海洋生境刀鲚菌群PCR-DGGE指纹图谱构建及分析

为了分析海洋生境刀鲚(Coilia nasus)体内及生长环境菌群结构,作者采用免培养16S r DNA的PCR-DGGE指纹图谱技术,对刀鲚鳃、肠道壁、肠道内容物及水体环境中的菌群结构进行了对比分析。结果表明:变性梯度为35%~55%、浓度为8%的聚丙烯酰胺凝胶,150V 60℃下电泳10 h,DGGE带谱的分离效果较好;刀鲚鳃、肠道壁、肠道内容物及水体样品指纹图谱上分别显示出24、19、14和29条信号强度不同的条带;相同样品重复组细菌结构相似度在80%以上,差异不显著;不同样品之间,刀鲚鳃与海水聚为一支,具有较高的相似度为52%,肠壁与肠内容物相似度为41%。样品菌群主要以未培养菌为主,主要包括变形菌、放线菌和厚壁菌。本文首次成功构建海洋生境刀鲚菌群16S r DNA的PCR-DGGE指纹图谱。     

应用样条插值提高GRAPES模式物理过程反馈精度

GRAPES (Global/Regional Assimilation and PrEdiction System) 模式动力框架中垂直方向变量的跳层设置采用Charney-Phillips分布,在整层上进行位温、水物质的计算,物理过程中在半层上对其进行处理。这样在GRAPES模式中,进入物理过程之前和物理过程计算完毕之后,都要采用线性插值进行整层和半层之间物理量的转换。由于线性插值精度欠佳,为提高上述反馈过程的精度,并保证水物质的正定性,该研究引入样条插值,并在水物质的插值过程中进行保单调处理,有效减小了位温场、水物质场的预报偏差,并提升了模式的综合预报性能。     

Fusion of high-resolution DEMs derived from COSMO-SkyMed and TerraSAR-X InSAR datasets

Voids caused by shadow, layover, and decorrelation usually occur in digital elevation models (DEMs) of mountainous areas that are derived from interferometric synthetic aperture radar (InSAR) datasets. The presence of voids degrades the quality and usability of the DEMs. Thus, void removal is considered as an integral part of the DEM production using InSAR data. The fusion of multiple DEMs has been widely recognized as a promising way for the void removal. Because the vertical accuracy of multiple DEMs can be different, the selection of optimum weights becomes a key problem in the fusion and is studied in this article. As a showcase, two high-resolution InSAR DEMs near Mt. Qilian in northwest China are created and then merged. The two pairs of InSAR data were acquired by TerraSAR-X from an ascending orbit and COSMO-SkyMed from a descending orbit. A maximum likelihood fusion scheme with the weights optimally determined by the height of ambiguity and the variance of phase noise is adopted to syncretize the two DEMs in our study. The fused DEM has a fine spatial resolution of 10 m and depicts the landform of the study area well. The percentage of void cells in the fused DEM is only 0.13 %, while 6.9 and 5.7 % of the cells in the COSMO-SkyMed DEM and the TerraSAR-X DEM are originally voids. Using the ICESat/GLAS elevation data and the Chinese national DEM of scale 1:50,000 as references, we evaluate vertical accuracy levels of the fused DEM as well as the original InSAR DEMs. The results show that substantial improvements could be achieved by DEM fusion after atmospheric phase screen removal. The quality of fused DEM can even meet the high-resolution terrain information (HRTI) standard.     

LiDAR点云数据的电力线3维重建

利用LiDAR数据进行电力设施提取与建模可以克服传统工程测量电力巡线工作量大,危险性高,效率低下等缺点,但现有的电力线提取研究主要集中在电力线的分离与提取,并且拟合的精度不高。针对此问题本文提出了一种精度较高的电力线拟合方法。首先,根据电力线两端悬挂、中间自然下垂的特点,求解电力线拟合的最佳几何模型;然后,通过电力线的走向和端点,建立电力线拟合的最佳平面坐标系;最后,采用基于二次多项式限制的最小二乘法拟合电力线,解算出最优参数,生成最终电力线模型。对真实数据的处理和精度评价表明,本文方法不仅能够实现电力线的快速3维重建,而且能够达到较高的拟合精度。     

Variability of Atlantic Meridional Overturning Circulation in FGOALS-g2简

The variability of Atlantic Meridional Overturning Circulation （AMOC） in the pre-industrial control experiment of the Flexible Global Ocean-Atmosphere-Land System model, Grid-point Version 2 （FGOALS-g2） was investigated using the model outputs with the most stable state in a 512-yr time window from the total 1500-yr period of the experiment. The period of AMOC in FGOALS-g2 is double peaked at 20 and 32 years according to the power spectrum, and 22 years according to an auto-correlation analysis, which shows very obvious decadal variability. Like many other coupled climate models, the decadal variability of AMOC in FGOALS-g2 is closely related to the convection that occurs in the Labrador Sea region. Deep convection in the Labrador Sea in FGOALS-g2 leads the AMOC maximum by 3-4 years. The contributions of thermal and haline effects to the variability of the convection in three different regions [the Labrador, Irminger and Greenland-Iceland- Norwegian （GIN） Seas] were analyzed for FGOALS-g2. The variability of convection in the Labrador and Irminger Seas is thermally dominant, while that in the colder GIN Seas can be mainly attributed to salinity changes due to the lower thermal expansion. By comparing the simulation results from FGOALS-g2 and 11 other models, it was found that AMOC variability can be attributed to salinity changes for longer periods （longer than 35 years） and to temperature changes for shorter periods.     

Assessment of future climate change over East Asia due to the RCP scenarios downscaled by GRIMs-RMP

This study assesses future climate change over East Asia using the Global/Regional Integrated Model system—Regional Model Program (RMP). The RMP is forced by two types of future climate scenarios produced by the Hadley Center Global Environmental Model version 2 (HG2); the representative concentration pathways (RCP) 4.5 and 8.5 scenarios for the intergovernmental panel on climate change fifth assessment report (AR5). Analyses for the current (1980–2005) climate are performed to evaluate the RMP’s ability to reproduce precipitation and temperature. Two different future (2006–2050) simulations are compared with the current climatology to investigate the climatic change over East Asia centered in Korea. The RMP satisfactorily reproduces the observed seasonal mean and variation of precipitation and temperature. The spatial distribution of the simulated large-scale features and precipitation by the RMP is generally less reflective of current climatic conditions than that is given by the HG2, but their inter-annual variations in East Asia are better captured by the RMP. Furthermore, the RMP shows higher reproducibility of climate extremes including excessive heat wave and precipitation events over South Korea. In the future, strong warming is distinctly coupled with intensified monsoonal precipitation over East Asia. In particular, extreme weather conditions are increased and intensified over South Korea as follows: (1) The frequency of heat wave events with temperature greater than 30 °C is projected to increase by 131 and 111 % in the RCP 8.5 and 4.5 downscaling, relative to the current climate. (2) The RCP 8.5 downscaling shows the frequency and variability of heavy rainfall to increase by 24 and 31.5 %, respectively, while the statistics given by the RCP 4.5 downscaling are similar to those of the current climate.     

The impact of precipitation on speed–flow relationships along a UK motorway corridor

Although the fundamental traffic diagram provides the characteristics of a typical road traffic speed–flow relationship, little consideration has been given to the impact of adverse weather conditions on the relationship and the subsequent impact on local speed–flow. For the first time, this study uses precipitation radar along with a state-of-the art traffic information system to ascertain the relationship between speed–flow and precipitation on a UK transport corridor at the local (junction to junction) scale. It is evident that precipitation causes a significant reduction in speed and maximum flow on many links of the corridor as well as a downward reduction in the overall speed-flow relationship. With increased instances of heavy precipitation predicted in the UK as a result of climate change, these findings highlight the subsequent impact on journey travel times and associated economic costs.     

Representation of tropical subseasonal variability of precipitation in global reanalyses

Tropical subseasonal variability of precipitation from five global reanalyses (RAs) is evaluated against Global Precipitation Climatology Project (GPCP) and Tropical Rainfall Measuring Mission (TRMM) observations. The RAs include the three generations of global RAs from the National Center for Environmental Prediction (NCEP), and two other RAs from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC). The analysis includes comparisons of the seasonal means and subseasonal variances of precipitation, and probability densities of rain intensity in selected areas. In addition, the space–time power spectrum was computed to examine the tropical Madden-Julian Oscillation (MJO) and convectively coupled equatorial waves (CCEWs). The modern RAs show significant improvement in their representation of the mean state and subseasonal variability of precipitation when compared to the two older NCEP RAs: patterns of the seasonal mean state and the amplitude of subseasonal variability are more realistic in the modern RAs. However, the probability density of rain intensity in the modern RAs show discrepancies from observations that are similar to what the old RAs have. The modern RAs show higher coherence of CCEWs with observed variability and more realistic eastward propagation of the MJO precipitation. The modern RAs, however, exhibit common systematic deficiencies including: (1) variability of the CCEWs that tends to be either too weak or too strong, (2) limited coherence with observations for waves other than the MJO, and (3) a systematic phase lead or lag for the higher-frequency waves.     

Tree mortality in response to climate change induced drought across Beijing,China

Tree mortality in response to climate change induced drought has emerged as a global concern. Small changes of tree mortality rates can profoundly affect forest structure, composition, dynamics and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from natural stands (82 plots) in Beijing showed that tree mortality rates have increased significantly over the two decades from 1986 to 2006. In contrast, recruitment rates decreased significantly over this period. The increase in overall mortality rates resulted from an increase in tree deaths dominantly attributed to changes in temperature and precipitation resulting in drier conditions across latitudes, elevations, tree species, and tree sizes. In addition, the results showed that mortality rates of Chinese pine (Pinus tabuliformis) (β ₁ ?=?0.0874) as a result of climate change induce drought were much smaller than oak (Quercus) (β ₁ ?=?0.1583).