Soil erosion and its response to the changes of precipitation and vegetation cover on the Loess Plateau

Soil erosion is a major threat to our terrestrial ecosystems and an important global environmental problem. The Loess Plateau in China is one of the regions that suffered more severe soil erosion and undergoing climate warming and drying in the past decades. The vegetation restoration named Grain-to-Green Program has now been operating for more than 10 years. It is necessary to assess the variation of soil erosion and the response of precipita- tion and vegetation restoration to soil erosion on the Loess Plateau. In the study, the Revised Universal Soil Loss Equation （RUSLE） was applied to evaluate annual soil loss caused by water erosion. The results showed as follows. The soil erosion on the Loess Plateau between 2000 and 2010 averaged for 15.2 t hm-2 a 1 and was characterized as light for the value less than 25 t hm-2 a-1. The severe soil erosion higher than 25 t hm-2 a-~ was mainly distributed in the gully and hilly regions in the central, southwestern, and some scattered areas of earth-rocky mountainous areas on the Loess Plateau. The soil erosion on the Loess Plateau showed a deceasing trend in recent decade and reduced more at rates more than 1 t hm 2 a 1 in the areas suffering severe soil loss. Benefited from the improved vegetation cover and ecological construction, the soil erosion on the Loess Plateau was significantly declined, es- pecially in the east of Yulin, most parts of Yah＇an prefectures in Shaanxi Province, and the west of Luliang and Linfen prefectures in Shanxi Province in the hilly and gully regions. The variation of vegetation cover responding to soil erosion in these areas showed the relatively higher contribution than the precipitation. However, most areas in Qingyang and Dingxi pre- fectures in Gansu Province and Guyuan in Ningxia Hui Autonomous Region were predomi- nantly related to precipitation.     

丝阵Z箍缩早期消融等离子体动力学的二维数值模拟研究

采用理想磁流体力学模型,给出合理的二维(r, θ)质量注入边界条件,对丝阵Z箍缩早期消融等离子体的动力学过程进行了二维(r, θ)数值模拟研究,得到消融等离子体各参量以及磁场的二维时空分布.模拟结果表明,消融等离子体的运动包括四个主要阶段:首先向轴漂移,然后在轴线处滞止并形成先驱等离子体柱,随后先驱等离子体柱被压缩,最后缓慢膨胀.计算了不同丝阵半径和丝间距情况下消融等离子体到轴速度以及消融质量占丝阵总质量的份额,它们的变化规律与实验结果基本符合.通过     

An Experimenting Field Approach for the Numerical Solution of Multiphase Flow in Porous Media

In this work, we apply the experimenting pressure field technique to the problem of the flow of two or more immiscible phases in porous media. In this technique, a set of predefined pressure fields are introduced to the governing partial differential equations. This implies that the velocity vector field and the divergence at each cell of the solution mesh can be determined. However, since none of these fields is the true pressure field entailed by the boundary conditions and/or the source terms, the divergence at each cell will not be the correct one. Rather the residue which is the difference between the true divergence and the calculated one is obtained. These fields are designed such that these residuals are used to construct the matrix of coefficients of the pressure equation and the right‐hand side. The experimenting pressure fields are generated in the solver routine and are fed to the different routines, which may be called physics routines, which return to the solver the elements of the matrix of coefficients. Therefore, this methodology separates the solver routines from the physics routines and therefore results in simpler, easy to construct, maintain, and update algorithms.     

穆珠朗玛峰地区土壤中稀土元素的含量和分布

本文论述了珠穆朗玛峯地区土壤中稀土元素的含量,以及它们在土壤中的分布模式,并发现土壤中稀土元素的含量水平在很大程度上受土壤母质的制约。     

Garnet-bearing tonalitic porphyry from East Kunlun,Northeast Tibetan Plateau: implications for adakite and magmas from the MASH Zone

A garnet-bearing tonalitic porphyry from the Achiq Kol area, northeast Tibetan Plateau has been dated by SHRIMP U-Pb zircon techniques and gives a Late Triassic age of 213 ± 3 Ma. The porphyry contains phenocrysts of Ca-rich, Mn-poor garnet (CaO > 5 wt%; MnO < 3 wt%), Al-rich hornblende (Al₂O₃ ~ 15.9 wt%), plagioclase and quartz, and pressure estimates for hornblende enclosing the garnet phenocrysts yield values of 8–10 kbar, indicating a minimum pressure for the garnet. The rock has SiO₂ of 60–63 wt%, low MgO (<2.0 wt%), K₂O (<1.3 wt%), but high Al₂O₃ (>17 wt%) contents, and is metaluminous to slightly peraluminous (ACNK = 0.89–1.05). The rock samples are enriched in LILE and LREE but depleted in Nb and Ti, showing typical features of subduction-related magmas. The relatively high Sr/Y (~38) ratios and low HREE (Yb < 0.8 ppm) contents suggest that garnet is a residual phase, while suppressed crystallization of plagioclase and lack of negative Eu anomalies indicate a high water fugacity in the magma. Nd–Sr isotope compositions of the rock (εNd_T = −1.38 to −2.33; ⁸⁷Sr/⁸⁶Sr_i = 0.7065–0.7067) suggest that both mantle- and crust-derived materials were involved in the petrogenesis, which is consistent with the reverse compositional zoning of plagioclase, interpreted to indicate magma mixing. Both garnet phenocrysts and their ilmenite inclusions contain low MgO contents which, in combination with the oxygen isotope composition of garnet separates (+6.23‰), suggests that these minerals formed in a lower crust-derived felsic melt probably in the MASH zone. Although the rock samples are similar to adakitic rocks in many aspects, their moderate Sr contents (<260 ppm) and La/Yb ratios (mostly 16–21) are significantly lower than those of adakitic rocks. Because of high partition coefficients for Sr and LREE, fractionation of apatite at an early stage in the evolution of the magma may have effectively decreased both Sr and LREE in the residual melt. It is suggested that extensive crystallization of apatite as an early phase may prevent some arc magmas from evolving into adakitic rocks even under high water fugacity.     

2015年2月21日内蒙古风雪沙尘天气特征

利用高空、地面常规观测资料和NCEP再分析资料,针对2015年2月21日内蒙古中部阴山北麓地区暴风雪转强沙尘暴天气,进行了对比分析。结果表明:该次天气过程受强冷空气影响,由高空蒙古冷涡迅速发展加强产生。地面冷锋形成降雪,锋区风力较大,形成了暴风雪,随后受副冷锋影响,风力明显增强,产生沙尘暴天气。暴风雪与沙尘暴差异表现在:(1)冷涡、冷锋是主要影响系统,但天气系统影响部位不同,暴风雪多发生在锋区及暖区中,沙尘暴多发生在锋区后部的强冷平流控制区中。(2)水汽条件差异明显,暴风雪相对湿度需要大于70%,沙尘暴相对湿度小于30%。(3)大气层结需求不同,暴风雪对不稳定层结要求不高,沙尘暴对不稳定层结和深厚的混合层有较高的要求。(4)暴风雪发生时气温骤降,沙尘暴发生时温度缓慢持续下降。     

冬季西北太平洋海表温度异常对太平洋风暴轴影响的数值试验

采用Ｔ２１Ｌ５大气环流模式，详细探讨了冬季西北太平洋海表温度异常对太平洋风暴轴的影响。结果表明：冬季西北太平洋暖海表温度异常能显著增强异常区北侧及下游地区的斜压性，天气尺度扰动方差、扰动动能以及涡动热量通量等也在此风暴轴入口区得到增强，由此揭示出外热源强迫对太平洋风暴轴的维持和发展起重要作用。     

Influence of air-sea interaction on SSTA in different spacial scales

-In this paper, the factors for SSTA development in finite sea area of low latitudes are discussed with simpler linearized equations, According to the coupling conditions at the interface of atmosphere and ocean, we studied the horizontal scale relations of air-sea coupled system satisfying the dynamical and thermodynamical requirements, From the fluctuation viewpoint, the relation of horizontal scales and wave numbers are presented for a linear atmosphere-ocean coupled system with the same time scales. At last part of the paper, the state of fluctuations is examined for different sea scales under certain given atmospheric scale with a simpler two-layer coupled model, and some significant results obtained.     

中国人口老龄化水平测度与空间关联研究

人口老龄化水平是关系到我国经济社会和谐发展的重要问题.基于国际通用标准,采用多项指标对人口老龄化水平进行综合测度,在此基础上,采用空间自相关分析方法,研究人口老龄化水平的空间关联规律.结果表明:自1997年以来,我国人口老龄化水平逐年升高,各省份差异明显,且差异有逐渐增大的趋势;人口老龄化水平的全局空间依赖性并不高,但是局部空间集聚规律却很明显,表现为人口老龄化水平高—高分布区由东部向中西部集中,人口老龄化水平低—低分布区向西南及东北北部移动,而高—低分布与低—高分布的地区则向我国东南部及西部部分地区扩散.     

利用湖州台形变观测资料检测地震激发的地球球形自由振荡

By using the digital observations of the pendulum tiltmeter, water tube tiltmeter,extensometer and volumetric strainmeter at Huzhou station and with the power spectrum density estimation method,we acquired the_0S_5-_0S_50 fundamental sphere free oscillations caused by the Japan earthquake on March 11,2011,then compared it with the PREM model. The relative errors are mostly bigger than 1.2‰. The extensometer and volume strainmeter can clearly detect _0S_2,_0S_3and_0S_4,which are closely related to the deep structure and earth's interior.