Tidally-induced melting events as the origin of south-pole activity on Enceladus

The intense activity at the south pole of Enceladus hints at an internal water reservoir. However, there is no direct evidence of liquid water at present and its long-term stability in the interior remains problematic. By modeling heat production and transfer in the ice shell in a spherical geometry, we show that tidal heating naturally leads to a concentration of convective hot upwellings in the south polar region, favoring the preservation of liquid water at depth. We show that large volumes of water are produced within the ice shell at the south pole during periods of elevated orbital eccentricity (3–5 times the present-day value). Strong lateral variations in the melt production and crystallization rates result in stress concentration in the south polar region, thus providing an explanation for the tectonic activity observed today. We predict that an internal ocean may be sustained over the long term as the consequence of repeated periods with elevated orbital eccentricity, leading to episodic melting and resurfacing events.     

Study on daily surface evapotranspiration with SEBS in Tibet Autonomous Region简

The estimation of surface evapotranspiration （ET） with satellite dataset is one of the main subjects in the understanding of climate change, disaster monitoring and the circulation of water vapor and energy in Tibet Autonomous Region （TAR）. This research selects satellite images on January 11, April 6, July 31 and October 19 in 2010 as the representative of winter, spring, summer and autumn respectively, estimates the distribution of daily surface ET based on the surface energy balance system （SEBS） along with potential evapotranspiration （PET） and ET derived from Penman-Monteith （P-M） method. The results are obtained as follows. （1） The seasonal distribution of ET and PET basically decreases from the southeast part to the northwest part of TAR. Although ET and PET have similar spatial distributions, there are still some differences to estimate the extreme values especially the maximum value in the middle and southeastern parts of TAR. No matter what kind of methods we adopted, the maximum value of ET and PET always appears in summer, followed by autumn or spring while that in winter is the smallest. （2） In order to better understand the accuracy of SEBS model in the estimation of ET, we compared the ET from SEBS and the ET obtained from P-M method. Results show that the ET from SEBS could estimates the variation trend of actual ET, but it slightly underestimates or overestimates the value of ET as a whole, especially for those areas with thick forest. （3） The spatial distribution of Normalized Difference Vegetation Index （NDVI） exhibits a decreasing trend from the southeast part to the northwest part of TAR which displays remarkable consistency of distributions between ET and vegetation index. ET is well positively related to NDVI, minimum, mean, maximum air temperature and sunshine duration in different seasons while negatively related to precipitation, relative humidity and wind speed in summer.     

Evolution of the Archean crust in Finland

An Archean age for Finnish rocks in the range 2500–3000 Ma has been determined north of the NW-striking Ladoga—Raahe shear belt. The Archean may be divided into two main units: the granitoid association and the greenstone-belt association. The complex is characterized by stockwork tectonics. The granitoid association forms the basement infrastructure and the greenston-belt association forms the suprastructure which is present in synforms between granitoid diapirs. The infrastructure has been subjected to ultrametamorphism, and the second and third generation palingenetic magmas so formed have intruded the suprastructure. The granitoid association contains widespread migmatized relicts of the greenstone-belt association, indicating that the latter originally covered much larger areas, but the granitoids are also thought to be partly transformed primitive ensialic crust on which rocks of the greenstone-belt association were deposited. The Archean rocks have been deformed in at least four subsequent phases, of which part developed in Proterozoic time. The youngest deformation is the overthrust of the granulite belt of Lapland towards SSW. NWSE striking transcurrent faults played a major role in Proterozoic time and affected cratonized Archean crust. On the whole the greenstone belts in eastern and northern Finland form a NNW-trending zone 750 km long. On a geochemical basis the volcanic rocks of the greenstone belts can be divided into two groups: tholeiites with a low potassium content and extremely low aluminium content and a calc-alkalic group with some alkalic affinities.     

Research on model testing of a new ultrasonic multi-wave detecting method

The traditional crack exploring method with echo （reflected wave） in metals is called the ＂single-wave detecting method＂ that uses a probe of single weight. This method is not able to detect directly the size and shape of the crack and the result can only be obtained by relative comparison, that is to compare the echo amplitudes of the unknown quantity （crack） with the known quantity （regular artificial crack） to determine the equivalent size and shape of a certain crack.     

Molodensky边值问题中解析延拓法g1项的小波算法

运用小波分析理论研究了Molodensky边值问题的计算方法，论证了该类问题的计算对于精化重力场模型的意义，即可以放弃考虑地球密度的各种重力改正。针对解析延拓法，证明g1项奇异积分在Chauchy主值意义下的存在性。计算结果表明，该算法具有快速、准确的特征，特别适用大范围计算g1项的值，这为精化重力场提供了现实可能性。     

松辽盆地白垩系砂岩长石碎屑的钠长石化作用

松辽盆地白垩系砂岩以长石岩屑砂岩和岩屑长石砂岩为特征。砂岩中发育长石碎屑、岩屑等不稳定组分，而且随着埋藏深度加深（成岩作用加强）钾长石逐渐减少并最终在2700m以下消失。斜长石碎屑中钠长石组分逐渐增多，钙长石组分逐渐减少，最终形成纯钠端元的钠长石。在成岩过程中长石碎屑的钠长石化主要有3种方式：①由离子交代作用导致长石碎屑的钠长石化；②长石碎屑边缘钠长石次生生长；③与长石碎屑溶解伴生的新生钠长石作用。结合热动力学平衡原理分析，斜长石的钠长石化基本不受成岩温度和压力的制约，而钾长石的钠长石化需要较高的成岩温度和压力作用才能进行。因此，斜长石的钠长石化可见于成岩早期，而钾长石的钠长石化只发生于成岩晚期。     

青藏高原边界层高度特征对大气环流动力学效应的数值试验

利用NCAR的全球气候模式 (CCM3) 及第二次青藏高原边界层观测试验的研究结果, 对青藏高原上大气边界层高度的作用进行了研究, 分析了夏季青藏高原地区与长江流域上空的环流状况。研究表明:青藏高原的边界层高度特征对高原东南部地区以及长江流域出现强烈的垂直上升运动及其低层辐合、高层辐散存在着显著的动力效应, 深厚的高原边界层特征将使长江流域夏季区域性的云量及降水明显增加, 河套地区与黄河流域的夏季云量及降水有所减少。     

青藏高原对流云团东移发展的不稳定特征

利用1998年6~7月的逐时GMS红外TBB资料、T106的客观分析资料以及沿长江5个站的探空资料，对青藏高原上的对流云团东移维持发展的环流背景条件进行了分析。研究表明:高层气流辐散、低层气流辐合的垂直结构，高低空急流的引导作用，高原东南部和长江流域充沛的水汽条件以及大气层结的不稳定性是造成青藏高原上空对流云团东移的前提条件。     

青藏高原及其典型区域土壤湿度的分布和变化特征

基于土壤湿度融合分析产品及气象观测资料,分析了青藏高原及其典型区域的土壤湿度分布特征以及影响因素.结果表明：青藏高原土壤湿度与高原降水季节有较好的对应关系,降水量多的季节对应大的土壤湿度,反之亦然,即夏季土壤湿度最大,春季和秋季次之,冬季最小;高原外围土壤相对较湿,中部较干,夏季土壤高湿度区从藏东南向西北、塔里木盆地向藏东北扩展,冬季土壤高湿度区向藏东南和塔里木盆地收缩;土壤湿度垂直层次呈现出浅层和深层低、中间层高的特点,从浅层到深层土壤湿度的变化幅度逐渐减小;高原典型区域土壤湿度逐日变化规律与高原区域平均的土壤湿度时间演变接近一致,降水量的多少和湿润区、半干旱区土壤湿度高低值有较好的对应关系,湿润区垂直梯度大,干旱区和半干旱区垂直梯度小;蒸发量、风速、气温以及植被状况均会影响到土壤湿度的分布特征.     

The Thermodynamic Structure of Arctic Coastal Fog Occurring During the Melt Season over East Greenland

An automated method to classify Arctic fog into distinct thermodynamic profiles using historic in-situ surface and upper-air observations is presented. This classification is applied to low-resolution Integrated Global Radiosonde Archive (IGRA) soundings and high-resolution Arctic Summer Cloud Ocean Study (ASCOS) soundings in low- and high-Arctic coastal and pack-ice environments. Results allow investigation of fog macrophysical properties and processes in coastal East Greenland during melt seasons 1980–2012. Integrated with fog observations from three synoptic weather stations, 422 IGRA soundings are classified into six fog thermodynamic types based on surface saturation ratio, type of temperature inversion, fog-top height relative to inversion-base height and stability using the virtual potential temperature gradient. Between 65–80% of fog observations occur with a low-level inversion, and statically neutral or unstable surface layers occur frequently. Thermodynamic classification is sensitive to the assigned dew-point depression threshold, but categorization is robust. Despite differences in the vertical resolution of radiosonde observations, IGRA and ASCOS soundings yield the same six fog classes, with fog-class distribution varying with latitude and environmental conditions. High-Arctic fog frequently resides within an elevated inversion layer, whereas low-Arctic fog is more often restricted to the mixed layer. Using supplementary time-lapse images, ASCOS microwave radiometer retrievals and airmass back-trajectories, we hypothesize that the thermodynamic classes represent different stages of advection fog formation, development, and dissipation, including stratus-base lowering and fog lifting. This automated extraction of thermodynamic boundary-layer and inversion structure can be applied to radiosonde observations worldwide to better evaluate fog conditions that affect transportation and lead to improvements in numerical models.