川西高原甘孜黄土与印度季风演化关系

川西高原甘孜黄土地层的磁化率、土壤颜色、碳酸盐含量综合分析表明，早在1.15Ma前，印度季风就已影响本地区，并且印度季风与同期影响黄土高原的东亚夏季风相比，似有共同的盛衰变化，尤其是0．5Ma前更为相似，说明印度季风与东亚季风有共同的驱动机制；但0．5Ma以后，印度季风对本地区的影响呈逐步衰减之势，这可能与青藏高原又隆升到一个新的临界高度有关，从而阻挡了印度季风的水汽输入。另外，黄土高原揭示的L9、L15极端冷干事件，甘孜黄土反映较弱。而黄土高原反映的L6冷干事件，甘孜黄土表现的却是极端冷湿事件，青藏高原东北部若尔盖湖心记录也有同样反映。     

关于东亚季风演变的问题讨论

评述了有关亚洲季风形成时代的主要观点,根据晚新生代青藏高原阶段性隆起和亚洲自然环境的演变,将亚洲季风的形成过程划分为无季风,准季风,海洋型季风和大陆型季风４个阶段,大陆型季风即现代季风,它是第四纪中期青藏高原隆起达到３０００ｍ以上的产物,因为亚洲中部温带沙漠出现,典型风成黄土普遍堆积,网纹红土发育,动植物群转型等均发生在１．２ＭａＢ．Ｐ．左右。指出青藏高原隆起过程中非线性气候效应,是古海洋型季风向     

南亚季风产生的动力学分析和数值试验

采用动力学分析和数值试验的方法研究和讨论了地形的热力因素对南亚季风产生的作用和影响,结果表明：没有地形效应的热力强迫只能同热带地区的低频振荡,不能在副热带地区形成稳定的季风环流;南亚地区的地形效就和经向热力强迫的共同作用是形成南亚季风环流的必要条件。     

南海季风试验综述

介绍了在中国科学家为主力、在我国及其周边地区开展的第1次大型的国际性大气-海洋科学试验-南海季风试验（1996-2000年）。该试验研究有助于揭示大气活动及其与水圈间相互作用的内在规律，不断提高我国重大灾害性天气气候预报的准确率和服务水平，显著增强气象防灾减灾能力；同时，南海季风试验研究中所揭示出一些新的科学认识，对全球能量和水份循环试验计划这一世界性的重大气候研究也具有重要意义。     

太阳黑子对南海季风爆发及热带风暴活动的影响

利用１９４９－１９９８年的资料,以统计分析的方法,对太阳黑子及南海季风爆发、热带风暴活动的相互关系进行了初步探讨。结果表明,太阳黑子极值年与南海季风爆发的时间有一定的对应关系,与热带风暴活动有一定的相关性。峰值年南海季风爆发时间偏早,热带风暴生成个数及登陆个数均偏少,且活动期偏短。     

1994年6月东亚季风异常的数值模拟

用ＭＭ５区域气候模式对１９９４年６月东亚季风进行了数值模拟。模式模拟的月平均环流和降水与实况相接近。１９９４年６月东亚季风活动十分异常,中国东南部的西南季风,西太平洋副热带高压,南亚高压出现了两次突变性的北跳,对此模式均做出阵产好的模拟。     

南海西南部海区近200ka来的动力环境与东亚古季风

包括南海在内的热带海洋是东亚夏季风的发源地,分析其动力环境特征的的演变历史,可提供东亚古季风活动的海洋证据。对取自该海区的NS93-5柱状样做了详细的粒度分析,结合氧内闰素地层结果、微体古生物观察统计和CaCO3测试资料,尝试采用高精度的粒度分析作为替代性指标,讨论近200ka以来的水动力及古生产力变化特征。结果认为,自末次盛冰期以来该海区的海洋动力环境发生了明显的变化,而在此之前则变化不显著,在倒数第2次冰期中由于夏季风作用致该局部区域上升流发育和海面温度偏高。古生产力变化规律一般是：在冰期较高,并呈稳定或上升趋势;在间冰期较低,出现下降现象。近200ka来的特殊情况出现于全新世早期,古生产力达到最高值。通过与黄土高原及其它地区的古季风环境对比,发现东亚古季风区内在全新世和末次盛冰期的遥相关较好,而在倒数第2次冰期中存在明显差别,说明在冬季风和夏季风的相互作用下,产生了特定时期内典型季风区的局部海洋区域性特征。     

用模糊聚类分型方法作盛夏南海热带气旋路径预报

本文对1960～2002年盛夏在南海海域活动的热带气旋进行分析,引入模糊数学理论中的模糊动态聚类分析方法,对欧洲气象中心(ECMWF)500hPa层位势高度场的格点资料进行形势分类,用计算机自动寻找最佳相似组合,进行天气形势分类,然后选取与热带气旋路径密切相关的环流场、物理量动力因子及自身特性因子,用多元回归方法建立盛夏南海热带气旋路径预报模式,结果表明该模式预报能力有明显提高.     

Era-interim Forced Simulation of the Indian Summer Monsoon

Abstract

In the present study, mean rainfall for the months of June-July-August-September (JJAS) during summer monsoon is simulated over India and its adjoining regions for a period between 1982 and 2006. The study was carried out using Regional Climate Model (RegCM) version 4.6 at a resolution of 25?km. The simulated mean JJAS monsoon rainfall was validated against the observational IMD data. Comparison of JJAS seasonal mean summer rainfall for the first decade 1982–1991, with the later decade 1997–2006 indicate that the intensity of rainfall increases over Indian land-mass during the later decade under the forced conditions of Era-Interim. The observed JJAS mean rainfall indicates two maximum rainfall areas i.e. the Western Ghats and the Himalayan region. A significant bias is observed in the central and Jammu and Kashmir (J&K) region. The JJAS mean seasonal surface air temperature distribution at 0.25?×?0.25-degree grids resolution shows a decreasing trend of temperature over the Indian landmass.     

Nitrogen dynamics during the Arabian Sea Northeast Monsoon

This investigation focused on the weaker and less well understood of the two Arabian Sea monsoonal wind phases, the NE Monsoon, which persists for 3–4 months in the October to February period. Historically, this period has been characterized as a time of very low nutrient availability and low biological production. As part of the US JGOFS Arabian Sea Process Study, 17 stations were sampled on a cruise in January 1995 (late NE Monsoon) and, 15 stations were sampled on a cruise in November 1995 (early NE Monsoon). Only the southern most stations (10° and 12°N) and one shallow coastal station were as nutrient-depleted as had been expected from the few relevant prior studies in this region. Experiments were conducted to ascertain the relative importance of different nitrogenous nutrients and the sufficiency of local regeneration processes in supplying nitrogenous nutrients utilized in primary production. Except for the southern oligotrophic stations, the euphotic zone concentrations of NO₃⁻ were typically 5–10-fold greater than those of NO₂⁻ and NH₄⁺. There was considerable variation (20–40-fold) in nutrient concentration both within and between the two sections on each cruise. All nitrogenous nutrients were more abundant (2–4-fold) later in the NE Monsoon. Strong vertical gradients in euphotic zone NH₄⁺ concentration, with higher concentrations at depth, were common. This was in contrast to the nearly uniform euphotic zone concentrations for both NO₃⁻ and NO₂⁻. Half-saturation constants for uptake were higher for NO₃⁻ (1.7 μmol kg⁻¹ (s.d.=0.88, n=8)) than for NH₄⁺ (0.47 μmol kg⁻¹ (s.d.=0.33, n=5)). Evidence for the suppressing effect of NH₄⁺ on NO₃⁻ uptake was widespread, although not as severe as has been noted for some other regions. Both the degree of sensitivity of NO₃⁻ uptake to NH₄⁺ concentration and the half-saturation constant for NO₃⁻ uptake were correlated with ambient NO₃⁻ concentration. The combined effect of high affinity for low concentrations of NH₄⁺ and the effect of NH₄⁺ concentration on NO₃⁻ uptake resulted in similarly low f-ratios, 0.15 (s.d.=0.07, n=15) and 0.13 (s.d.=0.08, n=17), for early and late observations in the NE Monsoon, respectively. Stations with high f-ratios had the lowest euphotic zone NH₄⁺ concentrations, and these stations were either very near shore or far from shore in the most oligotrophic waters. At several stations, particularly early in the NE Monsoon, the utilization rates for NO₂⁻ were equal to or greater than 50% the utilization rates for NO₃⁻. When converted with a Redfield C : N value of 6.7, the total N uptake rates measured in this study were commensurate with measurements of C productivity. While nutrient concentrations at some stations approached levels low enough to limit phytoplankton growth, light was shown to be very important in regulating N uptake at all stations in this study. Diel periodicity was observed for uptake of all nitrogenous nutrients at all stations. The amplitude of this periodicity was positively correlated with nutrient concentration. The strongest of these relationships occurred with NO₃⁻. Ammonium concentration strongly influenced the vertical profiles for NO₃⁻ uptake as well as for NH₄⁺ uptake. Both NO₂⁻ and NH₄⁺ were regenerated within the euphotic zone at rates comparable to rates of uptake of these nutrients, and thus maintenance of mixed layer concentrations did not require diffusive or advective fluxes from other sources. Observed turnover times for NH₄⁺ were typically less than one day. Rapid turnover and the strong light regulation of NH₄⁺ uptake allowed the development and maintenance of vertical structure in NH₄⁺ concentration within the euphotic zone. In spite of the strong positive effect of light on NO₂⁻ uptake and its strong negative effect on NO₂⁻ production, the combined effects of much longer turnover times for this nutrient and mixed layer dynamics resulted in nearly uniform NO₂⁻ concentrations within the euphotic zone. Responses of the NE Monsoon planktonic community to light and nutrients, in conjunction with mixed layer dynamics, allowed for efficient recycling of N within the mixed layer. As the NE Monsoon evolved and the mixed layer deepened convectively, NO₂⁻ and NO₃⁻ concentrations increased correspondingly with the entrainment of deeper water. Planktonic N productivity increased 2-fold, but without a significant change the new vs. recycled N proportionality. Consequently, NO₃⁻ turnover time increased from about 1 month to greater than 3 months. This reflected the overriding importance of recycling processes in supplying nitrogenous nutrients for primary production throughout the duration of the NE Monsoon. As a result, NO₃⁻ supplied to the euphotic zone during the NE Monsoon is, for the most part, conserved for utilization during the subsequent intermonsoon period.     

Monsoon response of the Somali Current and associated upwelling

The Somali Current typically develops in different phases in response to the onset of the summer monsoon. Each of these phases exists quasistationary for some time ranging from weeks to months. These periods of rather constant circulation patterns are separated by periods of rapid transition.In the early phase of the monsoon response, during May, with weak southerly winds off Somalia, a cross equatorial inertial current develops which turns offshore a few degrees north of the equator with a coastal upwelling wedge just north of the offshore flow. North of that region, an Ekman upwelling regime exists all the way up the coast. At the onset of strong winds in June, a northern anticyclonic gyre develops north of 5°N and a second cold wedge forms north of 8°–9°N, where that current turns offshore. The most drastic change of upwelling pattern occurs in the late phase of the summer monsoon, August/September, when the southern cold wedge propagates northward, indicating a break-down of the two-gyre pattern and development of a continuous boundary current from south of the equator to about 10°N. The wedge propagation during 1976–1978 is discussed, based on satellite observations (EVANS and BROWN, 1981), moored station data during 1978, 1979 and shipboard hydrographic data during 1979. A simple relation between the decrease of local monsoon winds offshore and wedge propagation cannot be determined.The southward coastal undercurrent, which is part of the Ekman upwelling regime north of 5° during the early summer monsoon, seems to turn offshore between 3° and 5°, probably due to a zonal excursion of depth contours in that area. With the spin-up of the deep-reaching northern gyre the undercurrent is extinguished during July to August but seems to get reestablished after the coalescence of the two gyres.     

西南季风和热带气旋耦合的暴雨过程诊断分析

本文用NCEP/NCAR再分析资料、常规观测资料、FY-2C卫星云图、风廓线资料及自动站资料分析了热带气旋"碧利斯"的路径、陆上维持、暴雨成因.结果表明:"碧利斯"登陆后折向西行与冷空气到达黄淮一带有关,以后折向西偏南行,是受大陆高压南侧东北气流引导;"碧利斯"在陆上维持长、登陆后具有明显的不对称结构,与它处在鞍形场的有利流场、副热带高压从其东面加强西伸、正值西南季风爆发有关;暴雨的发生,与其"处在有利的气候背景,低压环流以罕见的路径从较北的纬度跨越广西"有关:更重要的是西南季风激发西南急流,西南急流输送水汽和释放潜热,利于热带气旋环流的维持,也为暴雨提供充足的水汽条件;急流轴左侧为正切变涡度区,既有利于热带低压环流的维持,又有利于强对流的发生;急流加强风的垂直切变,促使对流风暴不断生成.强降水的发生与西南急流的加强和向下扩展相关,急流指数变化对暴雨短时临近预报有较好预示性.     

东亚夏季风环流的动力统计诊断

本文对东亚夏季风环流作了动力统计诊断,其方法是将高、低层的偏差风场看作一个整体进行复EOF分析。诊断结果表明:偏差风场的第一模态直接与东亚夏季风环流有关,可称为季风模态;第二模态则与PJ波列关系密切,可称为PJ模态;季风模态存在两个平衡态,东亚夏季风也有两个平衡态;季风模态存在强弱的年际变化,其与东亚夏季风强弱的年际变化和菲律宾附近对流的年际变化均具有很好的对应关系;东亚夏季风和季风模态还存在明显的年代际变化。     

黄海海域侏罗纪地层新知

钻井揭示黄海海域发育中、上侏罗统,可建立两个孢粉化石组合,时代分属中、晚侏罗世;与中国其他地区侏罗系相比,该区侏罗系独具特色。地化分析表明,黄海海域侏罗系发育厚度巨大的烃源岩,展现了良好的油气勘探前景。     

Features of Monsoon,Typhoon and Sea Waves in the Taiwan Strait

For Future cross-sea passage spanning the Taiwan Strait, no matter what kind of scheme is adopted, its design, construction, and administration are closely related to marine hydrological and meteorological environmental elements. In this article, based on a great number of observed data, analyses for wave, typhoon, and monsoon conditions in the Taiwan strait region are made and their distributional features and character values are given. Especially, the wave height and occurrence frequencies of disastrous waves are analyzed, and the values of design wave parameters (wave height and period with a given return period) are estimated to use for the reference of the scheme optimization and project preliminary program of cross-sea passage spanning the strait.     

Features of Monsoon, Typhoon and Sea Waves in the Taiwan Strait

For Future cross-sea passage spanning the Taiwan Strait, no matter what kind of scheme is adopted, its design, construction, and administration are closely related to marine hydrological and meteorological environmental elements. In this article, based on a great number of observed data, analyses for wave, typhoon, and monsoon conditions in the Taiwan strait region are made and their distributional features and character values are given. Especially, the wave height and occurrence frequencies of disastrous waves are analyzed, and the values of design wave parameters (wave height and period with a given return period) are estimated to use for the reference of the scheme optimization and project preliminary program of cross-sea passage spanning the strait.