Intercomparison of snow water equivalent observations in the Northern Great Plains          下载免费PDF全文

Samuel E. Tuttle  Jennifer M. Jacobs  Carrie M. Vuyovich  Carrie Olheiser  Eunsang Cho 《水文研究》2018,32(6):817-829

In the Northern Great Plains, melting snow is a primary driver of spring flooding, but limited knowledge of the magnitude and spatial distribution of snow water equivalent (SWE) hampers flood forecasting. Passive microwave remote sensing has the potential to enhance operational river flow forecasting but is not routinely incorporated in operational flood forecasting. We compare satellite passive microwave estimates from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) to the National Oceanic and Atmospheric Administration Office of Water Prediction (OWP) airborne gamma radiation snow survey and U.S. Army Corps of Engineers (USACE) ground snow survey SWE estimates in the Northern Great Plains from 2002 to 2011. AMSR‐E SWE estimates compare favourably with USACE SWE measurements in the low relief, low vegetation study area (mean difference = ?3.8 mm, root mean squared difference [RMSD] = 34.7 mm), but less so with OWP airborne gamma SWE estimates (mean difference = ?9.5 mm, RMSD = 42.7 mm). An error simulation suggests that up to half of the error in the former comparison is potentially due to subpixel scale SWE variability, limiting the maximum achievable RMSD between ground and satellite SWE to approximately 26–33 mm in the Northern Great Plains. The OWP gamma versus AMSR‐E SWE comparison yields larger error than the point‐scale USACE versus AMSR‐E comparison, despite a larger measurement footprint (5–7 km² vs. a few square centimetres, respectively), suggesting that there are unshared errors between the USACE and OWP gamma SWE data.  相似文献   

Acidification at the Surface in the East Sea: A Coupled Climate-carbon Cycle Model Study     

Young-Gyu Park  Kyung-Hee Seol  Kyung-On Boo  Johan Lee  Chunho Cho  Young-Hwa Byun  Seongbong Seo 《Ocean Science Journal》2018,53(3):437-448

This modeling study investigates the impacts of increasing atmospheric CO₂ concentration on acidification in the East Sea. A historical simulation for the past three decades (1980 to 2010) was performed using the Hadley Centre Global Environmental Model (version 2), a coupled climate model with atmospheric, terrestrial and ocean cycles. As the atmospheric CO₂ concentration increased, acidification progressed in the surface waters of the marginal sea. The acidification was similar in magnitude to observations and models of acidification in the global ocean. However, in the global ocean, the acidification appears to be due to increased in-situ oceanic CO₂ uptake, whereas local processes had stronger effects in the East Sea. pH was lowered by surface warming and by the influx of water with higher dissolved inorganic carbon (DIC) from the northwestern Pacific. Due to the enhanced advection of DIC, the partial pressure of CO₂ increased faster than in the overlying air; consequently, the in-situ oceanic uptake of CO₂ decreased.  相似文献   

Real-time acceleration monitoring-based rapid earthquake response for ports in Korea     

Chang-Guk Sun  Hyung-Ik Cho  Byung-Sun Jeong 《Marine Georesources & Geotechnology》2018,36(5):564-578

To establish viable earthquake counterplans for ports in Korea, data regarding earthquake motion on the ground and in buildings must be collected using acceleration monitoring systems. Acceleration monitoring-based strategies for port facilities are useful not only for ensuring rapid responses during and after earthquakes but also for regional data collection to assist reliable seismic design. Acceleration monitoring systems were installed at coastal facility sites in target ports, including a soil site to represent the facility and a rock site as a reference. The systematic earthquake alert software was designed to help them in decision-making about a possible seismic hazard and its reporting. The earthquake alert system was composed of two sequential functional software systems sharing an acceleration monitoring database applied to the target ports. The earthquake response software system triggers an alarm based on the peak ground acceleration per second computed from the monitored data. Then, the earthquake hazard estimation software system evaluates possible earthquake-induced site-specific geotechnical hazards linked to the peak ground acceleration. The integrated system was successfully operated and was able to rapidly provide an emergency report containing event records and geotechnical earthquake hazards during the September 2016 Gyeongju earthquake, the largest recorded earthquake in Korea.  相似文献   

Conceptualizing a multi-layered shingle aquifer model based on volcanic stratigraphy and water inflow to lava caves in Jeju Island,Korea     

Ung San Ahn  Dong-Chan Koh  Joonghyeok Heo  Byong-Wook Cho  Taehee Kim  Byoung-Woo Yum 《水文研究》2021,35(8):e14316

Volcanic aquifers supply a substantial portion of water resources in many parts of the world, including islands, and their productivity depends strongly on volcanic stratigraphy, which exhibits considerable heterogeneity. We investigated water inflow to lava tube caves formed from numerous basaltic lava flows in the northeastern coastal area of Jeju Island after storm events and monitored relative inflow rates monthly over 1 year to characterize groundwater flow processes in the upper parts of volcanic aquifers, and to evaluate the applicability of the previous hydrogeological models proposed for the island. Considerable water inflow arose shortly after storms from exposed palaeosol layers on the walls of the caves. The monthly monitoring results showed that wall inflow associated with these palaeosol layers is substantial. In both cases, discharge from ceiling drips was much less and more temporally variable compared to wall inflow discharge. Water flowing into the caves was rapidly drained through the floor at all monitoring sites. The lateral extent of the palaeosol layers was identified using drill core logs near the cave and outcrops in the coastal area. Based on these results, we inferred that multiple perched aquifers are formed by low-permeability palaeosol layers between lava flows, which are connected by vertical flows at discontinuities in the palaeosol layer, eventually reaching the basal aquifer. This study revealed the water inflow processes observed in lava tube caves constrained by palaeosol layers, and established a hydrogeological conceptual model incorporating multiple perched aquifers in both coastal and mountainous areas associated with extensive palaeosol layers formed during volcanic hiatuses. This finding would help elucidate recharge, groundwater flow, and contaminant transport processes in many volcanic aquifers that are not adequately represented by the previous models, and contribute to better management of groundwater in those areas.  相似文献   

An investigation into robust spectral indices for leaf chlorophyll estimation   总被引：2，自引：0，他引：2  

Russell Main  Moses Azong Cho  Renaud Mathieu  Martha M. O’Kennedy  Abel Ramoelo  Susan Koch 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):751-761

Quantifying photosynthetic activity at the regional scale can provide important information to resource managers, planners and global ecosystem modelling efforts. With increasing availability of both hyperspectral and narrow band multispectral remote sensing data, new users are faced with a plethora of options when choosing an optical index to relate to their chosen or canopy parameter. The literature base regarding optical indices (particularly chlorophyll indices) is wide ranging and extensive, however it is without much consensus regarding robust indices. The wider spectral community could benefit from studies that apply a variety of published indices to differing sets of species data. The consistency and robustness of 73 published chlorophyll spectral indices have been assessed, using leaf level hyperspectral data collected from three crop species and a variety of savanna tree species. Linear regression between total leaf chlorophyll content and bootstrapping were used to determine the leafpredictive capabilities of the various indices. The indices were then ranked based on the prediction error (the average root mean square error (RMSE)) derived from the bootstrapping process involving 1000 iterative resampling with replacement. The results show two red-edge derivative based indices (red-edge position via linear extrapolation index and the modified red-edge inflection point index) as the most consistent and robust, and that the majority of the top performing indices (in spite of species variability) were simple ratio or normalised difference indices that are based on off-chlorophyll absorption centre wavebands (690–730 nm).  相似文献   

推断勒夫波相速度的圆形台阵微震新技术     

T.Tada  I.Cho  Y.Shinozaki  张晨侠  郑国栋  张宇  丁广 《世界地震译丛》2011,(1)

介绍了简单而又新颖的公式,使用微震的二分量,即圆形台阵记录的水平运动直接推断勒夫波相速度(cL)时,这些公式具有帮助作用。我们的公式与一般用于推断瑞雷波相速度(cR)的微震探测技术的空间自相关(SPAC)方法的公式类似。虽然SPAC方法现有的理论确实提供了估计cL的可能性,但这只能通过求解非线性的方程组才能实现,而其中待求解的未知数也包括cR以及瑞雷波?勒夫波的幂分配比。相反,在我们公式中cL是出现的唯一未知数。基于我们推荐公式——我们称为SPAC+L、SPAC-L和CCA-L(其中CCA表示无中心圆形台阵)法——的cL估算法的现场适用范围通过2个测试点的分析结果说明。在所提出的3种技术中,SPAC+L法由于表现最佳而出名。3种方法的有效波长范围下限是台阵半径r的2～5倍区域,上限是10～25r的区域。近年来,提出了类似的仅涉及cL的圆形台阵微震技术,但与它们相比,我们在此给出的方法,不是在数理计算上繁冗更少,就是在数学上更为简单。  相似文献   

Lower atmospheric anomalies following the 2008 Wenchuan Earthquake observed by GPS measurements     

Shuanggen Jin  L. Han  J. Cho 《Journal of Atmospheric and Solar》2011,73(7-8):810-814

The Mw=8.0 Wenchuan Earthquake occurred on May 12, 2008 at the Longmen Shan fault, the western Sichuan Basin, China, killing more than ten thousand people in several cities and causing large economic losses. Global Positioning System (GPS) observations have provided unique insights on this event, including co-seismic ionospheric disturbances, co-/post-seismic crustal deformations and fault slip distributions. However, the processes and the driving mechanisms are still not clear, particularly possible seismo-lower atmospheric–ionospheric coupling behaviors. In this paper, the lower atmospheric (tropospheric) variations are investigated using the total zenith tropospheric delay (ZTD) from GPS measurements around this event. It has the first found co-seismic tropospheric anomalies during the mainshock with an increase and then a decrease, mainly in the zenith hydrostatic delay component (ZHD), while it is also supported by the same pattern of surface-observed atmospheric pressure changes at co-located GPS site that are driven by the ground-coupled air waves from ground vertical motion of seismic waves propagation. Therefore, the co-seismic tropospheric disturbances (CTD) indicate again the acoustic coupling effect of the atmosphere and the solid-Earth with air wave propagation from the ground to the top atmosphere.  相似文献   

Geotechnical parameter estimation in tunnelling using relative convergence measurement     

Kook‐Hwan Cho  Min‐Kwang Choi  Seok‐Woo Nam  In‐Mo Lee 《国际地质力学数值与分析法杂志》2006,30(2):137-155

Accurate estimation of geotechnical parameters is an important and difficult task in tunnel design and construction. Optimum evaluation of the geotechnical parameters have been carried out by the back‐analysis method based on estimated absolute convergence data. In this study, a back‐analysis technique using measured relative convergence in tunnelling is proposed. The extended Bayesian method (EBM), which combines the prior information with the field measurement data, is adopted and combined with the 3‐dimensional finite element analysis to predict ground motion. By directly using the relative convergence as observation data in the EBM, we can exclude errors that arise in the estimation of absolute displacement from measured convergence, and can evaluate the geotechnical parameters with sufficient reliability. The proposed back‐analysis technique is applied and validated by using the measured data from two tunnel sites in Korea. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Practical modified scheme of linear shallow-water equations for distant propagation of tsunamis   总被引：2，自引：0，他引：2  

Yong-Sik Cho  Dae-Hee Sohn  Seung Oh Lee 《Ocean Engineering》2007,34(11-12):1769-1777

A simple but practical numerical model describing a distant propagation of tsunamis is newly proposed by introducing an additional term to the existing modified scheme. The numerical dispersion of the proposed model is manipulated to replace the physical dispersion of the linear Boussinesq equations without any limitation. The new model developed in this study is applied to propagation of a Gaussian hump over a constant water depth and the predicted free surface displacements are compared with available analytical solutions. A very reasonable agreement is observed.  相似文献   

Application of CASI Hyperspectral Image to Analysis of the Distribution of Hydrogen-Fluoride-Damaged Vegetation in Gumi,Korea     

Hangnan Yu  Jong-Yeol Lee  Woo-Kyun Lee  Guishan Cui  Jung-Kil Cho  Gwangjae Wei  Lan Li 《Journal of the Indian Society of Remote Sensing》2017,45(2):317-326

On the night of 27th Sept 2012, a hydrogen fluoride (HF) storage tank exploded in the industrial area of Gumi, Korea. In this study, an attempt was made to detect the damaged vegetation using a hyperspectral image. Assuming that HF was the most significant stressor of vegetation near the blast site, our results indicated that the difference in reflectance values between the 786 and 801 nm wavelengths became negative (?) and fluctuated from ?5 to ?160 in the affected vegetation. On the other hand, positive (+) values were found in the non-affected vegetation. The combination of normalized difference vegetation index (NDVI) and simple ratio (SR) was used [named combined vegetation index (CVI) in this study] to assess the accuracy of these measurements. Among 150,965 pixels that were defined as damaged vegetation, about 2.8 % were analyzed incorrectly in this study. As a result, factors such as wind direction, distance from the accident spot, elevation, and aspect were shown to affect damage distribution.  相似文献