2005年登陆我国热带气旋特征分析

热带气旋是影响我国沿海的主要灾害性天气系统之一, 它产生的狂风、暴雨、巨浪和风暴潮, 给沿岸地区人民生命和国家财产安全带来严重威胁。而严重的台风灾害, 往往是台风登陆引起的。为进一步研究登陆热带气旋的活动规律, 总结了2005年登陆我国热带气旋的特点, 结果表明:2005年登陆我国热带气旋具有登陆季节短、登陆地点分布异常、台风比例异常偏高、灾害损失极为严重的特点。同时, 还讨论了2005年登陆我国热带气旋异常的气候原因, 并指出未来几年登陆热带气旋和台风的年频数处在上升趋势中。     

郑州市区环境空气污染趋势分析

以2003年郑州市环境空气污染的主要监测指标为依据,分析了郑州市空气污染现状,并根据1994~2003年10年来的监测数据,对空气污染特征和污染趋势进行了分析,结论是:郑州市空气污染在近10年呈下降趋势。     

Historical trophic evolutions and their ecological responses from shallow lakes in the middle and lower reaches of the Yangtze River: Case studies on Longgan Lake and Taibai Lake

The evolutions of diatom floras and the total phosphorous (TP) concentrations in the historical period were reconstructed for two lakes, Longgan and Taibai in the middle Yangtze River,based on high resolutional fossil diatom study from two sediment cores and an established regional diatom-TP transfer function. The TP concentration in Longgan Lake changed slightly in the range of 36-62 μg/L and kept its middle trophic level in the past 200 years. The changes of diatom assemblages reflect a macrophyte-dominated history of the lake. During the nineteenth century, the lake TP concentration increased comparatively, corresponding to the increase in abundance of benthic diatoms. The progressive increase of epiphytic diatoms since the onset of the twentieth century indicates the development of aquatic plants, coinciding with the twice drops of water TP level. The TP concentration in Taibai Lake kept a stable status about 50 μg/L before 1953 AD, while diatoms dominated by facultative planktonic Aulacoseira granulata shifted quickly to epiphytic diatom species, indicating a rapid expansion of aquatic vegetation. During 1953-1970 AD, the coverage of aquatic plants decreased greatly inferred by the low abundance of epiphytic diatoms as well as declined planktonic types, and the reconstructed TP concentration shows an obvious rising trend firstly, suggesting the beginning of the lake eutrophication. The lake was in the eutrophic condition after 1970, coinciding with the successive increase of planktonic diatoms. The comparison of the two lakes suggests the internal adjustment and purification function of aquatic plants for nutrients in water. The discrepancy of TP trends in the two lakes after 1960 reflects two different patterns of lake environmental response to human disturbance. Sediments in Taibai Lake clearly recorded the process of lake ecological transformation from the macrophyte-dominated stage to the algae-dominated stage. The limits of TP concentration (68-118 μg/L) in the transitional state can be considered as the critical value between the two stable ecosystems. Further work will be necessary to provide more evidence from the sediments in more eutrophic lakes for the primary inference. The reconstructive TP level and the inference of aquatic plants from fossil diatoms in different lakes, as well as their comparison provide a scientific basis for ecological restoration of eutrophic lakes in research regions.     

川滇强震震前短期阶段地震活动空间异常特征

对1973年以来川滇地区21次6级以上强震的震前地震活动进行了全时空扫描,发现大多数强震在孕育中期至短期阶段,震源附近会出现两条或两条以上3级或4级中小地震条带。与强震孕育中期阶段相比,在强震孕育的短期阶段中小地震条带方向出现明显偏转,偏转角度为15°~150°。中小地震活动在空间上的这种动态异常,可作为强震孕育、发展至短期阶段的一项标志。     

Analysis of a large extent aeromagnetic survey near the geomagnetic equator (Minas Gerais,Brazil)

A large extent aeromagnetic survey, covering a 9°×9° degree of a Precambrian shield area in SE Brazil, was used to analyse long wavelength magnetic anomalies with the purpose of determining the magnetic structure of the lithosphere.Data analysis based on a novel approach to the estimation of the parameters in the statistical model ofSpector andGrant (1970), reveals a highly magnetized lower crust, bounded by an essentially non-magnetic upper mantle. The highly magnetized layer can be associated with a higher density lower crust model, derived from gravity and seismic data available in the area, suggesting a compositional transition from upper to lower crust.It was also verified that the operation of reduction to the pole, which is singular at the geomagnetic equator, performs quite satisfactorily at the low geomagnetic inclination of the area, bringing into accordance the long wavelength anomalies with the structural trends.     

中全新世云南寻甸地区气候演化过程及其驱动机制初步研究

通过对云南寻甸仙人洞XR1石笋进行TIMS-U系测年、氧碳同位素、有机碳含量分析,重建了寻甸地区中全新世季风气候演化模式:(1)8.0～6.0kaB.P.为温暖湿润期;(2)6.0～5.1kaB.P.为气候突变期,气候由温湿变为冷干;(3)5.1～2.1kaB.P.为凉干期。通过石笋有机碳含量与石笋δ18O记录对比,认为石笋有机碳可以反映气候变化,但是存在滞后效应。最后,利用XR1石笋δ18O记录与北半球33°N太阳辐射量,本文初步分析了云南寻甸地区中全新世气候变化的驱动因素:寻甸地区中全新世气候的整体变化趋势受33°N太阳辐射量控制,同时受中全新世火山活动的影响。      

双台子河口重金属污染的沉积记录

根据双台子河口沉积柱中微量金属的含量及沉积物的粒度参数,结合137Cs放射性比活度精确定年,研究了双台子河口的沉积速率和重金属的污染变化特征,并利用地累积指数法评价了重金属的污染程度。137Cs计年的结果表明,沉积柱的平均沉积速率为1.3cm/a。沉积物的粒径从底层向表层逐渐变细,反映了水动力条件的减弱。绝大多数重金属的含量基本上都是自底部向上逐渐增加。重金属元素与细粒沉积物(63μm)均具有较好的正相关性,说明细粒物质对重金属具有较高的吸附能力。采用地累积指数对沉积柱中重金属元素的垂向变化进行了评价,发现除Cd元素外,大部分元素均未受到污染(Igeo0)。推测Cd的污染可能主要与20世纪90年代起至今人类活动对双台子河口产生的影响逐渐增加有关。     

天然热释光技术在南海东部表层沉积物油气潜力勘查中的应用

应用热释光技术对南海东部海域(13.00°~22.00°N、117.00°~119°30′E)42个站位的表层沉积物样品进行分析测量,结合气烃组合指标C1/(C2+C3)及甲烷碳同位素判别地表气烃的成因类型,并有效指示了海底深部油气藏散失引起的放射性异常,研究还发现热释光在不同沉积粒径中的测试剂量不同,结果为黏土质粉砂大于砂质粉砂;热释光也与部分化学元素含量有关,与稀土金属Nb、金属元素Zr呈显著正相关,与微量元素S、Ba呈负相关;天然热释光还与不同区块的沉积物酸解气烃甲烷、丙烷、异丁烷呈强烈正相关。数理统计分析结果表明沉积物的热释光和气烃的异常值完全吻合。     

5月青藏高原上空环流与北疆夏季降水的关系

基于1961—2016年5—8月西藏高原环流指数、NCEP再分析资料和新疆96个气象观测站点的降水资料,通过相关分析和合成分析,研究了5月青藏高原上空环流与北疆夏季降水的关系,以及两者之间可能影响的物理机制。结果表明:(1)5月西藏高原环流指数Ⅰ与北疆夏季降水有较好的相关性,相关系数为0.38;(2)5月西藏高原环流指数Ⅰ的强弱变化会影响500hPa的夏季环流特征、夏季地表至300 hPa的水汽通量输送,当指数偏强时,夏季环流形势的配置和水汽输送均有利于北疆夏季降水,反之,则不利于北疆夏季降水;(3)夏季西藏高原环流指数Ⅰ和北疆夏季降水、5月西藏高原环流指数Ⅰ的关系密切,并且5月西藏高原环流指数Ⅰ和青藏高原5月、夏季的感热通量有明显的负相关,通过高原的热力持续性作用,5月西藏高原环流指数Ⅰ的强弱可以影响北疆夏季降水的多少。     

青藏高原四季划分方法探讨

利用中国气象局国家气象信息中心提供的青藏高原60个测站1961~2007年逐日气温资料,分析常用的四季划分方法在高原的适用性,指出各种四季划分方法的不足和局限,并根据四季持续时间的合理性、物候特征、海拔高度、气候（温度）分布特征等因素提出了针对不同的生产、生活目的而建立的新四季划分方法。探讨认为：（1）根据高原物候特征和气温相结合的方式得到的＂物候四季划分方法＂即＂4℃-12℃-10℃-1℃＂对高原农牧业尤为适合;（2）＂海拔季节划分方法＂对高原旅游和人们衣着尤为适合,海拔季节划分方法把高原分成二个区：海拔4000m以上四季划分方法为＂5℃-12℃-12℃-5℃＂,4000m以下四季划分方法为＂5℃-15℃-15℃-5℃;＂（3）＂生活季节划分方法＂对高原不同区域的生产生活尤为适合,生活季节划分方法将高原分为三个区：Ⅰ区四季划分方法为＂6℃-16℃-16℃-6℃＂,Ⅱ区四季划分方法为＂5℃-12℃-12℃-5℃＂,Ⅲ区四季划分方法＂7℃-7℃＂划分春冬和秋冬,不存在夏季。最后,综合以上各种方法的优缺点,初步定义＂高原普适季节划分方法＂即＂5℃-15℃-15℃-5℃＂为高原总体的四季划分方法,对高原整体的国民经济和政府活动、旅游、人们的衣着、生活生产、季节类产品的销售具有总体的指导意义。