Neuzeitlicher Schadstofftrend: Polycylische aromatische Kohlenwasserstoffe (PAK) in aquatischen und terrestrischen Sedimenten     

Hubert Hellmann 《洁净——土壤、空气、水》2003,31(2):85-96

A Recent Contamination Trend: Polycylic Aromatic Hydrocarbons (PAHs) in Aquatic and Terrestrial Sediments Concentrations of polycylic aromatic hydrocarbons (PAHs) measured in aquatic sediments of small, medium‐sized or very large inland lakes, of estuaries as well as in terrestrial sediments from Germany, the UK, Finland, and the USA were plotted in 10 trend curves over the period from 1800 to 1990. The segments of the bore cores were dated for their deposition age. For comparability of the results, the trend is preferentially shown by the guide parameter fluoranthene. Until the 19th century, a constant background value of C_Fluo = 10…50 μg/kg was observed in all regions. Then a steep increase in concentration followed, reaching in the aquatic sediments a maximum in the period 1940 to 1965, while the individual fluoranthene values ranged widely from 90 to 2400 μg/kg. In several regions, a more or less distinct decrease superseded this maximum, although this development did not appear in terrestrial sediments, in one estuary, and in remote forest lakes in Finland. The trend curves reflect the atmospheric deposition of PAHs in airborne dust and in some cases the import through runoff via rivers. Thus, the sediment profiles depict the development of air pollution by pyrogenic contaminants over more than a century. Sediment profiles from rivers can be used only with a high degree of reservation, because of the irregularity and low representativity of the sedimentation.  相似文献   

Hydrologic and geomorphic effects of temporary ice‐dammed lake formation during jökulhlaups     

Matthew J. Roberts  Fiona S. Tweed  Andrew J. Russell   skar Knudsen  Timothy D. Harris 《地球表面变化过程与地形》2003,28(7):723-737

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Late Holocene climates of the Near East deduced from Dead Sea level variations and modern regional winter rainfall     

Yehouda Enzel  Revital Bookman  David Sharon  Haim Gvirtzman  Uri Dayan  Baruch Ziv  Mordechai Stein 《Quaternary Research》2003,60(3):263-273

The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr⁻¹ average isohyet during 1940–1990 are largely synchronous and in phase (70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between climatic changes in the Levant, reflected by level changes, and culture shifts in this region.  相似文献   

黄河上游河南县地面大气冰核观测分析   总被引：7，自引：2，他引：7       下载免费PDF全文

李淑日黄庚  胡志晋 《应用气象学报》2003,14(Z1):41-48

用Bigg型混合云室对2001年8月黄河上游青海省河南县的地面大气冰核浓度进行了观测,分析发现(1)青海省河南县冰核浓度低于北京20世纪90年代的测值,但高于大连、西安和兰州(20世纪60年代)等地的测值,同时也高于黄河上游的玛曲(2000年)、西宁(1989年)两地的测值,高温核尤其偏高.(2)降水时大气冰核浓度减少,降水的冲刷可能是其主要原因.(3)当地冰核浓度和气压成正相关.(4)大气冰核浓度受风向的影响,无风时测值较小,偏东风时测值较大,高温核浓度增加明显.  相似文献   

新疆天山山区大气冰核浓度的测量及分析   总被引：5，自引：0，他引：5  

李艳伟  杜秉玉 《南京气象学院学报》2003,26(3):364-370

利用2001年6、7月份在新疆天山山区两个取样点取得的冰核资料，计算了山区中的冰核浓度，研究了冰核平均浓度日变化、日际变化的规律，并分析了天山山区冰核浓度与一些气象因子的关系及可能原因。得出以下结论：天山山区的大气冰核主要来源于地面土壤，比较缺乏；冰核浓度易受气象因子、地表状况的影响，日变化和日际变化明显．  相似文献   

大气边界层气象学研究综述   总被引：5，自引：2，他引：5  

张强 《干旱气象》2003,21(3):74-78

文中回顾了大气边界层气象学的发展历史，总结了目前大气边界层气象学的主要进展，并指出国内外在未来大气边界层气象学研究方面面临的一些主要科学问题，以及对未来大气边界层气象学的发展方向提出若干建议，同时还指出了大气边界层气象学在思想上和方法上应该注意的一些相关问题。  相似文献   

Photochemistry of N2O4 Adsorbed on Ice Surfaces at 193 nm     

Akio Susa  Seiichiro Koda 《Journal of Atmospheric Chemistry》2003,45(2):197-217

A multi-layer deposited ice film was prepared through water vapor deposition on a Ni plate in a vacuum chamber at 90 K, and was used as it was or after annealing at 140 K. NO₂ was adsorbed as N₂O₄ approximately 90 K on the ice film prepared as above, and irradiated by 193 nm excimer laser light. The time-of-flight (TOF) spectra of the desorbed species, i.e., NO₂, NO, O₂ and O, were measured by a quadrupole mass spectrometer. The photochemical process obeyed an one-photon process. The relative yields of the products and their TOF spectra were dependent on the preparation condition of the ice film and also varied with the continuation of the laser irradiation. From the ice film annealed at 140 K, NO₂, NO and O₂ were desorbed with an approximate ratio of 1:1:0.01. From the non-annealed film, the relative yield of NO₂ was much smaller than that of NO. The TOF spectrum of NO from the non-annealed ice film consisted of distinctly different two components corresponding to the 1700 and 100 K translational temperature, respectively. The fast component was lost when additional ice was deposited on the adsorbed N₂O₄. NO was supposed to be a predissociation product from the electronically excited NO₂ prepared through the photodissociation of N₂O₄.  相似文献   

冬春季格陵兰海冰变化与初夏中国气温/降水关系的初步分析   总被引：3，自引：5，他引：3  

陈明轩  管兆勇  徐海明 《高原气象》2003,22(1):7-13

采用英国Hadley中心GISST海冰面积资料，NCEP／NCAR再分析资料以及中国地面降水和气温资料，运用EOF分解，小波分析和合成分析等方法，初步探讨了格陵兰岛两侧附近冬春季海冰面积变化特征及其与初夏6月中国气温和降水的关系，结果表明，格陵兰岛东西两侧海冰面积呈显著反相变化，并且具有明显的年际和年代际周期性振荡，冬春季格陵兰－寻威海海冰与初夏6月中国长江以北气温（降水）正相关（反相关），与长江以南气温（降水）反相关（正相关），而对于戴维斯海峡－拉布拉多海海冰则具有相反的相关型，大尺度500hPa环流合成分析初步表明，冬春季格陵兰附近海冰面积变化伴随着北极极涡环流和北半球阻塞高压的持续异常，海冰变化可能是影响初夏中国气温和降水的因子之一。  相似文献   

海洋和大气对Chandler摆动激发的贡献   总被引：1，自引：0，他引：1       下载免费PDF全文

廖德春  廖新浩  周永宏 《地球物理学报》2003,46(4):455-461

用1985～1995年期间海洋角动量变化序列和大气角动量变化序列,分析它们对Chandler摆动的激发能量以及它们与天文观测激发的相干性. 结果表明，在Chandler摆动频带内，海洋角动量变化提供的激发能量大约占观测激发的64髎，其中洋底压力变化起主导作用；NCEP/NCAR(美国国家环境预测中心/国家大气研究中心)和JMA(日本气象厅)大气角动量变化提供的激发能量分别为观测激发的23髎和214髎. 海洋激发与观测激发的相干系数约为0.52，接近99髎置信度下限(0.54)，海洋激发的相位滞后观测激发约19°；NCEP/NCAR和JMA的大气激发与观测激发的相干系数分别为0.32和0.37，大气激发的相位超前观测激发分别约47°和19°. 用更短期间(9年、6年)的海洋和大气角动量序列与更长期间(16、39年)的大气角动量序列作分析表明，在Chandler摆动频带内，无论是它们的激发能量，还是它们与观测激发之间的相干系数都呈现很大的变化，而且这些变化具有某种程度的随机性.  相似文献   

A Case Study of Satellite Synthetic Aperture Radar Signatures of Spatially Evolving Atmospheric Convection over the Western Atlantic Ocean     

Steven M. Babin  Todd D. Sikora  Nathaniel S. Winstead 《Boundary-Layer Meteorology》2003,106(3):527-546

A case study of a particularly intense cold air outbreak over the northAtlantic Ocean extending from the northeast coast of the UnitedStates to the Gulf Stream is described. A RADARSAT satellite synthetic apertureradar (SAR) image of this outbreak dramatically illustrates the spatialevolution of convection. Nearly coincident images from the National Oceanic and Atmospheric Administration's Advanced Very HighResolution Radiometer are used to compare many interesting features.In addition, National Weather Service rawinsonde data, National Data Buoy Center buoy data, and Woods Hole Oceanographic Institute Coastal Mixing and Optics mooring data arepresented. We use these data to help describe the spatial evolution of the atmospheric boundary-layer processes involved in this outbreak.Rows of cellular convective clouds begin to appear some distance offshore and then slowly increase in horizontal diameter and wavelength in the downwind direction, with a subsequent jump in cloud diameter downwind of the Gulf Stream North Wall (GSNW). The SAR image shows a similar evolution of sea-surface footprints of these boundary-layer features. This change in boundary-layer structure is attributed to corresponding changes in static stability. About 300 km south of the GSNW in the SAR image, an even larger jump in cell diameter appears and the cells becomenon-uniform with bright crescents and filled semi-circles on thedownwind sides of the cells. These are believed to be surface effectsof gust fronts induced by the mesoscale cellular convection and enhanced by the overall northwesterly flow.  相似文献