南极内陆冰盖表面地貌特征监测系统设计及应用分析

南极内陆冰盖表面的特征与冰盖表面年际降雪量、冰盖表面风速有关,冰盖表面地貌特征主要包括雪面粗糙度、雪层软硬度,这些特征对内陆车队行进过程中的设备运输具有重要的参考价值。文中提出了车载自动化监测冰盖雪面特征的方法,并进行了监测系统的设计与数据分析;该系统包括以雪地车颠簸幅度代表的雪面凹凸程度(即雪面粗糙度),以GPS模块监测车辆行进距离,以激光测距监测雪地车车辙深度来表征雪面软硬度。通过数据采集系统的实时监测软件平台,实现了冰盖表面地貌特征的监测;该系统分别于2012年11月和2014年11月在中国第29次南极和31次南极考察中进行了监测应用,通过对以上监测数据的分析,初步给出了中山站至昆仑站沿途的冰盖表面粗糙度及雪面软硬度结果。     

基于二维激光观测的溢油及其乳化过程散射模式研究进展

合成孔径雷达(SAR)以其高分辨率、能不受雨云影响实施全天时全天候全方位监测,在海面溢油灾害应急监测过程中发挥着越来越重要的作用。溢油是因为海面油膜抑制了毛细波和重力波,在SAR图像上呈暗斑而被识别。然而,海面溢油的乳化过程直接影响SAR对海面溢油后向散射截面的观测精度。本研究以物理海洋学和激光原理以及海面电磁散射理论为基础,通过实验利用激光扫描仪观测海面溢油粗糙度,分别与溢油特征参数、后向散射系数建立对应关系;耦合海面溢油参数与后向散射截面的关系,利用电磁散射数值建模方法,建立海面溢油散射模型,研究海面溢油乳化过程对微波后向散射截面的影响。本项目的研究将为SAR监测海面溢油量、溢油厚度及油品分布格局提供了可能;将进一步揭示海面溢油的散射机制,提高SAR海面监测溢油的精度和能力。     

冰封河道综合糙率计算方法比较与分析

综合糙率是冰封河道水力计算的重要输入参数。根据水流连续性和力的平衡原理,分别推导得到冰封河道综合糙率的通用公式,并选取抛物线形、矩形和梯形作为典型断面,系统地总结Pavlovskiy、Einstein、Lotter、Sabaneev、Larsen、改进的Larsen等常见公式由通用公式基于何种假定（分区的湿周、流速或水力半径相等）简化得到。采用水槽实测数据和野外观测资料,对比上述公式的计算精度,结果表明改进的Larsen公式的计算结果与实测值吻合较好,推荐在工程设计中使用。前5种公式误差较大的原因在于分区的流速、水力半径相等对于冰封河道不具有普适性,尤其是Lotter公式和Pavlovskiy公式在冰盖和河床糙率差异较大时会明显低估冰封河道的综合糙率,在工程设计中应慎重采用。     

Characteristics and Causes of Changes of Pan Evaporation in China During 1957-2001

Evaporation is an important component of surface heat and water balance, and is affected directly by land use and climate change. This paper studies the changes of evaporation in China associated with the global climate change, and explores characteristics of the corresponding regional water cycle variations. The 20-cm-caliber pan evaporation measurements collected from 427 meteorological stations in China from 1957 to 2001 are analyzed to disclose the small-pan evaporation variation trend in China and the associated causes. The results show that although the annual average temperature over China exhibits an upward tendency of 0.2°C/10 yr for the past 45 years,the pan evaporation on the whole has decreased by －34.12mm/10 yr. Nonetheless, a significant increase of pan evaporation is observed in a few areas such as the northern part of the Greater Hingan Mountains in Northeast China and the Beishan Mountains in Inner Mongolia. The largest decrease of pan evaporation lies in East China, northern parts of Northwest China,South China, and southern Tibet. An analysis of energy balance and aerodynamics using Penman's formula proves that the drop of pan evaporation in East China is mainly due to a significant decline of source energy for evaporation, while that in West China is mostly attributed to an aerodynamic reduction. The analysis on tendencies of various meteorological and other related factors shows that wind speed and sunshine hours are two most important factors causing the pan evaporation reduction in China.     

硬性结构面粗糙度系数量化确定及其工程应用

本文通过对硬性节理表面粗糙度系数JRC量化确定的研究,对包括Barton推荐标准曲线在内的大量结构面起伏曲线矢量化分析,利用期望值的概念反映结构面起伏曲线粗糙度JRC,建立JRC与起伏曲线高度、坡度两个因素的经验公式,为Barton理论公式法快速预测结构面参数提供了充足条件,并用理论公式法预测成果与试验成果进行对比分析。     

高速公路路基结构分析及动变形设计方法

考虑汽车运动荷载,基于实测路面不平整资料,对影响动荷载的因素进行分析,提出了动力设计荷载参数的建议值。通过Odemark模量和厚度当量假定,将公路结构简化为3层体系,并利用弹性动力学原理及Fourier变换方法获得了路基顶面动变形的计算式。结合现有规范关于路面弯沉控制的思想,考虑路面路基的相互作用及协调变形,给出了路基顶面的动变形控制标准和确定方法,依据此标准提出了一种路基动变形控制设计的方法。最后以3种典型沥青公路结构为例,进行了路基动变形控制设计。     

BOUNDARY LAYER STRUCTURE IN TYPHOON SAOMAI (2006): UNDERSTANDING THE EFFECTS OF EXCHANGE COEFFICIENT

Recent studies have shown that surface fluxes and exchange coefficients are particularly important to models attempting to simulate the evolution and maintenance of hurricanes or typhoons.By using an advanced research version of the Weather Research and Forecasting(ARW)modeling system,this work aims to study the impact of modified exchange coefficient on the intensity and structures of typhoon Saomai(2006)over the western North Pacific.Numerical experiments with the modified and unmodified exchange coefficients are used to investigate the intensity and structure of the storm,especially the structures of the boundary layer within the storm.Results show that,compared to the unmodified experiment,the simulated typhoon in the modified experiment has a bigger deepening rate after 30-h and is the same as the observation in the last 12-h.The roughness is leveled off when wind speed is greater than 30 m/s.The momentum exchange coefficient(CD)and enthalpy exchange coefficient(CK)are leveled off too,and CD is decreased more than CK when wind speed is greater than 30 m/s.More sensible heat flux and less latent heat flux are produced.In the lower level,the modified experiment has slightly stronger outflow,stronger vertical gradient of equivalent potential temperature and substantially higher maximum tangential winds than the unmodified experiment has.The modified experiment generates larger wind speed and water vapor tendencies and transports more air of high equivalent potential temperature to the eyewall in the boundary layer.It induces more and strong convection in the eyewall,thereby leading to a stronger storm.     

强风条件下海面拖曳系数和粗糙长度研究

进一步研究强风条件下海-气湍流动量交换以及海浪特征,有助于提高数值天气模式对台风强度演变、移动路径以及恶劣海况的预报能力。依照前人的方法将台风分为风向与浪向(1)相同,(2)相反,和(3)交叉3个扇形区,并结合台风路径数据,得到了浮标数据相对于台风的方位。分别对3种类型的浮标数据进行分析,进而发现了波浪高度和相速度随风速增加而变化的规律。并利用GWW参数化方案计算出摩擦速度(u_*)、拖曳系数(C_DN)和粗糙长度(z₀)。将这些结果与前人代表性的研究论文中所用观测数据和所得研究结论进行比较,结果表明二者有较强的一致性。该研究证明GWW参数化方案在强风条件下依然有很好的适用性。     

A motion correction on direct estimations of air-sea fluxes from a buoy

A flux system deployed on a moored buoy has been described, which is capable of directly estimating the airsea fluxes after removing the contamination in the signal due to buoy motion. A triple loop fitting method has been demonstrated for determining the three angular offsets between measurement axes of the sonic anemometer and motion pack. The data collected in an experiment in the Northern Huanghai Sea is used to correct the three sonic anemometer measurements of turbulent wind for buoy motion. The effective removal of wave-scale motion from the spectra and cospectra are demonstrated. Estimates of along-wind momentum flux, sensible heat flux and latent heat flux calculated by the eddy correlation method based on data obtained by sonic anemometer 81000V are shown to be in the same trend and scale with those determined by the bulk aerodynamic method after motion correction. The motion correction not only greatly improve the estimation of the momentum flux but also has a great impact on the calculated sensible heat flux.     

Shear tests of interfaces between calcareous sand and steel

Abstract

Various modified direct shear tests on the interface between calcareous sand and steel with different degrees of roughness were conducted in this article, and the different interface property results between calcareous sand-steel and siliceous sand-steel were compared. It was found that: (1) Under various normal stresses, the limit shear stress at the interface reaches the peak value when the groove depth is at the critical value Rcr. Further, when the flat width is at a critical value Gcr, the limit interface shear stress reaches to that of a grooved surface with a flat width of zero. (2) The magnitudes of Rcr and Gcr are related to the gradation and grain size of sand. For the calcareous sand tested, Rcr and Gcr are three times and seven times the mean grain size, respectively. (3) When the intersection angle between the symmetrical V-shaped grooves and the direct shear direction equals to 45°, the limit interface shear stress reaches the peak value and no significant increase is observed at the larger intersection angle. (4) Under the same interface testing conditions with siliceous and calcareous sands, the interface friction angle of the calcareous sand is ～5°–6° greater than that of siliceous sand.