Effects of atmospheric stability conditions on heat fluxes from small water surfaces in (semi-)arid regions

Atmospheric stability conditions over the water surface can affect the evaporative and convective heat fluxes from the water surface. Atmospheric instability occurred 72.5% of the time and resulted in 44.7 and 89.2% increases in the average and maximum estimated evaporation, respectively, when compared to the neutral condition for a small shallow lake (Binaba) in Ghana. The proposed approach is based on the bulk-aerodynamic transfer method and the Monin-Obukhov similarity theory (MOST) using standard meteorological parameters measured over the surrounding land. For water surface temperature, a crucial parameter in heat flux estimation from water surfaces, an applicable method is proposed. This method was used to compute heat fluxes and compare them with observed heat fluxes. The heat flux model was validated using sensible heat fluxes measured with a 3-D sonic anemometer. The results show that an unstable atmospheric condition has a significant effect in enhancing evaporation alongside the sensible heat flux from water surfaces.     

A continuous seismic profile survey of Windermere

Continuous seismic profile devices, modified for use in freshwater have been used on Windermere to determine the total thickness of lakebed sediments and the morphology of the underlying bedrock. The survey detected two overdeepened irregularly shaped rock basins. The northerly one approaches 110 feet (34 m) below sea level and contains 70 feet (21 m) of sediment. The corresponding dimensions of the Southern basin are 120 feet (37 m) and 130 feet (40 m) respectively. Glacial scouring is postulated as the origin of the rock basins. Some profiles show two types of sediment; the higher parts of which are known to be Post Glacial.     

Methods to calculate sedimentation rates of floodplain soils in the middle region of the Elbe River

This study presents different methods to quantify the historic and recent sedimentation of floodplain soils along the Elbe River. These methods include the comparison of surface elevations, the quantification of sedimentation with the aid of anthropogenic and geogenic tracers, sediment trap studies, and the calculation of load balances. Selected results from sites at the lower section of the middle Elbe River are presented and verified. The results show that several methods are suitable. In future work it should be possible, depending on the available soil and sediment data, to calculate sedimentation in Elbe River floodplain and the loss of retention volume for larger areas.     

The solubility of calcite,strontianite and witherite in NaCl solutions at 25°C

The solubility of CaCO₃ (calcite), SiCO₃ (strontianite), and BaCO₃ (witherite) has been determined in NaCl solutions from 0.1 to 6 m at 25°C. Activity coefficients estimated from Pitzer's equations with higher order interaction terms (θ and Ψ) were used to extrapolate the results to infinite dilution. Thermodynamic values of $\text{pK}{}_{\mathrm{sp}}\text{= 8.46 ± 0.03,9.13 ± 0.03}$ and $\text{8.56 ± 0.04}$ were found, respectively, for CaCO₃, SrCO₃ and BaCO₃ at 25°C. These results are in reasonable agreement with literature data. Since Pitzer parameters for the interactions of CO₃^2? with Ca²⁺, Sr²⁺ and Ba²⁺ were not used, our results indicate that they are not necessary at low values of $\text{P}{}_{\mathrm{co2}}$.     

Estimating historic lake stages from one‐time snapshot,the Shuttle Radar Topography Mission of 2000

Lake studies play an important role in water management, ecology and other environmental issues. Monitoring lake stages is typically the first step on the lake studies. However, for the Prairie Pothole Region (PPR) of North America with millions of small lakes and potholes, onsite measurements for lake stages are almost impossible with the conventional gage stations due to the limited accessibility to lakes and the requirement of economical and human resources. To overcome this limitation, we employed the remote‐sensing approach to extract lake stages in PPR for bulk processing. To estimate lake stages, several image‐processing techniques were used with the Shuttle Radar Topography Mission (SRTM) data in January, 2000, a one‐time snapshot useful in historic lake level reconstruction. In this research, image processing techniques, for example, averaging, Fast Fourier Transform (FFT), Lee‐Sigma filtering were applied and masking with Canny Edge Detector (CED) and semi‐automated contouring were developed for lake stage estimation. In terms of simplicity, averaging might be useful if 1·5 m of the local bias for the study area in stage estimates. However, the FFT and Lee‐Sigma methods were slightly better than averaging. Masking with CED and semi‐automated contouring provided outstanding accuracy in the estimation. The masking and contouring methods provided ± 0·5 m of stage differences for relatively large lakes greater than 10 km² when compared with stage reading in spite of their calculation complexities and was shown as the best approaches among implemented methods in this study. Copyright © 2010 John Wiley & Sons, Ltd.     

Ice mass change in Greenland and Antarctica between 1993 and 2013 from satellite gravity measurements

We construct long-term time series of Greenland and Antarctic ice sheet mass change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of mass variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of mass loss than other methods before 2000, while the Antarctic ice sheet appears heavily influenced by interannual variations.     

基于层次化P2P协议的网格空间数据库系统模型

针对传统空间数据库技术的不足,充分结合网格空间数据管理的新特点,提出了一种适合于网格环境的空间数据库系统模型(grid peer-spatial database management system,GPeer-SDBMS)。该模型运用P2P协议Tapestry构建了基于网格的层次化分布式空间数据库,不仅利用数据库的模式差异将网格空间数据库划分为由相同模式节点组成的多个虚拟节点集合,实现了空间数据的分布式存储,而且还对查询算法进行了有效的改进,并通过实验验证了查询算法的高效性。     

The Kenticha rare-element pegmatite,Ethiopia: internal differentiation,U–Pb age and Ta mineralization

The Kenticha rare-element pegmatite, a globally important tantalite source in the Neoproterozoic Adola Belt of southern Ethiopia, is a highly fractionated, huge (2,000 m long and up to 100 m thick), subhorizontal, sheet-like body, discordantly emplaced in ultramafic host rock. It corresponds to the spodumene subtype of the rare-element pegmatite class and belongs to the lithium–cesium–tantalum petrogenetic family. The Kenticha pegmatite is asymmetrically zoned from bottom to top into granitic lower zone, spodumene-free intermediate zone, and spodumene-bearing upper zone. A monomineralic quartz unit is discontinuously developed within the upper zone. Whole-rock data indicate an internal geochemical differentiation of the pegmatite sheet proceeding from the lower zone (K/Rb ~36, K/Cs ~440, Al/Ga ~2,060, Nb/Ta ~2.6) to the upper zone (K/Rb ~19, K/Cs ~96, Al/Ga ~1,600, Nb/Ta ~0.7). The latter one is strongly enriched in Li₂O (up to 3.21%), Rb (up to 4,570 ppm), Cs (up to 730 ppm), Ga (up to 71 ppm), and Ta (up to 554 ppm). Similar trends of increasing fractionation from lower zone to upper zone were obtained in muscovite (K/Rb 23–14, K/Cs 580–290, K/Tl 6,790–3,730, Fe/Mn 19–10, Nb/Ta 6.5–3.8) and columbite–tantalite (Mn/Mn + Fe 0.4–1, Ta/Ta + Nb 0.1–0.9). The bottom-to-top differentiation of the Kenticha pegmatite and the Ta mineralization in its upper part are principally attributed to upward in situ fractionation of a residual leucogranitic to pegmatitic melt, largely under closed system conditions. High MgO contents (up to 5.05%) in parts of the upper zone are the result of postmagmatic hydrothermal alteration and contamination by hanging wall serpentinite. U–Pb dating of Mn-tantalite from two zones of the Kenticha pegmatite gave ages of 530.2 ± 1.3 and 530.0 ± 2.3 Ma. Mn-tantalite from the Bupo pegmatite, situated 9 km north of Kenticha, gave an age of 529.2 ± 4.1 Ma, indicating coeval emplacement of the two pegmatites. The emplacement of the pegmatites is temporally related to postorogenic granite magmatism, producing slightly peraluminous, I-type plutons in the area surrounding the Kenticha pegmatite field. Fractionated members of this suite might be envisaged as potential parental magmas.