厚度对月壤微波辐射亮温的影响

基于嫦娥系列卫星微波辐射计数据的月壤厚度反演是中国月球科学研究的重要目标之一。基于辐射传输方程,数值模拟了不同频率、（FeO+TiO₂）含量和表面温度条件下厚度对月壤微波辐射亮温的影响;基于嫦娥二号卫星微波辐射计（Chang’E Lunar Microwave Sounder,CELMS）数据,结合Apollo 计划获取的月壤厚度资料及其他月壤厚度资料,系统分析了厚度对CELMS观测数据的影响。结果表明：频率、（FeO+TiO₂）含量、表面温度对亮温的影响远大于厚度对亮温的影响,是基于CELMS数据进行月壤厚度反演的重要影响因素;低频、低（FeO+TiO₂）含量、低温条件下,厚度对CELMS数据的影响最大;利用3 GHz、凌晨时刻的CELMS数据进行月陆地区月壤厚度反演可行。研究结果对基于嫦娥系列卫星CELMS数据的月壤厚度反演具有重要参考意义。     

月面形貌仿真设计及在嫦娥三号任务中的应用

月面形貌仿真可以为嫦娥三号着陆前地形建立及视觉导航仿真测试提供逼真的三维月面环境。利用分形随机算法并结合月面撞击坑与石块的数学分布模型,在实现月面数字地形的基础上利用纹理映射和纹理融合的方法为月面地形添加纹理,完成了月面逼真三维环境的构建。结合导航相机的外方位元素和光照条件,实现了对该仿真月面环境的模拟环拍,支撑了嫦娥三号发射前月球车导航相机数据获取、地形建立、通行代价图计算、月球车路径规划等遥操作任务过程仿真测试。测试结果表明,仿真月面三维地形具有良好的视觉效果,满足了巡视器导航相机测试验证对精细月面地形和纹理的需求,为导航相机测试验证提供了有效的月面形貌仿真数据。     

月表地貌起伏形态分异特征及分级标准研究

月球地貌是月球表面发生的地质和地貌过程的结果,月球地貌单元的划分和等级分类体系的构建是月球地貌学研究的基础,也是月球地貌图制图的基础和关键科学问题。地貌学是研究形态和成因的科学,高程和起伏度是最基本的地貌指标。本文基于LOLA（Lunar Orbiter Laser Altimeter） DEM数据以及LOLA和SELENE TC（Terrain Camera）融合的DEM数据（SLDEM2015,文中简称SLDEM）,利用均值变点法确定月表起伏度计算的最佳窗口,并以起伏度100 m、200 m、300 m、700 m、1500 m及2500 m为阈值将月球表面分为微起伏平原（< 100 m）、微起伏台地[100 m, 200 m）、微小起伏丘陵[200 m, 300 m）、小起伏山地[300 m, 700 m）、中起伏山地[700 m, 1500 m）、大起伏山地[1500 m, 2500 m）及极大起伏山地（≥ 2500 m）地貌7个类型。划分结果显示：微起伏平原主要分布在月海平原区域、部分有玄武岩充填的撞击盆地的盆底区域以及撞击坑坑底区域;微起伏台地主要分布在月海和月陆区域的交界区域;微小起伏丘陵主要分布在月溪和皱脊等构造单元区域;小起伏山地主要分布在撞击坑中央峰及坑底断裂区域;中起伏山地主要分布在撞击坑坑底和坑壁过渡区域、撞击坑坑壁和坑缘过渡区域、撞击盆地盆底与盆壁过渡区域以及盆壁与盆缘过渡区域;大起伏和极大起伏山地主要分布在撞击坑坑壁区域及撞击盆地盆壁区域。本文确定的月表起伏度分级标准可以对月表数字地貌分类体系的构建和月球地貌图集的编研提供定量标准和重要参考。     

嫦娥一号月球地形模型的一些应用研究

利用嫦娥一号绕月卫星激光高度计数据获取得到的新的360 阶次的地形模型CLTMs03,开展了初步应用研究,包括对嫦娥一号CCD立体相机数据进行了校对,发现并了解立体相机分析中的约900 m的垂向系统误差;利用撞击坑计数法,基于标校后的照相数据对嫦娥一号地形中新发现的玉兔火山区域的年龄特征进行了分析;结合新的CLTM-s03 地形模型和CEGM-02 重力场模型,新证实了西拉德撞击坑是一个布格质量瘤异常区域。     

Testing intra-site transfer functions: an example using chironomids and water depth

Most calibration data sets used to infer past environmental conditions from biological proxies are derived from many sites. An alternative strategy is to derive the calibration data set from within a single site. Transfer functions derived from such intra-site calibration data sets are usually applied to fossil assemblages from the focal lake, but a recent development has been to apply these transfer functions to other sites. Transfer functions derived from intra-site calibration data sets can have impressive cross-validation performance, but that gives little indication of their performance when applied to other sites. Here, we develop transfer functions for lake depth from intra-lake chironomid calibration data sets in Norway and Alaska and test the resulting models by cross-validation and against known depth in external lakes. Lake depth is a statistically significant predictor of chironomid assemblages at all these lakes, and most intra-lake transfer functions perform reasonably well under cross-validation, but their performance against external data is erratic. Downcore reconstructions from transfer functions developed on different lakes are dissimilar. Ignoring the poorly performing transfer functions, only 3 of 14 downcore reconstructions are statistically significant. Few assemblages downcore had good modern analogues in the calibration data set, even when the core was from the same lake as the calibration data set. We conclude that intra-site calibration data sets can find site-specific rather than general relationships between species and the environment and thus should be applied with care and to external sites only after careful and critical validation.     

Morphological differentiation characteristics and classification criteria of lunar surface relief amplitude

Lunar landforms are the results of geological and geomorphic processes on the lunar surface. It is very important to identify the types of lunar landforms. Geomorphology is the scientific study of the origin and evolution of morphological landforms on planetary surfaces. Elevation and relief amplitude are the most commonly used geomorphic indices in geomorphological classification studies. Previous studies have determined the elevation classification criteria of the lunar surface. In this paper,...     

月表形貌特征研究进展及趋势分析

在月球探测及科学研究过程中,对月表形貌特征的认识和分析是月球探测计划的关键任务之一,有助于理解和揭示月球的形态特征及空间分异规律,对于分析月球岩石构造、估算月表年龄、反演月壤厚度、恢复月球的起源和演化历史等都具有重要意义。从月表形貌特征的塑造及表达、宏观特征的分析与定量刻画、月表撞击坑的识别与分类及空间分异特征等几方面进行了归纳和分析,提出了未来月表形貌的研究方向,包括全月球形貌特征的多级分区划分、撞击坑类型的划分、全月球撞击坑空间分异特征及规律的研究、基于撞击坑空间分布探讨月球演化、基于形貌特征的比较行星学研究等。     

Image resolution and evaluation of genetic hypotheses for planetary landscapes

The spatial resolution of image data tends to constrain the horizontal length scale of genetic hypotheses that are addressable by those data. No ‘simple’ formula exists when image resolution is sufficient to test a given geomorphic process, which is dependent on what characteristics are diagnostic of the particular process. Genetic hypotheses should be formulated along the lines of the “multiple working hypotheses” concept as described in a classic paper by Chamberlin [J. Geol. 5 (1897) 837]. An essential element of a viable working hypothesis is a clear indication of the characteristics predicted by, or a consequence of, the hypothesis. An untestable hypothesis is not an effective working hypothesis. The history of the study of lunar sinuous rilles is outlined as an illustration of the influence of image resolution and the formulation of genetic hypotheses on the subsequent advancement of understanding of the problem. Sinuous rilles on Venus and Mars, and controversial sinuous ridges on Mars are also reviewed. In the lunar case, the three-order-of-magnitude improvement in spatial resolution provided by Lunar Orbiter photographs over Earth-based telescopic photographs did not result in definitive examination and elimination of published hypotheses for the formation of sinuous rilles. Topographic data obtained from cartographically controlled Apollo orbital photographs, along with important observations and samples obtained by the astronauts on the lunar surface, did test and exclude several hypotheses. The formulation of a genetic hypothesis, including testable consequences of that hypothesis, is a greater determinant of its ultimate utility to the scientific community than is the image resolution available at any given time.     

The lunar and solar daily geomagnetic variations at Sabhawala and Hyderabad

Summary . The first four harmonics of the lunar, L, and the solar, S, daily geomagnetic variations in the H, D and Z elements are determined for the observatories at Sabhawala and Hyderabad. Also included are similar results for Alibag with the main lunar terms separated into parts of oceanic and ionospheric origin. The data used are the alternate hourly mean values of H, D and Z for locally selected quiet days during the IQSY period, 1964–66. The predominances of the first lunar harmonic of H at Sabhawala and Alibag, and of the second solar harmonic at Sabhawala, are pointed out and discussed. The ratios of the seasonal ranges of both L and S to the respective annual mean ranges are found relatively enhanced in two of the seasons, in comparison with. the average global values for these latitudes for the IGY/C (sunspot maximum) period. This would indicate an inverse relationship of these ratios with solar activity.     

全月球撞击坑形貌特征的识别与多指标表达

全月球撞击坑数据是支撑月表形貌研究以及月球工程探测和科学研究的重要基础性数据,其全面性、精确性是衡量一个国家科技水平甚至综合国力的重要指标。基于嫦娥一号、Clementine多光谱等探月数据,智能化人工提取了全月球106030 个直径大于500 m的撞击坑,在IAU 公布的有名称的撞击坑及其描述形貌特征指标的基础上,建立了描述全月球撞击坑形貌特征的指标体系并获得了所有撞击坑指标的属性值。针对现阶段尚无一套完整的全月球撞击坑数据库的现状,采用面向对象的Geodatabase数据模型组织全月球撞击坑数据,构建了包含位置、大小、形状、坡度、方向、中央峰、辐射纹等7 个大类52 个小类指标的全关系型数据库,其可对撞击坑空间数据和属性数据进行一体化管理,实现了对撞击坑数据的存储、检索、处理和应用,为其他月球科学研究基于数据库进行数据挖掘和应用提供了海量基础数据,为后续月球其他资源数据库的构建提供借鉴。今后将进一步完善更新维护全月球数据库的工作。     

Estimating Climate-Change Impacts on Colorado Plateau Snowpack Using Downscaling Methods

This study develops observed climate-based downscaling transfer functions that are used with general circulation model (GCM) output to assess potential global-change impacts on Upper Colorado Plateau, USA, water resources. Daily automated snow water equivalent stations are used with 700 mb atmospheric circulation to determine empirical transfer functions. Downscaling methodologies using multiple regression and neural networks are evaluated, with the neural network results explaining approximately 70%of the daily snowfall variance. The neural network-based transfer functions are used with the GENESIS GCM to simulate snowfall characteristics in both a 1xCO₂ and a 2xCO₂ climate. While the total precipitation simulated by the 2xCO₂ analysis remains nearly the same as today, less will fall as snow; specifically, snow water equivalence shows significant reduction (except in the Green River Basin) as the snow season is reduced by 58 days on average.     

Estimating Climate-Change Impacts on Colorado Plateau Snowpack Using Downscaling Methods

This study develops observed climate-based downscaling transfer functions that are used with general circulation model (GCM) output to assess potential global-change impacts on Upper Colorado Plateau, USA, water resources. Daily automated snow water equivalent stations are used with 700 mb atmospheric circulation to determine empirical transfer functions. Downscaling methodologies using multiple regression and neural networks are evaluated, with the neural network results explaining approximately 70%of the daily snowfall variance. The neural network-based transfer functions are used with the GENESIS GCM to simulate snowfall characteristics in both a 1xCO₂ and a 2xCO₂ climate. While the total precipitation simulated by the 2xCO₂ analysis remains nearly the same as today, less will fall as snow; specifically, snow water equivalence shows significant reduction (except in the Green River Basin) as the snow season is reduced by 58 days on average.     

Diatoms as indicators of climatic and limnological change in Swedish Lapland: a 100-lake calibration set and its validation for paleoecological reconstructions

This study investigated the distribution of subfossil diatom assemblages in surficial sediments of 100 lakes along steep ecological and climatic gradients in northernmost Sweden (Abisko region, 67.07° N to 68.48° N latitude, 17.67° E to 23.52° E longitude) to develop and cross-validate transfer functions for paleoenvironmental reconstruction. Of 19 environmental variables determined for each site, 15 were included in the statistical analysis. Lake-water pH (8.0%), sedimentary loss-on-ignition (LOI, 5.9% and estimated mean July air temperature (July T, 4.8%) explained the greatest amounts of variation in the distribution of diatom taxa among the 100 lakes. Temperature and pH optima and tolerances were calculated for abundant taxa. Transfer functions, based on WA-PLS (weighted averaging partial least squares), were developed for pH (r² = 0.77, root-mean-square-error of prediction (RMSEP) = 0.19 pH units, maximum bias = 0.31, as assessed by leave-one-out cross-validation) based on 99 lakes and for July T (r² = 0.75, RMSEP = 0.96 °C, max. bias = 1.37 °C) based on the full 100 lake set. We subsequently assessed the ability of the diatom transfer functions to estimate lake-water pH and July T using a form of independent cross-validation. To do this, the 100-lake set was divided in two subsets. An 85-lake training-set (based on single limnological measurements) was used to develop transfer functions with similar performance as those based on the full 100 lakes, and a 15-lake test-set (with 2 years of monthly limnological measurements throughout the ice-free seasons) was used to test the transfer functions developed from the 85-lake training-set. Results from the intra-set cross-validation exercise demonstrated that lake-specific prediction errors (RMSEP) for the 15-lake test-set corresponded closely with the median measured values (pH) and the estimations based on spatial interpolations of data from weather stations (July T). The prediction errors associated with diatom inferences were usually within the range of seasonal and interannual variability. Overall, our results confirm that diatoms can provide reliable and robust estimates of lake-water pH and July T, that WA-PLS is a robust calibration method and that long-term environmental data are needed for further improvement of paleolimnological transfer functions.     

The mapping of induced currents around the Kenya Rift: a comparison of techniques

Summary. Single-station and inter-station transfer functions are derived from data recorded by a magnetometer array in and around the Kenya Rift Valley. Different methods of presentation of the transfer function estimates are compared in terms of their ability to define lateral variations in electrical conductivity. When, as in East Africa, the conductivity structure is complex and three-dimensional, by far the most useful method of presentation is to use the transfer functions to simulate the anomalous internal fields associated with regional current flow at a particular azimuth. The use of inter-station rather than single-station transfer functions is almost essential where the amplitudes of anomalous horizontal fields are of the same size or greater than the normal fields. Horizontal field transfer functions prove to be just as useful as those usually calculated for the vertical component, and provide strong additional constraints on the internal current system.
Maps of simulated vertical and horizontal fields of internal origin indicate the importance of current channelling around the Rift Valley. A conductor just to the east of Nairobi apparently funnels regionally induced currents into two conductors associated with the Rift and dome; one at shallow depths beneath the Rift floor, and a deeper body to the east.     

Does a one point sample adequately characterize the lake environment for paleoenvironmental calibration studies?

A major goal of paleolimnological studies is the quantification of past environmental conditions. This is accomplished by computing transfer functions relating organism assemblages to environmental factors. The environmental data are typically comprised of a point sample of water chemistry and other environmental parameters that are collected at the same time as a surface sediment sample. We explore whether the year of sampling of the environmental variables affects the parameterization of organism-environment relations, in particular chironomids, ostracodes and diatoms. Canonical correspondence analyses revealed that the year of sampling is of secondary importance when relating the organism assemblages to environmental variables, but only with the major explanatory variables. A chironomid-inferred bottom water temperature partial least squares transfer function revealed similar performance statistics between the years. Taxon optima and tolerances were computed for both years using weighted averaging, and the results are comparable. A paired t-test computed on the proxy-inferred bottom water temperature values indicated that the results between the 2 years are not statistically different. The results of this study provide guarded optimism that the methodology of estimating transfer functions as currently applied is not entirely determined by the particular year when the data were collected, although more case studies are needed.     

月球陨石: 月球的物质组成及其演化历史的见证

月球陨石是遭受小行星物质撞击溅飞出来的月球岩石样品,是研究月球物质成分和演化历史的重要对象。自1979年发现和确认了第一块月球陨石（ALHA 81005）之后,至今已收集到136块月球陨石样品。虽然Apollo计划和Luna计划回收了382kg月球样品,但由于飞船登陆采样位置有限,月球陨石对了解月球的物质组成和成因演化提供了重要补充。除了少量具有结晶结构的岩石类型以外,大部分月球陨石为碎屑岩,这些碎屑岩主要有三类：高地斜长角砾岩、月海玄武质角砾岩、和高地斜长质-月海玄武质混合角砾岩。根据岩性分析,尤其是岩屑,月球陨石中存在斜长岩、玄武岩、辉长岩、橄长岩、苏长岩、KREEP岩。在月球陨石中逐渐发现了不少克里普岩组分,其中SaU169中VHK的富KREEP成分可能代表了月球中的原始富KREEP岩浆源,这为探索月球中KREEP成因提供重要信息。据研究,现已发现了6对溅射成对月球陨石,同时,发现了9个可能的月球陨石来源区域。后成合晶现象的发现对月球表面冲击变质作用研究具有重要的意义。此外,月球陨石同位素年龄和稀有气体成分研究不但获得了月球岩石结晶和月壳形成过程,同时获得了月球表面的冲击变质历史。     

Some features of the seasonal variation of geomagnetic lunar tides

Summary. Mean hourly values have been analysed month by month for a number of stations for which long runs of data are available. It is found that there is an annual variation in the M₂ lunar tide, there being a global enhancement of the tide around January. There is also some evidence from the phase changes with latitude that, near the solstices, the lunar current system consists not of pairs of vortices, one in each hemisphere, but of single vortices with foci in the summer hemisphere.     

A comparison of time and frequency domain geomagnetic sounding

Summary. A three-site geomagnetic data set from the Borders region of southern Scotland is used to examine the empirical relationships established by differential geomagnetic sounding experiments. A time domain analysis of such relationships reveals time domain transfer functions which appear to be almost independent of time. A frequency domain analysis is then used to illustrate both a significant phase rotation and a significant dependence on period of the equivalent frequency domain response functions. The formalism of conventional geomagnetic sounding is re-examined. It is found that difference fields are not required to establish the appropriate horizontal field relationships.     

Paleohydrology inferred from diatoms in northern latitude regions

Several recent studies have successfully applied diatom-based paleolimnological techniques to infer past hydrological changes in arctic and subarctic regions. For example, we summarize arctic studies that attempt to determine changes in peat water content, flood frequency, river discharge, effective moisture and ice cover in northern regions. Some of the investigations are still in preliminary stages, but represent innovative approaches to study arctic and subarctic paleohydrology. New data demonstrate that lake depth, which may be related to changing hydrological conditions, is a significant variable influencing the distributions of diatom taxa in lake surface sediment calibration sets from Wood Buffalo National Park (WBNP), on the border of Alberta and the Northwest Territories, Canada, and from Fennoscandia (mainly northwest Finland). Weighted averaging regression and calibration methods were used to develop quantitative inference models for lake depth using diatom assemblages preserved in surface sediments. The predictive abilities of the transfer functions were relatively high (for WBNP r² = 0.70 and RMSE = 2.6 m, and for Fennoscandia r² = 0.88 and RMSE = 1.8 m). However, evaluating the transfer functions using jack-knifing procedures indicated lower predictive abilities, possibly reflecting the relatively small sample size and/or short gradients used in these calibration sets. Such transfer functions can be used to track overall trends in lake levels, and provide an objective assessment as to directions of changing lake levels. Any interpretations of inferred lake levels, especially those related to climate change, must be made cautiously and must include some understanding of the local, present-day hydrological system.     

Modelling diatom responses to climate induced fluctuations in the moisture balance in continental Antarctic lakes

The water chemistry of lake systems on the edge of the Antarctic continent responds quickly to changes in the moisture balance. This is expressed as increasing salinity and decreasing lake water level during dry periods, and the opposite during wet periods. The diatom composition of the lakes also changes with these fluctuations in salinity and lake water depth. This is important, as their siliceous remains become incorporated into lake sediments and can provide long-term records of past salinity using transfer functions. In order to develop transfer functions, diatoms and water chemistry data were inter-calibrated from five different East Antarctic oases, namely the Larsemann Hills, the Bølingen Islands, the Vestfold Hills, the Rauer Islands and the Windmill Islands. Results indicate that salinity is the most important environmental variable explaining the variance in the diatom flora in East Antarctic lakes. In oligo- saline lakes the variance is mainly explained by lake water depth. This dataset was used to construct a weighted averaging transfer function for salinity in order to infer historical changes in the moisture balance. This model has a jack-knifed r² of 0.83 and a RMSEP of 0.31. The disadvantage of this transfer function is that salinity changes in oligo-saline lakes are reconstructed inaccurately due to the edge effect and due to the low species turnover along the salinity gradient at its lower end. In order to infer changes in the moisture balance in these lakes, a second transfer function using weighted averaging partial least squares (with two components) for depth was constructed. This model has a jack-knifed r² of 0.76 and a RMSEP of 0.22. Both transfer functions can be used to infer climate driven changes in the moisture balance in lake sediment cores from oligo-, hypo-, meso- and hyper-saline lakes in East Antarctic oases between 102–75°E. The transfer function for lake water depth is promising to track trends in the moisture balance of small freshwater lakes, where changes in shallow and deep-water sediments are readily reflected in changing diatom composition.