DERIVATION OF FLUXES FROM PROFILES OVER A MODERATELY HOMOGENEOUS FOREST     

FRED C. BOSVELD 《Boundary-Layer Meteorology》1997,84(2):289-327

Measurements of fluxes and profiles of wind andtemperature are performed in the roughness layer ofa moderately homogeneous forest location. Weinvestigate to what extent vertical scalar fluxescan be derived from profile measurements. Theinfluence of inhomogeneities in the upwind terrainis investigated with footprint analysis and with aninhomogeneous surface-layer model. Four methods toestimate displacement height are suggested, amongthem is a method involving the structure parameterof the vertical wind. All methods give a decrease ofdisplacement height with increasing wind speed,while roughness length is found to increase withincreasing wind speed. For near-neutral conditionsdimensionless temperature gradients are found to besubstantially lower than the surface-layer valuesfound in the literature for homogeneous terrain with lowvegetation. Dimensionless shear however iscomparable with the surface-layer value. The heightof the roughness layer is 20 times the roughnesslength. Two schemes with locally derived surfaceparameters are tested to derive friction velocityand sensible heat flux from the profilemeasurements. These site specific schemes performsatisfactorily. A third scheme based on surface parameters chosen a priorifrom the literatureperforms significantly worse especially for low windspeed and unstable cases.  相似文献   

大别造山带地壳S波速度结构   总被引：19，自引：5，他引：19       下载免费PDF全文

王椿镛  宋建立 《地球物理学报》1997,40(3):337-346

在大别造山带深地震测深剖面H维P波地壳速度结构的基础上,从地震记录的水平分量得到S波地壳速度结构,并用P波和S波的资料共同约束地壳的组成.剖面上大多数炮点的记录均显示了清晰的Sg和SmS震相.在埠塔寺炮和金拱炮的记录上还较清晰地显示出莫霍界面的反射转换震相PmS,表明在相应的范围内莫霍界面是一级间断面.在Pn和SmS震相都比较强的记录截面图上缺少相应的Sn震相,表示在上地幄顶部泊松比随深度急剧增大,在这一深度上物质可能存在局部熔融状态.剖面的地壳泊松比模型表明,上地壳在深度10km以内泊松比为025左右,仅北淮阳弧后复理石带较低,为0.23；扬子板块和华北板块的下地壳泊松比为0.26-0.27；在大别选山带,上地壳下部泊松比为0.22-0.24,而下地壳泊松比为0.27-0.30,其中超高压变质带最高.P、S波速度和泪松比表明超高压变质带下地壳主要由基性麻粒岩组成.大别造山带中、下地壳组成的横向不均匀性反映了在三叠纪造山作用期间扬子板块向华北板块俯冲,以及存在与地慢物质相联系的岩浆侵入体.  相似文献   

地气测量在叶县—邓县—南漳地学剖面研究中的应用   总被引：7，自引：0，他引：7  

伍宗华  金仰芬 《岩石学报》1995,11(3):333-342

本剖面横跨华北地台南缘，秦岭造山带和杨子地台北缘。在剖面上系统地采集了壤中气、土壤和气溶胶样品，分别测定Ｃｒ、Ｃｏ、Ｎｉ、Ｃｕ、Ｐｈ、Ｚｎ等微量元素以及Ｈｇ气、Ｈｇ土、Ｒｎ、ＣＨ４、ＣＯ２等气体组分，研究了它们的空间分布特征，并结合剖面沿线的地质和地震资料，讨论了异常与岩性分布、地质构造和找矿靶区之间的关系。研究结果表明，宽坪群和二郎坪群是找寻多金属矿的有利层位；龙王集至龙门集一带是找油气的有利地段；潦河附近的Ｆ（１４）断裂带是一条规模较大的含金破碎带。这次试验的结果还表明，地气测量用于研究厚层的松散层覆盖下的地质构造具有良好的前景。  相似文献   

Wind profiles in the boundary layer over Kharagpur associated with synoptic scale systems     

D K Paul  S P Ghanekar  B S Murthy  K G Vernekar 《Journal of Earth System Science》1995,104(2):317-326

Doppler sodar wind data for the boundary layer over Kharagpur obtained during MONTBLEX-1990 at a height interval of 30 m from surface up to 1500 m have been analysed for the periods when intense synoptic scale disturbances from north Bay of Bengal moved along the eastern end of the monsoon trough. The variation in the vertical wind profile in the lower boundary layer over Kharagpur during the passage of synoptic scale disturbances has been discussed in the paper. The analysis indicates that the mean winds over Kharagpur veered with height in the lower boundary layer near the surface suggesting divergence over Kharagpur when the system lay south/southwest of the station. No such veering has been noticed when the centre of the system lay very close to the station.  相似文献   

小秦岭元古界剖面的保护及意义   总被引：1，自引：2，他引：1  

贾忆  王力 《陕西地质》1995,(2)

处于中国南北元古界之衔接部位的小秦岭元古界剖面具有重要的科研价值，1982年列为陕西省自然保护点，已采取了有效的保护措施予以保护，还应进一步提高研究、开发和保护水平。  相似文献   

100-200km热层大气光电离率及电子密度剖面对太阳活动的响应          下载免费PDF全文

陈耀武  洪儒珍 《地球物理学报》1992,35(2):142-149

本文利用新的太阳EUV辐射资料、中性大气结构模式及大气成分的吸收及电离特性,计算了100-200km大气的光电离率随高度、太阳天顶角及太阳活动的变化,求得了E-F₁谷的变化特征;利用完整的光化模式求得了电子密度随太阳天顶角的变化及对太阳活动的响应,并与IRI模式作了比较.结果表明,1.太阳活动指数与光电离率间的相关关系一般为正,但在一定的高度范围内,或在天顶角大于临界值X_cr=60°时,两者之间可出现负相关;2.太阳活动明显地影响E-F₁谷高与谷厚,当天顶角不变时,谷高与谷厚均与太阳活动成正相关;3.本模式与IRI间的偏差因子明显随高度及太阳天顶角而变化.  相似文献   

自由对流与稳定层结边界层风廓线的解析表达和边界层顶抽吸速度   总被引：4，自引：0，他引：4  

赵鸣 《大气科学》1992,16(1):18-28

基于近年来对自由对流和稳定边界层湍流交换特征的研究,求解边界层运动方程,得到这两种层结下边界层风的解析表达式.所得廓线与边界层特性参数符合观测特征.还求出了这二种层结下边界层顶抽吸速度的解析表达及其与某些参数的关系.结果表明,抽吸速度与层结有关,其特征可从物理上加以解释.  相似文献   

简易纵剖面仪及其在岩体结构面粗糙度系数研究中的应用   总被引：5，自引：1，他引：5  

杜时贵 《地质科技情报》1992,11(3):91-95

本文介绍了自制简易纵剖面仪的基本原理、主要部件及其操作要点。简易纵剖面仪具有原理简单、设备轻便、操作简便、实用效果好且速度快等优点。用简易纵剖面仪可快速绘制大量结构面表面轮廓曲线,以便进行JRC统计分析和结构面抗剪强度的统计估算,克服了由于样本数少而估算结果代表性差的缺陷;还可以从统计角度研究结构面JRC和抗剪强度的尺寸效应、各质异性和各向异性等问题,为客观地综合评价岩体结构面抗剪强度提供可靠依据。文末根据实用效果指出简易纵剖面仪在工程实践中的广阔应用前景。  相似文献   

Apport de la modélisation géophysique pour la compréhension de la structuration du pas de Calais     

Bruno Minguely  Jean-Louis Mansy  Michel Everaerts  Geoffrey M. Manby  Olivier Averbuch 《Comptes Rendus Geoscience》2005,337(3):305-313

This study is based on an analysis of seismic, gravimetric and magnetic data to model the structure of the Dover Straits area. The Dover Straits are set in a transitional position within the Brabant para-autochthon, which lies between the Ardennes allochthon to the south and the Brabant Massif to the north. The seismic profiles show that this area is characterised by several superimposed Mesozoic basins, whose evolution has been controlled by the reactivation of Lower Palaeozoic faults. In common with the adjacent Weald–Wessex and southern North Sea basins, the Dover Straits area records a Jurassic extensional phase and a post-Cretaceous tectonic inversion. The geophysical modelling reveals the presence of a basement to these Mesozoic basins that exhibits Ordovician to Silurian structures, which cannot be detected on the seismic reflection profiles. In contrast to earlier interpretations, the modelling presented here suggests that the Brabant Massif continues southward beyond the Dover Straits and under the Brabant para-autochthon. Gravity data also provides evidence for the presence of granitic body at depth, in the vicinity of Km 27 on the seismic profile, which may have driven the uplift of the Silurian rocks in the area of the Straits. Similar granitic intrusions have been proposed to explain gravity anomalies along the Rhenohercynian Margin in Belgium, eastern and southern England. The geophysical modelling demonstrates the continuity of the basement and Mesozoic basin structures across the Dover Straits, suggesting a common geological evolution of the adjacent southern England–northern France regions. To cite this article: B. Minguely et al., C. R. Geoscience 337 (2005).  相似文献   

四川盆地下中三叠统盐系地层古地磁研究与成盐条件有关问题探讨          下载免费PDF全文

林耀庭  何金权 《盐湖研究》2005,13(4):1-4

四川盆地下中三叠统嘉陵江组—雷口坡组(T1j-T2L)盐系地层蒸发岩发育,是我国海相碳酸盐岩沉积区探盐找钾的重要地区层位。现通过四川盆地下中三叠统盐系地层古地磁样品的系统采集和测试工作,首次在我国建立了古地磁磁性地层剖面,并根据测定结果,结合地质资料,探索了四川盆地下中三叠统(T1j-T2L)成盐古气候条件及其时代归属等有关问题。  相似文献