Primary Study of the Mechanism of Eddy Shedding from the Kuroshio Bend in Luzon Strait

The mechanism of the anticyclonic eddy's shedding from the Kuroshio bend in Luzon Strait has been studied using a nonlinear 2 1/2 layer model, in a domain including the North Pacific and South China Sea. The model is forced by steady zonal wind in the North Pacific. Energy analysis is adopted to detect the mechanism of the eddy shedding. Twelve experiments with unique changes of wind forcing speed (to obtain different Kuroshio transports at Luzon Strait) were performed to examine the relationship between the Kuroshio transport (KT) and the eddy shedding events. In the reference experiment with KT of 22.7 Sv (forced with zonal wind idealized from the annual mean wind stress from the COADS data set), the interval of eddy shedding is 70 days and the shed eddy centers at (20°N, 117.5°E). When the Kuroshio bend extends westward, the southern cyclonic perturbation grows so rapidly as to form a cyclonic eddy (18.5°N, 120.5°E) because of the frontal instability in the south of the Kuroshio bend. In the evolution of the cyclonic eddy, it cleaves the Kuroshio bend and triggers the separation of the anticyclonic eddy. In statistical terms, anticyclonic eddy shedding occurs only when KT fluctuates within a moderate range, between 21 Sv and 28 Sv. When the KT is larger than 28 Sv, a stronger frontal instability south of the Kuroshio bend tends to generate a cyclonic eddy of size similar to the width of the Luzon Strait. The bigger cyclonic eddy prevents the Kuroshio bend from extending into the SCS and does not lead to eddy shedding. On the other hand, when the KT decreases to less than 21 Sv, the frontal instability south of the Kuroshio bend is so weak that the size of corresponding cyclonic eddy is smaller than half the width of the Luzon Strait. The cyclonic eddy, lacking power, fails to cleave the Kuroshio bend and cause separation of an anticyclonic eddy; as a result, no eddy shedding occurred then, either.     

青岛冷水团的生成与演变研究

本文基于现场观测资料并结合FVCOM三维海洋模式的模拟结果,研究了2010年青岛冷水团生消过程和演变机制。结果表明,山东半岛东南海域的中层冷水是青岛冷水团的雏形,于4月中旬演变为青岛冷水团,位于青岛东南外海40m以下的盐度锋面中;刻画了青岛冷水团的消亡过程:5月青岛冷水团的北部底层水并入南黄海底层冷水中,构成南黄海的西部冷中心;而南部水团面积大幅减小,温盐特征大幅上升;6月上旬,青岛冷水团完全被南黄海底层冷水吞并,青岛冷水团完全消亡;揭示了青岛-石岛近海反气旋涡、黄海冷水团锋面密度环流对青岛冷水团的作用,前者是青岛冷水团存在的动力机制,后者加剧了底层海域的水平热量交换,促使了青岛冷水团的消亡。     

基于切向超滤技术的胶体有机碳和无机氮分离及物源初探

利用切向超滤技术对九龙江口天然水体中胶体相(1 kDa～0. 45μm)、真溶解相(1 kDa)和"溶解相"(0. 45μm)的溶解有机碳和无机氮进行了分离与提取,初步探讨了水环境因子对其理化特性的影响机制,进而探讨了它们的来源和转化.结果表明,切向超滤过程的膜空白和质量平衡符合技术要求;溶解有机碳、亚硝酸盐氮、氨氮、硝酸盐氮和无机氮存在形式以真溶液相(1 kDa)为主,其在胶体相中的质量浓度分别为0. 207～0. 810 mg/dm3、0. 001～1. 870μg/dm3、ND～2. 08μg/dm3、0. 62～79. 30μg/dm3和1. 07～81. 10μg/dm3;胶体态溶解有机碳(COC)含量主要受陆源输入控制.     

Dynamic of ENSO towards upwelling and thermal front zone in the east coast of Peninsular Malaysia

The El Ni?o Southern Oscillation(ENSO) is a natural phenomenon that relates to the fluctuation of temperatures over the Pacific Ocean. The ENSO significantly affects the ocean dynamics including upwelling event and coastal front. A recent study discovered the seasonal upwelling in the east coast of Peninsular Malaysia(ECPM), which is significant to the fishery industry in this region. Thus, it is vital to have a better understanding of the influence of ENSO towards the coastal upwelling and thermal front in the ECPM. The sea surface temperature(SST) data achieved from moderate resolution imaging spectroradiometer(MODIS) aboard Aqua satellite are used in this study to observe the SST changes from 2005 to 2015. However, due to cloud cover issue, a reconstruction of data set is applied to MODIS data using the data interpolating empirical orthogonal function(DINEOF) to fill in the missing gap in the dataset based on spatial and temporal available data. Besides, a wavelet transformation analysis is done to determine the temperature fluctuation throughout the time series. The DINEOF results show the coastal upwelling in the ECPM develops in July and reaches its peak in August with a clear cold water patch off the coast. There is also a significant change of SST distribution during the El Ni?o years which weaken the coastal upwelling event along the ECPM. The wavelet transformation analysis shows the highest temperature fluctuation is in 2009–2010 which indicates the strongest El Ni?o throughout the time period. It is suggested that the El Ni?o is favourable for the stratification in water column thus it is weakening the upwelling and thermal frontal zone formation in ECPM waters.     

青藏高原冬季积雪与华南前汛期降水年际变率的联系

利用1979—2018年青藏高原(简称高原,下同)卫星积雪数据集、华南地区261站逐日降水及ERA5再分析资料,探讨了高原冬季积雪与华南前汛期降水的联系。结果表明：1)高原西部积雪与华南前汛期降水的正相关关系最为稳定,其主要影响前汛期的锋面降水,对夏季风降水的影响较小;2)华南前汛期在高原西部积雪偏多年比偏少年偏早20 d,使得前汛期降雨日数偏多,持续时间偏长,总降水量偏多,而降水强度受积雪的影响较小;3)高原积雪偏多年,积雪的冷却作用形成了低层异常反气旋环流,而东亚沿岸为“+-+”的位势高度异常,中纬度“西高东低”的环流配置有利于中高纬冷空气南侵,使得华南上空温度偏低,同时偏强偏南的西太平洋副热带高压加强了低纬地区偏南气流和水汽输送。3—4月锋面在华南北部南北摆动,4月初偏北干冷空气南侵和偏南暖湿气流的持续北推使得锋面加强,触发了前汛期的较早建立;积雪偏少年冷空气和偏南暖湿气流均较弱,华南北部锋面在4月初中断,4月中下旬华南北部锋面在偏北弱冷空气和偏南暖湿气流的共同作用下重新建立,从而华南前汛期开始偏晚。     

Integrative Monsoon Frontal Rainfall Experiment(IMFRE-I):A Mid-Term Review

The mei-yu season,typically occurring from mid-June to mid-July,on average,contributes to 32%of the annual precipitation over the Yangtze-Huai River Valley(YHRV)and represents one of the three heavy-rainfall periods in China.Here,we briefly review the large-scale background,synoptic pattern,moisture transport,and cloud and precipitation characteristics of the mei-yu frontal systems in the context of the ongoing Integrative Monsoon Frontal Rainfall Experiment(IMFRE)field campaign.Phase one of the campaign,IMFRE-I,was conducted from 10 June to 10 July 2018 in the middle reaches of the YHRV.Led by the Wuhan Institute of Heavy Rain(IHR)with primary support from the National Natural Science Foundation of China,IMFRE-I maximizes the use of our observational capacity enabled by a suite of ground-based and remote sensing instruments,most notably the IHR Mesoscale Heavy Rainfall Observing System(MHROS),including different wavelengths of radars,microwave radiometers,and disdrometers.The KA350(Shanxi King-Air)aircraft participating in the campaign is equipped with Ka-band cloud radar and different probes.The comprehensive datasets from both the MHROS and aircraft instruments are combined with available satellite observations and model simulations to answer the three scientific questions of IMFRE-I.Some highlights from a previously published special issue are included in this review,and we also briefly introduce the IMFRE-II field campaign,conducted during June-July 2020,where the focus was on the spatiotemporal evolutions of the mei-yu frontal systems over the middle and lower reaches of the YHRV.     

地形上空边界层流中低层锋面结构的理论研究Ⅱ:暖锋、均匀地转流

利用一个有地形、边界层摩擦作用、简化的二层浅水锋面模型,在理论上研究了地形上空边界层流动中地面暖锋的结构及环流分布特征问题。暖锋的坡度主要取决于其暖域地转流、锋面移速,它随锋面移速增大而减小,这与冷锋特征相反。地形对暖锋坡度的影响作用较小。与无地形作用时相比,静止性暖锋冷域中,位于锋面界面附近的闭合正环流系,当暖锋位于地形上游,其伸展范围增大;当暖锋位于迎风坡时,其伸展范围缩小,中心位置上抬;锋面移至背风坡时,其伸展范围重新增大。对于冷域中远离地面暖锋的另一支正环流系来说,当暖锋位于地形上游或迎风坡时,它可被地形完全阻塞于背风侧,地形高度越高,地形阻塞作用越大。在暖锋锋区附近主要存在三支垂直上升运动带：（a）由于边界层摩擦辐合作用,导致在地面暖锋后缘暖区中形成一支水平尺度较小、强度较大的垂直运动带,它随着暖锋移速增大而减弱。该垂直运动带,当暖锋位于地形迎风侧,强度增加;暖锋位于地形背风侧,其强度减弱。（b）在锋区暖域沿锋面存在均匀的上升运动,（c）在冷域远离地面暖锋处,存在一支水平范围较宽,其中心位于边界层顶部附近的垂直运动带,当暖锋位于迎风坡时,这支垂直运动带可被地形阻塞于地形背风侧。     

2001年华西秋雨时空分布特点及其成因分析

分析了2001年华西秋雨的时空分布特点和大尺度环流背景及天气系统的主要特征, 并对秋雨形成的主要物理机制进行了诊断和分析。结果显示, 2001年秋季, 华西地区阴雨日数多, 雨区集中, 强降水时段集中在9月份。该月, 巴尔喀什湖地区500 hPa呈准稳定的低压槽, 其上不断有短波分裂东移, 携带冷空气经高原东移, 与强大的副热带高压西南侧的东南暖湿气流和来自孟加拉湾的西南暖湿气流交汇于四川盆地、陇南、陕南一带, 致使该地区持续阴雨天气。诊断分析表明, 9月, 青藏高原地区对流旺盛, 水汽凝结释放潜热, 使其成为一个强大的热源中心; 而江淮、江南一带多受西北太平洋副热带高压控制, 盛行下沉气流, 为热源低值区; 四川盆地处于高原高能量带与盆地以东低能量带之间的能量锋区。此能量锋区的存在促使从巴尔喀什湖低压槽分裂东移的短波槽在该地区发展。同时, 东路冷空气的渗入进一步加大了能量锋区的强度, 激发不稳定能量释放, 造成了四川盆地部分地区出现大暴雨甚至特大暴雨。     

华南前汛期的锋面降水和夏季风降水Ⅰ. 划分日期的确定

前汛期暴雨常常引发华南地区的洪涝, 但是前汛期降水的预报能力却相当低.降水的预报在很大程度上依赖于对降水性质的理解, 而华南前汛期降水通常被认为只是锋面性质的降水.事实上, 南海夏季风在6月(甚至5月)就可以影响到华南地区并产生季风对流降水.因此, 华南前汛期包含了两种不同性质的降水, 即锋面降水和夏季风降水, 如何区分它们是非常重要的.为了区分它们, 利用NCEP/NCAR再分析资料、 CMAP资料和中国730站降水资料, 分析气候平均(1971～2000年)状态下锋面降水和季风降水期间大气性质和特征的差异, 得到华南前汛期夏季风降水开始的基本判据: 100 hPa纬向风由西风转为东风并维持5天以上.利用该判据得出气候平均条件下的华南夏季风降水开始于5月24日, 并得到1951～2004年逐年华南前汛期锋面降水和季风降水的划分日期.合成分析的结果表明, 得到的划分日期是基本合理的, 因为它将锋面降水和季风降水期间大气特点的显著差别区分开来.     

GEOLOGY OF THE TAPLEJUNG WINDOW AND FRONTAL BELT, FAR EASTERN NEPAL HIMALAYA

GEOLOGY OF THE TAPLEJUNG WINDOW AND FRONTAL BELT, FAR EASTERN NEPAL HIMALAYA1　PecherA .Deformationandmetamorphismeassociesaunezonedecisaillement :Exampledugrandchevauchementcen tralHimalayan (MCT) [M ].Thesed’Etat,UnivGrenoble ,France ,1978.35 4. 2　RaiSM .LesnappesdeKathmandudtduGosainkund ,HimalayaduNepalcentral[M ].Thesededoctoral,Univ .Grenoble ,France ,1998.2 44 . 3　SchellingD ,AritaK .Thrusttectonics ,crustalshortening ,andthestructureofthe…