Possible relationship between western North Pacific tropical cyclone activity and Arctic Oscillation

This study found that Arctic Oscillation (AO) has a significant influence on tropical cyclone (TC) activities in the western North Pacific during the boreal summer (July, August, and September). During low- (high-) AO years, more TCs formed over east (west) of 150° E, recurved in the east (west), and passed over the midlatitudes (southeast Asian region), including Korea and Japan (South China Sea and south China), compared to the high- (low-) AO years. In particular, the TC passage frequency difference between the two periods showed a dipole-like pattern between the regions of Southeast and Northeast Asia. The differences between these two periods were caused by a stronger anticyclonic circulation located around Korea and Japan during high-AO years. This circulation played a significant role in blocking the movement of TCs toward Korea and Japan during high-AO years. Instead, TCs moved westward toward the SCS and southern China along the easterly and southeasterly steering flow of this anticyclonic circulation. As a result, TC lifetime and intensity were shorter and weaker during high-AO years.     

Characteristics and Nonlinear Growth of the Singular Vector Related to a Heavy Rainfall Case over the Korean Peninsula

In this study,singular vectors related to a heavy rainfall case over the Korean Peninsula were calculated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) adjoint modeling system.Tangent linear and adjoint models include moist physical processes,and a moist basic state and a moist total energy norm were used for the singular-vector calculations.The characteristics and nonlinear growth of the first singular vector were analyzed,focusing on the relationship between the basic state and the singular vector.The horizontal distribution of the initial singular vector was closely related to the baroclinicity index and the moisture availability of the basic state.The temperature-component energy at a lower level was dominant at the initial time,and the kinetic energy at upper levels became dominant at the final time in the energy profile of the singular vector.The nonlinear growth of the singular vector appropriately reflects the temporal variations in the basic state.The moisture-component energy at lower levels was dominant at earlier times,indicating continuous moisture transport in the basic state.There were a large amount of precipitation and corresponding latent heat release after that period because the continuous moisture transport created favorable conditions for both convective and nonconvective precipitation.The vertical propagation of the singular-vector energy was caused by precipitation and the corresponding latent heating in the basic state.     

黄海深部结构与中朝-扬子块体结合带在海区位置的地球物理研究

以黄海及其邻区为研究对象 ( 32～ 4 2°N ,1 2 0～ 1 30°E) ,以研究区的空间重力异常、布格重力异常和地震层析成像数据为基础 ,在研究区中分辨出方向各异的主要断裂带并给出它们的分布。对在朝鲜半岛存在的一条近SN向分布的断裂带进行了重点讨论。根据重力数据、莫霍深度分布特点和层析成像的结果 ,认为该断裂带的两侧应属于不同的构造地质单元 ;提出该断裂带与五莲—青岛断裂带和济州岛南缘断裂带一起组成了中朝与扬子块体在黄海海区的边界结合带的认识 ;并推测在三叠纪的晚期 ,沿郯庐断裂带和该断裂带曾分别发生过左旋和右旋走滑。受SN向挤压应力的作用 ,(下 )扬子块体被平移嵌入到中朝块体之中。因此 ,两个块体在海区的结合带为一个巨大的“Z”字型的入构造     

Rosetta target asteroid 2867 Steins: An unusual E‐type asteroid

Abstract— ESA's Rosetta spacecraft will fly by main‐belt asteroid 2867 Steins on September 5, 2008. We obtained new visible wavelength spectra of 2867 Steins on December 19, 2006 (UT), using the Palomar 5 m telescope and the facility Double Spectrograph. Two sets of spectra, taken ～3 h apart, one half of the rotation period for 2867 Steins, show it to be an E‐type asteroid. The asteroid displays a 0.50 μm feature that is considered diagnostic of the E(II) sub‐class, but is deeper than any previously observed E‐type. This feature is most likely due to the presence of oldhamite (CaS) on the asteroid's surface. Also, the observed Steins spectra are far redder than any other known E‐types. There is potential evidence for heterogeneity on hemispheric scales, one side of the asteroid appearing to be significantly redder than the other. No known recovered meteorite sample matches the unusual spectra of 2867 Steins, but the closest analog would be similar to an enstatite achondrite (aubrite).     

Comments on ``Direct Radiative Forcing of Anthropogenic Aerosols over Oceans from Satellite Observation"

Previous observational studies have estimated anthropogenic aerosol direct radiative forcing over oceans without due consideration of cloudy-sky aerosols.However,when interaction between clouds and aerosols located below or above the cloud level is taken into account,the aerosol direct radiative forcing is larger by as much as 5 W m-2 in most mid-latitude regions in the Northern Hemisphere.     

Characteristics of the changes in tropical cyclones influencing the South Korean region over the recent 10 years (2001–2010)

Through the investigation of tropical cyclone (TC) characteristics related to climate change, this study found that the frequency of TCs occurring over the Western North Pacific has recently decreased slightly, while their average intensity has increased. The number of overall TCs that passed within the vicinity of South Korea has also been reduced, but the number of strong typhoons in the area, those with maximum wind speeds of more than 44 m/s, has significantly increased. These changes are closely related to the following phenomena. (1) The average genesis region of TCs that influence South Korea has moved eastward. Accordingly, the TCs tend to strengthen as they move westward for long distances along the Intertropical Convergence Zone (ITCZ) trade easterlies and the southern boundary of the North Pacific Subtropical High (NPSH). (2) The NPSH and Asia Monsoon trough, which are known to affect TC tracks, have extended to the northwest and southeast. This has caused TCs that travel to higher latitudes and curve back toward the Korean Peninsula to become more frequent. (3) TCs have approached the Korean Peninsula without hitting land. In addition, the sea surface temperature became higher than it was before. These factors have caused TCs to maintain their strength or become stronger than before.     

High-resolution circulation forecasting of the Maenggol Channel, south coast of Korea

The Maenggol Channel and Uldolmok Strait, located on the south-west coast of Korea, have notably strong and complex currents due to tidal effects and to local geological factors. In these areas, electric power has been generated using strong tidal currents, the speed of which is more than 3 m/s during spring tides. The region also provides a shortcut for navigation. These tidal conditions are therefore sometimes useful, but may also cause terrible accidents or severe economic damage, in the absence of accurate information regarding ocean conditions. In April 2014, the passenger ferry MV Sewol capsized in the Maenggol Channel, with 295 passengers killed and 9 still missing. While this was unquestionably a man-made disaster, strong currents were one of the contributing causes. It was also difficult to conduct scuba diving rescue operations given strong current speeds, and accurate prediction of the time when the tide would turn was thus critically needed. In this research, we used the high-resolution coastal circulation forecasting system of KOOS (Korea Operational Oceanographic System) for analysis and simulation of strong tidal currents in such areas with many small islands, using measurements and modeling from this research area. For accurate prediction of tidal currents, small grid size-modeling was needed, and in this study, we identified a suitable grid size that offers efficiency as well as accuracy.     

Simulation of Storm Surge and Wave Due to Typhoon Isewan (5915)

An integrally coupled wave-tide-surge model was developed and then applied to the simulation of the wave-typhoon surge for the typhoon Isewan (typhoon Vera (5915)), which is the strongest typhoon that has struck Japan and caused incalculable damage. An integrally coupled tide-surge-wave model using identical and homogeneous meshes in an unstructured grid system was used to correctly resolve the physics of wave-circulation interaction in both models. All model components were validated independently. The storm surge and wave properties such as the surge height, the significant wave height, wave period and direction were reproduced reasonably under the meteorological forcing, which was reprocessed to be close to the observations. The resulting modeling system can be used extensively for the prediction of the storm surge and waves and the usual barotropic forecast.     

Low genetic diversity in the endangered marine alga Silvetia siliquosa (Ochrophyta: Fucaceae) and the implication to conservation

Although significant research efforts have been targeted toward conservation and management of endangered terrestrial flora and fauna, attempts have been limite...     

Influence of the Arctic Oscillation on the TC activity around Taiwan

This study discovered that strong positive correlations exist between the frequency of tropical cyclones (TC) during the summer around Taiwan and the Arctic Oscillation (AO) during the preceding March to May period. In positive AO years, during the preceding spring to summer period, anomalous cyclone and anomalous anticyclone were strongly developed at low and middle latitudes, respectively. Because of such a distribution of pressure system, in Taiwan, Korea, and Japan during the positive AO years, anomalous southeasterlies, which play the role of anomalous steering flows in transferring TCs to these regions, were strengthened. On the other hand, in southern China and the Indochina Peninsula during the positive AO years, anomalous northwesterlies, which prevent the transfer of TCs to these regions, were strengthened. Moreover, such a distribution of pressure system strengthening during the positive AO years led TCs to occur, move, and recurve more eastward in the western North Pacific in positive AO years as compared with the negative AO years. Contrarily, during the negative AO years, TCs showed the tendency to pass over the South China Sea from the Philippines and move west toward southern China and the Indochina Peninsula. Eventually, the intensity of TCs in these years was lower than that of TCs in positive AO years due to the topographic effects from a high TC passage frequency in mainland China.