南亚高压在高原建立的路径类型及其分析

利用1948-2006年NCEP／NCAR逐日再分析资料分析了南亚高压的移动路径、特征及其触发机制。根据高压的移动情况及其环流等特征发现,南亚高压的移动路径分为东路型,南路型和西路型。对比不同路径的温度场、风场及热源整层积分场等特征,发现不同路径之间存在很大差异。通过SVD分析以及合成分析发现,高原附近热源强弱配置的差异是造成路径差异的可能原因;同时,高原地区热力、动力作用造成的中低纬度的大气长波波型配置对路径的影响也至关重要。     

Impact of the thermal state of the tropical western Pacific on onset date and process of the South China Sea summer monsoon

Since the early or late onset of the South China Sea summer monsoon （SCSM） has a large impact on summer monsoon rainfall in East Asia, the mechanism and process of early or late onset of the SCSM are an worthy issue to study. In this paper, the results analyzed by using the observed data show that the onset date and process of the SCSM are closely associated with the thermal state of the tropical western Pacific in spring. When the tropical western Pacific is in a warming state in spring, the western Pacific subtropical high shifts eastward, and twin cyclones are early caused over the Bay of Bengal and Sumatra before the SCSM onset. In this case, the cyclonic circulation located over the Bay of Bengal can be early intensified and become into a strong trough. Thus, the westerly flow and convective activity can be intensified over Sumatra, the Indo-China Peninsula and the South China Sea （SCS） in mid-May. This leads to early onset of the SCSM. In contrast, when the tropical western Pacific is in a cooling state, the western Pacific subtropical high anomalously shifts westward, the twin cyclones located over the equatorial eastern Indian Ocean and Sumatra are weakened, and the twin anomaly anticyclones appear over these regions from late April to mid-May. Thus, the westerly flow and convective activity cannot be early intensified over the Indo-China Peninsula and the SCS. Only when the western Pacific subtropical high moves eastward, the weak trough located over the Bay of Bengal can be intensified and become into a strong trough, the strong southwesterly wind and convective activity can be intensified over the Indo-China Peninsula and the SCS in late May. Thus, this leads to late onset of the SCSM. Moreover, in this paper, the influencing mechanism of the thermal state of the tropical western Pacific on the SCSM onset is discussed further from the Walker circulation anomalies in the different thermal states of the tropical western Pacific.     

亚洲夏季风建立格局和南海季风爆发特征及其成因初探

使用１９８０￣１９８６年欧洲中期预报中心（ＥＣＭＷＦ）格点资料和１９８０￣１９９２年日本地球静止气象卫星（ＧＭＳ）观测到的黑体辐射（ＴＢＢ）资料，分析了南海季风爆发和亚洲夏季风建立格局及其可能机制。发现亚洲夏季风建立征兆最早出现在中南半岛－南海地区，随后自该地区分别向西、向东扩展；中南半岛地区是东亚季风和印度季风的天然分界线，其两侧夏季风的建立特征和形成机制迥然不同。亚洲夏季风自东向西逐渐建立的格     

南海台风边界层湍流小波分析

利用小波变换（WT）对香港天文台飞机观测台风“妮妲”（1604）资料进行分析,研究在不稳定、不均匀的台风边界层中湍流涡旋的垂直传输作用。在0.1～5 Hz惯性子区内横风和顺风分量功率谱密度能较好符合-5/3幂律。小波分析显示：横风的小波功率谱峰值集中在1 km之下,顺风分量的小波功率谱峰值集中在1～6km之间;眼区动量通量的主要贡献尺度为2.3 km,眼区外主要贡献尺度在1～2 km,中低层为较小尺度（<1.0km）;湍流功能(TKE)的生成尺度主要集中在4 km之下。这项研究定量描述了南海北部台风边界层各个区域湍流结构的差异特征,讨论了对台风边界层通量参数化的可能影响。     

A Modeling Study of the Effects of Anomalous Snow Cover over the Tibetan Plateau upon the South Asian Summer Monsoon

The effect of anomalous snow cover over the Tibetan Plateau upon the South Asian summer monsoon is investigated by numerical simulations using the NCAR regional climate model (RegCM2) into which gravity wave drag has been introduced. The simulations adopt relatively realistic snow mass forcings based on Scanning Multi-channel Microwave Radiometer (SNINIR) pentad snow depth data. The physical mechanism and spatial structure of the sensitivity of the South Asian early summer monsoon to snow cover anomaly over the Tibetan Plateau are revealed. The main results are summarized as follows. The heavier than normal snow cover over the Plateau can obviously reduce the shortwave radiation absorbed by surface through the albedo effect, which is compensated by weaker upward sensible heat flux associated with colder surface temperature, whereas the effects of snow melting and evaporation are relatively smaller.The anomalies of surface heat fluxes can last until June and become unobvious in July. The decrease of the Plateau surface temperature caused by heavier snow cover reaches its maximum value from late April to early May. The atmospheric cooling in the mid-upper troposphere over the Plateau and its surrounding areas is most obvious in May and can keep a fairly strong intensity in June. In contrast, there is warming to the south of the Plateau in the mid-lower troposphere from April to June with a maximum value in May.The heavier snow cover over the Plateau can reduce the intensity of the South Asian summer monsoon and rainfall to some extent, but this influence is only obvious in early summer and almost disappears in later stages.     

华南大范围暴雨副热带高压的演变特征及可能机制

利用多时间尺度ＮＣＥＰ／ＮＣＡＲ再分析资料、ＴＢＢ资料，通过合成分析、动力诊断、理论探讨和数值模拟等方法，对华南暴雨发生时副热带高压的短期变异进行了探讨。结果表明，华南暴雨发生前副热带高压有一西伸一东撤的过程，而华南暴雨发生在副高东撤到接近最东时。利用Ｌ９Ｒ１５谱模式模拟了孟加拉湾异常热源对副热带高压西仲的影响，数值模拟结果表明孟加拉湾异常热源可能是副热带高压西伸的可能机制。而正的涡度的局地变化可能是副高东撤的因素。     

温度,盐度和风应力对南海海流模拟的影响

用美国普林斯顿大学海洋模式（ＰＯＭ）对南中国海的年平均海流进行了数值模拟,对温盐结构和风应力在海流形成中的作用进行了较详细的讨论。结果表明,仅有温盐水平不均匀分布也可以驱动海水而生成南海海流,但此种海流的结构较乱,最大流速只有３０～４０ｃｍ·ｓ－１。若温盐无水平结构,则在风应力驱动下,南海海流的结构较为有序,且最大流速可增至６０～７０ｃｍ·ｓ－１。在温盐水平分布不均匀并有风应力的作用时,生成的南海海流与仅有风应力作用时的海流场较相似,说明在南海海流的形成中,风应力的作用更为重要。海面自由高度的分析也证明了上述结论。     

近47a华南前汛期旱涝特征

采用华南61站47a（1958-2004年）前汛期（4-6月）逐日降水资料,利用统计方法对华南前汛期的旱涝特征进行了研究。结果表明：47a来华南有12个涝年和12个旱年发生,较严重的旱涝年主要发生在20世纪50年代末至70年代中期以及90年代以后;前汛期旱涝变化以2～4a的年际尺度周期最为显著;4、5月旱涝的年代际变化特征较为一致,而5月与6月在年代际尺度上具有一定的反位相变化特征;地理分布上,可将华南地区前汛期降水分为5个旱涝异常气候区。近47a来桂南、粤西和东南沿海地区呈现旱—涝—旱的变化特征,而桂北区由旱转涝趋于雨涝的趋势明显,东北部山区由涝转旱趋于干旱的趋势明显。     

南水北调中线水源地河水地球化学特征与流域侵蚀

丹江口水库及其上游流域是南水北调中线工程的水源地,本文讨论了水源地河流水化学与锶同位素(87Sr/86Sr)组成变化特征,目的在于了解水源地流域河流地表水溶质的物质来源以及岩石风化侵蚀过程和人为活动的影响。流域内河流水化学组成以Ca2+、HCO3-为主,Mg2+和SO42-次之,反映了碳酸盐岩风化溶解起控制作用的典型特征。水化学分析表明水源地河水受到工农业活动等人为因素的影响;河流87Sr/86Sr同位素地球化学研究表明,流域岩石风化输入至少存在三个不同端员(硅酸岩、石灰岩和白云岩)之间的混合。水源地流域内硅酸岩和碳酸岩的风化侵蚀速率分别为38.6和4.4 t/km2.a,总岩石风化侵蚀速率高于全球河流平均值。     

下扬子南黄海沉积盆地构造地质特征

南黄海盆地作为下扬子块体之上的大型叠合盆地,海相构造层保存完整,陆相断拗构造层也较为发育,盆地地质结构复杂,构造变形强烈,利用最新的地质地球物理资料和解释成果,对低勘探程度的南黄海盆地进行了研究,认为盆地演化大致经历了克拉通被动陆缘初始发育阶段—南缘前陆北缘被动陆缘过渡阶段—南北对冲前陆定型阶段—滨太平洋弧后陆内调整四个阶段。南黄海盆地属于台地—断拗复合地质结构,中、新生代为具有盆内隆起带的断陷箕状结构,且中、新生代多期构造运动在盆地原型改造和后期沉积发育上起着至关重要的作用,尤其印支—燕山早期运动、燕山中期黄桥运动和喜马拉雅期盐城运动与盆地地层变形、沉积发育、断裂发育及构造样式等盆地要素演化密切相关,进而导致盆地垂向地质结构和构造变形的层次性极为显著,而中生代燕山期和新生代喜马拉雅期两期构造岩浆活动则与滨太平洋域的动力学背景相关。