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31.
Donghyun Lee Seung-Ki Min Changyong Park Myoung-Seok Suh Joong-Bae Ahn Dong-Hyun Cha Dong-Kyou Lee Song-You Hong Seong-Chan Park Hyun-Suk Kang 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(2):129-137
Time of Emergence (ToE) is the time at which the signal of climate change emerges from the background noise of natural climate variability, and can provide useful information for climate change impacts and adaptations. This study examines future ToEs for daily maximum and minimum temperatures over the Northeast Asia using five Regional Climate Models (RCMs) simulations driven by single Global Climate Model (GCM) under two Representative Concentration Pathways (RCP) emission scenarios. Noise is defined based on the interannual variability during the present-day period (1981-2010) and warming signals in the future years (2021-2100) are compared against the noise in order to identify ToEs. Results show that ToEs of annual mean temperatures occur between 2030s and 2040s in RCMs, which essentially follow those of the driving GCM. This represents the dominant influence of GCM boundary forcing on RCM results in this region. ToEs of seasonal temperatures exhibit larger ranges from 2030s to 2090s. The seasonality of ToE is found to be determined majorly by noise amplitudes. The earliest ToE appears in autumn when the noise is smallest while the latest ToE occurs in winter when the noise is largest. The RCP4.5 scenario exhibits later emergence years than the RCP8.5 scenario by 5-35 years. The significant delay in ToEs by taking the lower emission scenario provides an important implication for climate change mitigation. Daily minimum temperatures tend to have earlier emergence than daily maximum temperature but with low confidence. It is also found that noise thresholds can strongly affect ToE years, i.e. larger noise threshold induces later emergence, indicating the importance of noise estimation in the ToE assessment. 相似文献
32.
Balasubramanian Sundarabalan Palanisamy Shanmugam Yu-Hwan Ahn 《Ocean Science Journal》2016,51(1):67-86
Modeling of the wave-induced underwater light fluctuations at near-surface depths in coastal oceanic waters is challenging because of the surface roughness and strong anisotropic effects of the light field. In the present work, a simple and computationally efficient radiative transfer model is used for the wind-driven sea surface for simulating underwater light fields such as downwelling irradiance (Ed), upwelling irradiance (Eu), and upwelling radiance (Lu) in a spatial domain. It is an extension of our previous work that essentially combines the air–sea interface of the wind-driven sea surface with transmittance and reflectance along with the diffuse and direct components of the homogenous and inhomogeneous water column. The present model simulates underwater light fields for any possible values of absorption and backscattering coefficients. To assess the performance of the model, the Ed, Eu, and Lu profiles predicted by the model are compared with experimental data from relatively clear and turbid coastal waters. Statistical results show significantly low mean relative differences regardless of the wavelength. Comparison of the simulated and in-situ time series data measured over rough sea surfaces demonstrates that model-observation agreement is good for the present model. The Hydrolight model when implemented with the modified bottom reflectance and phase function provides significantly better results than the original Hydrolight model without consideration of the bottom slope and vertically varying phase function. However, these results are non-spatial and have errors fluctuating at different wavelengths. To further demonstrate the efficiency of the present model, spatial distribution patterns of the underwater light fields are simulated based on the measured data from a coastal station for different solar zenith angles (under sunny condition). Simulated wave-induced fluctuations of the underwater lights fields show a good consistency with in-situ data for a few near-surface depths. The present model also provides a reasonable approximation for simulating wave-induced effects on the downward irradiance field and its anisotropic conditions caused by the surface roughness, wavelength and angle of incidence. 相似文献
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35.
This paper presents a shear load transfer function and an analytical method for estimating the load transfer characteristics
of rock-socketed drilled shafts subjected to axial loads. A shear load transfer (f–w) function of rock-socketed drilled shafts is proposed based on the constant normal stiffness (CNS) direct shear tests. It
is presented in terms of the borehole roughness and the geological strength index (GSI) so that the structural discontinuities
and the surface conditions of the rock mass can be considered. An analytical method that takes into account the coupled soil
resistance effects is proposed using a modified Mindlin’s point load solution. Through comparisons with load test results,
the proposed methodology is in good agreement with the general trend observed in in situ measurements and represents an improvement
in the prediction of the shear behavior of rock-socketed drilled shafts. 相似文献
36.
Bo?Kyung?Kim HyoungMin?Joo Boyeon?Lee Dong-Hun?Lee In-Young?Ahn Sun-Yong?HaEmail author 《Ocean Science Journal》2018,53(4):621-630
Red and green snow caused by snow algal blooms is common on glaciers and snowfields worldwide. Reddish and greenish snow samples containing algae were collected at the vicinity of penguin rockeries on King George Island (62°13′S, 58°47′W, near the King Sejong Station), Antarctica in February 2017 to investigate their physiology. Eight pigments and six fatty acids were detected from the samples. No difference in pigment and fatty acid (FA) composition was found between reddish and greenish snow samples. In contrast, spectral profiling and mycosporine-like amino acids (MAAs) were different between reddish and greenish snow. Particularly in greenish snow, a high absorbance between 450–600 nm was observed. The average MAA concentration was 316.0 μg g-1 in greenish snow, which was higher than that of reddish snow (278.2 μg g-1). The MAA to Particulate organic carbon (POC) ratio (mg (g C)-1) for reddish snow (6.2 mg (g C)-1) was higher than that of greenish snow (2.6 mg (g C)-1). These results suggest that reddish and greenish snow are considered to be the same species based on pigment and FA composition. Compared with photoprotective pigments, MAAs offer snow algae a more effective photoprotection strategy to promote tolerance of natural levels of ultraviolet radiation (UVR). 相似文献
37.
Systematic Geometric Image Measurement Errors of Circular Object Targets: Mathematical Formulation and Correction 总被引:2,自引:0,他引:2
The use of circular object targets is very common in spatial photogrammetric object reconstruction. An object circle is projected on to the image plane as an ellipse if the object plane and the image plane are not parallel to each other. The image co-ordinates of the centre of the ellipse are usually determined automatically by means of digital image processing. These co-ordinates are then used as observations for a subsequent reconstruction of the three dimensional object point. The image co-ordinates of the centre of the ellipse and the true co-ordinates of the projected centre of the circular object target are not identical; thus eccentricity is caused, resulting in systematic geometric image measurement errors. This paper describes the functional context of this eccentricity for a typical target/camera set-up. The possible solutions for a correction of this systematic eccentricity error are derived. Guidelines for the correct combination of object target sizes and exposure distances, guaranteeing reliable image point measurements and accurate object point determination, are proposed. 相似文献
38.
Ho?Gul?Kim Dong?Kun?LeeEmail author Chan?Park Yoonjung?Ahn Sung-Ho?Kil Sunyong?Sung Gregory?S.?Biging 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(11):2987-3019
Landslides are one of the most dangerous types of natural disasters, and damage due to landslides has been increasing in certain regions of the world because of increased precipitation. Policy decision makers require reliable information that can be used to establish spatial adaptation plans to protect people from landslide hazards. Researchers presently identify areas susceptible to landslides using various spatial distribution models. However, such data are associated with a high amount of uncertainty. This study focuses on quantifying the uncertainty of several spatial distribution models and identifying the effectiveness of various ensemble methods that can be used to provide reliable information to support policy decisions. The area of study was Inje-gun, Republic of Korea. Ten models were selected to assess landslide susceptibility. Moreover, five ensemble methods were selected for the aggregated results of the 10 models. The uncertainty was quantified using the coefficient of variation and the uncertainty map we developed revealed areas with strongly differing values among single models. A matrix map was created using an ensemble map and a coefficient of variation map. Using matrix analysis, we identified the areas that are most susceptible to landslides according to the ensemble model with a low uncertainty. Thus, the ensemble model can be a useful tool for supporting decision makers. The framework of this study can also be employed to support the establishment of landslide adaptation plans in other areas of the Republic of Korea and in other countries. 相似文献
39.
S. E. Ahn C. S. Park H. M. Kim 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(6):711-716
This paper is intended to compare the hazard rate from the Bayesian approach with the hazard rate from the maximum likelihood
estimate (MLE) method. The MLE of a parameter is appropriate as long as there are sufficient data. For various reasons, however,
sufficient data may not be available, which may make the result of the MLE method unreliable. In order to resolve the problem,
it is necessary to rely on judgment about unknown parameters. This is done by adopting the Bayesian approach. The hazard rate
of a mixture model can be inferred from a method called Bayesian estimation. For eliciting a prior distribution which can
be used in deriving a Bayesian estimate, a computerized-simulation method is introduced. Finally, a numerical example is given
to illustrate the potential benefits of the Bayesian approach. 相似文献
40.
Dependence of the amount of open magnetic flux on the direction of the interplanetary magnetic field
The power generated by the solar wind—magnetosphere dynamo is proportional to the amount of the open magnetic flux Φ. It is difficult to use this fact in determining observationally the dependence of Φ on the orientation of the interplanetary magnetic field vector. It is shown that, for a simple vacuum superposition of the earth's dipole field and a uniform magnetic field, Φ is very closely proportional to sin θ/2) for a wide range of the intensity of the uniform field, where θ denotes the polar angle of the interplanetary magnetic field vector in the Y-Z plane of solar-magnetospheric coordinates. 相似文献