A simple method using climatic variables to estimate canopy temperature,sensible and latent heat fluxes in a winter wheat field on the North China Plain

Estimation of evapotranspiration from a crop field is of great importance for detecting crop water status and proper irrigation scheduling. The Penman–Monteith equation is widely viewed as the best method to estimate evapotranspiration but it requires canopy resistance, which is very difficult to determine in practice. This paper presents a simple method simplified from the Penman–Monteith equation for estimating canopy temperature (T_c). The proposed method is a biophysically‐sound extended version of that proposed by Todorovic. The estimated canopy temperature is used to calculate sensible heat flux, and then latent heat flux is calculated as the residual of the surface energy balance. An eddy covariance (EC) system and an infrared thermometer (IRT) were installed in an irrigated winter wheat field on the North China Plain in 2004 and 2005, to measure T_c, and sensible and latent heat fluxes were used to test the modified Todorovic model (MTD). The results indicate that the original Todorovic model (TD) severely underestimates T_c and sensible heat flux, and hence severely overestimates the latent heat flux. However, the MTD model has good capability for estimating T_c, and gives acceptable results for latent heat flux at both half‐hourly and daily scales. The MTD model results also agreed well with the evapotranspiration calculated from the measured T_c. Copyright © 2008 John Wiley & Sons, Ltd.     

Morphological responses ofLimnocythere inopinata (Ostracoda) to hydrochemical environment factors

Living ostracod and hydrochemical samples were collected synchronously from more than 50 lakes and small water body in the eastern edge area of the Tibetan Plateau, Northern Tibetan, Southern Tibet and mid-Tibet. The comparison of the adult body length ofLimnocythere inopinata and hydrochemical parameters of their habitats shows that a quantitative relationship exists between the adult body length and salinity expressed as conductivity. An empirical formula to reconstruct paleosalinity is suggested first and applied to salinity reconstruction of CE-2 core from Cuoe Lake, Tibet. The method is verified by comparing its outcome with results of other environment reconstruction methods.

     

Vegetation and peat accumulation steer Holocene tidal–fluvial basin filling and overbank sedimentation along the Old Rhine River,The Netherlands

In the transformation from tidal systems to freshwater coastal landscapes, plants act as eco-engineering species that reduce hydrodynamics and trap sediment, but nature and timing of the mechanisms of land creation along estuaries remains unclear. This article focuses on the Old Rhine estuary (The Netherlands) to show the importance of vegetation in coastal landscape evolution, predominantly regarding tidal basin filling and overbank morphology. This estuary hosted the main outflow channel of the river Rhine between ca 6500 to 2000 cal bp , and was constrained by peat during most of its existence. This study reconstructs its geological evolution, by correlating newly integrated geological data and new field records to varying conditions. Numerical modelling was performed to test the inferred mechanisms. It was found that floodbasin vegetation and resulting organic accumulation strongly accelerated back-barrier infill, by minimizing tidal influence. After tidal and wave transport had already sufficiently filled the back-barrier basin, reed rapidly expanded from its edges under brackish conditions, as shown by diatom analysis and datings. Reed growth provided a positive infilling feedback by reducing tidal flow and tidal prism, accelerating basin infilling. New radiocarbon dates show that large-scale crevassing along the Old Rhine River – driven by tidal backwater effect – only started as nutrient-rich river water transformed the floodbasin into an Alder carr in a next phase of estuary evolution. Such less dense vegetation promotes crevassing as sediments are more easily transported into the floodbasin. As river discharge increased and estuary mouth infilling progressed, crevasse activity diminished around 3800 to 3000 cal bp , likely due to a reduced tidal backwater effect. The insights from this data-rich Holocene study showcase the dominant role that vegetation may have in the long-term evolution of coastal wetlands. It provides clues for effective use of vegetation in vulnerable wetland landscapes to steer sedimentation patterns to strategically adapt to rising water levels.     

Mantle metasomatism and generation of Early Permian ultramafic rocks in northern North China CratonSCIEI北大核心CSCD

华北克拉通北部高寺台晚古生代环状杂岩体是一套富单斜辉石的超镁铁质岩,是研究华北北部地幔碳酸盐化熔体交代作用的理想对象,同时也是华北克拉通北部晚古生代岩浆活动与深部碳循环联系的纽带。作者在岩体西部边缘识别出一套早二叠世早期富铁角闪单斜辉石岩,形成时代为297.8±3.4Ma。结合岩体东部辉石岩早泥盆世和早石炭世的成岩年龄,表明高寺台超镁铁质杂岩体可能是晚古生代多期岩浆侵位的产物。其次,高寺台环状超镁铁质杂岩体缺少大面积辉长岩和闪长岩、硫化物和Cu-Ni-PGE矿化,单斜辉石成分具有裂谷带堆晶岩矿物特征,角闪石也具有相对低的结晶温度(933~947℃)和压力(287~323MPa)及水含量(4.06%~5.10%),而且区域上尚未发现同期环状杂岩体和蛇绿岩,与岛弧拼贴到陆块后沿俯冲带延伸数万米侵位的阿拉斯加型环状杂岩体明显不同。另外,前人的研究显示,与铬铁矿中富镁单斜辉石包裹体平衡的苦橄质母岩浆显示出OIB的特征,具有强烈的重稀土分馏、富Nb和高Nb/La,异常高的Ca/Al和(La/Yb)N,低的Ti/Eu、Zr/Sm和Hf/Sm,这些特征都表明苦橄质母岩浆起源于石榴石相软流圈地幔,且源区遭受过显著的碳酸盐熔体交代。单斜辉石岩中单斜辉石及角闪石成分及其平衡岩浆成分记录了母岩浆与岩石圈地幔相互作用后的岩浆演化过程,也显示出比母岩浆弱的源区碳酸盐熔体交代印记。此外,岩浆房在地壳浅部经历了多期深部岩浆补给和富铁熔体贯入,同时带来热量和挥发分,触发晶粥体活化,促进了岩浆的上升运移。高寺台环状超镁铁质杂岩体具有板内成因特征,可能是陆内岩石圈伸展的产物。华北克拉通北部晚石炭世-早二叠世三个岩浆事件峰期很好地对应着全球三次升温和CO_(2)回升事件,岩石圈伸展能有效促进强烈的中酸性岩浆活动及起源于碳酸盐化地幔的基性岩浆释放出大量的CO_(2),它们可能是晚石炭末期-早二叠世早期全球大气CO_(2)回升的贡献者之一。     

Verification of Plasma Chemical Models of the Ionospheric D Region of the According to Radiophysical Data from Mikhnevo Geophysical Observatory

Geomagnetism and Aeronomy - The results of a comparison of three different plasmochemical models of the ionospheric D region during C- and X-class X-ray flares are presented. Four-, five- and...     

Fourier Coefficients Variation with Angle for Fracture Detection and Fluid Discrimination in Tilted Transversely Isotropic Media

Surveys in Geophysics - Fracture detection and fluid discrimination play significant roles in the field of geothermics, hydrogeology, and exploration geophysics. However, it is still a challenging...     

Gold-Bearing Placer Assemblages in the East of the Siberian Platform: Origin and Prospects

Geology of Ore Deposits - For the first time, based on a study of the typomorphic features of placer gold and its distribution patterns, the predicted gold potential of the east of the Siberian...     

Deformation characteristics of inherently anisotropic granular media under repeated traffic loading: a DEM study

Acta Geotechnica - The cardioid-shaped loading path induced by moving traffic has been reproduced in the virtual element test of granular media using the discrete element method (DEM). The DEM...     

Modeling of the Correlation Between Mineral Size and Shale Pore Structure at Meso- and Macroscales

Mathematical Geosciences - Inorganic pore structures are critical to understand the oil and gas transport and storage properties of unconventional reservoirs. However, it can be difficult to...     

Characterizing uncertainty in geotechnical design of energy piles based on Bayesian theorem

It is known that a lot of uncertainties are involved in geotechnical design of energy piles. In this paper, a Bayesian updating framework is presented to characterize those uncertainties. The load-transfer model is developed to predict the thermomechanical response of energy piles. Considering the cross-case variability of the uncertainty in the axial strains of pile, the global model bias is firstly calibrated by establishing a comprehensive database consisting of 12 energy pile cases. Furthermore, the uncertainty in input parameters is considered in the Bayesian updating of model bias in a specific case. The variability of the uncertain parameters is effectively reduced after updating. The coefficient of variation of prediction is decreased from 0.34 to 0.13. The present framework can well quantify uncertain factors and improve the accuracy and reliability of the prediction model.