长江流域旱涝典型年大气水汽输送

利用我国125个探空站一日两次自地面至100hpa共11个层次上的观测资料,对长江流域典型夏涝年(1980年)和夏旱年(1985年)我国大气中水汽总输送场、涡动输送场及散度场进行了计算分析。结果表明:当水汽总输送场从西北、西南和东南三支气流携带的水汽交汇于长江流域,且整个水汽输送场稳定持久,则在水汽辐合带附近导致大量降水,形成洪涝;反之,当三支气流微弱不稳定,不能形成水汽辐合带条件,则形成干旱。涡动输送亦反映出类似的特征。稳定且强盛的西南气流水汽输送是形成降水的主要条件和原因。     

Phosphorus and nitrogen limitation of algal biomass across trophic gradients

Regression results based on data from 46 northern temperate lakes show that total phosphorus (TP) is the best predictor for phytoplankton (as chl-a) at lower trophic levels, TP < 200 mg · m^–3. A regression including both TP and TN as regressors is the best predictor for lakes with TP > 200 mg · m^–3. However, the good correlation is probably due to a high correlation between lake average chl-a (all years observed) and lake average TP and TN. Within single hypereutrophic lakes, TN alone is the best predictor. It was not possible to identify a medium trophic domain where TN and TP in combination was the best predictor for chl-a. The ratio TN:TP in the water decreases from about 40 to about 5 with increasing trophic level. Optimum TN:TP ratio for algal species with high abundance during late summer and autumn reflects this decreasing ratio, but within a lesser range, i.e., 20 to 5. In contrast, TN:TP ratios for species abundant during the early vernal period showed no, or an inverse, relation to the TN:TP ratio of the water.     

Historical changes in sediments of Pyramid Lake,Nevada, USA: consequences of changes in the water balance of a terminal desert lake

Sediment cores from the shallow and deep basins of Pyramid Lake, Nevada, revealed variations in composition with depth reflecting changes in lake level, river inflow, and lake productivity. Recent sediments from the period of historical record indicate: (1) CaCO₃ and organic content of sediment in the shallow basin decrease at lower lake level, (2) CaCO₃ content of deep basin sediments increases when lake level decreases rapidly, and (3) the inorganic P content of sediments increases with decreasing lake volume. Variations in sediment composition also indicate several periods for which productivity in Pyramid Lake may have been elevated over the past 1000 years. Our data provide strong evidence for increased productivity during the first half of the 20th Century, although the typical pattern for cultural eutrophication was not observed. The organic content of sediments also suggests periods of increased productivity in the lake prior to the discovery and development of the region by white settlers. Indeed, a broad peak in organic fractions during the 1800's originates as an increase starting around 1600. However, periods of changing organic content of sediments also correspond to periods when inflow to the lake was probably at extremes (e.g. drought or flood) indicating that fluctuations in river inflow may be an important factor affecting sediment composition in Pyramid Lake.     

青藏高原地表净辐射的气候学研究

根据作者提出的地表净辐射各分量的气候学计算方法，计算出青藏高原及其周边地区１７３站的净辐射和其各分量的年，月平均通量密度，并分析其地理分布特征。指出高原主体为总辐射，有效辐射的高值区，地表净辐射场在冬，夏季有较大差异。冬季为一弱正值区，相对低中心呈块状散布在祁连山区等几个地区；夏季因夜雨及地表湿润的缘故，高原大部地区的地表净辐射反有加强。各地净辐射年变化基本形式与总辐射相似。有效辐射年变化一般呈双     

保靖葫芦磷矿床地质特征及矿床成因

葫芦磷矿床位于古丈背斜南西端,含磷岩系赋存于震旦系陡山沱组下部,总厚度10m、分为A—B—C—D—E—F沉积序列。矿体呈层状,产状稳定,平均厚1m。P_2O_5平均品位氧化矿石为27％;原生矿石为20％,主要由胶磷矿(氟磷灰石)和隐晶石英、以及有机碳和黄铁矿组成。磷矿形成于陆棚至陆坡的静水环境。成矿物质来自海底岩石溶解、地壳深部、海底火山和海洋生物的磷质,它们在盆地中浓缩,在化学和生物化学作用下,磷质局部富集、沉淀成矿。矿床被认为是化学和生物化学沉积成因。     

Extremely low temperatures in the stratosphore and very low total ozone amount above northern and central Europe during winter 1989

On 1 February 1989, -83.5°C was recorded in 27.8 hPa over Hohenpeißenberg, the lowest temperature in the 22-year series. This was measured together with a very low total ozone amount of 266 DU. This may be compared with nearly twice this amount on 27 February 1989. The situation was very unusual: following an extremely cold winter in the Arctic stratosphere, the stratospheric cold pole was located over southern Scandinavia on 1 February in a very southerly position. The analyzed temperatures of -92 °C in 30 hPa were also unusual. Even though the low ozone amounts over Hohenpeißenberg were probably dynamically caused, an additional very small ozone decrease due to heterogeneous reactions in altitudes from 23–28 km, where the temperatures lie below -80 °C, cannot be ruled out. Extinction measurements by the orbitting SAGE II instrument indeed show polar stratospheric clouds over Europe near 50° N during the period 31 January–2 February. Also, polar stratospheric clouds were previously observed over Kiruna at similarly low temperatures and signs of a corresponding small ozone decrease were noted there.     

北京地区太阳紫外辐射的观测与分析研究

利用北京地区太阳辐射和其它常规气象观测资料，得到了到达地面的太阳紫外辐射的计算公式，并将计算值与观测值进行了比较，两者吻合得比较好。最后给出了北京地区地面太阳紫外总辐射的变化趋势，计算结果表明，地面太阳紫外总辐射对大气浑浊度的变化比对大气臭氧总量的变化敏感得多。     

滆湖沉积物理化特征及磷释放腄

对滆湖表层底泥、柱状层祥和间隙水进行理化分析,模拟不同条件下的沉积物磷释放。结果表明,0～20cm深度范围内,各项理化指标变化较大;大于2cm后差异较小。当提高沉积物-水体系温度、降低氧含量(或Eh),提高pH及施以水动力作用时,可促进沉积物磷释放进程。无菌条件对磷释放有抑制作用。采用实验室模拟和间隙水浓度扩散模型计算得到的磷总释放量分别为10.65t/a和9.40t/a,其中湖面网围区释放量占全湖总量的28.2～35.4％。建议适度控制网围养殖规模,以减少内源磷污染。     

Total ozone response to major geomagnetic storms and changes in meteorological situations

Summary The total ozone response to strong major geomagnetic storms (A_p≥60) in winter along the 50° N latitudinal circle is studied. The results add to the recent results of Laštovička et al. (1992) obtained for European middle latitudes (∼50°N) and to the results of Mlch (1994). A significant response of total ozone is only observed in winter under high solar activity/E-phase of QBO conditions (E-max) and seems to be caused by geomagnetic storm-induced changes of atmospheric dynamics. There are two sectors along latitude 50°N, which are sensitive to forcing by geomagnetic storms both in total ozone and the troposphere — north-eastern Atlantic-European and eastern Siberia-Aleutian sectors. The total ozone response under E-max conditions manifests itself mainly as a large decrease in the longitudinal variation of ozone after the storm, which means an increase of ozone in Europe. The observed effects in total ozone consist in redistribution, not production or loss of ozone.     

沉管沉放的实时监测

介绍了在沉管隧道施工中,实时监测沉管沉放的一种测量方法.它利用全站仪观测数据,通过坐标系之间的坐标转换,实时计算沉管管体特征点的坐标,从而对沉管的沉放过程进行实时监测.