Projections of high resolution climate changes for South Korea using multiple-regional climate models based on four RCP scenarios. Part 2: precipitation

Precipitation changes over South Korea were projected using five regional climate models (RCMs) with a horizontal resolution of 12.5 km for the mid and late 21st century (2026-2050, 2076- 2100) under four Representative Concentration Pathways (RCP) scenarios against present precipitation (1981-2005). The simulation data of the Hadley Centre Global Environmental Model version 2 coupled with the Atmosphere-Ocean (HadGEM2-AO) was used as boundary data of RCMs. In general, the RCMs well simulated the spatial and seasonal variations of present precipitation compared with observation and HadGEM2-AO. Equal Weighted Averaging without Bias Correction (EWA_NBC) significantly reduced the model biases to some extent, but systematic biases in results still remained. However, the Weighted Averaging based on Taylor’s skill score (WEA_Tay) showed a good statistical correction in terms of the spatial and seasonal variations, the magnitude of precipitation amount, and the probability density. In the mid-21st century, the spatial and interannual variabilities of precipitation over South Korea are projected to increase regardless of the RCP scenarios and seasons. However, the changes in area-averaged seasonal precipitation are not significant due to mixed changing patterns depending on locations. Whereas, in the late 21st century, the precipitation is projected to increase proportionally to the changes of net radiative forcing. Under RCP8.5, WEA_Tay projects the precipitation to be increased by about +19.1, +20.5, +33.3% for annual, summer and winter precipitation at 1-5% significance levels, respectively. In addition, the probability of strong precipitation (≥ 15 mm d^-1) is also projected to increase significantly, particularly in WEA_Tay under RCP8.5.     

Spatial distribution of stream sediment pollution by toxic trace elements at Tourtit and Ichoumellal abandoned mining areas (central Morocco)

This study presents a diagnostic of the current state of 114 stream sediment samples by their elemental concentrations (Sb, Cd, Pb, As, Cu, Zn, Ni, Cr, and Hg), collected from Ighardayane upstream on an area of 15 km² located at the SE part of central Morocco where Tourtit and Ichoumellal, two abandoned mining sites of Stibnite, are located. Several approaches were used to model the analysis (i) enrichment factor (EF), (ii) sediment pollution index (IPS), (iii) probable effect concentration-quotients (PEC-Qs), and (iv) potential ecological risk index (PERI). Results show highly contaminated areas around the old mining sites by Sb As, Pb, and Cd. Cadmium and lead show 86.9 and 12.29% (respectively) of trace element pollution according to sediment pollution index. Twenty-eight percent of the sampled area is potentially highly toxic because of the presence of Hg, Pb, and Cd. The very similar distribution of pollution and toxicity of most analyzed trace elements may originate from the same source, which corresponds to mining wastes where we recorded the highest pollution and toxicity degrees. This environmental issue represents the combination of Tourtit and Ichoumellal anthropic sources responsible of Sb, As, Pb, and Cd release and a probable natural source of Hg “that needs a further study,” which contribute in the degradation of an aquatic ecosystem of the same area. Therefore, both ecotoxicological analysis and stream sediment quality management should be carried out to control this aquatic ecosystem toxication.     

Predicting the rainfall-triggered landslides in a forested mountain region using TRIGRS model

Landslides are natural disasters which can pose a serious threat to human and property in many areas around the world. The Transient Rainfall Infiltration and Grid-based Regional Slope-stability (TRIGRS) model was used to investigate the rainfall-induced shallow landslides in a forested mountain region, Korea. Various input data for TRIGRS model include time-varying rainfall, topographic characteristics, soil depth, material strength, and hydraulic properties. A series of calculations were conducted in determining the slope stability over the Jangheung region in Korea during the storm occurred on August 6, 1998. The results show that TRIGRS model captured about 64.1% of landslides that were extracted from the IKONOS2 imageries. The model demonstrated how the factor of safety changed with time during a storm considering both the transient and spatial responses of pore water pressure in its slope stability calculation.     

Analysis on pore pressure in an anisotropic seabed in the vicinity of a caisson

This paper presents an analysis of pore pressure around a caisson-type breakwater subjected to dynamic wave loading. Unlike previous investigations for wave-seabed-caisson interaction, cross-anisotropic soil behaviour is considered in this paper. Based on a linear poro-elastic theory, a finite element model is developed. A parametric study related to the effects of wave parameters, soil characteristics and geometry of caisson and rubble mound base on the pore pressure around a caisson is performed. The numerical results indicate that the effects of anisotropic soil behaviour on the wave-induced pore pressure in a sandy bed beneath a caisson are not negligible.     

滇西南地区地壳S波速度结构反演及强震孕震环境分析

基于滇西南地区31个宽频带地震台站记录的远震三分量波形数据,提取径向P波接收函数,以“中国地震科学实验场地区地壳剪切波速模型”为初始模型,进行精细化结构反演(垂向精度达2km级),并采用Bootstrap重采样技术进行统计和评估,获取了各台站下方的S波速度结构,结合地壳厚度、泊松比分布,对滇西南地区的地壳深部结构及强震孕震环境进行研究。结果表明:①研究区地壳S波速度分布在横向和垂向上均存在明显的非均匀特性。在中上地壳0～20km深度范围内存在明显且连续的低速层,平均厚度约15km,最大厚度达20km。在中下地壳20～28km深度范围内局部区域存在明显的低速层(厚度约8km),主要分布在普文断裂北端至阿墨江断裂中部区域(23°N附近),另外,在红河断裂附近和澜沧江断裂北部的局部区域也有分布; ②从孕震环境来看,景谷 M_S6.6 和 M_S5.8、墨江 M_S5.9 地震均发生在中上地壳低速层内,老挝 M_S6.0 地震发生在高、低速度的过渡区域。滇西南地区新生破裂带较为发育,地震波速的减小可能与地壳断裂或微裂隙中有流体的存在有关,研究区NW向新生破裂带的存在以及流体的长期作用,为带内高应变的突然释放提供了条件。另外,4个地震均发生在泊松比变化的高梯度带上,且地震发生处地壳厚度变化均较大。地壳厚度、泊松比变化剧烈的地区,地壳物质组成差异明显,壳内应变易于积累,有利于强震的诱发。     

Active control of highway bridges subject to a variety of earthquake loads

In this paper, a wavelet-fi ltered genetic-neuro-fuzzy(WGNF) control system design framework for response control of a highway bridge under various earthquake loads is discussed. The WGNF controller is developed by combining fuzzy logic, discrete wavelet transform, genetic algorithms, and neural networks for use as a control algorithm. To evaluate the performance of the WGNF algorithm, it is tested on a highway bridge equipped with hydraulic actuators. It controls the actuators installed on the abutments of the highway bridge structure. Various earthquakes used as input signals include an artifi cial earthquake, the El-Centro, Kobe, North Palm Springs, Turkey Bolu, Chi-Chi, and Northridge earthquakes. It is proved that the WGNF control system is effective in mitigating the vibration of the highway bridge under a variety of seismic excitation.     

2011年西北太平洋海平面异常及其与拉尼娜和负印度洋偶极子的联系

西北太平洋海平面异常模态在纯拉尼娜事件与拉尼娜和负印度洋偶极子（IOD）事件同时发生时表现出完全不同的形态。在纯拉尼娜事件期间,西北太平洋海平面呈现显著的正异常;而2010/2011拉尼娜事件期间西北太平洋海平面明显降低,呈显著的负异常,其与印度洋负IOD事件密切相关。研究结果表明,负IOD事件能在热带西太平洋驱动显著的西风异常,由此减弱了拉尼娜峰值期间西北太平洋海平面正异常。同时,在负IOD峰值期的9月,在日经线附近存在显著的风应力旋度正异常,激发负的海平面异常以Rossby波的形式向西传播,并在第二年6月抵达菲律宾以东海域,维持并加强该海域海平面负异常,进而对北赤道流分叉点位置及输运产生重要的影响。     

Strategy for the meteorological and environmental airborne observations over the Korean Peninsula

Aircraft campaigns for the meteorological and environmental research have been conducted in regional and global scales. The aircraft is increasingly considered as one of the best platforms to get the atmospheric three-dimensional information, especially over sea. We discuss the airborne observation plan and payloads designed for the aircraft campaigns over the Korean Peninsula. The main goals of the campaigns are to (i) conduct precipitation (snow) enhancement experiments with observations of the microphysical properties of clouds, dominantly in winter, (ii) monitor the severe weather generally in summer, (iii) characterize the climate change composition and the outflow of pollution from the Asian continent of the troposphere over the Korean Peninsula generally in spring or fall, and (iv) validate satellite and ground-based remote measurements of tropospheric composition generally in spring or fall.     

Impact of local sea surface temperature anomaly over the western North Pacific on extreme East Asian summer monsoon

In this study, the anomalous characteristics of observed large-scale synoptic fields in the extreme East Asian summer monsoon (EASM) years are analyzed, and the impact of the local sea surface temperature (SST) anomaly over the western North Pacific (WNP) on the extreme EASM is investigated through sensitivity experiments of 28?years EASM simulations to the local SST over the WNP. The observation analysis reveals that the extreme EASM is influenced more by anomalous large-scale atmospheric features such as monsoon circulations and the western North Pacific subtropical high than the local SST anomaly over the WNP. However, the results of the sensitivity experiments show that the local SST anomaly has an implicit impact on the extreme EASM. The patterns of differences in precipitation between the experiment forced by observed SST in each year and the experiment forced by climatological SST over the WNP are opposite to anomaly patterns of observed precipitation in the extreme EASM years. This is because the SST anomaly over the WNP plays a role in reducing precipitation anomaly by changing surface latent heat flux and monsoon circulations. In particular, the local SST anomaly over the WNP decreases anomalies of large-scale circulations, i.e., the local Hadley and the Walker circulations. Thus, the local SST anomaly over the WNP plays a role in decreasing the interannual variability of the EASM.