Variation in soil saturated hydraulic conductivity along the hillslope of collapsing granite gullies

Saturated hydraulic conductivity (K_s) affects the soil hydrological process and is influenced by many factors that exhibit strong spatial variations. To accurately measure K_s and its scale, spatial variability and relationship with collapsing gullies, we analysed four double-ring infiltrometer diameters in three soil layers during in situ experiments designed to measure K_s in two typical collapsing gullies (three slope sites) in Tongcheng County of China. The results showed that K_s increased with increasing inner ring diameter, but no significant difference existed between inner diameters of 30 and 40 cm. The K_s in red soil layers was higher than that in sandy soil layers, the transition layers had the lowest values. K_s also varied with slope position, gradually decreasing with distance from the gully head. The suggestion is that the spatial variation in K_s is affected not only by the intrinsic soil properties but also by the interaction with the collapsing gully.     

2012年江苏扬州M 4.9地震前地磁垂直分量日变双低点异常

2012年6月13日和7月10日华东地区部分地磁台垂直分量日变形态出现双低点异常,首次异常出现后37天,于7月20日发生江苏扬州M 4.9地震,震中位于低点位移分界线附近。分析认为,在强震前由于应力变化,引起孕震体环境中介质电导率等电磁性质发生改变,区域地磁场垂直分量日变曲线出现相位和幅度变化,说明地磁垂直分量日变双低点异常与地震的孕育和发生相关。     

Development and application of a spatially‐distributed Arctic hydrological and thermal process model (ARHYTHM)

A process‐based, spatially distributed hydrological model was developed to quantitatively simulate the energy and mass transfer processes and their interactions within arctic regions (arctic hydrological and thermal model, ARHYTHM). The model first determines the flow direction in each element, the channel drainage network and the drainage area based upon the digital elevation data. Then it simulates various physical processes: including snow ablation, subsurface flow, overland flow and channel flow routing, soil thawing and evapotranspiration. The kinematic wave method is used for conducting overland flow and channel flow routing. The subsurface flow is simulated using the Darcian approach. The energy balance scheme was the primary approach used in energy‐related process simulations (snowmelt and evapotranspiration), although there are options to model snowmelt by the degree‐day method and evapotranspiration by the Priestley–Taylor equation. This hydrological model simulates the dynamic interactions of each of these processes and can predict spatially distributed snowmelt, soil moisture and evapotranspiration over a watershed at each time step as well as discharge in any specified channel(s). The model was applied to Imnavait watershed (about 2·2 km²) and the Upper Kuparuk River basin (about 146 km²) in northern Alaska. Simulated results of spatially distributed soil moisture content, discharge at gauging stations, snowpack ablations curves and other results yield reasonable agreement, both spatially and temporally, with available data sets such as SAR imagery‐generated soil moisture data and field measurements of snowpack ablation, and discharge data at selected points. The initial timing of simulated discharge does not compare well with the measured data during snowmelt periods mainly because the effect of snow damming on runoff was not considered in the model. Results from the application of this model demonstrate that spatially distributed models have the potential for improving our understanding of hydrology for certain settings. Finally, a critical component that led to the performance of this modelling is the coupling of the mass and energy processes. Copyright © 2000 John Wiley & Sons, Ltd.     

云贵川地区ZTD垂直剖面格网模型

利用ERA5大气再分析资料研究ZTD高程尺度因子的精细时间变化特征,构建顾及高程尺度因子精细时间变化的云贵川地区ZTD垂直剖面格网模型(YZTD-H模型)。以云贵川地区探空站分层ZTD数据作为参考值,检验YZTD-H模型的精度,并将其与GPT2w模型和GPT3模型进行比较。结果表明,顾及精细时间变化和垂直剖面变化的YZTD-H模型在时间维度和垂直剖面维度上均表现出较好的稳定性。     

近30年青藏高原年平均0cm地温的分布和变化特征

选取青藏高原40个测站1970～2002年各月平均0cm地温资料，通过EOF、二阶多项式函数和小波分析等方法，对青藏高原年平均0cm地温的时空分布特征进行了研究。结果表明，青藏高原年平均0cm地温EOF展开的第一特征向量反映了高原地温分布的一致性，而第二、三特征向量分别揭示了高原地温分布受到各种中、小尺度天气系统和海拔高度制约的事实。高原地温空间异常可分为4个气候区，即东北部、南部、主体和西部。高原地温各分区代表站的二阶多项式反映出近30年高原东北部地温呈降温趋势；南部呈增温趋势；高原主体和西部具有高一低一高的抛物线型变化趋势。高原地温各分区皆有3a和准7a的振荡周期。     

利用高精度全站仪实现跨河水准测量的可靠性分析

从实际实施跨河水准测量的两种方法所得结果精度的比较,并利用三角高程测量单向观测的高差计算公式及对跨河水准测量的高差中数中误差进行的估算,验证了利用高精度全站仪实现高精度跨河水准测量的可靠性。     

冬季北极涛动和北极海冰变化对东亚气候变化的影响

本文简要回顾了冬季北极涛动 (北大西洋涛动 )和北极海冰面积变化对东亚气候变化的影响、研究中存在的问题以及目前亟待解决的科学问题。     

变荷载下双层地基一维非线性固结近似解析解

目前考虑土体非线性压缩及渗透特性的双层地基非线性固结解均假定土体固结系数保持不变,能反映固结系数变化的双层地基非线性固结解还很鲜见。引入经典的e- 和e- 非线性关系描述土体的非线性压缩、渗透特性,在假定双层地基上、下土层压缩指数与渗透指数比值 相等且不等于1的基础上,得到变荷载下考虑土体固结系数变化的双层地基一维非线性固结近似解。该解答在 1条件下可退化为已有的 1时双层地基一维非线性固结解。基于此解探讨了双层地基上、下土层参数的相对比值对非线性固结性状的影响。结果表明：单面排水条件下 越小,下层土与上层土的相对压缩性越低、相对渗透性越高,则双层地基非线性固结速率越快;减小 值,增加双层地基中压缩性小、渗透性高的土层的厚度,会加快地基的固结速率。     

岩体结构面各向异性变异系数的尺寸效应研究

岩体结构面的各向异性与尺寸效应特征对其力学性质影响较大,综合考虑两者之间的相互关系对工程岩体稳定性评价具有重要意义。全面分析不同尺度结构面的各向异性分布,提出考虑正交方向三维形貌参数的各向异性变异系数AVC3D。通过渐进覆盖法统计4组天然岩体结构面10种不同采样尺寸的各向异性变异系数及其尺寸效应规律。结果表明：各向异性变异系数均随结构面尺寸增大而减小至定值,其与结构面尺寸具有较好的负对数函数关系;通过归一化处理,各向异性变异系数与结构面尺寸呈现较好的线性函数关系,表明各向异性变异系数具有分形结构,分维数D可以实现其尺寸效应的规律统计。该方法揭示了影响结构面形貌特征方向性变化的最大有效倾角 和粗糙系数C的增长幅度会随采样尺寸增大趋于稳定的变化机制,体现了当结构面达到各向异性尺寸效应的阈值后,会呈现出稳定的各向异性规律。     

4种再分析气温资料在羌塘国家级自然保护区的适用性研究

利用1979 - 2018年羌塘国家级自然保护区边缘的3个气象站点狮泉河（西部）、 申扎（中部）和安多（东部）的观测气温（OT）, 与ERA-Interim（ET）、 NCEP/NCAR（NT1）、 NCEP/DOE（NT2）和JRA-55（JT）4种再分析气温资料, 从年际变化和年变化两方面采用多年气温变化趋势、 均方差、 相关性等参数方法在羌塘自然保护区进行了适用性研究。结果表明： 从多年平均气温年际变化来看, 4种再分析资料在狮泉河（西部）的适用性较差, JRA-55资料在安多（东部）和申扎（中部）的适用性较好, 且冬季再分析气温资料与观测气温的相关性好于夏季; 从多年平均气温年变化来看, 均表现为冬季（1月或12月）最低, 夏季（7月或8月）最高的“单峰型”变化。综合来看, JRA-55资料在羌塘自然保护区的适用性较好, ERA-Interim对多年气温趋势变化表现不准确, NCEP/NCAR和NCEP/DOE与观测气温相比显著偏低。