Enhanced biological activity by an anticyclonic warm eddy during early spring in the East Sea (Japan Sea) detected by the geostationary ocean color satellite

The high primary production enhanced by anticyclonic eddies and hourly variation pattern in the productivity during the spring season in the East Sea were first investigated using the first Korean Geostationary Ocean Color Imager (GOCI). Even though the stratification for a seasonal spring bloom is not well developed in the water column in early April in the East Sea, a physical upward water flux movement at the periphery of the anticyclonic eddies could remain the phytoplankton in euphotic zone to sustain high chlorophyll-a concentration conditions in the Ulleung Basin. At this time, nutrients were no major controlling factor for phytoplankton growth since concentrations of major nutrients (nitrate, silicate, and phosphate) were relatively high in the observed eddy sites based on the observation data from the Korean Oceanographic Data Center (KODC). The estimated mixed layer depth (MLD) significantly shallower at the periphery supports for this mechanism. The hourly primary productivity estimation based on a Carbon-based Productivity Model (CbPM) provides a bimodal pattern along the time especially in L1 with an approximately one order magnitude difference between the lowest and highest values of productivities on 5 April, 2011. Potential possibilities for this large discrepancy in the hourly productivity and some thoughts on a short time in situ incubation method were discussed.     

Detecting massive green algae (Ulva prolifera) blooms in the Yellow Sea and East China Sea using Geostationary Ocean Color Imager (GOCI) data

The historically massive bloom of the green macroalgae Ulva prolifera reported in June?CAugust 2008 around the Qingdao, Yellow Sea, East China Sea and Japan coasts has recurred in a similar season and region. On June 13, 2011, around Qingdao, China, the world??s first Geostationary Ocean Color Imager (GOCI) detected an enormous bloom of floating green algae, which originated from the nearshore Subei Bank, China. The large floating green algae patches were observed along and across the Yellow Sea and in the East China Sea during 2011 summer by various oceanic cruises. To detect the massive macroalgae blooms from space, we analyzed their spectral characteristics from in situ optical measurements and satellite-derived green algae spectra. An ??Index of floating Green Algae for GOCI?? (IGAG) was developed from the multiple spectral band ratios using three wavelengths (555, 660, 745 nm), which the spectral response of green algae reflected at 555, 745, and 865 nm and absorbed at 660 and 680 nm. The results were compared with those obtained by the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and Korea Ocean Satellite Center (KOSC) approaches. An advantage of the IGAG method was that muted or subtle signals of floating green algae were enhanced and separated from surrounding complex water signals. Although maps of floating green algae derived by the other approaches delineated dense green algae, they were less sensitive to subtle (less dense) features and in cases of nearby cloudy or complex water conditions. The floating green algae maps from IGAG provided a more robust estimate of wide floating green algae blooms than those derived using NDVI, EVI, or KOSC approaches. The IGAG approach should be useful for tracing and monitoring changes in green algae blooms on regional and global scales.     

Comparison of Turbulent Flows and Suspended Sediment Particle Motions Simulated around a Submerged Breakwater Using RANS and LES

Beach erosion is a serious problem that can be aggravated by human-made structures, and the modeling of breaking waves near the coast and around coastal st     

Favorable versus unfavorable synoptic backgrounds for indirect precipitation events ahead of tropical cyclones approaching the Korean Peninsula: A comparison of two cases

This study identifies favorable synoptic backgrounds for indirect precipitation events over the Korean Peninsula that occur well in advance of tropical cyclone (TC) landfall. Two TCs, i.e., Rammasun (2002) and Maemi (2003) that made landfall and produced heavy rainfall over the Peninsula are compared. Although both had a remarkably similar accumulated rainfall pattern over the peninsula, the temporal evolutions of hourly rainfall were different. Only Maemi had an indirect precipitation event in conjunction with a midlatitude trough to its north. The confluent flows at middle-to-upper levels were strengthened due to the increased pressure gradient between the midlatitude trough and the subtropical high, and the warm advection by the confluent flows also became stronger near the confluent zone. By contrast, Rammasun encountered the subtropical ridge while moving northward, which results in slow recurvature and reduction of the thermal gradient over the peninsula. The highly baroclinic synoptic backgrounds in the Maemi case lead to the midlevel frontogenesis. Budget analyses using the three-dimensional frontogenesis equation revealed that the horizontal deformation forcing had a primary role in generating the front. The front was associated with a thermally direct circulation that contributed to strong ascent and indirect precipitation over the peninsula well in advance of the landfall of Maemi. Moreover, the indirect precipitation could intensify due to the abundant low-level moisture supply to the frontal zone by the southerly wind on the east side of the TC.     

Antecedent mid-tropospheric frontogenesis caused by the interaction between a tropical cyclone and midlatitude trough: a case study of Typhoon Rusa (2002)

This study examines antecedent mid-tropospheric frontogenesis (AMF) resulting from the interaction between Typhoon Rusa (2002) and a midlatitude trough over the Korean Peninsula. In this event, the AMF contributed to the first peak in the time series of rainfall in Gangneung (37.75°N, 128.90°E), occurring about 12 h before the time of the extratropical transition (ET) process of the tropical cyclone (TC). Using observations and high-resolution model outputs, we showed that the AMF contributed to the antecedent rainfall in Gangneung during the first rainfall period when Gangneung was located outside of Rusa's sphere of direct influence. A Weather Research Forecasting (WRF) model experiment was conducted to diagnose the frontogenetical features and associated precipitation processes in detail. The experiment revealed that the AMF was mainly forced by the horizontal deformation forcing (HDF). The direction of the HDF was oriented from southwest to northeast in the middle part of the peninsula. The HDF increased positively due to the confluence of the southeasterlies from the TC and the northwesterlies emanating from the midlatitude trough. The experiment also suggested that the mid-tropospheric moisture originated from the subtropical ocean and deposited into the frontal region by the southerlies on the eastern periphery of the TC, which enhanced the convergence of moisture flux in the frontal region during the first rainfall period. The thermally direct circulation associated with the AMF lead to the mid-tropospheric saturation, which enhanced the precipitation of the first rainfall event together with the orographically forced convection at the low level above Gangneung.     

西藏阿里札达盆地的“翘板式”形成机制

西藏阿里札达地区基本构造格架是由-系列褶皱、断裂、岩浆岩带和动力变质带组成的一套北西向构造系统，起源于晚侏罗世以来印度-欧亚板块俯冲-碰撞和陆内会聚作用。按照板块运动时间顺序，可区分出早、晚两阶段构造组合。早阶段构造组合与板块俯冲-碰撞有关，形成缝合带-陆缘弧系统；晚阶段构造组合与陆内会聚有关，形成基底断块系统。札达盆地与高喜马拉雅断块隆起存在盆-山耦合关系，藏南谷地基底断块的翘板式运动是形成盆地的主要控制因素。     

Low carbon scenarios and policies for the power sector in Botswana

The Government of Botswana has pledged a nationally determined contribution (NDC) as a commitment to the Paris Agreement. For the power sector, the NDC states that the government expects renewable energy (RE) to meet 25% of peak electricity demand by 2030. However, due to high initial cost of RE technologies, the government plans to maintain a coal-based power system in the future. Therefore, the purpose of this paper is to examine Botswana’s national plan from an economic perspective, using scenario and cost analysis, to explore the possibility of the power sector’s low carbon transition in the light of Botswana’s NDC. Five scenarios are designed to reflect a range of investment cost changes of RE technologies. While most scenarios only achieve 19% (P3, P4 and P5) and 54% (P6) of the NDC’s power sector target, the P7 scenario far exceeds the goal by achieving 188% of the NDC target. Furthermore, as the difference of levelized cost of electricity among the scenarios is minimal, the P7 scenario is the most attractive pathway for the government. Even for other scenarios, the government should still deploy the suggested capacity of solar photovoltaic (PV) as it is both economically and socially beneficial in the long term. However, in these cases, the government’s political will to meet the NDC’s power sector target and to promote the solar PV industry will be critical in designing future power sector policies.

Key policy insights

• Model results show coal as the cheapest resource for electricity generation in Botswana up to 2030, but the cost competitiveness of solar photovoltaic (PV) against coal will continue to increase over time.

• It is economically and socially beneficial to adjust the current national plan and substitute some share of coal with solar PV in the future energy mix.

• Government support is critical in achieving the power sector’s NDC target, as cost reduction of solar PV alone does not guarantee success.

• Encouraging independent power producers (IPP) with financial support mechanisms would be a suitable business model for developing the renewable energy industry.

     

Numerical simulation of load distributive compression anchor installed in weathered rock layer

Acta Geotechnica - This paper presents a finite element model for a load distributive compression anchor (LDCA). In an LDCA, the load applied to the strands is transmitted to the grout and ground...     

Estimate of Coastal Water Depth Based on Aerial Photographs Using a Low-Altitude Remote Sensing System

Ocean Science Journal - Observing coastal water depths is very important to understand physical processes of the coastal environment and manage coastal resources. In this study, a low-altitude...     

A seismic survey to detect natural gas hydrate in the East Sea of Korea

Recently, several countries have conducted projects to explore and develop natural gas hydrate, which is one of the new alternative energy resources for the future. In Korea, a five-year national research project was initiated in 2000. As part of this project, a seismic survey was performed in the East Sea of Korea to quantify the potential magnitude and distribution of natural gas hydrates. Multi-channel seismic data and core samples have been acquired and recovered in the survey area. Analysis of seismic data show clear bottom simulating reflectors (BSRs), seismic blank zones (or wipe-out zones) with velocity pull-up structure, and pock-marks. In this study, we present the results of seismic surveys which indicate the existence of natural gas hydrates in Korean offshore areas. These results will be applied to select areas for coring (or drilling) and detailed exploration such as 2D seismic survey with long offset or 3D seismic in the future.