The phytoplankton of some saline lakes in Central Asia     

Yoshiko Kawabata  Hiroyuki Nakahara  Yukio Katayama  Norio Ishida 《International Journal of Salt Lake Research》1997,6(1):5-16

The Aral Sea, Lake Balkhash, and Lake Kamyslybas are closed lakes in Central Asia. They range from oligosaline to metasaline. The salinity of the Aral Sea has increased by more than 30 g L⁻¹ since widespread irrigation began in its catchment area. Few studies of the phytoplankton have been conducted on these lakes since extensive irrigation started. The investigation reported here compares the flora of phytoplankton in these saline lakes. In the Small Aral Sea, phytoplankton density gradually decreased with increasing electrical conductivity (EC) (∼ salinity), but there was no such relation in Lake Balkhash and Lake Kamyslybas. In the Aral Sea, Dinophyceae and Bacillariophyceae were frequently observed in most areas of high EC value, and Cyanophyceae were most conspicuous in the area of medium and lower EC values. In Lake Balkhash, Cyanophyceae were most conspicuous, but Chlorophyceae were also noticeable. Most Cyanophyceae in Aral Sea formed filaments with heterocysts. The distinct characteristic of the phytoplankton of the Lake Balkhash was that all dominant species form colonies covered with a gelatinous film. Siliceousplankton diversity gradually decreased with increasing EC values in the Aral Sea and Lake Balkhash.  相似文献   

利用步长模拟对青藏高原涡度方差测量法的质量评价   总被引：1，自引：0，他引：1  

S. Metzger  马耀明  T.Markkanen  M. G 《地球科学进展》2006,21(12):1260-1267

利用痕迹模拟方法对青藏高原两处地方涡度方差的测量数据进行了质量分析，揭示了其空间和时间结构。分析表明高达1/3的测量没有达到必要的数据正确假设。尽管这样对潜热、CO2、动量通量的测量基本通过测试，可以适用于基础研究，但是经常发现特定的风矢量违背基本假设条件。感热通量的测量允许使用不间断的连续测量法，然而由于局地地形的影响少量评估指数未能合理解释，但能够指示出组织结构及用于导出边界层中尺度流体模型假说。  相似文献   

青藏高原黑碳气溶胶传输及沉降的季节特征模拟分析     

韩永翔  孙海波  刘建慧  赵天良  S.L.Gong 《干旱气象》2014,(3):319-325

根据全球气溶胶气候模式GEM-AQ/EC的1995~2004年模拟,分析了青藏高原大气黑碳气溶胶的来源、传输及沉降季节特征。研究表明:青藏高原黑碳气溶胶主要来自自由对流层和大气边界层的输送。相对于自由对流层的黑碳输送,紧邻青藏高原的南亚、东亚以及东南亚大气边界层的输送更有效,它形成了青藏高原由北向南、自西往东黑碳气溶胶浓度和沉降明显递增的基本分布形态。横跨欧亚大陆自由对流层的黑碳气溶胶由西向东向青藏高原的输送全年不变,夏季输送路径最北但强度最弱,冬季路径最南而强度最强。大气边界层黑碳气溶胶的输送受控于亚洲季风环流变化,来自南亚的黑碳气溶胶在春季越过孟加拉湾传输进入高原东南部,夏季则可翻越喜马拉雅山抵达青藏高原南部腹地;同时我国中部排放的黑碳气溶胶也在东亚夏季风向北扩展中驱动它从东向西往青藏高原东北部传输。从秋季到冬季,随着夏季风撤退,南亚黑碳源区向青藏高原传输衰退,东亚冬季风的反气旋性环流的南侧及西南侧的偏东风携带秋季我国东南部源区和冬季东南亚源区黑碳气溶胶向青藏高原东南部传输。受青藏高原明显的暖湿季和干冷季气候影响,干湿沉降分别主导了青藏高原冬季和夏季黑碳沉降,夏季青藏高原黑碳气溶胶沉降总量大多超过8~10 kg·km-2,在高原东北部的最高值超过40 kg·km-2。冬季青藏高原黑碳气溶胶沉降量最低,大部地区黑碳沉降低于5 kg·km-2。青藏高原黑碳沉降的冬夏季节相差约为2~8倍。  相似文献   

A study of two post-common envelope binary systems     

K. M. Exter †  D. L. Pollacco  P. F. L. Maxted  R. Napiwotzki  S. A. Bell 《Monthly notices of the Royal Astronomical Society》2005,359(1):315-327

  相似文献   

Two new pulsating hot subdwarf stars from the Edinburgh-Cape survey     

D. Kilkenny  D. O'Donoghue  L. Crause  C. Engelbrecht  N. Hambly  H. MacGillivray 《Monthly notices of the Royal Astronomical Society》2009,396(1):548-552

We report the discovery of very rapid pulsations in two hot subdwarf stars from the Edinburgh-Cape blue object survey. The short periods, small amplitudes and multiperiodicity establish these stars as members of the class of rapidly-pulsating sdB stars. The spectrograms of both stars, however, show relatively strong He  ii 4686 and they are therefore more properly classified as sdOB. The light curve of EC 01541−1409 is dominated by two strong (∼1 per cent) variations with frequencies near 7114 and 7870 μHz (periods near 140.6 and 127.1 s), though at least five frequencies are present with amplitudes above about 0.002 mag. The light curve of EC 22221−3152 appears to be generated by at least 10 frequencies in the range 5670–11850 μHz (about 175–85 s) with amplitudes between about 0.01 and 0.001 mag, including the first overtone of the strongest variation. Somewhat surprisingly, this number of frequencies is detectable in observing runs as short as 3 h, probably due to the fact that the detected frequencies are well-separated.  相似文献   

Two new pulsating DB Stars from the EC survey, EC 04207−4748 and EC 05221−4725     

D. Kilkenny  D. O'Donoghue  L. A. Crause  N. Hambly  H. MacGillivray 《Monthly notices of the Royal Astronomical Society》2009,397(1):453-457

We report the discovery of pulsations in two DB stars found in the Edinburgh–Cape blue object survey. The light curve of EC 04207−4748 appears to be dominated by a strong variation at  2235 μHz  (447 s) and its first overtone near 4475 μHz (223 s). Two other peaks appear in the periodograms of all three data sets for this star; near  2370 μHz  (∼420 s) and  3000 μHz  (∼333 s), though these are less accurately defined. EC 05221−4725 is less easy to specify with the currently available data; it appears to have one coherent frequency near  1114 μHz  (898 s), but is obviously multiperiodic and probably has several more frequencies near the one clearly observed.  相似文献   

The pulsating DA white dwarf star EC 14012−1446: results from four epochs of time-resolved photometry     

G. Handler  E. Romero-Colmenero  J. L. Provencal  K. Sanchawala  M. A. Wood  I. Silver  W.-P. Chen 《Monthly notices of the Royal Astronomical Society》2008,388(3):1444-1456

The pulsating DA white dwarfs are the coolest degenerate stars that undergo self-driven oscillations. Understanding their interior structure will help us to understand the previous evolution of the star. To this end, we report the analysis of more than 200 h of time-resolved CCD photometry of the pulsating DA white dwarf star EC 14012−1446 acquired during four observing epochs in three different years, including a coordinated three-site campaign. A total of 19 independent frequencies in the star's light variations together with 148 combination signals up to fifth order could be detected. We are unable to obtain the period spacing of the normal modes and therefore a mass estimate of the star, but we infer a fairly short rotation period of  0.61 ±0.03 d  , assuming the rotationally split modes are  ℓ= 1  . The pulsation modes of the star undergo amplitude and frequency variations, in the sense that modes with higher radial overtone show more pronounced variability and that amplitude changes are always accompanied by frequency variations. Most of the second-order combination frequencies detected have amplitudes that are a function of their parent mode amplitudes, but we found a few cases of possible resonantly excited modes. We point out the complications in the analysis and interpretation of data sets of pulsating white dwarfs that are affected by combination frequencies of the form   f _A + f _B − f _C   intruding into the frequency range of the independent modes.  相似文献   

King Canute muses in the South Seas: Why aren’t Pacific Islands transitioning to low carbon sea transport futures?     

《Marine Policy》2017

Transition to low carbon sea transport is a logical response to the extreme dependency of the Pacific Islands region on imported fossil fuel, its significant vulnerability to the effects of climate change and the critical shipping needs of Pacific Island countries (PICs). Building on previous work in low carbon sea transport in the Pacific, this paper further considers the barriers to achieving such transition by assessing, through a ‘post-Paris Agreement’ lens, the Intended Nationally Determined Contributions (INDCs) submitted by PICs and contrasting these to the near total lack of investment and planning for low carbon transition in the transport sector with the parallel occurrence in the electricity sector where ~USD 2 billion of donor investment is deployed or queued despite electricity using only ~20% of fossil fuel across the region. Consistent with recent international studies, inadequate and inappropriate financing and policy have been identified as dominant transition barriers for low carbon sea transport development in PICs. This paper further examines the regional level barriers to policy development, and finds them inhibited by the silo nature of the major regional actors. The implications that the Paris Agreement has for climate financing to support the essential research and capacity development needed to underpin a successful low carbon sea transport transition strategy at any useful scale and speed are also considered in this paper.  相似文献   

末次冰消期以来东海内陆架古环境演化   总被引：18，自引：2，他引：16  

徐方建  李安春  肖尚斌  万世明  刘建国  张永超 《沉积学报》2009,27(1):118-127

通过对位于浙—闽沿岸泥质带的EC2005孔岩性、粒度以及AMS14C年代分析,探讨了研究区自末次冰消期以来的古沉积环境演化,认为是湖水或海水深度、气候变化等综合影响的结果。岩芯底部60.20～41.00 m（17.3～13.1 ka BP）为湖泊三角洲沉积序列,可划分为前三角洲—三角洲前缘—三角洲平原三个沉积亚相,物质来源主要是湖盆流域物质的输入。随着海平面的逐渐上升,海水自13.1 ka BP开始侵入研究区,形成了41.00 m的海相沉积地层,可划分为前滨—近滨—浅海三个沉积亚相,与海平面变化曲线具有良好的对应。自12.3 ka BP开始,研究区受到沿岸流影响,长江物质开始影响研究区,7.3 ka BP以来主要是来自长江的悬浮体在沿岸流作用下输送沉积而形成,稳定的泥质沉积物开始形成。全球性重要气候事件如新仙女木事件、8.2 ka冷事件在东海内陆架沉积物中也得到了良好揭示。  相似文献   

陇中黄土高原LAS在非均匀下垫面的观测优势及其在区域陆面模式验证中的初步应用     

郝小翠  张强  杨泽粟  黄菁 《冰川冻土》2017,39(5):1057-1064

目前通用的通量观测技术涡动相关仪（EC）在区域陆面模式验证中存在能量不闭合和空间代表性有限的问题,寻求改进EC观测热通量的新技术是提高陆面模式验证效果的关键环节,大孔径闪烁仪（LAS）的出现有效改善了这一现状。基于黄土高原定西站2010年1月和6月的同步综合观测资料以及目前比较有代表性的陆面过程模式CLM的模拟数据,分析研究了LAS对EC观测地表能量不平衡问题的改进以及LAS对EC在区域陆面模式验证中的提高,结果表明：LAS可有效解决EC观测存在的地表能量不平衡问题,提高EC的地表能量闭合度,在非均匀下垫面LAS观测优势突出;利用LAS观测的感热通量进行区域陆面模式的验证,能够很大程度地避免EC能量不闭合和空间尺度不匹配在验证中造成的偏差,LAS观测更适合于大尺度模拟的验证,验证效果更好。  相似文献