A dipole wind curl pattern induced by Taiwan Island and its effect on upper stratification in the northeastern South China Sea

Using hydrographic data sampled during four successive late summer-early autumn cruises in 2004-2007, vertical stratification along transects in the lee of Taiwan Island was analyzed to investigate upper ocean responses to orographically induced dipole wind stress curl (WSC). Results indicate that mixed-layer depth (MLD) and its relationship with thermocline depth varied under different local wind forcings. Average MLD along the transects from the 2004 to 2007 cruises were 18.5,30.7,39.2 and 24.5m, respectively. The MLD along the transects deepened remarkably and resulted in thermocline ventilation in 2005 and 2006, whereas ventilation did not occur in 2004 and 2007. Estimates indicate that frictional wind speed was the major factor in MLD variations. To a large degree, the combined effects of frictional wind speed and Ekman pumping are responsible for the spatial pattern of MLD during the cruises.     

第二次国际印度洋科学考察计划(IIOE-2)介绍

为纪念首次国际印度洋科学考察计划(International Indian Ocean Expedition,IIOE)成功实施50周年,进一步推动印度洋多学科交叉的新认识,政府间海洋学委员会(Intergovernmental Oceanographic Commission,IOC)、国际海洋研究科学委员会(Scientific Committee on Oceanic Research,SCOR)和印度洋全球海洋观测系统计划(Indian Ocean Global Ocean Observing System,IOGOOS)在2015年联合启动了第二次国际印度洋科学考察计划(Second International Indian Ocean Expedition,IIOE-2,2015—2020年)。本文简要回顾了首次IIOE的发起、实施和主要成果,介绍了IIOE-2的主要内容和我国的优先参与方向,呼吁我国科学家将IIOE-2与我国"一带一路"倡议相结合,更加积极地参与IIOE-2国际合作,推动在印度洋环流与气候、海洋生态系统与可持续发展、地球生物化学循环、海底科学等领域取得新的科学进展。     

Mesoscale structure of the central South China Sea detected by SCSMEX Buoy and Argo float

We addressed the mesoscale structure variation of the central South China Sea (SCS) with the measurements by a long-lived Argo float and a high-resolution ATLAS buoy during 1998–2002. T-S diagram indicates cooling and freshening events in 2000 and 2001 with lower salinity (0.5–0.8) and lower temperature (1–1.7°C). Significant decrease in the net heat flux and increase in the precipitation suggest that the cooling and freshening is due to extra forcing by the atmosphere. Additional to large year-to-year changes, intraseasonal variability is moderate in the research area. The axis of the maximum intraseasonal temperature and salinity signals are mainly located on the thermocline. Typically, amplitude and period of intraseasonal temperature is about 2°C and 40–60 days, and that of salinity is 0.3–0.5 and 35–60 days. Rapidly-changing winds, heat flux, and precipitation are critical in controlling the intraseasonal fluctuations of the mixed layer of the area. Studies on heat and freshwater balance in the mixed-layer further suggest that horizontal advection plays an important role in intraseasonal fluctuation in the upper ocean. In addition, the energetic mesoscale propagation radiated from the east boundary is linked to the intraseasonal variability in winter.     

内蒙古自治区达尔罕茂明安联合旗黑沙庙钨多金属矿特征

矿(化)体主要赋存于奥陶系包尔汉图群哈拉组二段安山岩中。为在后期热液岩浆侵入形成的脉体及与围岩接触带上钨矿化强烈。主要矿化特征为局部强烈的孔雀石化、褐铁矿化、碳酸岩化及高岭土化、铅锌矿化,形成侵染状、细脉状及密集的星点状钨多金属矿分布于岩石中。结合化探资料,异常亦由钨多金属矿(化)体引起。     

基于固有振动频率的危岩安全监测试验研究

危岩体在经历地震和强降雨之后其抗滑力下降,从而导致重力作用失稳,是一种常见的破坏形式。危岩块体的失稳破坏取决于岩体结构面的状况,随着结构面的张开及黏结程度下降,危岩块体会发生失稳而崩塌,基于常规位移监测方法难以达到危岩块体监测预警的目的。而固有振动频率可以有效反映岩体的物理力学参数的变化,进而可以对其安全性做出预判。基于模型试验,在保持下滑力不变的情况下,通过固有振动频率来对滑坡内部的黏结力和摩擦力等力学指标进行分析。通过实际静摩擦力是否达到最大静摩擦力的方法来科学判识岩体的稳定情况。试验结果得出：计算的摩擦力可以有效分析岩体的安全性,并证明固有振动频率在降低至6 Hz以下,岩体开始趋于破坏。同时,得出由于摩擦力破坏后期占据抗滑力的比重逐渐升高,最高达到抗滑力的80%,从而造成破坏末期摩擦力不降反升的情况。基于固有振动频率的监测,可对岩体的损伤做出定量判断,也可评估岩体静摩擦力指标,从而实现扰动后岩体的安全评价。这种基于振动模态的岩体安全监测与损伤评价新的技术思路,将在实际工程中发挥重大作用。     

An interdecadal change of tropical cyclone activity in the South China Sea in the early 1990s

Tropical cyclone (TC) genesis in the South China Sea (SCS) during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994- 2008, about twice that during 1979-1993 (27). During the TC peak season (July-September, JAS), there were 43TCs from 1994-2008, but only 17 during 1979-1993. For July in particular, 13TCs formed from 1994-2008, but there were none during 1979-1993. The change in TC number is associated with changes of key environmental conditions in atmosphere and ocean. Compared to 1979-1993, the subtropical high was significantly weaker and was displaced more eastward during 1994-2008. In the former period, a stronger subtropical high induced downward flow, inhibiting TC formation. In the latter period, vertical wind shear and outgoing longwave radiation all weakened. Mid-level (850-500hPa) humidity, and relative vorticity were higher. Sea surface temperature and upper layer heat content were also higher in the area. All these factors favor TC genesis during the latter period. The decadal change of TC genesis led to more landfalling TCs in Southern China during the period 1994-2008, which contributed to an abrupt increase in regional rainfall.     

南海障碍层的季节变化及其与海面通量的关系

对气候平均态的温度和盐度分析证实,夏、秋季南海南部上层海洋存在障碍层现象.决定障碍层出现的关键因素是净淡水通量,而障碍层的深度和厚度分布则受风场的显著影响,障碍层受混合层和等温层发展的调制.夏季,南海南部上层海洋在东南向Ek-man水平输运以及东侧下降运动双重因素作用下,较淡的水体在南海东南侧堆积,混合层底部高温水脱离混合层保留在等温层中,造成障碍层在南海东南侧最为深厚,达到30 m.最厚障碍层出现的位置和最厚"南海暖水"出现的位置几乎重合,障碍层的"热障"作用促进了"南海暖水"的发展.     

南印度洋偶极子及其影响研究进展

回顾了对南印度洋副热带海气相互作用的研究,总结了南印度洋偶极子事件背景下的气候变化。印度洋海表温度的方差表明南印度洋是整个印度洋海温变率最强的区域,年际海温变化最显著的特征就是海温呈现西南—东北向的偶极子型分布,被称为南印度洋偶极子(Southern Indian Ocean Dipole, SIOD)。南印度洋海温偶极子的形成主要是受大尺度大气环流调整的影响。南印度洋副热带反气旋环流异常引起了印度洋热带东风异常和副热带西风异常的变化,影响了潜热通量、上升流和Ekman热输送,进而引起了海温变化。SIOD对热带和热带外大气环流也有影响,尤其会影响亚洲夏季风降水异常,例如我国的降水异常和南印度洋偶极子海温异常具有显著相关关系。此外,SIOD模态所引起的经向环流异常与南海、菲律宾地区的反气旋环流异常也有紧密联系。     

利用回归模型模拟卫星跟踪海洋漂流浮标轨迹

分析浮标漂流速度和表层地转流、风海流结果表明：浮标漂流速度和表层地转流具有良好相关性。针对卫星跟踪漂流浮标运动的准地转性,建立了以海表地转流为主要回归自变量的几种回归模型,用以模拟浮标漂流轨迹,以期对浮标运动特性有进一步的认识。对南海中伴随涡旋运动的2个浮标模拟试验显示,诸多模型中以海表地转流、风海流及背景流为自变量的回归模型模拟浮标漂流轨迹效果较好。利用该回归模型,模拟出南海2个漂流浮标轨迹和真实轨迹距离偏差较小且二者运动趋势基本一致。通过分析回归模拟所得风海流、海表地转流及背景流发现：涡旋中心附近浮标漂移主要受地转流的控制,而涡旋边缘处风海流起到关键性作用,正是这部分贡献使得浮标能够进入（脱离）涡旋。背景流的空间分布决定着浮标漂移的最终去向,特别是背景流方向改变的区域,背景流的存在使得模拟浮标轨迹能够像真实轨迹一样运移。     

TRMM卫星降雨雷达观测的南海降雨空间结构和季节变化

利用热带降雨计划卫星（TRMM）获得的雷达降雨资料，对南海及其周边区域（简称南海地区）降雨的空间分布和季节特征进行了研究。结果表明：南海地区的降雨在空间上分布很不均匀，同时具有显著的季节变化。除了副高活动、季风潮、冬季冷涌和热带低压活动等天气过程，南海周边广泛分布的山地地形对该地区的降雨分布也产生强烈影响，降雨呈现南部高于北部、东部高于西部的分布特征。与CAMP和台站资料相比，PR观测具有更丰富的空间结构，能够更好地体现降雨随时间和空间变化的特征、反映高大的山地地形对降雨分布的影响。