The Data Depth-weight-kernel Estimation of the Model Error of Satellite Orbit Determination

It is an objective fact that there exists error in the satellite dynamic model and it will be transferred to satellite orbit determination algorithm, forming a part of the connotative model error. Mixed with the systematic error and random error of the measurements, they form the unitive model error and badly restrict the precision of the orbit determination. We deduce in detail the equations of orbit improvement for a system with dynamic model error, construct the parametric model for the explicit part of the model and nonparametric model for the error that can not be explicitly described. We also construct the partially linear orbit determination model, estimate and fit the model error using a two-stage estimation and a kernel function estimation, and finally make the corresponding compensation in the orbit determination. Beginning from the data depth theory, a data depth weight kernel estimator for model error is proposed for the sake of promoting the steadiness of model error estimation. Simulation experiments of SBSS are performed. The results show clearly that the model error is one of the most important effects that will influence the precision of the orbit determination. The kernel function method can effectively estimate the model error, with the window width as a major restrict parameter. A data depth-weight-kernel estimation, however, can improve largely the robustness of the kernel function and therefore improve the precision of orbit determination.     

西方政治生态学的地理学研究进展与启示

随着全球生态环境问题的日益凸显,政治生态学以关注造成环境问题的政治因素为研究内核,成为不同学科共同探索的研究领域。地理学以人地关系为立足点,深化政治生态学研究的空间性和政治性。论文首先通过对西方政治生态学理论脉络进行梳理,发现政治生态学根源于早期环境批判思想、西方马克思主义、后结构主义以及后人类主义理论,并与地理学的发展相辅相成。其次,对近30年西方地理学与政治生态学的相关研究成果进行分析发现,现有的研究议题主要聚焦于生态经济与绿色发展、生态治理与环境保育、生态身份与微观政治及生态客体与能动性4个方面。在此基础上,论文总结了相关研究对中国地理学进行政治生态学研究的借鉴意义,并进一步提出立足中国本土进行政治生态学研究未来需要关注的方向。     

Development of gullies and sediment production in the black soil region of northeastern China

Gully erosion is an important environmental hazard in the black soil region of northeastern China. It is a primary sediment source in the region which needs appropriate soil conservation practices. Gully incision in rolling hills typical of this region was monitored using real-time kinematic GPS to assess the rates of gully development and the resultant sediment production. From 2002 to 2005, gully heads in the study area retreated between 15.4 and 33.5 m, giving an average retreat rate of 8.4 m yr^− 1. Field measurements showed that total sediment production due to gully erosion during the three years ranged between 257 and 1854 m³ yr^− 1, which is equivalent to 326 to 2355 t yr^− 1, with gully-head retreat accounting for 0 to 21.7% (4.4% in average). The sediment delivery ratio was especially high during the summer rainy season (56% in average). Sediment production by ephemeral gullies and permanent gullies was 1.5 times greater than that from surface erosion. Gully heads retreated faster in the spring freeze–thaw period than in the summer. The stage of gully development could be identified based on short-term changes in the gully erosion rate.     

人类活动对塔里木河年径流影响量的估算

塔里木河流域与环境的研究，一直是近年来新疆环境演化和可持续发展研究的热点问题。大规模的区域开发活动对该流域生态环境产生了根本性的影响，区域整体生态环境趋于恶化。本文通过对年径流量累积曲线和年径流量的相关分析，估算出人类活动对塔里木河各河段的年径流量变化及其对生态环境造成的影响。     

喀斯特地区地表温度空间降尺度方法初探

喀斯特地区地形起伏大,常规的降尺度方法及所选择的因子对其不适用。该文根据喀斯特地区的特点,选取反射率、遥感指数及高程因子为尺度因子,通过随机森林模型建立MODIS第31、32波段辐射亮度数据和尺度因子之间的非线性关系,构建适合喀斯特地区的随机森林(Karst Random Forest,KRF)模型,成功将空间分辨率为1 km的热红外辐射亮度降至100 m,最后利用劈窗算法反演得到空间分辨率为100 m的地表温度。将KRF方法与仅考虑常规因子的多因子随机森林回归模型(MTVRF)和热锐化算法(TsHARP)对比,结果表明:1)在不同高差的喀斯特地区,KRF方法可较大程度提高地表温度降尺度精度,均方根误差(RMSE)在遵义市西北部和贵阳市以南地区分别为2.46 K和1.45 K,较MTVRF模型分别降低了0.1419 K和0.2928 K,较TsHARP算法分别降低了0.6204 K和0.6953 K,且在地形起伏度较低的喀斯特山区城市(贵阳市以南)表现更好;2)在喀斯特地区不同地类上,KRF方法效果也较好,其中植被区域最优,RMSE为1.41 K,破碎的裸土区域RMSE为1.84 K。研究显示,考虑特殊尺度因子的KRF方法可提高喀斯特地区地表温度的降尺度精度,为该地区以地表温度为基础的研究提供更精细可靠的地表温度产品。     

利用决策级融合进行遥感影像分类

提出了一种基于决策级融合的遥感影像分类方法。该方法对遥感影像特征以最大似然分类器进行预分类,应用Adaboost算法将分类的结果进行决策级融合,实现影像的分类。实验结果表明,该方法的分类精度较传统分类方法有明显的提高。     

西藏朋曲流域不同地貌部位流动沙丘粒度特征

沙丘粒度特征不仅能反映沙丘沙物质的来源与动力,也可以体现地形对风沙流运移的改变。对西藏朋曲流域不同地貌部位流动沙丘表层沉积物的粒度特征进行分析。结果表明：（1）朋曲流域流动沙丘表层沉积物粒度组分以中沙（46.51%）和细沙（40.52%）为主,粗沙（5.87%）与极细沙（5.87%）次之,黏土（0.37%）与粉沙（0.85%）含量最低。流动沙丘表层沉积物平均粒径1.41—2.32 Φ,分选系数0.45—0.79 Φ,偏度0.01—0.24,峰度0.98—1.80。（2）从河漫滩到河流阶地到山坡,流动沙丘粒度逐渐变小,频率分布曲线逐渐变高变窄,粒径越来越集中,沿主导风向自西南向东北概率累积曲线斜率逐渐增大,分选性逐渐变好。（3）河漫滩至河流高级阶地流动沙丘表层沉积物随海拔升高粒径变小,坡麓至坡顶随海拔升高粒径变大,分选却变好,表明山坡上沙丘与阶地上沙丘的沙物质来自于不同河段的河床或河漫滩。     

区域生态承载力预警评估方法及案例研究

本文针对国家资源环境承载能力监测预警评估中生态承载力评估的需求,探讨了生态承载力及预警的定义与内涵,从预警角度提出区域生态承载力评价的内容与方法,并以京津冀地区为例开展了案例研究。主要结论为：生态承载力是指生态系统提供服务功能、预防生态问题、保障区域生态安全的能力。生态承载力预警评估的实质是评估人类活动是否及在多大程度上影响生态系统在水源涵养、水土保持、防风固沙等主要服务功能的提供,是否产生了生态环境问题,是否影响到区域的生态安全。其评价流程主要包括：区域生态承载力评价指标选取及评价方法和阈值的确定、生态承载力预警状况及变化趋势分析、成因解析等内容。本文提出的生态承载力预警评价的方法及案例,可为全国及区域生态承载力的评估提供基础。     

Validation of the effects of temperature simulated by multi-model ensemble and prediction of mean temperature changes for the next three decades in China

Using series of daily average temperature observations over the period of 1961–1999 of 701 meteorological stations in China, and simulated results of 20 global climate models (such as BCCR_BCM2.0, CGCM3T47) during the same period as the observation, we validate and analyze the simulated results of the models by using three factor statistical method, achieve the results of multi- model ensemble, test and verify the results of multi-model ensemble by using the observation data during the period of 1991–1999. Finally, we analyze changes of the annual mean temperature result of multi-mode ensemble prediction for the period of 2011–2040 under the emission scenarios A2, A1B and B1. Analyzed results show that: (1) Global climate models can reproduce Chinese regional spatial distribution of annual mean temperature, especially in low latitudes and eastern China. (2) With the factor of the trend of annual mean temperature changes in reference period, there is an obvious bias between the model and the observation. (3) Testing the result of multi-model ensemble during the period of 1991–1999, we can simulate the trend of temperature increase. Compared to observation, the result of different weighing multi-model ensemble prediction is better than the same weighing ensemble. (4) For the period of 2011–2040, the growth of the annual mean temperature in China, which results from multi-mode ensemble prediction, is above 1 °C. In the spatial distribution of annual mean temperature, under the emission scenarios of A2, A1B and B1, the trend of growth in South China region is the smallest, the increment is less than or equals to 0.8 °C; the trends in the northwestern region and south of the Qinghai-Tibet Plateau are the largest, the increment is more than 1 °C.     

一种新的水面蒸发计算方法

本文应用相似理论,提出一个考虑自由对流和强迫对流相结合的水面蒸发模式,并用实测资料对蒸发模式作了检验。