Satellite estimates and subpixel variability of rainfall in a semi-arid grassland

卫星估雨精度的不确定性受到当地降雨类型和像元内降雨非均匀性影响,而结合这两个关键因素开展半干旱草原卫星估雨的研究有限.2009年夏,我们在中国锡林郭勒半干旱草原用多部微雨雷达和雨量计构建了9 km卫星像元降雨观测网,观测了像元内降雨非均匀性(空间变异系数CV),并评估了卫星估雨精度.结果表明:(1)CV值受像元内平均降雨量,降雨类型,降雨云面积及移向等影响,如高Cv值的降雨过程大多为平均降雨量小,对流性降雨过程,降雨云边缘像元CV值较高;(2)TRMM 3B42V7卫星估雨产品适用性较好,CMORPH和PERSIANN次之,但TRMM 3B42V7易在半干旱草原湖泊处高估降雨.     

Beidou satellite maneuver thrust force estimation for precise orbit determination

Beidou satellites, especially geostationary earth orbit (GEO) and inclined geosynchronous orbit (IGSO) satellites, need to be frequently maneuvered to keep them in position due to various perturbations. The satellite ephemerides are not available during such maneuver periods. Precise estimation of thrust forces acting on satellites would provide continuous ephemerides during maneuver periods and could significantly improve orbit accuracy immediately after the maneuver. This would increase satellite usability for both real-time and post-processing applications. Using 1 year of observations from the Multi-GNSS Experiment network (MGEX), we estimate the precise maneuver periods for all Beidou satellites and the thrust forces. On average, GEO and IGSO satellites in the Beidou constellation are maneuvered 12 and 2 times, respectively, each year. For GEO satellites, the maneuvers are mainly in-plane, while out-of-plane maneuvers are observed for IGSO satellites and a small number of GEO satellites. In most cases, the Beidou satellite maneuver periods last 15–25 min, but can be as much as 2 h for the few out-of-plane maneuvers of GEO satellites. The thrust forces acting on Beidou satellites are normally in the order of 0.1–0.7 mm/s². This can cause changes in velocity of GEO/IGSO satellites in the order of several decimeters per second. In the extreme cases of GEO out-of-plane maneuvers, very large cross-track velocity changes are observed, namely 28 m/s, induced by 5.4 mm/s² thrust forces. Also, we demonstrate that by applying the estimated thrust forces in orbit integration, the orbit errors can be estimated at decimeter level in along- and cross-track directions during normal maneuver periods, and 1–2 m in all the orbital directions for the enormous GEO out-of-plane maneuver.     

基于像元二分模型的森林郁闭度遥感估算

实现森林郁闭度的高精度估测,对于森林资源的监测与管理具有非常重要的意义。本文以小兴安岭带岭林业实验管理局为研究区,基于植被指数的像元二分模型进行了森林郁闭度的遥感反演,结果表明:模型的预估精度达到89.01%,决定系数R2达到0.859,RMSE为0.039,模型的一致性较好,可以实现大区域范围森林郁闭度的监测,满足了林业经营管理的需求。     

基于独立成分分析的高光谱图像降维及分割

高光谱图像的高维数给图像的进一步处理带来了困难,为了解决这一问题,本文提出了一种基于独立成分分析的高光谱图像降维分割方法。首先,利用波段子空间划分和标准差对高光谱图像预处理,选择部分波段的高光谱图像作为实验对象;然后利用基于负熵的快速不动点算法对实验数据解混,再根据平均绝对权重系数对波段排序并选取;最后使用模糊C均值聚类算法对降维后的图像进行分割。实验结果表明,该方法能够有效实现高光谱图像降维,并获得较好的分割结果。     

基于模糊集理论的彩色图像融合分割

基于二维直方图的图像分割方法综合考虑目标像素灰度值及其邻域的平均灰度,通过确定阈值进行图像分割,本质属于硬决策方法。由于位于阈值附近的像素在分割时具有不确定性,硬决策法容易产生错误分割。因此,本文基于模糊集理论提出一种融合分割方法,利用隶属度函数对基于二维直方图分割中存在的不确定性建模,并通过模糊推理综合利用彩色图像各颜色通道的信息。实验结果表明,本文所提方法相较传统的阈值方法有更好的分割效果。     

湘江下游河床沉积物元素地球化学背景值估算

本研究对湘江下游河床沉积物进行了元素地球化学分析,在认识沉积物元素地球化学特征、甄别人为源与自然源重金属的基础上,估算了沉积物的元素地球化学背景值。结果表明:SiO2、TiO2、Al2O3、Fe2O3、K2O等主量元素及V、Co、Cr、Ba、Sc、U、Sr、Ga、Ge、Rb、Nb、Y、REE等微量元素在沉积物中含量变化相对稳定(Cv<0.2),分布相对均匀,且富集不明显(EF<2.0,Sr明显亏损)。而MnO、MgO、CaO、Na2O、P2O5等主量元素,及Cd、Mn、Cu、Pb、Zn等重金属在沉积物中含量变化大(Cv>0.25),分布极不均匀,且沉积物中重金属明显富集(EF>2.0)。主成分及Pearson线性相关性分析显示,沉积物中不明显富集的微量元素主要赋存于难溶硅酸盐矿物相中,为自然源元素。而沉积物中显著富集的重金属主要赋存于铁—锰氧化物等矿物相中,为有人为源叠加的元素。故针对不同来源特征的元素用不同的方法进行了背景值计算,求得沉积物中47个元素的背景值。再利用元素比值等方法对所得背景值进行检验。结果表明,本文得到的湘江沉积物元素背景值合理,可用作流域沉积物重金属污染评价参考。     

高海拔多年冻土区路基工程行为对低温多年冻土长期影响的监测研究

青藏铁路路基创造性采用了主动冷却路基的设计理念修建而成,目前铁路已经安全运营超过10年。青藏铁路路基修筑在多年冻土之上,路基下部冻土温度变化是衡量路基是否稳定的关键因素。基于长期（2008—2019年）地温观测资料,对昆仑山垭口南坡青藏铁路K980+000低温多年冻土区块石路基坡脚至坡脚外30 m范围内的冻土上限变化、年际地温变化、季节性地温变化进行分析,研究了路基工程行为对低温多年冻土的长期影响机制。结果表明：冻土地温不断升高,冻土上限逐年下移;与天然孔比较,路基坡脚处地温增温幅度反而较小,主要可能受块石路基冷却效应的影响;冷季与暖季呈现出不对称的增温趋势。冻土路基普遍增温的趋势仍然存在,出于对多年冻土的保护与保证工程稳定性的考虑,应尽量采用冷却路基的思想修建路基。同时,应加强对路基的监测,分析长期增温过程后路基稳定性变化,并对路基下部冻土的变化做出定量研究。     

西秦岭中—晚三叠世构造属性:来自将其那梁侵入杂岩体的年代学及地球化学证据

西秦岭造山带印支早期的构造环境仍存在较多争论,选择西秦岭将其那梁杂岩体进行详细的年代学、岩石学及地球化学分析,以期对该科学问题进行深入探讨。将其那梁杂岩体由石英闪长岩和花岗斑岩组成,石英闪长岩LA-ICP-MS锆石U-Pb年龄为(240.0±1.5) Ma,形成时代为中三叠世,属于早印支期。将其那梁杂岩体具有富钾(K₂O=3.09%~3.54%)、富碱(K₂O+Na₂O=6.44%~7.20%)和过铝质(A/CNK=1.05~1.56)特征,Mg^#值(54~67)较高,属于过铝质高钾钙碱性岩类。将其那梁杂岩体石英闪长岩和花岗斑岩具有相似的微量元素及稀土元素组成,轻重稀土元素分馏明显(LREE/HREE=8.19~14.63),呈右倾特征,显示无或弱负Eu异常(δEu=0.87~1.03),具有亏损Nb、Ta、Zr等高场强元素和富集Ba、Rb、Sr等大离子亲石元素的地球化学特征。岩石地球化学特征指示,将其那梁杂岩体主要源于下地壳高钾变基性岩的部分熔融,且有幔源物质参与其中。结合区域地质背景,认为将其那梁杂岩体形成于火山弧构造环境,可能与中—晚三叠世阿尼玛卿—勉略洋向北俯冲有关,反映了中—晚三叠世西秦岭地区具有活动大陆边缘的属性。     

东昆仑地区驼路沟钴(金)矿床硅质钠长岩锆石U-Pb定年及Hf同位素特征研究

东昆仑驼路沟钴(金)矿床是青海省发现的首个独立大型喷流沉积型矿床,说明容矿围岩为一套海相火山-沉积岩系。本文在野外调查的基础上,对该矿区短沟矿段YM1坑口的硅质钠长岩进行岩石学、LA-ICP-MS锆石UPb年代学及Hf同位素分析。结果表明,区内钠长岩的形成年龄为(457.3±4.6)Ma,佐证了该矿区喷流作用成岩与成矿的同时性;另外获得9.20~1.10 Ga和2.40~2.50 Ga的2个年龄集中区,说明了研究区基底演化和源区物质的复杂性。Hf同位素显示为两个集中区,其中年龄峰值422~459 Ma的锆石获得εHf(t)值为-0.61~12.72,表明锆石母岩主要为新生的地壳物质,指示硅质钠长岩的形成与海底火山喷发作用密切相关;另外0.85~1.10 Ga的锆石εHf(t)值为-15.09~-0.07,其锆石母岩中主要为再造的古老地壳,表明该区基底源区物质的复杂性。通过区域对比分析,认为驼路沟矿区含矿火山-沉积岩系形成时代与钠长岩年龄、成矿年龄非常接近,喷流沉积时代应为晚奥陶世。     

Heat Flow Distribution and Thermal Mechanism Analysis of the Gonghe Basin based on Gravity and Magnetic Methods

Geothermal resource is indispensable as a clean, renewable, stable and cheap resource. Nowadays in China, the Gonghe Basin, located in northeastern Qinghai Province, has been thought to be a promising geothermal area. To explore geothermal energy potential in and around the Gonghe Basin, geophysical means including magnetic and gravity methods were used to plot distribution. Firstly, we inversed Moho depth and Curie point depth in and around the basin using gravity and magnetic data, respectively, through an improved Parker–Oldenburg algorithm. Secondly, seven different thermal models were established, considering radiogenic heat, basement depth, anomalous heat source and simulated corresponding temperature field and heat flow. These were analyzed numerically and we found the high heat flow in the Gonghe Basin co-acted with radiogenic heat, an anomalous heat source and conductive heat. The distribution of seismic activities indicates that the Langshan–Wuwei–Gonghe Fault might have provided channels for transporting heat effectively.