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河北省石家庄地区晚更新世晚期古菱齿象-披毛犀动物群及其古气候

河北省石家庄市郊区地下7～24m的古滹沱河沉积物中产出丰富的大型哺乳类化石:诺氏古菱齿象(Palaeoloxodon naumanni)、原始牛(Bos primigenius)、杨氏水牛(Bubalus youngi)、披毛犀(Coelodonta antiquitatis)、鹿(Cervus sp.)、四不像鹿(E...     

Temporal and depth distribution of microepiphytes on Posidonia oceanica (L.) Delile leaves in a meadow off Tunisia

A survey on the epiphytic microorganisms growing on Posidonia oceanica leaves was conducted along a depth transect along the coast of Eastern Tunisia (Mahdia). Samples were collected by SCUBA diving at depths of 3, 5, 10 and 12 m in July 2008 and January 2009. A total of 58 microepiphyte taxa were identified. Multivariate analyses revealed temporal and spatial variation of the abundance of epiphytic microalgae. Water motion, light availability, temperature and motility of species seem to be responsible of temporal and bathymetric variations of epiphytic microalgae. Unlike diatoms, dinoflagellates were more abundant in deep waters, suggesting that they are more vulnerable to hydrodynamics. The significant correlation between leaf area index and abundance of epiphytic species indicates that the phenological parameters of the host plant influence the abundance of the epiphytic microorganisms. Among the epiphytic dinoflagellates, our data showed a great number of potentially toxic species (Alexandrium minitum, Amphidinium carterae, Karenia selliformis, Coolia monatis, Karlodinium veneficum, Ostreopsis siamensis, Prorocentrum concavum, Prorocentrum minimum, Prorocentrum rathymum and Prorocentrum lima). These species were more abundant in the deep station under more sheltered conditions than found at inshore shallower stations, which are subjected to high water motion.     

The turbidity maxima of the northern Jiangsu shoal-water in the Yellow Sea,China

The Yellow Sea general circulation model coupled to a sediment transport model with and without surface waves was implemented to study sediment distribution and resuspension in the northern Jiangsu shoal-water (NJSW) in March and April 2006–2008. With surface wave, the general features of model simulated turbidity maxima agreed well with the MODIS remote sensing data. Without wave, the turbidity maxima moved offshore with much reduced suspended sediment concentration (SSC). This demonstrated that surface waves played a dominant role over the tides to form the turbidity maxima in the region. The study also found that NJSW exported sediments to the Yellow Sea and East China Sea through offshore and southern boundaries. As March and April 2008 was a wind anomalous year with a decreased wind speed over last three years, the wind generated waves in the region were also reduced, leading to lower sediment resuspension and SSC in that year.     

Multitime scale variations of sea surface temperature in the China seas based on the HadISST dataset

The variability of the sea surface temperature(SST) in the China seas has been studied in seasonal,interannual and interdecadal scales based on the monthly data of HadISST spanning from 1870 to 2007. The main results obtained are SST in the China offshore changes most actively at the seasonal scale with the intensity diminishing from north to south,as the temperature differences between summer and winter reaching 17 and 4 C in the northern and southern areas,respectively. Moreover,seasonal variation near the coastal regions seems relatively stronger than that far from the coastline;significant interannual variations are detected,with the largest positive anomaly occurring in 1998 in the overall area. But as far as different domains are concerned,there exists great diversity,and the difference is also found between winter and summer. Differed from the seasonal variations,where the strongest interannual variability takes place,resides to the south of that of the seasonal ones in the northern section,nevertheless in the South China Sea,the most significant interannual variability is found in the deep basin;interdecadal changes of summer,winter and annual mean SST in different domains likewise present various features. In addition,a common dominant warming in recent 20 a are found in the overall China offshore with the strongest center located in the vicinity of the Changjiang Estuary in the East China Sea,which intensifies as high as 1.3 C during the past 130 a.     

近30年来绵阳市城市用地扩展模式研究

城市用地扩展不仅是评价城市化水平的重要测度指标,也是土地利用/覆被变化(LUCC)研究重要领域之一.本文以多时相、多源空间数据为基础,采用RS专题信息提取与GIS空间叠加分析技术,选择扩展强度指数、紧凑度、分形维数、重心转移指数、扩展方位指数等5个景观结构与变化指标,系统地分析了中国科技城绵阳城市用地扩展模式与时空分异...     

Spatio-temporal variations in ecological spaces and their ecological carrying status in China’s mega-urban agglomerations

Journal of Geographical Sciences - The rapid expansion of China’s urban agglomerations in recent decades has resulted in over-occupied ecological spaces and increased ecological pressure that...     

热带海温变化对云南初夏干湿转换季节雨量的影响

通过相关分析、诊断分析以及数值模拟试验来研究热带海温异常对云南初夏干温转换季节雨量变化的影响，研究表明前期热带海温异常对云南初夏干湿转换季节雨量有明显的影响，海温与雨量的显著关相关区与Walker环流的上升下沉支相对应。提前的时间尺度越长，海温所提供的可预报信息越少；时间尺度越短，提供的可预报信息越大。诊断分析及 数值模拟研究还表明在赤道中东太平洋的暖位相期，孟加拉湾地区的季风低压和初夏索马里附近的越赤道气流及印度洋西南季风减弱，反之则加强。海温变化通过海气相互作用影响到季风活动，从而对云南初夏干湿转换季节雨量产生影响。     

High-resolution modeling study of the Kuroshio path variations south of Japan

A high-resolution ocean general circulation model （OGCM） is used to investigate the Kuroshio path variations south of Japan. The model reproduces many important features of the Kuroshio system including its interannual bimodal variability south of Japan. A decreasing trend of the spatial averaged relative vorticity is detected when the Kuroshio takes the non-large meander （NLM） path, and during the transition period from the NLM to the large meander （LM）, a sudden release of velocity shear corresponds well to the weakening of the Shikoku recirculation gyre （SRG）, which plays a key role in modulating the Kuroshio path variations. Analysis of eddy energetics indicates that baroclinic instability is mainly responsible for the formation of the LM. In addition, further analysis shows that the strength of the SRG could be largely influenced by the baroclinic Rossby wave adjustment process, forced by the wind stress curl anomalies in the North Pacific basin, based on the model investigation. It is suggested that the cyclonic disturbances might account for the weakening of the SRG, and act as a remote trigger for the baroclinic instability of the Kuroshio south of Japan.     

Linking hydrological variations at local scales to regional climate teleconnection patterns

Climate patterns over preceding years affect seasonal water and moisture conditions. The linkage between regional climate and local hydrology is challenging due to scale differences, both spatially and temporally. In this study, variance, correlation, and singular spectrum analyses were conducted to identify multiple hydroclimatic phases during which climate teleconnection patterns were related to hydrology of a small headwater basin in Idaho, USA. Combined field observations and simulations from a physically based hydrological model were used for this purpose. Results showed statistically significant relations between climate teleconnection patterns and hydrological fluxes in the basin, and climate indices explained up to 58% of hydrological variations. Antarctic Oscillation (AAO), North Atlantic Oscillation (NAO), and Pacific North America (PNA) patterns affected mountain hydrology, in that order, by decreasing annual runoff and rain on snow (ROS) runoff by 43% and 26% during a positive phase of NAO and 25% and 9% during a positive phase of PNA. AAO showed a significant association with the rainfall-to-precipitation ratio and explained 49% of its interannual variation. The runoff response was affected by the phase of climate variability indices and the legacy of past atmospheric conditions. Specifically, a switch in the phase of the teleconnection patterns of NAO and PNA caused a transition from wet to dry conditions in the basin. Positive AAO showed no relation with peak snow water equivalent and ROS runoff in the same year, but AAO in the preceding year explained 24 and 25% (p < 0.05) of their variations, suggesting that the past atmospheric patterns are equally important as the present conditions in affecting local hydrology. Areas sheltered from the wind and acted as a source for snow transport showed the lowest (40% below normal) ROS runoff generation, which was associated with positive NAO that explained 33% (p < 0.01) of its variation. The findings of this research highlighted the importance of hydroclimatic phases and multiple year variations that must be considered in hydrological forecasts, climate projections, and water resources planning.