Geostrophic Wind, Gradient Wind, Thermal Wind And The Vertical Wind Profile – A Sample Analysis Within A Planetary Boundary Layer Over Arctic Sea-Ice     

R. Roth  M. Hofmann  C. Wode 《Boundary-Layer Meteorology》1999,92(2):327-339

For the interpretation of many boundary-layer field experiments the geostrophic wind is needed as an external parameter. However, quite often and especially in remote areas this wind is not known at all or difficult to determine because there are not enough measurements of the surface pressure.Here it is shown how measurements carried out with the HELIPOD system, a helicopter-borne meteorological turbulence measuring system, may be used to evaluate the geostrophic wind. This is done by the analysis of the pressure field at different heights. An additional analysis of the temperature field in the same heights allows for the discussion of the quality of the derived geostrophic wind. An intercomparison with the vertical wind profile enables us to discuss the influence of the curvature of the isobars. From this, finally, also the gradient wind can be estimated.  相似文献   

Diurnal SST warming in the Bay of Biscay: satellite measurements and model prediction     

Huang Weigen  I. S. Robinson  N. C. Wells 《海洋学报(英文版)》1999,18(2):167-176

INTRODUCTIONIt has long been recognized that a diurnal thermal cycle occurs in the upper layer of the ocean(Stommel et al., 1969; Price and Weller, 1986). Interest in the subject has revived in recentyears due to the importance of resolving the diurnal cycle for correctly coupling the ocean and atmosphere (Lukas, 1991 ). While the study of the diurnal cycle is of intrinsic scientific interest, italso offers the benefit to remote sensing scientists of identifying the bias caused by the di…  相似文献   

Application of an optical nitrate profiler to high- and low-turbidity coastal shelf waters     

Yanpei Zhuang  Yangjie Li  Xizhen Liu  Shichao Tian  Bin Wang  Zhongqiang Ji  Haiyan Jin  Jianfang Chen 《海洋学报(英文版)》2023,42(1):103-108

Here, we report the results of high-resolution nitrate measurements using an optical nitrate profiler(in situ ultraviolet spectrophotometer, ISUS) along transect across a high-turbidity shelf(East China Sea) and a lowturbidity shelf(Chukchi Sea). The ISUS-measured nitrate concentrations closely reproduced the results measured by conventional bottle methods in low-turbidity waters. However, for high-turbidity waters of the East China Sea(salinity<30), a correction factor of 1.19 was required t...  相似文献   

Experiments on the effect of inflow and outflow sequences on suspended sediment exchange rates     

Michael M&#;ller  Giovanni De Cesare  Anton J. Schleiss 《国际泥沙研究》2017,32(2)

In laboratory experiments, the influence of inflow and outflow sequences on the behavior of fine sedi-ment was investigated. The experimental set-up consisted of two interconnected rectangular basins, between which water was moved back and forth. Suspended sediment concentration in the main basin as well as the sediment exchange rates were derived from turbidity measurements.The suspended sediment ratio, SSR, and sediment exchange rates (influx sediment rate, ISR, and evacuated sediment rate, ESR) were measured. In twenty test runs, a parametric study on the magnitude and frequency of inflow and outflow cycles, the relative duration between inflow and outflow sequences, the initial sediment concentration, and the intake position was done. An initial test with stagnant water described the set-tling behavior of fine sediment and served as a reference scenario.The test results show that settling of fine particles near the intake/outlet structure can be considerably reduced by the nature of the inflow and outflow sequences. High cycle magnitude and frequency lead to maximum suspended sediment ratio in the system. For low discharges, the evolution of suspended sediment concentration cannot be directly correlated to the inflow and outflow cycles. However, compared to"no operation"conditions, the suspended sediment ratio could be increased by 10%to 40%locally. For high discharge, the evolution of suspended sediment concentration correlated with discharge cycles and suspended sediment ratios between 50%and 80%higher than for stagnant water could be achieved. Similar ratios could be obtained when the intake is located closer to the bottom or to the free water surface.Meanwhile, the overall sediment balance remained in equilibrium over the test period, indicating that the influx and evacuated sediment rates are not significantly influenced by the inflow and outflow cycles.  相似文献   

Evaluation of wind effects on a supertall building based on full‐scale measurements     

Q. S. Li  J. Q. Fang  A. P. Jeary  C. K. Wong  D. K. Liu 《地震工程与结构动力学》2000,29(12):1845-1862

This paper describes the results obtained from the full‐scale measurements of wind effects on a 70‐storey building in Hong Kong. The building which has a height of approximately 370 m is the second tallest structure in Hong Kong. The field data such as wind speed, wind direction and wind‐induced acceleration responses have been measured since 1995 including the close passage of two typhoons; typhoon Sally and typhoon Kent. Detailed analysis of the field data is conducted. The full‐scale measurements are compared with the wind tunnel results obtained in the Boundary Layer Wind Tunnel Laboratory at Western Ontario University. The amplitude‐dependent characteristics of damping and natural frequency that were obtained by using the random decrement technique are investigated. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

光电测距三角高程代替三等水准测量相关技术问题研究     

柴华 《测绘信息与工程》2010,35(2):40-41

分析了光电测距三角高程的误差,探讨了光电测距三角高程代替三等水准测量相关技术问题,给出了一些有益的结论。  相似文献   

GPS第三频载波及民用码的信号质量分析     

吴继忠  杨荣华 《测绘信息与工程》2010,35(5):22-24

介绍了L5载波的特点,分析了L5载波对GPS测量的影响,用实测数据分析了三频载波的信噪比及各个民用码的噪声水平。  相似文献   

2011年日本东北大地震（M_W=9.0）震间与震前变形场特征及其对强震预测的启示          下载免费PDF全文

朱守彪 《地球物理学报》2020,63(2):427-439

强震震前(preseismic)动力学过程的研究对于地震预测具有十分重要的意义,但由于观测资料的限制,目前对强震前孕震区力学状态及其演化过程的认识还非常有限.2011年日本东北9.0特大地震(Tohoku-Oki)发生在GPS观测台站最为密集的地区,为研究特大地震震间(interseismic)与震前的变形状态提供了难得的机会.文中将利用日本东北大地震之前连续的GPS观测资料,分别计算震间与震前的速度场与变形场.通过对比分析发现,日本东北地区(Tohoku)震前的应变状态与震间的有很大的不同,震间的变形主要受到太平洋板块向日本海沟北西西向的俯冲挤压作用所控制,其主压应变以近东西向压缩为主,日本东北地区的运动方向与太平洋板块的运动方向大体一致.但是,临近地震前(震前)日本东北地区的运动方向发生了很大变化,震前30天的连续GPS观测结果显示,速度场的优势方向经常变换,间歇性地出现与太平洋板块运动方向相反的情况.这意味着震前孕震区的力学状态发生了很大的改变.这种变化可能与震前破裂成核或慢滑移及慢地震等过程有关,这些过程将加速或促进大地震的发生,从而为大地震的发生准备了力学条件.值得特别强调的是,这些现象都是可以通过直接观测能够发现的大地震之前的异常现象.由此可见,加密GPS站点进行连续观测,寻找震前变形异常区以及探索异常的物理机制对于地震预测预报有重要的科学意义.  相似文献   

藏南羊卓雍错湖面大气湍流特征观测分析   总被引：2，自引：1，他引：1  

沈鹏珂  张雪芹 《湖泊科学》2019,31(1):243-255

湍流运动是大气边界层的本质特征,是地表与大气之间能量和物质交换的主要方式.本文利用2016和2017年4-10月藏南羊卓雍错湖泊涡动观测资料,分析了湖面大气湍流方差和湍流特征量的统计和变化特征.结果表明：（1）不稳定层结下,三维风速分量和超声虚温、水汽密度、CO₂密度的无量纲标准差随稳定度变化符合Monin-Obukhov相似理论的"1/3"或"-1/3"次幂律,垂直风速的拟合效果最好;稳定层结下,除CO₂密度无量纲标准差与稳定度无明显关系外,其他量基本上满足相似性规律;中性条件下,以上物理量的无量纲标准差分别趋近常数：3.57、3.93、0.77、20.91、6.35和11.96.（2）水平方向平均湍流强度（0.60和0.58）大于垂直方向（0.13）,三维方向湍流强度与平均风速的变化呈显著负相关,相关系数分别为-0.39、-0.42和-0.34.（3）湖面湍流动能随风速呈线性增长,增长率达0.45 m/s;近中性层结时湍流动能最大,层结越稳定或不稳定湍流动能均减小.（4）湖泊下午到傍晚动量输送较强,13：00-22：30时间段平均动量通量达0.091 kg/（m·s²）;热量输送以潜热为主,潜热通量日平均值（77.3 W/m²）是感热通量（14.6 W/m²）的5.3倍,感热和潜热通量日变化峰值分别出现在5：30（22.4 W/m²）和16：00（106.6 W/m²）.  相似文献   

Damage localization and quantification of earthquake excited RC-frames     

P. S. Skjrbk  S. R. K. Nielsen  P. H. Kirkegaard  A. . akmak 《地震工程与结构动力学》1998,27(9):903-916

In the paper a recently proposed method for damage localization and quantification of RC-structures from response measurements is tested on experimental data. The method investigated requires at least one response measurement along the structures and the ground surface acceleration. Further, the two lowest time-varying eigenfrequencies of the structure must be identified. The data considered are sampled from a series of three RC-frame model tests performed at the structural laboratory at Aalborg University, Denmark during the autumn of 1996. The frames in the test series were exposed to two or three series of ground motions of increasing magnitude. After each of these runs the damage state of the frame was examined and each storey of the frame were classified into one of the following six classifications: undamaged, cracked, lightly damaged, damaged, severely damaged or collapse. During each of the ground motion events the storey accelerations were measured by accelerometers. After application of the last earthquake sequence to the structure the frames were cut into pieces and each of the beams and columns was statically tested and damage assessment was performed using the obtained stiffnesses. The damage in the storeys determined by the suggested method was then compared to the damage classification from the visual inspection as well as the static tests. It was found that especially in the cases where the damage is concentrated in a certain area of the structure a very good damage assessment is obtained using the suggested method. © 1998 John Wiley & Sons, Ltd.  相似文献