3D aquifer characterization using stochastic streamline calibration     

Minchul Jang 《Advances in water resources》2007

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Calibration of the Pyranometer Sensitivity Using the Integrating Sphere     

Bu-Yo Kim  Kyu-Tae Lee  Il-Sung Zo  Sang-Ho Lee  Hyun-Seok Jung  Se-Hun Rim  Jeong-Pil Jang 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(4):639-648

The pyranometer for observing the solar radiation reaching the surface of the earth is manufactured by various companies around the world. The sensitivity of the pyranometer at the observatory is required to be properly controlled based on the reference value of the World Radiometric Center (WRC) and the observatory environment; otherwise, the observational data may be subject to a large error. Since the sensitivity of the pyranometer can be calibrated in an indoor or outdoor calibration, this study used a CSTM-USS-4000C Integrating Sphere by Labsphere Inc. (USA) to calibrate the sensitivity of CMP22 pyranometer by Kipp&Zonen Inc. (Netherlands). Consequently, the factory sensitivity of CMP22 was corrected from 8.68 μV·(Wm^?2)^?1 to 8.98 μV·(Wm^?2)^?1, and the result from the outdoor calibration according to the observatory environment was 8.90 μV·(Wm^?2)^?1. After the indoor calibration of the pyranometer sensitivity, the root mean square error (RMSE) of the observational data at the observatory on a clear day without clouds (July 13, 2017) was 7.11 Wm^?2 in comparison to the reference pyranometer. After the outdoor calibration of the pyranometer sensitivity based on these results, the RMSE of the observational data was 1.74 Wm^?2 on the same day. Periodic inspections are required because the decrease of sensitivity over time is inevitable in the pyranometer data produced at the observatory. The initial sensitivity after indoor calibration (8.98 μV·(Wm^?2)^?1) is important, and the sensitivity after outdoor calibration (8.90 μV·(Wm^?2)^?1) can be compared to the data at the Baseline Surface Radiation Network (BSRN) or can be used for various studies and daily applications.  相似文献   

Impacts of Shallow Convection Processes on a Simulated Boreal Summer Climatology in a Global Atmospheric Model     

Song-You Hong  Jihyeon Jang 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):361-370

This study investigates the impacts of shallow convection schemes on a simulated seasonal climatology in the Global and Regional Integrated Model system (GRIMs). The eddy-diffusivity scheme of Tiedtke (TDK) is evaluated, focusing on the dependency upon deep convection schemes. Drying and warming near the top of the planetary boundary layer (PBL) and opposing effects above are observed. The height of PBL is reduced due to the increase of thermal stability near the PBL top. The weakened PBL turbulence is partly compensated with the increased downward solar radiation due to the reduction of low clouds. These effects are pronounced over the oceans, which leads to the modulation of tropical precipitation. It is found that the original TDK scheme shows similar behavior regardless of the choice of deep convection schemes. A revised TDK scheme that explicitly couples the PBL and shallow convection processes is proposed and evaluated. The proposed scheme generally improves the simulated climatology over the results with the original TDK scheme, along with further improvement in the case of the revised deep convection scheme. Our results indicate that the role of the shallow convection scheme needs to be carefully examined to improve the performance of atmospheric models, with a focus on modulated PBL and deep convection processes.  相似文献   

Shear wave velocity and attenuation structure for the shallow crust of the southern Korean peninsula from short period Rayleigh waves     

Heeok Jung  Yong-seok Jang  Jung Mo Lee  Wooil M. Moon  Chang-Eob Baag  Ki Young Kim  Bong Gon Jo   《Tectonophysics》2007,429(3-4):253-265

We analyzed the short period Rayleigh waves from the first crustal-scale seismic refraction experiment in the Korean peninsula, KCRUST2002, to determine the shear wave velocity and attenuation structure of the uppermost 1 km of the crust in different tectonic zones of the Korean peninsula and to examine if this can be related to the surface geology of the study area. The experiment was conducted with two large explosive sources along a 300-km long profile in 2002. The seismic traces, recorded on 170 vertical-component, 2-Hz portable seismometers, show distinct Rayleigh waves in the period range between 0.2 s and 1.2 s, which are easily recognizable up to 30–60 km from the sources. The seismic profiles, which traverse three tectonic regions (Gyeonggi massif, Okcheon fold belt and Yeongnam massif), were divided into five subsections based on tectonic boundaries as well as lithology. Group and phase velocities for the five subsections obtained by a continuous wavelet transform method and a slant stack method, respectively, were inverted for the shear wave models. We obtained shear wave velocity models up to a depth of 1.0 km. Overall, the shear wave velocity of the Okcheon fold belt is lower than that of the Gyeonggi and Yeongnam massifs by  0.4 km/s in the shallowmost 0.2 km and by 0.2 km/s at depths below 0.2 km. Attenuation coefficients, determined from the decay of the fundamental mode Rayleigh waves, were used to obtain the shear wave attenuation structures for three subsections (one for each of the three different tectonic regions). We obtained an average value of Q_β^− 1 in the upper 0.5 km for each subsection. Q_β^− 1 for the Okcheon fold belt ( 0.026) is approximately three times larger than Q_β^− 1 for the massif areas ( 0.008). The low shear wave velocity in the Okcheon fold belt is consistent with the high attenuation in this region.  相似文献   

Examination of multi-perturbation methods for ensemble prediction of the MJO during boreal summer     

In-Sik Kang  Pyong-Hwa Jang  Mansour Almazroui 《Climate Dynamics》2014,42(9-10):2627-2637

The impact of initialization and perturbation methods on the ensemble prediction of the boreal summer intraseasonal oscillation was investigated using 20-year hindcast predictions of a coupled general circulation model. The three perturbation methods used in the present study are the lagged-averaged forecast (LAF) method, the breeding method, and the empirical singular vector (ESV) method. Hindcast experiments were performed with a prediction interval of 10 days for extended boreal summer (May–October) seasons over a 20 year period. The empirical orthogonal function (EOF) eigenvectors of the initial perturbations depend on the individual perturbation method used. The leading EOF eigenvectors of the LAF perturbations exhibit large variances in the extratropics. Bred vectors with a breeding interval of 3 days represent the local unstable mode moving northward and eastward over the Indian and western Pacific region, and the leading EOF modes of the ESV perturbations represent planetary-scale eastward moving perturbations over the tropics. By combining the three perturbation methods, a multi-perturbation (MP) ensemble prediction system for the intraseasonal time scale was constructed, and the effectiveness of the MP prediction system for the Madden and Julian oscillation (MJO) prediction was examined in the present study. The MJO prediction skills of the individual perturbation methods are all similar; however, the MP‐based prediction has a higher level of correlation skill for predicting the real-time multivariate MJO indices compared to those of the other individual perturbation methods. The predictability of the intraseasonal oscillation is sensitive to the MJO amplitude and to the location of the dominant convective anomaly in the initial state. The improvement in the skill of the MP prediction system is more effective during periods of weak MJO activity.  相似文献   

Large Eddy Simulation of Open Ocean Deep Convection with Application to the Deep Water Formation in the East Sea (Japan Sea)     

Y. Noh  C. J. Jang  J-.W. Kim 《Journal of Oceanography》1999,55(2):347-367

Various important features could be found on the open ocean deep convection and the subsequent deep water formation from large eddy simulation (LES), and the results were applied to the East Sea (Japan Sea). It was found that under a strong cold wind outburst with the heat flux of 1000 Wm⁻² for 5 days generates a deep convection which can penetrate to the depth 1500 m, but under the continuous cooling with the heat flux of 250 Wm⁻² the growth of a mixed layer is suppressed at 700 m. The effects of the spatial and temporal variations of the surface forcing were investigated with regard to the penetrative depth of convection, the generation of baroclinic eddies, the volume of the water mass formation, and the intensity of the rim current. The deep water formations in the intermediate and deep layer of the East Sea were explained in terms of the simulation results, and the intensity of the consequent circulation and the volume of water mass formation were compared with the observation data. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Creating Spatial Information Infrastructures: Towards the Spatial Semantic Web – Edited by Peter van Oosterom and Sisi Zlatanova     

Zorica Nedovi&#;-Budi&#;  Sung-Gheel Jang 《Transactions in GIS》2010,14(1):89-91

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A simple model to predict the effect of volume fraction,diameter, and length of fibres on strength of fibre reinforced brittle matrix composites     

T. Kundu  H.S. Jang  Y. H. Cha  C. S. Desai 《国际地质力学数值与分析法杂志》2000,24(7):655-673

A simplified model is presented to predict the strength variations of brittle matrix composites, reinforced by steel fibres, with the variations of fibre parameters—length, diameter and volume fraction. This model predicts that its tensile and flexural strength increase non‐linearly with the fibre volume fraction. It also predicts that similar non‐linear behaviour should be observed with the reduction of the fibre diameter when other parameters are kept constant. The experimental results support both these theoretical predictions. It is also explained why an increase in the fibre length does not always significantly increase the fracture toughness. The objective of this paper is not to explain and understand in great detail the science of all phenomena responsible for the strength increase of fibre reinforced brittle matrix composites, but to provide a simple engineering explanation as to why its strength increases with the fibre addition, and how this increase can be quantitatively related to the variations in fibre parameters—fibre volume fraction, fibre length and diameter. These simplifying steps are needed to provide a tool that the practicing engineers can use to predict the brittle matrix strength variation with the fibre parameters. In the area of geomechanics, the results presented here can be used to assess and predict the behaviour of fibre‐reinforced earth. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献