南极冰盖地形数据库BEDMAP 2述评

南极冰盖物质收支与不稳定性对全球气候变化和海平面升高有着重要影响,而冰盖厚度和冰下地形则是研究南极冰盖的物质平衡、动力及不稳定性极为重要的参数。自20世纪50年代以来,国际上针对南极冰盖开展了大量的冰雷达以及重、磁测量,这些测量结果被汇集并形成冰厚和冰下地形数据库,进而服务于冰盖模式和地球系统研究,最新推出的成果便是BEDMAP 2(Bedrock Mapping Project 2)。首先介绍了BEDMAP 2的数据来源、结构以及数据处理,并讨论了数据的质量评价,然后分析了BEDMAP 2中展示的整个南极冰盖与冰下地形及其特点。最后,对于BEDMAP 2对中国在南极冰盖考察和研究方面的作用进行了一些讨论与展望。     

Retrieval of aerosol optical properties over a vegetation surface using multi-angular,multi-spectral,and polarized data

An algorithm to retrieve aerosol optical properties using multi-angular,multi-spectral,and polarized data without a priori knowledge of the land surface was developed.In the algorithm,the surface polarized reflectance was estimated by eliminating the atmospheric scattering from measured polarized reflectance at 1640 nm.A lookup table （LUT） and an iterative method were adopted in the algorithm to retrieve the aerosol optical thickness （AOT,at 665 nm） and the （A）ngstr（o）m exponent （computed between the AOTs at 665 and 865 nm）.Experiments were performed in Tianjin to verify the algorithm.Data were provided by a newly developed airborne instrument,the Advanced Atmosphere Multi-angle Polarization Radiometer （AMPR）.The AMPR measurements over the target field agreed well with the nearby ground-based sun photometer.An algorithm based on Research Scanning Polarimeter （RSP） measurements was introduced to validate the observational measurements along a flight path over Tianjin.The retrievals were consistent between the two algorithms.The AMPR algorithm shows potential in retrieving aerosol optical properties over a vegetation surface.     

Parameterizations of surface radiation in the semiarid grasslands of Inner Mongolia under clear-sky conditions using MODIS data

A set of improved and efficient radiation parameterization schemes for surface radiation balance components under clear- sky conditions was developed by using general surface measurements and MODIS data. The set of schemes was then adapted for regions similar to the present study sites under different grazing intensities and varying degrees of drought in the semiarid grasslands of Inner Mongolia. Specifically, we mainly improved two schemes for estimating downward shortwave and longwave radiation at the surface, which could be applied to regions with certain degrees of drought. The validation datasets were from ground-based observations at various grazing sites during the growing season （May to September） of different drought years, 2005 and 2006. Through comparisons of parameterized versus measured radiation values, the increased or modified factors in the original schemes demonstrated improved estimation accuracy, and the rationalities of input parameters and variables were analyzed. The regional instantaneous net radiation estimations had root-mean-square errors of less than 30 W m-2 compared with ground measurements at the sites during the study period. The statistical results showed the improved schemes are suitable for estimating surface net radiation in regional semiarid areas during the growing season. Analyses of the sensitivity of the schemes to corresponding variables were conducted to ascertain the major error sources of the schemes and potential variables for improving the performance of the schemes in agreement with observations.     

海洋潮汐浪溅区混凝土表面氯离子浓度计算模型

海洋混凝土结构的表面氯离子浓度反映了海洋氯化物环境的腐蚀作用强度,是海洋混凝土结构耐久性分析和定量设计的重要参数。本文依据国内外不同地区的大量自然暴露试验数据,通过数理统计和回归分析,确定了各种海洋环境条件下表面氯离子浓度的统计特征值,分析了海洋潮汐浪溅区混凝土中氯离子的传输机理和积聚规律,揭示了水胶比对混凝土表面氯离子浓度的影响规律,进而综合考虑水胶比、胶凝材料种类和时变特性等因素的影响,建立了海洋潮汐浪溅区混凝土表面氯离子浓度的改进计算模型。结合国内外各种表面氯离子浓度经验模型的预测结果和海洋自然暴露试验的实测数据,对比验证了所建立表面氯离子浓度计算模型的有效性和适用性,为海洋氯化物环境下混凝土结构的耐久性设计和服役寿命分析提供了重要边界条件。     

16项测绘地理信息标准通过审查

<正>7月2日,国家测绘地理信息局标准化工作委员会在西安组织召开标准审查会,由国家测绘标准化研究所承担的16项测绘地理信息标准通过审查。这些标准包括强制性国家标准《国家基本比例尺地图测绘基本技术规定》,推荐性国家标准《国家基本比例尺地图图示地形图图式》、《国家基本比例尺地图正射影像地图》、《国家基本比例尺地图地形图》、《数字城市地理信息公共平台运行服务质量规范》,行业标准《数字表面模型航天摄影测量生产技术规范》、《基础地理信息数字产品1∶50000数字表面模型》等。     

Impacts of the Lowest Model Level Height on Tropical Cyclone Intensity and Structure简

Variable thicknesses in the lowest half-ηmodel level （LML） are often used in atmospheric models to compute surface diagnostic fields such as surface latent and sensible heat fluxes.The effects of the LML on simulated tropical cyclone （TC）evolution were investigated in this study using the Weather Research and Forecasting （WRF） model.The results demonstrated notable influences of the LML on TC evolution when the LML was placed below 12 m.The TC intensification rate decreased progressively with a lowering of the LML,but its ultimate intensity change was relatively small.The maximum 10-m winds showed different behavior to minimum sea level pressure and azimuthally-averaged tangential winds,and thus the windpressure relationship was changed accordingly by varying the LML.The TC circulation was more contracted in association with a higher LML.Surface latent heat fluxes were enhanced greatly by elevating the LML,wherein the wind speed at the LML played a dominant role.The changes in the wind speed at the LML were dependent not only on their profile differences,but also the different heights they were taken from.Due to the enhanced surface heat fluxes,more intense latent heat release occurred in the eyewall,which boosted the storm＇s intensification.A higher LML tended to produce a stronger storm,and therefore the surface friction was reinforced,which in turn induced stronger boundary layer inflow together with increased diabatic heating.     

The hiatus and accelerated warming decades in CMIP5 simulations

Observed hiatus or accelerated warming phenomena are compared with numerical simulations from the Coupled Model Intercomparison Project Phase 5 （CMIP5） archives,and the associated physical mechanisms are explored based on the CMIP5 models.Decadal trends in total ocean heat content （OHC） are strongly constrained by net top-of-atmosphere （TOA） radiation.During hiatus decades,most CMIP5 models exhibit a significant decrease in the SST and upper OHC and a significant increase of heat penetrating into the subsurface or deep ocean,opposite to the accelerated warming decades.The shallow meridional overturning of the Pacific subtropical cell experiences a significant strengthening （slowdown） for the hiatus （accelerated warming） decades associated with the strengthened （weakened） trade winds over the tropical Pacific.Both surface heating and ocean dynamics contribute to the decadal changes in SST over the Indian Ocean,and the Indonesian Throughflow has a close relationship with the changes of subsurface temperature in the Indian Ocean.The Atlantic Meridional Overturing Circulation （Antarctic Bottom Water） tends to weaken （strengthen） during hiatus decades,opposite to the accelerated warming decades.In short,the results highlight the important roles of air-sea interactions and ocean circulations for modulation of surface and subsurface temperature.     

稳恒水波的Fourier近似解研究

A computational method for steady water waves is presented on the basis of potential theory in the physical plane with spatial variables as independent quantities. The finite Fourier series are applied to approximating the free surface and potential function. A set of nonlinear algebraic equations for the Fourier coefficients are derived from the free surface kinetic and dynamic boundary conditions. These algebraic equations are numerically solved through Newton＇s iterative method, and the iterative stability is further improved by a relaxation technology. The integral properties of steady water waves are numerically analyzed, showing that （1） the set-up and the set-down are both non-monotonic quantities with the wave steepness, and （2） the Fourier spectrum of the free surface is broader than that of the potential function. The latter further leads us to explore a modification for the present method by approximating the free surface and potential function through different Fourier series, with the truncation of the former higher than that of the latter. Numerical tests show that this modification is effective, and can notably reduce the errors of the free surface boundary conditions.     

三维激光扫描技术在墓葬保护中的应用

三维激光扫描技术已逐渐应用到考古研究中。传统的扫描成果CAD图在考古研究中略显单调,而三维模型只能通过专业软件才能观看,如何使扫描成果得到更全面地展示,将是今后三维激光扫描服务于文物考古的重要方向。以墓葬扫描为例,采用Leica Scanstation 2扫描仪获取几何点云数据,并利用Cyclone软件,采用标靶和人工选点相结合的方法实现多站点点云数据配准,然后利用Geomagic Studio完成后期三维建模,最后利用Cloud Word、Deep Exploration及3D max等软件完成相关成果的展示。     

中心城区不透水表面与城市热岛效应关系研究

不透水地表作为城市土地覆盖类型的重要组分,其分布格局与密度大小对城市生态系统服务功能会产生相反且决定性的作用,其中对地表的增温效应是城市热岛问题关注的核心内容。本研究通过线性光谱混合分解模型提取城市不透水地表,基于Landsat TM6热红外波段数据的单窗算法反演地表温度,并进行两者的关系研究。结果表明:城市不透水地表与地温空间分布格局呈现高度相似性,其数值都随距城市中心距离增加而逐渐减小,定量分析表明两者具有明显的指数相关关系。