南极长城站验潮站数据处理和潮汐特点初步分析

继在南极中山站建成我国南极首个永久性验潮站后,2012年1月在南极长城站又建成了我国南极第二个永久性验潮站。通过对长城站验潮站相关数据进行分析处理,得到了验潮基准系统的水准网平差结果和验潮仪零点标定结果,以及长城站附近海域海洋潮汐170个分潮的调和常数,并据此进行了潮汐预报,同时分析了长城站潮汐余水位的变化特征,探讨了利用附近的Antarctic Base Prat验潮站的余水位改正长城站潮汐预报的可行性,结果表明使用Antarctic Base Prat验潮站余水位改正长城站潮汐预报,可以显著提高长城站验潮站潮汐预报的精度,余水位改正后2014时段的潮汐预报中误差为±3.42 cm,明显好于改正前的预报中误差±10.43 cm。     

黄土高原发展过程中的五大转折

1 Introduction W hatim portanttransform ations have taken place during the form ation ofthe Loess Plateau in China? Research on this problem has especially im portantscientific significance forus to learn ofthe evolution oftheLoessPlateau and predictthe f…     

Modeling the history of Lake of the Woods since 11,000 cal yr B.P. using GIS

Because of differential isostatic rebound, many lakes in Canada have continued to change their extent and depth since retreat of the Laurentide Ice Sheet. Using GIS techniques, the changing configuration and bathymetry of Lake of the Woods in Ontario, Manitoba, and Minnesota were reconstructed for 12 points in time, beginning at 11,000 cal yr B.P. (9.6 ¹⁴C ka B.P.), and were also projected 500 years into the future, based on the assumption that Lake of the Woods continued to have a positive hydrological budget throughout the Holocene. This modeling was done by first compiling a bathymetric database and merging that with subaerial data from the Shuttle Radar Topography Mission (SRTM). This DEM file was then adjusted by: (1) isobase data derived from Lake Agassiz beaches prior to 9000 cal yr B.P. (8.1 ¹⁴C ka B.P.) and (2) modeled isostatic rebound trend analysis after 9000 cal yr B.P. Just after the end of the Lake Agassiz phase of Lake of the Woods, only the northernmost part of the basin contained water. Differential rebound has resulted in increasing water depth. In the first 3000 years of independence from Lake Agassiz, the lake transgressed >50 km to the south, expanding its area from 858 to 2857 km², and more than doubling in volume. Continued differential rebound after 6000 cal yr B.P. (5.2 ¹⁴C ka B.P.) has further expanded the lake, although today it is deepening by only a few cm per century at the southern end. In addition, climate change in the Holocene probably played a role in lake level fluctuations. Based on our calculation of a modern hydrological budget for Lake of the Woods, reducing runoff and precipitation by 65% and increasing evaporation from the lake by 40% would end overflow and cause the level of the lake to fall below the outlets at Kenora. Because this climate change is comparable to that recorded during the mid-Holocene warming across the region, it is likely that the area covered by the lake at this time would have been less than that determined from differential isostatic rebound alone.     

Grassland productivity in an alpine environment in response to climate change

Situated in a climatically stressful environment, alpine grassland is sensitive to subtle climate changes in its productivity. We remedy the current deficiency in studying grassland productivity by taking the integrated effect of all relevant factors into consideration. The relative importance of temperature, rainfall and evaporation to the alpine grassland productivity in western China was determined through analysis of their relationship with the normalized difference vegetation index (NDVI) between 1981 and 2000. Climate warming stimulated grassland productivity in the 1980s, but hampered it in the 1990s. Temperature is more important than rainfall to grassland productivity early in the growing season. However, their relative importance is reversed late in the growing season. Monthly summer month rainfall modified by maximum monthly temperature is a good predictor of alpine grassland productivity at 62.0 per cent. However, the best predictor is water deficiency, which is able to improve the estimation accuracy to 78.3 per cent. Hence, the impact of temperature on grassland productivity is better studied indirectly through evaporation.     

北京耕地流失的时空动态与调控途径研究

在国际学术前沿土地变化科学的概念框架下, 耕地非农化及其调控机制研究成为核心问 题之一。研究中国快速城市化地区耕地非农化的驱动力及其调控机制, 不仅是现实的迫切需求, 也可在国际相关学术领域做出独特贡献。以北京为案例进行研究发现: 1996~2004 年北京土地利 用变化中, 大多数地类转换都与耕地直接有关, 耕地流失是北京土地利用变化的核心问题; 城镇 扩展主要占用耕地, 且耕地生产力高的平原地区因建设占用而流失的耕地量大; 远郊山区耕地被 建设占用的压力相对较小, 但被生态用地占用的压力相对较大; 人口增长、经济发展、政府行为与 决策是北京等经济快速发展地区耕地流失的重要驱动因素, 解决途径关键在于寻求耕地保护与 耕地非农利用之间的平衡点、积极发挥土地管理政策的调控作用。     

阿克苏河流域的面雨量序列及其与径流关系

以数字高程模型 (DEM) 的1km×1km网格数据为基础,对阿克苏河流域14个气象站和水文站的1961~2000年的年降水资料进行了自然正交分解 (EOF),通过回归分析,建立主要特征向量与地理因子的插值模型,给出了一个面雨量序列的计算方法,为建立气候要素的区域平均序列提供了一个有效的解决方案,并由此推算出年阿克苏流域平均年降水量的空间分布以及面雨量序列。径流量与面雨量之比 (R/P) 平均为0.43,最高为0.69 (1997年),最低为0.30 (1963年)。计算出的阿克苏河流域面雨量序列与阿克苏河实测径流量序列的趋势变化率分别为5.79×10⁸ m³/10a和4.29×10⁸ m³/10a,两者均表现出增加趋势,但面雨量的增加速率要比径流量大一些,年际变化幅度也要大,面雨量和径流量的变差系数Cv值分别为0.17和0.13。阿克苏河年径流量的变化与夏季0^oC层高度、年面雨量有着十分密切的关系,表明20世纪90年代以来新疆气候的变化是阿克苏河流域径流稳定增加的一个非常重要的因素。     

黄土不同指标的古环境意义探讨

在确认“黄土也是古土壤”的前提下,对新近发现的位于黄土高原西北部沙漠黄土边界带的彭阳剖面进行了烧失量、色度、磁化率、粒度、CaCO3等环境变化代用指标的系统测试。通过建立土壤发育指数和红化指数,探讨了各指标与古土壤发育强度之间的关系。根据古土壤的发育强度,初步建立了800 ka BP生态脆弱区的高分辨率环境图谱。此图谱与公认的海洋氧同位素曲线、洛川剖面可以进行良好的对比,并揭示出更多的环境变化信息。     

民勤绿洲水资源利用与生态系统退化分析

石羊河流域生态平衡失调,生态系统退化在我国干旱、半干旱地区内陆河流域中具有典型的代表性。通过对石羊河流域近代地表水资源开发及其绿洲变迁,近年来流域用水量分配,降水特征及其对植被的影响,流域下游民勤绿洲地下水位、水质的变化等因素多年来观测研究,认为：降水量对天然植被的生长没有大的作用;由于人口的增加,流域地表水资源分配不均,水资源开发过度,地下水位急剧下降,造成流域生态系统退化。流域经济因素促进社会因素的变化,社会因素的变化导致自然环境的变迁,社会、经济、自然诸因素相互作用,通过水资源的变化驱动石羊河流域生态系统的变化。     

Spatio-temporal dynamics of land cover and land surface temperature in Ganges-Brahmaputra delta: A comparative analysis between India and Bangladesh

Land use and land cover (LULC) change in the Ganges-Brahmaputra delta (GBD) poses significant challenges towards future environmental sustainability of the region and requires regional scale monitoring of key bio-physical variables and changes in their inter-relationship over space and time. Focusing on the southern part of the lower GBD region along the international border of India and Bangladesh, this study examined the spatio-temporal variability of LULC change and its relationship with Land Surface Temperature (LST). Furthermore, LULC-LST relationships were compared between Indian and Bangladesh part and its trend in and around big cities (with more than 1 million population) and towns (with more than 100,000 population) was investigated. Results showed that LST changes were predominantly driven by LULC changes on both sides of the border. Urban growth is the dominant form of LULC change, and the rate of land change was faster in 2005–2010 time period than 1989–2005. Over the period of 21 years, mean January LST decreased by approximately 1.83 °C in Indian part and 1.85 °C in the Bangladesh part. Areas that changed from to rural from agricultural experienced decrease in mean LST, whereas those areas that changed to urban from either agriculture or rural, experienced increase in mean LST. The relationship between LULC and LST are same on both sides of the Indo-Bangladesh border. In bigger cities like Kolkata (in India) and Khulna (in Bangladesh), there is a high spatial variability in relationship between LULC and LST compared to large towns. The LULC-LST relationship in large towns in India was influenced by proximity to Kolkata and coastal areas, whereas in Bangladesh no such influence was evident. The results and the data produced in this study are crucial for monitoring LULC changes, for developing spatial decision support system, and thus will be helpful to address the current challenges of land management in the GBD region. Changes in the LULC and LST are important indicators of GBD's environmental health and access its vulnerability and thus the present findings serve as baseline information for future studies seeking to examine the impact of differential policies on the LULC change in the region.     

汕头市土地利用空间格局的景观生态学分析

根据不同利用类型土地生态效应的异同,对汕头市2003年1∶1万比例尺土地更新调查数据的土地分类系统进行调整,将全部土地景观划分为耕地、林地、园地、草地、居民点及工矿、交通、裸土地和水域等8类.在GIS的支持下,提取各类型土地景观斑块的数目、面积和周长等信息,据此对斑块景观的数量、面积和形状等特征,以及区域景观的多样性、均匀度和优势度,集中性和区际意义等进行分析,从而总结出全市范围及六区一县土地利用空间格局的景观生态学特征.