Topographic and atmospheric corrections of gravimetric geoid determination with special emphasis on the effects of harmonics of degrees zero and one     

L. E. Sjöberg 《Journal of Geodesy》2001,75(5-6):283-290

 The topographic and atmospheric effects of gravimetric geoid determination by the modified Stokes formula, which combines terrestrial gravity and a global geopotential model, are presented. Special emphasis is given to the zero- and first-degree effects. The normal potential is defined in the traditional way, such that the disturbing potential in the exterior of the masses contains no zero- and first-degree harmonics. In contrast, it is shown that, as a result of the topographic masses, the gravimetric geoid includes such harmonics of the order of several centimetres. In addition, the atmosphere contributes with a zero-degree harmonic of magnitude within 1 cm. Received: 5 November 1999 / Accepted: 22 January 2001  相似文献   

珠穆朗玛峰地区大气气溶胶元素成分的监测及分析   总被引：9，自引：8，他引：9  

张仁健  邹捍  王明星  周立波  朱光华 《高原气象》2001,20(3):234-238

对珠穆朗玛峰地区大气气溶胶化学民分进行了观测和分析。初步分析结果表明，珠峰地区大气气溶胶以Al,Ca,Si,K,Fe等地壳元素为主，地壳元素占总元素浓度的82％以上。S,Pb等与人类活动影响有关的污染元素含量很低。元素S浓度为91．64ng.m^-3，元素Pb浓度仅为2．93ng.m^-3，接近于格陵兰地区的浓度，从气富集因子来看，来自地壳成分元素的富集因子要小于北京地区。而As,Pb等与人类活动有关的气溶胶元素的富集因子也比北京地区低得多。研究表明，人类活动对珠峰地区的影响很小。  相似文献   

中国西北大气沙尘光学特性的数值试验   总被引：8，自引：11，他引：8  

成天涛  沈志宝 《高原气象》2001,20(3):291-297

利用 1991年 2月下旬～ 5月中旬HEIFE张掖和沙漠站的大气浑浊度观测、地面辐射观测及同期卫星资料 ,借助NCARCCM 3中的辐射模式CRM ,模拟估算了我国西北大气沙尘气溶胶的部分光学参数 ,单次散射反照率 (ω0 )和光学厚度比 [k(τλ=8～ 14 /τλ=0 .55) ]。计算结果表明 ,清洁天ω0 和k(τλ =8～ 14 /(τλ =0 .55)在沙漠和绿洲均为 0 .94和 0 .1;浑浊天ω0 在绿洲为 0 .90 ,沙漠为 0 .84 ;k(τλ=8～ 14 /τλ =0 .55)在绿洲为 0 .3 ,沙漠为 0 .4。在气候模式中 ,可将我国西部沙尘源区大气沙尘的ω0 和k(τλ =8～ 14 /τλ=0 .55)分别取为 0 .88和 0 .3。  相似文献   

1998年青藏高原东部及其邻近地区大气热源与南海夏季风的关系   总被引：12，自引：12，他引：12  

简茂球  罗会邦 《高原气象》2001,20(4):381-387

利用 1998年 5 8月南海季风试验期间的站点观测资料及NCEP再分析资料 ,计算了大气热源和水汽汇 ,并分析了南海季风爆发前后季风区对流层温度演变及其热力机制。结果表明 :南海夏季风的爆发与季风区对流层中高层南北温度梯度的逆转密切相关。南北温度梯度最先在孟加拉湾以东季风区发生逆转 ,半个月后在印度半岛及其以西地区逆转。季风爆发前中南半岛北部对流层中高层的迅速增温是由感热和潜热共同造成的 ,而华南及南海北部地区的增温则是由暖平流所致。 5、6月高原东部对流层中高层由非绝热加热造成的显著增温对东亚夏季风的北进和维持是非常重要的。 5、6月高原地区热源以感热为主 ;7、8月感热和潜热共同起作用  相似文献   

The High Concentration Tails Of The Probability Density Function Of A Dispersing Scalar In The Atmosphere   总被引：1，自引：0，他引：1  

R. J. Munro  P. C. Chatwin  N. Mole 《Boundary-Layer Meteorology》2001,98(2):315-339

The distribution function for concentrations of a scalar pollutant dispersing in the turbulent atmosphere has a finite domain that is bounded above and below. Three methods, based on extreme value statistics, are used to obtainestimates for the upper bound and to describe the high concentration tailbehaviour of the distribution; all three methods are applied to concentrationdata obtained from experimental atmospheric releases. Quantile quantile (QQ)plots are used to assess the goodness of fit of the resulting estimates of thedistribution, and also to compare the performance of the three methods. Thepredicted values for the upper bound are orders of magnitude less than thesource concentration, illustrating that molecular diffusion has a large effecton the high concentrations.  相似文献   

强弱南海夏季风活动及大气季节内振荡   总被引：26，自引：0，他引：26  

Li Chongyin  Long Zhenxi  Zhang Qingyun 《大气科学进展》2001,18(6):1146-1160

应用ＮＣＥＰ再分析资料和中国降水资料，分析研究了对应南海强、弱夏季风的环流形势及其与之相应的中国东部的降水异常。其结果表明，由强、弱夏季风所引起的中国气候异常是完全不同（甚至反相）的。分析大气季节内振荡（ＩＳＯ）的活动还表明，对应大气强（弱）南海夏季风，南海地区 ８５０ ｈＰａ也有强（弱）大气 ＩＳＯ；而强、弱南海夏季风环流（２００ ｈＰａ和 ８５０ ｈＰａ）主要由异常的大气ＩＳＯ所激发。本研究还揭示了南海地区大气ＩＳＯ的变化往往与江淮地区大气ＩＳＯ的变化反相，例如南海地区的强（弱）大气ＩＳＯ常与江淮流域的弱（强）大气ＩＳＯ相对应。对于大气ＩＳＯ的强度，一般多表现出局地激发特征，经向传播相对较弱。  相似文献   

无线电掩星反演大气参数误差分析及应用进展   总被引：3，自引：1，他引：3  

蒋虎  黄珹  严豪键 《地球物理学进展》2001,16(1):82-88

本文详细分析了影响空间GPS无线电掩星反演大气参数方法的主要误差源，其中包括信噪比误差，精密定轨误差，电离层模制误差，多路径效应和时钟改正等误差，并且介绍了国内外在无线电掩星领域的一些应用研究进展。  相似文献   

Analysis And Simulation Of Surface-Layer Winds Using Multiplicative Cascade Models With Self-Similar Probability Densities   总被引：1，自引：0，他引：1  

Michael K. Lauren  Merab Menabde  Geoffrey L. Austin 《Boundary-Layer Meteorology》2001,100(2):263-286

Statistical analysis techniques based on multiplicative cascades are investigated for use with surface-layer wind data sets collected in the atmospheric boundary layer over flat farm land. The data were found to exhibit multiscaling statistics, allowing the surface-layer winds to be simulated with the use of multiplicative random cascades. The study found evidence that, for the surface-layer at least, these cascade models (andhence the methods of multifractal analysis) should be applied in separate ways to the microscale inertial range, and the mesoscale. This is at odds with the view found in the existing literature, which proposes a `universal multifractal' model to replace the widely held view that there exists separate microscale, mesoscale and synoptic scales for which the processes governing each are different. At least two separate ranges of scaling are suggested for surface-layer wind data, corresponding to the microscale inertial range and the mesoscale. For the case of the mesoscale range, a self-similar distribution of weighting factors was found for the wind speed data themselves, rather than for an intermediate (dissipation) field, as is required for themicroscale data.  相似文献   

Synoptic circulation and stream discharge in the Great Lakes basin, USA     

R. V. Rohli  A. J. Vega  M. R. Binkley  S. D. Britton  H. E. Heckman  J. M. Jenkins  Y. Ono  D. E. Sheeler 《Applied geography (Sevenoaks, England)》2001,21(4)

Impacts on water resources caused by human activity, natural climate variation and long-term climate change are unclear in the US Great Lakes region. Improved understanding of the impact of atmospheric circulation on stream discharge variability into the Lakes is thus important. In this analysis, monthly surface and mid-tropospheric circulation patterns suggest that surface pressure variations over Missouri and Illinois are most strongly correlated to discharge. The mid-tropospheric patterns most directly related to discharge place the Great Lakes in a trough-to-ridge flow pattern. The analysis confirms that at this scale, lee shore advection resulting in ‘lake-effect’ precipitation is not very important to regional discharge, and neither are variations in the Pacific–North American teleconnection.  相似文献   

单波高精度测距系统的研究   总被引：12，自引：0，他引：12  

张学庄  王爱公 《测绘学报》1996,25(3):186-189

本文介绍了测距精度优于１０＾－６的自动高精度测距系统的构成、原理及春应用。  相似文献