimum and north Antarctic Zone waters covered the Conrad Rise for about 650 a. After 9300 cal a BP, solar insolation strongly influenced sea surface temperature and primary productivity in the Southern Ocean. In the high‐latitude Indian Sector, productivity increased 1500 a after the onset of late Holocene neoglaciation. Periodic δ¹⁸O and cold‐water diatom taxa spikes (at intervals of 200 and 300–500 a, respectively) occurred after 9300 cal a BP, probably associated with solar activity. Fluctuations in short‐term sea surface temperature and cold‐water taxa are synchronous with changes in δD observed in an east Antarctic ice core. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Wintertime Arctic Oscillation Harbinger of Spring Floods in the Mouth Areas of the North-Eastern European Rivers     

Gorelits  O. V.  Kryjov  V. N.  Rakcheeva  E. A.  Ermakova  G. S. 《Water Resources》2022,49(5):836-844

Water Resources - Based on 1965–2020 series we have shown relationships between the features of the water runoff of the spring flood in mouths of large rivers of North-Eastern Europe and the...  相似文献   

Effects of high-resolution land cover and topography on local circulations in two different coastal regions of Korea: a numerical modeling study   总被引：2，自引：0，他引：2  

Ju-Hee Jeong  Sang-Keun Song  Hwa Woon Lee  Yoo-Keun Kim 《Meteorology and Atmospheric Physics》2012,118(1-2):1-20

The effects of high-resolution land cover (LC) and topography (TP) on coastal wind circulations were evaluated in two different coastal regions of Korea (i.e. a southwestern coast (SWC), including a fairly complex coastline and a number of islands, and an eastern coast (EC), including a simple coastline with high mountains) during spring 2007. These analyses were performed based on a numerical modeling approach, using data sets with different resolutions, such as the LC and TP from the U.S. Geological Survey (USGS-LC and USGS-TP: a 900-m resolution), the LC from the Environmental Geographic Information System (EGIS-LC: a 90-m), and the TP from the Shuttle Radar Topography Mission (SRTM-TP: a 90-m). The combined effects of the LC and TP on the spatial distributions of the coastal winds in the SWC region during the day were somewhat higher than those of the EC region, mainly due to the daytime land surface warming or the extension of the coastal area resulting from changes in the LC. At night, the effects of the EC region were more apparent along the coastline and adjacent sea. From the correlation analyses, the effect of the LC on the vertical wind distributions on land during the day was higher in the SWC region than in the EC region and vice versa for the effect of the TP. In particular, large effects of the LC and TP occurred in the EC region at night and at sea due to the differences in the surface conditions and elevations resulting from the changes in the LC and TP, respectively. In addition, the circulation of coastal winds from the near surface to the upper levels occurred at a relatively high elevation in the EC region (about 1,500?m) relative to the SWC region (about 600?m).  相似文献   

Climate change effects on tropical night days in Seoul, Korea   总被引：1，自引：0，他引：1  

Kyung-Ja Ha  Kyung-Sook Yun 《Theoretical and Applied Climatology》2012,109(1-2):191-203

In Seoul (37.57°N, 126.97°E), South Korea (located at mid-latitudes), the frequency of tropical night (TN) days, which have been defined as days with a minimum temperature greater than 25°C, have shown an increase due to the effects of temperature and water vapor. It was found that TN days accounted for almost 10.2% (July) and 22.1% (August) of the total number of days in respective months during the last decade in Seoul, and these figures may be increasing with climatic change. The daytime and nighttime sky on TN days can contain water vapor when the monsoonal southwesterly flow prevails. This strong wind may induce moisture advection from the warm ocean, and consequently, there is much larger specific humidity over the city during TN days in comparison to non-TN days. The effect of climatic change on the specific humidity is related to an increase in the number of TN days, which has shown an upward trend of 13-day/100-year and is significantly modulated by both water vapor and air temperature during July and August. Moreover, the relative role of water vapor in increasing the frequency of TN days has become much more significant after the 1960s in comparison to that of air temperature, which may be attributed to urbanization in Seoul since the 1960s.  相似文献   

Current status of ENSO prediction skill in coupled ocean–atmosphere models     

Emilia K. Jin  James L. Kinter III  B. Wang  C.-K. Park  I.-S. Kang  B. P. Kirtman  J.-S. Kug  A. Kumar  J.-J. Luo  J. Schemm  J. Shukla  T. Yamagata 《Climate Dynamics》2008,31(6):647-664

The overall skill of ENSO prediction in retrospective forecasts made with ten different coupled GCMs is investigated. The coupled GCM datasets of the APCC/CliPAS and DEMETER projects are used for four seasons in the common 22 years from 1980 to 2001. As a baseline, a dynamic-statistical SST forecast and persistence are compared. Our study focuses on the tropical Pacific SST, especially by analyzing the NINO34 index. In coupled models, the accuracy of the simulated variability is related to the accuracy of the simulated mean state. Almost all models have problems in simulating the mean and mean annual cycle of SST, in spite of the positive influence of realistic initial conditions. As a result, the simulation of the interannual SST variability is also far from perfect in most coupled models. With increasing lead time, this discrepancy gets worse. As one measure of forecast skill, the tier-1 multi-model ensemble (MME) forecasts of NINO3.4 SST have an anomaly correlation coefficient of 0.86 at the month 6. This is higher than that of any individual model as well as both forecasts based on persistence and those made with the dynamic-statistical model. The forecast skill of individual models and the MME depends strongly on season, ENSO phase, and ENSO intensity. A stronger El Niño is better predicted. The growth phases of both the warm and cold events are better predicted than the corresponding decaying phases. ENSO-neutral periods are far worse predicted than warm or cold events. The skill of forecasts that start in February or May drops faster than that of forecasts that start in August or November. This behavior, often termed the spring predictability barrier, is in part because predictions starting from February or May contain more events in the decaying phase of ENSO.  相似文献   

Ternary forecast of heavy snowfall in the Honam area,Korea     

Keon Tae SOHN  Jeong Hyeong LEE  Young Seuk CHO 《大气科学进展》2009,26(2):327-332

The objective of this study is to improve the statistical modeling for the ternary forecast of heavy snowfall in the Honam area in Korea. The ternary forecast of heavy snowfall consists of one of three values, 0 for less than 50 mm, 1 for an advisory (50–150 mm), and 2 for a warning (more than 150 mm). For our study, the observed daily snow amounts and the numerical model outputs for 45 synoptic factors at 17 stations in the Honam area during 5 years (2001 to 2005) are used as observations and potential pre...  相似文献   

Shock waves in the large-scale structure of the Universe     

Dongsu Ryu  Hyesung Kang 《Astrophysics and Space Science》2009,322(1-4):65-70

Cosmological shock waves are induced during hierarchical formation of large-scale structure in the universe. Like most astrophysical shocks, they are collisionless, since they form in the tenuous intergalactic medium through electromagnetic viscosities. The gravitational energy released during structure formation is transferred by these shocks to the intergalactic gas as heat, cosmic-rays, turbulence, and magnetic fields. Here we briefly described the properties and consequences of the shock waves in the context of the large-scale structure of the universe.  相似文献