长安少陵塬黄土含水条件与控制因素研究

 根据长安少陵塬杨湾黄土剖面含水层的调查、含水量、孔隙度测定和粒度分析,研究了黄土含水层与隔水层的分布、含水条件及其与第四纪气候变化的关系。结果表明,长安杨湾剖面黄土地层含水量变化代表了与以往研究不同的变化类型,含水量峰值出现在黄土层中,低值出现在红色古土壤层中；从上向下含水量与孔隙度呈波动变化规律；在所研究的剖面中出现的5个含水层均由黄土层构成,隔水层由红色古土壤构成。研究剖面中含水层与隔水层的水理性质主要是它们形成时的气候不同决定的。红色古土壤的隔水性是由于温湿气候条件下的粘土化作用产生的，黄土层的含水空间发育好主要是当时相对冷干的气候条件下的较弱的成壤作用造成的。含水空间发育较好的黄土层和粘化强的红色古土壤隔水层的存在是该黄土剖面中地下水富集的两个基本条件。     

沙漠地区春季近地层气象要素分布规律的观测研究

利用2005年1月至2006年4月朱日和地区20 m气象塔的风向、风速、气温、相对湿度的观测资料,分析沙漠地区春季近地层气象要素的分布规律。结果表明: 春季温度回升,风速最大,相对湿度最小,利于起沙,故沙尘天气频繁。风速满足幂指数率分布规律,并且幂指数m能够很好的反映出风速梯度的变化情况;在沙尘暴、扬沙、背景、浮尘的天气条件下,春季近地面层风速梯度依次增大,湍流动量、热量交换系数依次减小;风向以西南为主。浮尘、扬沙天气各气层平均增温率分别大于或小于同时段的背景大气;沙尘暴期间温度下降,平均降温率为0.61 ℃\5h-1。春季相对湿度的平均递减率(递增率)与平均增温率(降温率)的大小正相关。浮尘天气相对湿度的平均递减率大于同时段的背景大气;扬沙天气相对湿度的平均递减率小于同时段的背景大气;沙尘暴天气相对湿度增大,平均增大率为2.80%\5h-1。     

大理近地层山谷盆地湖陆风及湍流特征分析

研究湖陆风特征不仅能够为提高天气气候的预测能力奠定基础,而且对风能资源的开发利用等具有重要的实用意义。利用大理国家气候观象台近地面通量观测系统的2007年3月－2008年5月资料,采用涡动相关法等分析了大理近地层中湖陆风、峡谷风特征及形成原因和影响因素。结果表明：大理地区白天以东风和东南风为主,夜间以西风和西南风为主。进一步对湍流和湍流通量特征分析发现,大理地区白天不稳定层结多于夜间;湍流强度白天强于夜间,并且随着风速的增大而减小;湍流通量具有明显的日变化特征,热量交换形式以潜热为主。     

南极普里兹湾海冰厚度的电磁感应探测方法研究

本文介绍一种由EM31-ICE型电磁感应仪和激光测距仪组合而成的船载电磁感应海冰厚度探测系统. 针对海冰和海水的电学特征,运用电磁感应技术提取探测系统至海冰下底面的距离,运用激光测距仪测量冰面粗糙度和探测系统至海冰上表面的距离,两组数据结合,实现了海冰厚度的探测. 通过南极现场探测数据分析,并与钻孔实测冰厚数据对比研究,定量分析了探测系统距离冰面的高度效应,建立了该系统冰厚测定值随高度变化的修正关系式,并对船载航行数据进行了系统校正. 与SCAR ASPeCt的冰厚数据对比分析,表明该系统能够获得可靠的海冰厚度并具有较高的精度,且能满足对极区大范围海冰厚度观测的需求.     

Elevation adjustments of paired natural levees during flooding of the Saskatchewan River

Natural levees control the exchange of water between an alluvial channel and its floodplain, but little is known about the spatial distribution and evolution of levee heights. The summer 2005 flood of the Saskatchewan River (Cumberland Marshes, east‐central Saskatchewan) inundated large areas of floodplain for up to seven weeks, forming prominent new deposits on natural levees along main‐stem channels. Measurements of flood‐deposit thickness and crest heights of 61 levee pairs show that the thickest deposits occur on the lower pre‐flood levee in 80% of the sites, though no clear relationship exists between deposit thickness and magnitude of height difference. Only 16% of the pairs displayed thicker deposits on the higher levee, half of which occurred at sites where relatively clear floodbasin waters re‐entered turbid channels during general flooding. Difference in crest elevation (ΔE) between paired levees is approximately log‐normally distributed, both before and after the flood, though with different mean values. Supplemental observations from tank experiments indicate that during near‐bankfull flows, temporally and spatially variable deposition and erosion occur on levees due to backwater effects associated with nearby channel bars and irregular rises of the channel bed forced by channel extension. During floods, preferential deposition in lows tends to even out crest heights. Copyright © 2009 John Wiley & Sons, Ltd.     

Dipping-interface Mapping Using Mode-separated Rayleigh Waves

Multichannel analysis of surface waves (MASW) method is a non-invasive geophysical technique that uses the dispersive characteristic of Rayleigh waves to estimate a vertical shear (S)-wave velocity profile. A pseudo-2D S-wave velocity section is constructed by aligning 1D S-wave velocity profiles at the midpoint of each receiver spread that are contoured using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. Based on the assumption that a dipping-layer model can be regarded as stepped flat layers, high-resolution linear Radon transform (LRT) has been proposed to image Rayleigh-wave dispersive energy and separate modes of Rayleigh waves from a multichannel record. With the mode-separation technique, therefore, a dispersion curve that possesses satisfactory accuracy can be calculated using a pair of consecutive traces within a mode-separated shot gather. In this study, using synthetic models containing a dipping layer with a slope of 5, 10, 15, 20, or 30 degrees and a real-world example, we assess the ability of using high-resolution LRT to image and separate fundamental-mode Rayleigh waves from raw surface-wave data and accuracy of dispersion curves generated by a pair of consecutive traces within a mode-separated shot gather. Results of synthetic and real-world examples demonstrate that a dipping interface with a slope smaller than 15 degrees can be successfully mapped by separated fundamental waves using high-resolution LRT.