Velocities and Temperatures of an Ellerman Bomb and Its Associated Features     

Heesu Yang  Jongchul Chae  Eun-Kyung Lim  Hyungmin Park  Kyuhyoun Cho  Ram Ajor Maurya  Donguk Song  Yeon-Han Kim  Philip R. Goode 《Solar physics》2013,288(1):39-53

We investigated the velocity and temperature characteristics of an Ellerman bomb (EB) and its associated features based on observations made with the Fast Imaging Solar Spectrograph (FISS) and a broadband TiO filter of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. In the TiO images of the photospheric level, we found a granular cell expanding in two opposite directions near the site of the EB. When one end of this granule reached the EB site, the transverse speed of the tip of the expanding granule rapidly decreased and the EB brightened. The wings of the Hα profile of the EB indicated that the EB was blueshifted up to 7 km?s^?1. About 260 s after the EB brightening, a surge was seen in absorption and varied from a blueshift of 20 km?s^?1 to a redshift of 40 km?s^?1 seen in the Hα and Ca ii 8542 Å lines. From the Doppler absorption width of the two lines determined by applying the cloud model, we estimated the mean temperature of the surge material to be about 29000 K and the mean speed of nonthermal motion to be about 11 km?s^?1. We discuss the physical implications of our results in terms of magnetic reconnection and processes related to it.  相似文献   

Benthic habitat quality change as measured by macroinfauna community in a tidal flat on the west coast of Korea     

Keun-Hyung Choi  Sung-Mi Lee  Sang-Min Lim  Mark Walton  Gyung-Soo Park 《Journal of Oceanography》2010,66(3):307-317

Yellow Sea tidal flats are internationally recognised for their contribution to biological diversity and yet are under enormous pressure from reclamation, pollution and overexploitation. The benthic macroinfauna community is the dominant community on these tidal flats and a reliable indicator of benthic environmental changes. We surveyed the current benthic macroinfauna community of the Ganghwa Southern Tidal Flat, the largest remaining Korean mud flat in the Yellow Sea, in order to examine changes in the environmental situation of this benthic ecosystem. The results show a significant decline in species diversity from the last survey made in 2003, and a shift in species composition with appearances of polychaetes indicative of pollution and physical disturbances and other opportunistic species becoming dominant in both density and biomass. The benthic community shift observed during the two study periods may be associated with increased nutrient pollution as well as increased physical disturbances in this area. However, we recognise the limitations of the data both in frequency and scope but believe the significant changes to the composition of the benthic fauna are sufficient to warrant concern. Observations are required to examine the extent to which these human activities induce benthic community shift in this tidal flat.  相似文献   

Rare earth elements in bottom sediments of major rivers around the Yellow Sea: implications for sediment provenance     

Zhaokai Xu  Dhongil Lim  Jinyong Choi  Shouye Yang  Hoisoo Jung 《Geo-Marine Letters》2009,29(5):291-300

Rare earth elements (REEs) of 91 fine-grained bottom sediment samples from five major rivers in Korea (the Han, Keum, and Yeongsan) and China (the Changjiang and Huanghe) were studied to investigate their potential as source indicator for Yellow Sea shelf sediments, this being the first synthetic report on REE trends for bottom sediments of these rivers. The results show distinct differences in REE contents and their upper continental crust (UCC)-normalized patterns: compared to heavy rare earth elements (HREEs), light rare earth elements (LREEs) are highly enriched in Korean river sediments, in contrast to Chinese river sediments that have a characteristic positive Eu anomaly. This phenomenon is observed also in primary source rocks within the river catchments. This suggests that source rock composition is the primary control on the REE signatures of these river sediments, due largely to variations in the levels of chlorite and monazite, which are more abundant in Korean bottom river sediments. Systematic variations in ΣLREE/ΣHREE ratios, and in (La/Yb)–(Gd/Yb)_UCC but also (La/Lu)–(La/Y)_UCC and (La/Y)–(Gd/Lu)_UCC relations have the greatest discriminatory power. These findings are consistent with, but considerably expand on the limited datasets available to date for suspended sediments. Evidently, the REE fingerprints of these river sediments can serve as a useful diagnostic tool for tracing the provenance of sediments in the Yellow Sea, and for reconstructing their dispersal patterns and the circulation system of the modern shelf, as well as the paleoenvironmental record of this and adjoining marginal seas.  相似文献   

Analytical solution for transient groundwater flow during slug test in vertical cutoff walls     

Jeehee Lim  Dongseop Lee  Hyun‐Jun Choi  Hangseok Choi 《国际地质力学数值与分析法杂志》2014,38(17):1855-1870

An analysis method for transient groundwater flow during slug tests performed in vertical cutoff walls is presented. The analytical solution for evaluating hydraulic conductivity of vertical cutoff walls is derived by applying the method of images to the previously developed analytical solution that is exclusively applicable to an infinite aquifer. Two distinct boundary conditions are considered to account for the configuration of the vertical cutoff wall: the wall‐soil formation interfaces with or without the existence of filter cakes, that is, constant‐head boundary and no‐flux boundary conditions. A series of type curves is constructed from the analytical solution and compared with those of a partially penetrated well within an aquifer. The constant‐head boundary condition provides faster hydraulic head recovery than the aquifer case. On the other hand, the no‐flux boundary condition leads to a delayed hydraulic head recovery. The greater the shape factor and well offset from the center of the cutoff wall, and the smaller the width of the cutoff wall, the greater the effect of the boundary condition observed in the type curves. This result shows the significance of considering proper boundary conditions at the vertical cutoff wall in analyzing slug tests. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Impact of climate change on the persistent turbidity issue of a large dam reservoir in the temperate monsoon region     

Hyungseok Park  Sewoong Chung  Eunju Cho  Kyoungjae Lim 《Climatic change》2018,151(3-4):365-378

Long-term discharge of turbid water from reservoirs after flood events is a major socioenvironmental problem in many countries, including Korea. This study used a suite of mathematical models to simulate the fate of turbidity flows in the Soyanggang Reservoir in Korea, an important source of drinking water for the Seoul Capital Area, in response to extreme floods based on the Representative Concentration Pathway 4.5 climate scenario. It evaluated the effectiveness of the selective withdrawal facility (SWF), installed recently in the Soyanggang Reservoir to control persistent turbidity. Extreme floods with a maximum daily inflow rate greater than the historical maximum observed in 2006 were projected to occur four times in this century. The fate and transport of turbidity flows were highly influenced by both the thermal stability of the reservoir and the season in which the flood event occurred. Thus, SWF operations should consider the timing of extreme events (i.e., the imminence of the autumn turnover) to mitigate the impact of high turbidity on the water supply and downstream ecosystem. It was found to be ineffective under extreme events if these occurred in two consecutive years. Current reservoir operations, which rely heavily on the SWF, are likely to be inadequate to overcome the negative effects of extreme-turbidity events on reliably providing safe water supplies. Coping with the worst event expected to occur in the future would require additional countermeasures such as bypassing high-turbidity water.  相似文献   

Development of an Operational Hybrid Data Assimilation System at KIAPS     

In-Hyuk Kwon  Hyo-Jong Song  Ji-Hyun Ha  Hyoung-Wook Chun  Jeon-Ho Kang  Sihye Lee  Sujeong Lim  Youngsoon Jo  Hyun-Jun Han  Hanbyeol Jeong  Hui-Nae Kwon  Seoleun Shin  Tae-Hun Kim 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):319-335

This study introduces the operational data assimilation (DA) system at the Korea Institute of Atmospheric Prediction Systems (KIAPS) to the numerical weather prediction community. Its development history and performance are addressed with experimental illustrations and the authors’ previously published studies. Milestones in skill improvements include the initial operational implementation of three-dimensional variational data assimilation (3DVar), the ingestion of additional satellite observations, and changing the DA scheme to a hybrid four-dimensional ensemble-variational DA using forecasts from an ensemble based on the local ensemble transform Kalman filter (LETKF). In the hybrid system, determining the relative contribution of the ensemble-based covariance to the resultant analysis is crucial, particularly for moisture variables including a variety of horizontal scale spectra. Modifications to the humidity control variable, partial rather than full recentering of the ensemble for humidity further improves moisture analysis, and the inclusion of more radiance observations with higher-level peaking channels have significant impacts on stratosphere temperature and wind performance. Recent update of the operational hybrid DA system relative to the previous 3DVar system is described for detailed improvements with interpretation.  相似文献   

Land response to atmosphere at different resolutions in the common land model over East Asia     

Daeun Kim  Yoon-Jin Lim  Minseok Kang  Minha Choi 《大气科学进展》2016,33(3):391-408

Towards a better understanding of hydrological interactions between the land surface and atmosphere, land surface models are routinely used to simulate hydro-meteorological fluxes. However, there is a lack of observations available for model forcing, to estimate the hydro-meteorological fluxes in East Asia. In this study, Common Land Model (CLM) was used in offline-mode during the summer monsoon period of 2006 in East Asia, with different forcings from Asiaflux, Korea Land Data Assimilation System (KLDAS), and Global Land Data Assimilation System (GLDAS), at point and regional scales, separately. The CLM results were compared with observations from Asiaflux sites. The estimated net radiation showed good agreement, with r =0.99 for the point scale and 0.85 for the regional scale. The estimated sensible and latent heat fluxes using Asiaflux and KLDAS data indicated reasonable agreement, with r = 0.70. The estimated soil moisture and soil temperature showed similar patterns to observations, although the estimated water fluxes using KLDAS showed larger discrepancies than those of Asiaflux because of scale mismatch. The spatial distribution of hydro-meteorological fluxes according to KLDAS for East Asia were compared to the CLM results with GLDAS, and the GLDAS provided online. The spatial distributions of CLM with KLDAS were analogous to CLM with GLDAS, and the standalone GLDAS data. The results indicate that KLDAS is a good potential source of high spatial resolution forcing data. Therefore, the KLDAS is a promising alternative product, capable of compensating for the lack of observations and low resolution grid data for East Asia.  相似文献   

Firm entry modes and Chinese business networks: Malaysian investments in Vietnam          下载免费PDF全文

Guanie Lim 《Singapore journal of tropical geography》2016,37(2):176-194

This paper examines the Malaysian Chinese firms that have expanded into Vietnam. Based on research and qualitative personal interviews with Malaysian Chinese firms that have invested in Vietnam, the paper unpacks the entry modes that these firms have undertaken. It argues that the Malaysian Chinese firms prefer joint ventures in their Vietnamese businesses to wholly‐owned subsidiaries and personal direct investments. This paper also argues that such investments are often embedded in social and intraethnic ties, which connect Malaysian Chinese firms with Vietnam's ethnic Chinese businessmen. To this end, these firms tend to rely on informal ties and nonmarket institutions in the form of the ethnic Chinese business networks. Nevertheless, the Malaysian Chinese firms are not averse to collaborating with nonethnic Chinese firms that enjoy a good relationship with the Vietnamese state. This observation is especially marked in the property and construction, and finance sectors.  相似文献   

A second-order particle tracking method     

Seok Lee  Heung-Jae Lie  Kyu-Min Song  Chong-Jeanne Lim 《Ocean Science Journal》2005,40(4):201-208

An accurate particle tracking method for a finite difference method model is developed using a constant acceleration method. Being assumed constant temporal and spatial gradients, the new method permits temporal-spatial variability of particle velocity. Test results in a solid rotating flow show that the new method has second-order accuracy. The performance of the new method is compared with that of other methods; the first-order Euler forward method, and the second-order Euler predictorcorrector method. The new method is the most efficient method among the three. It is more accurate and efficient than the other two.  相似文献   

Geochemical-mineralogical-characteristics of the pre-Holocene sediments in Haenam Bay, west coast of Korea     

D. I. Lim  H. N. Kim  H. S. Jung 《Geo-Marine Letters》2003,22(4):210-217

The geochemical and mineralogical characteristics of pre-Holocene core sediments from Haenam Bay, southwest coast of Korea, were examined for post-depositional diagenetic changes and used to assess the provenance of fine-grained sediments in the region. The geochemical and mineralogical compositions of the sediments vary very little with core depth (Holocene to pre-Holocene age), except for the upper part of the pre-Holocene sedimentary layer. In this case, smectite and chlorite are depleted, presumably due to intensive subaerial weathering and low pH conditions. Highly mobile elements (Ca, Mg, Na and K) were likely removed with the breakdown of labile minerals, such as carbonate minerals, feldspar, and clay minerals, during subaerial exposure of this layer, resulting in low weathering indices. In particular, the low smectite content (<5%) and low V/Al ratio (<13) suggest that the Holocene and pre-Holocene sediments along the southwestern coast of Korea did not originate from mainland China but rather mostly from the Korean Peninsula. This aspect has been a subject of debate since the mid-1970s.  相似文献