沙漠地区春季的大气浑浊度及沙尘大气对地面辐射平衡的影响   总被引：10，自引：8，他引：10  

沈志宝  文军 《高原气象》1994,13(3):330-338

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大孔隙与大孔隙率矿石的石蜡法体重测定中的修正问题   总被引：1，自引：0，他引：1  

胡正安 《铀矿地质》1994,(4)

以伽玛测井解释含量确定铀矿储量时，矿石体重应该是天然状态下的体重，当矿心孔隙度较大而有部分失水，并存在表面大孔隙时，封蜡法所测得的体重系统偏小。对此，本文改进了测定方法，提出了修正方案，并以某矿床为例分析了产生表面孔隙的原因及修正后的具体结果。  相似文献   

Surface sensible heat flux over a deep moist convective region and its interplay with synoptic and mesoscale features     

R. Pradhan  U. K. De  P. K. Sen 《Journal of Earth System Science》1994,103(3):353-367

The surface parameters are being evaluated using a methodology which considers the vertical temperature structure of MONTBLEX ’90. For this 30 metre micrometeorological tower data are utilised. In this process, a concept of isolated layers has been introduced. The parameters have been evaluated following two successive iterative processes to give a consistent value both in the flux-profile relation and the related similarity relation. The heat flux obtained using the present methodology, is then utilised to examine its interplay with the synoptic as well as mesoscale features. The existence of such an interplay is observed.  相似文献   

青藏高原地区云对地面有效辐射的影响：Ⅱ.强迫作用   总被引：2，自引：0，他引：2  

王可丽  钟强 《高原气象》1994,13(2):128-134

本文利用１９８２年８月－１９８３年７月青藏高原地面热源观测试验资料，讨论了与云对地面有效辐射强迫作用有关的参数的计算问题，并对这些参数的计算结果进行了分析。结果表明：晴空、全云条件下的地面有效辐射和云对地面有效辐射强迫作用的年平均日变化振幅有明显的地域差异；云对地面有效辐射的强迫作用春夏大，秋冬小，甘孜、拉萨、那曲和改则４站平均的年平均值为－２７．２Ｗ／ｍ＾２。?  相似文献   

青藏高原地区地表及行星反射率   总被引：5，自引：3，他引：5       下载免费PDF全文

孙治安  翁笃鸣 《应用气象学报》1994,5(4):394-401

文章讨论了利用ISCCP卫星观测资料确定青藏高原地区地表反射率的方法，在无积雪地区和季节，地表反射率可以ISCCP可见光反射率为基础，在模式计算过程中，假定紫外反射率以及红外与可见光反射率的比值分别为常数。敏感性试验表明，由这两个假设所产生的误差并不显著。在有积雪地区或季节，地表平均反射率可直接由ISCCP可见光反射率表示。试验结果与地面实际观测作了比较，除沙漠区外，两者比较一致。文中还计算了高原晴天行星反射率。经与ERBE卫星观测比较，发现从5月至9月高原周围沙漠区气溶胶对辐射平衡有较显著的影响。而在其  相似文献   

Species Composition and Some Ecological Notes on Diatom Communities of a Lotic Environment in Tarhunãh,Libya Artenzusammensetzung und einige ökologische Notizen über Diatomeengesellschaften eines lotischen Biotops in Tarhunãh/Libyen     

M. A. Khan 《洁净——土壤、空气、水》1994,22(1):28-31

Libya occupies a large part of the Sahara Desert, and is a predominantly arid country with extremely scarce freshwaters. Despite aridity, a distinct higher rainfall zone exists along its mediterranean coastal belt. A lotic environment (perennial stream) in Ain-Scersciara, Tarhunãh in northwest Libya was studied for the species composition of diatom communities and their ecological characteristics. The waters are generally alkaline (pH = 7.5) and of hard-water (conductivity = 2008 μS/cm) type. The epiphytic diatom growth on benthic filamentous algae was high (32 taxa) with Amphora veneta as a very common taxon. Gomphonema parvulum var. micropus was an important taxon found in scrapings from the leaves of macrophytes and stony substratum. Nitzschia and Navicula showed high species richness (9 taxa in each) followed by Gomphonema (6 taxa). The ecological attributes of the majority of taxa show an oligohalobe status and alkaliphilous indicator.  相似文献   

Surface sealing as influenced by slope angle and position of simulated stones in the top layer of loose sediments   总被引：1，自引：0，他引：1  

Jean Poesen 《地球表面变化过程与地形》1986,11(1):1-10

The influence of five different slope angles and two different positions of simulated stones in the top layer of a sandy and a silty sediment on surface sealing intensity is examined in the laboratory. Sealing intensity is assessed by studying changes of percolation rate through a sediment layer with simulated rainfall duration and by measuring cohesion of the 5 mm thick upper sediment layer, a measure of seal strength, by means of a torvane. Slope has a negative influence on sealing intensity. For a constant per cent of simulated stone cover, sealing intensity is lowest in the case of stones placed on the sediment surface compared to the case of stones pushed into the surface layer. Explanations for these findings are given and some implications are further discussed.  相似文献   

青藏高原积雪的分布特征及其对地面反照率的影响   总被引：7，自引：3，他引：7  

韦志刚  吕世华 《高原气象》1995,14(1):67-73

通过对１９８３年７月至１９９０年６月青藏高原主体５８个格点积雪资料进行ＥＯＦ分析发现，青藏高原主体积雪分布以西部兴都库什山脉。天山山脉以及南部喜马拉雅山脉为主；高原中部唐古拉山脉、北部昆仑山脉和东部巴颜喀拉山脉的积雪相对较少，青藏高原西部、南部的积雪变化与中部、北部和东部的积雪变化趋势存在反位相关系。另外，本文还对积雪对高原地面反照率的影响作了简单分析。  相似文献   

A new technique for determining the surface level of salt marshes and other uncompacted sedimentary environments     

Alan P. Carr 《地球表面变化过程与地形》1983,8(3):293-296

The method described involves the use of an electro-optical distance measurer mounted on a theodolite. Observations are taken onto a series of acrylic reflectors, aligned at right angles to the line of sight, and slope distances and vertical and horizontal angles are recorded. From these data it is possible to obtain surface heights to an accuracy of ±0·5 cm at 200 m and to avoid any direct disturbance of the site under investigation.  相似文献   

Growth Of The Summer Daytime Convective Boundary Layer At Anand     

S. G. Nagar  Ajit Tyagi  P. Seetaramayya  S. S. Singh 《Boundary-Layer Meteorology》2001,98(2):297-314

The heights of the daytime convective boundary layer (CBL), computed by a one-dimensional model for a bare soil surface at a semi-arid station,Anand, during the dry and hot summer month of May 1997, are presented. As input, the model requires surface heat flux, friction velocity and air temperature as functions of time. Temperature data at the one-metre level from a tower and sonic anemometer data at 9.5 m collected during the period 13–17 May 1997 in the Land Surface Processes Experiment (LASPEX-97) are used to compute hourly values of surface heat flux, friction velocity and Obukhov length following the operational method suggested by Holtslag and Van Ulden [J. Climate Appl. Meteorol. 22,517–529 (1983)]. The model has been tested with different values for the potential temperature gradient ( ) above the inversion. The model-estimated CBL heights comparefavourably with observed heights obtained from radiosonde ascents.  相似文献