青藏高原地区地表温度及其取值对大气长波辐射冷却的影响   总被引：4，自引：0，他引：4  

江灏  王可丽 《高原气象》1997,16(3):250-257

针对辐射传输模式在青藏高原地区的应用问题，使用Ｌｉｏｕ－Ｏｕ一维辐射传输模式及１９８２年８月￣１９８３年７月青藏高原热源观测实验期间青藏高原地面、高空与卫星观测资料，在高原辐射传输模式中区分了下垫面温度与地表空气温度的作用，并利用卫星观测资料对模式改进后的实际效果进行了验证；分析了地表温度的日变化和季节变化硬度，得到了下垫面温度的简单参数化方法。  相似文献   

青藏高原冬小麦田辐射能量收支的初步研究   总被引：7，自引：0，他引：7       下载免费PDF全文

张宪洲  王辉民 《应用气象学报》1997,8(2):236-241

通过对青藏高原冬小麦田净全辐射各分量的观测资料分析，论述了净全辐射及其各分量的日变化特征；计算得出冬小麦抽穗—乳熟期麦田平均反射率为13.3%，净全辐射占总辐射百分率:白天75%，包括夜间67.4%；指出了净全辐射和总辐射间存在良好的线性关系，给出了由总辐射计算净全辐射的经验公式。  相似文献   

Stabilization of swelling clays by Mg(OH)₂. Changes in clay properties after addition of Mg-hydroxide     

G. S. Xeidakis 《Engineering Geology》1996,44(1-4):107-120

Stabilization of the swelling clay structure is attempted by intercalation of Mg(OH)₂ and the development of a brucite interlayer between the clay layers. The properties of the product obtained by applying the technique, formulated as described in a previous work, are considered here. The materials used were Wyoming bentonite (USA), Fuller's Earth (UK), kaolinite, illite, lignite, and silica gels. The Mg(OH)₂-clay products were examined by the methylene blue dye test, X-ray diffraction analysis (XRD), differential thermal analysis (DTA), and derivative thermogravimetry analysis (DTGA). From the results obtained it is concluded that: the Mg-hydroxide is adsorbed by swelling clays both on their external and internal surface, whereas it is adsorbed on the external surface by non-swelling clays. The internally adsorbed phase of Mg-hydroxide forms an ill-defined interlayer of brucite, retarding swelling, whereas the external phase covers the particles modifying drastically their surface properties, like the adsorption of the MB dye. The material produced after precipitation of Mg-hydroxide on swelling clays (smectites) did not re-expand on wetting or after glycolation. The adsorption of MB dye was also reduced by some 80–90%, due to coating effect, preventing the measurements of the external surface area of the clay by polar molecules. The principal forces involved in the process are believed to be physical adsorption on the external surface, along with chemisorption and some chemical bonding, mostly in the internal surface. Cementation due to crystallization and, in the long term, some pozzolanic reactions take also place. Internal adsorption of the Mg-hydroxide is postulated to be in the form of positively charged mono- and/or small polymers and it is, chiefly, diffusion controlled. Since Mg-hydroxide is internally adsorbed by swelling clays, whereas Ca-hydroxide(lime) is not, and the (Mg, Ca)-clay aggregates are more stable than the Ca-clay or the Mg-one, the combination of the two hydroxides could give better results in soil stabilization than each hydroxide alone.  相似文献   

煤层倾角与覆岩变形破裂分带   总被引：7，自引：0，他引：7  

杜时贵  翁欣海 《工程地质学报》1997,5(3):211-217

地下采煤中三带(冒落带、裂隙带、弯曲带)高度的判断是预测采空引起地表变形破坏程度的依据。在诸多的影响因素中, 煤层倾角是控制三带高度的最主要因素。建立在实测统计基础上的经验范围值用于三带高度的判断带有一定的人为性。急倾斜煤层中冒落带和裂隙带高度随煤层倾角变化的规律已被褐示[7].通过弹塑性岩石材料的非线性有限元模拟, 本文提出了利用应力重分布图判断中、缓倾角煤层采空区覆岩三带高度的方法, 并应用于实际工程。  相似文献   

Comparison of Aircraft and Ground-Based FluxMeasurements during OASIS95     

P. R. Isaac  J. Mcaneney  R. Leuning  J. M. Hacker 《Boundary-Layer Meteorology》2004,110(1):39-67

Aircraft and ground-based measurements made during the1995 Australian OASIS field campaign are compared. The aircraft data were recorded during low-level flightsat 6 m above ground level and grid flights at altitudes of between 15 and 65 m, allin unstable atmospheric conditions. The low-level flights revealed an inadequate temperaturesensor response time, a correction for which was determined from subsequent work ina wind tunnel. Aircraft and ground-based measurements of mean wind speed, wind directionand air temperature agree to within 0.2 m s^-1, 4° and 0.9 °C respectively.Comparisons between aircraft and ground-based observations of the standarddeviations of vertical velocity, horizontal wind speed, air temperature and specifichumidity have slopes of 0.96, 0.97, 0.92 and 0.99 respectively but the observed scatter isroughly twice the random error expected due to the averaging length of the aircraft data andthe averaging period of the ground-based data. For the low-level flights, the ground-basedand aircraft measurements of sensible and latent heat flux show mean differences of 27 and-25 W m^-2 respectively, which reduce to 11 and -4 W m^-2 respectivelywhen analysis of aircraft data is limited to areas immediately adjacent to the fluxtowers. For the flights at 15 to 65 m above ground level, the mean differences between theground-based and aircraft measurements of sensible and latent heat flux are -22 and-1 W m^-2 respectively and these change to -1 and -7 W m^-2 respectively oncethe effect of surface heterogeneity is included. Aircraft and ground-based measurementsof net radiation agree to within 6% at one ground-based site but differ by 20% at a second.Aircraft measurements of friction velocity at 6 m above the ground agree well withground-based data, but those from flights between 15 and 65 m above ground level do not.This is because at these heights the aircraft measurements provide the local shear stress,not the surface shear stress. Overall, the level of agreement allows confidence in the aircraftdata provided due care is taken of instrument response times and differences in thesurfaces sampled by aircraft and ground-based systems.  相似文献   

Radiative Exchange in an Urban Street Canyon   总被引：1，自引：4，他引：1  

Ian N. Harman  Martin J. Best  Stephen E. Belcher 《Boundary-Layer Meteorology》2004,110(2):301-316

The influence of building geometry on the radiation terms ofthe surface energy balance is a principal reason for surfacetemperature differences between rural and urban areas.Methods exist to calculate the radiation balance in an urban area,but their validity across the range of urban geometries andmaterials has not been carefully considered.Here the exchange of diffuse radiation in an urban street canyon isinvestigated using a method incorporating all reflections of radiation.This exact solution is compared to two commonly used approximationsthat retain either no reflections, or just one reflection of radiation.The area-averaged net radiative flux density from the facets of the canyondecreases in magnitude monotonically as the canyon aspect ratio increases.The two approximate solutions possess unphysical differences from thismonotonic decrease for high canyon aspect ratios or low materialemissivities/high material albedos.The errors of the two approximate solutions are small for near blackbodymaterials and small canyon aspect ratios but can be an order ofmagnitude for intermediate material properties and deep street canyons.Urban street canyon models need to consider at least one reflectionof radiation and multiple reflections are desirable for full applicability.  相似文献   

Estimation of Regional Evapotranspiration by Combining Aircraftand Ground-Based Measurements     

P. R. Isaac  R. Leuning  J. M. Hacker  H. A. Cleugh  P. A. Coppin  O. T. Denmead  M. R. Raupach 《Boundary-Layer Meteorology》2004,110(1):69-98

Two methods are examined for combining measurements from instrumented aircraftand towers to estimate regional scale evapotranspiration. Aircraft data provided spatially averaged values of properties of the surface, the evaporative fraction and maximum stomatal conductance. These quantities are less sensitive to meteorological conditions than the turbulent fluxes of heat and water vapour themselves. The methods allowed aircraft data collected over several days to be averaged and thus to reduce the random error associated with the temporal under-sampling inherent in aircraft measurements. Evaporative fraction is estimated directly from the aircraft data, while maximum stomatal conductance is estimated by coupling the Penman–Monteith equation to a simple model relating surface conductance to the incoming shortwave radiation and specific humidity saturation deficit. The spatial averages of evaporative fraction and maximum stomatal conductance can then be used with routine tower data to estimate the regional scale evapotranspiration. Data from aircraft flights and six ground based sites during the OASIS field campaign in south–east New South Wales in 1995 have been used to check the methods. Both the evaporative fraction and the maximum stomatal conductance derived from the aircraft data give information on the spatial variability of the surface energy budget at scales from 10 to 100 km. Daily averaged latent heat fluxes estimated using these methods for the OASIS study region agree with the available observations in quasi-stationary conditions or in weakly non-stationary conditions when the data from several aircraft flights are averaged to reduce the impact of short term imbalances in the surface energy budget.  相似文献   

程海断裂带断层泥中石英碎砾表面SEM特征及断层活动状态的分析   总被引：4，自引：0，他引：4  

俞维贤  王彬  毛燕  杨继武 《中国地震》2004,20(4):347-352

根据断层泥中石英碎砾表面SEM特征的鉴定研究，可将程海断裂中、北段断层泥中石英碎砾表面SEM形貌特征分为6类，这表明该段断裂经历了长期多期次活动，强烈活动时间在中晚更新世；5件样品中均未见破裂类(Io)的石英颗粒，表明程海断裂全新世以来强烈活动的频度相对较低。石英碎砾表面机械作用特征的分类统计研究显示：程海断裂中、北段晚更新世以来，断层所经历的活动方式以粘滑活动为主。  相似文献   

Parameters of Land-Surface Processes for Gobi in North-West China   总被引：1，自引：0，他引：1  

Zhang Qiang  Huang Ronghui 《Boundary-Layer Meteorology》2004,110(3):471-478

Using data from the intensive observation period (May–June 2000) of the NWC-ALIEX (The Field Experiment on Interaction between Land and Atmosphere in Arid Region of North-west China), the characteristics and mechanisms of some key land-surface process over Gobi in a typical arid region of north-west China are analyzed and several parameters of land-surface processes are calculated. The weighted mean of the surface albedo over a typical arid region of the Dunhuang Gobi is calculated using the relative reflection as a weighting factor, and its value is 0.255 ± 0.021. After removing the influence of precipitation, the mean soil heat capacity over a typical arid region of the Dunhuang Gobi is 1.12 × 10⁶ J m^-3 K^-1,which is smaller than that observed in the Heihe (China) River basin Field Experiment (HEIFE). The mean soil heat diffusivity and conductivity are about half of those observed in HEIFE.  相似文献   

A Preliminary Analysis of Relations Between Tectonic Deformation of Sedimentary Cover and Basement in Kuqa Depression     

Liu Jie 《中国地震研究》2004,18(4):406-416

Study of seismic activity in the Kuqa area enables us to infer some possible active faults in basement from the epicentral distribution on different profiles. The relations between active faults in the basement and surface structures are analyzed and the difference between sedimentary cover and basement in their deformation characteristics and the genesis are discussed. The following conclusions have been drawn : ( 1 ) the epicentral distribution indicates that, the east Qiulitag and south and north Qiulitag deep faults in the basement correspond to the east and west Qiulitag anticlines, respectively. Moreover, deep faults also exist beneath the Yiqiklik and Yaken anticlines. It indicates that the formation of surface structures is controlled by deep structures; (2) A NE-trending strike-slip fault develops along the line from the western termination of Yiqiklik structure to Dongqiu Well 5 and a NW-trending active fault on the western side of Baicbeng. The two active faults across the tectonic strike are the main causes for tectonic segmentation of the Kuqa depression and possibly the cause for the middle segment (Kuqa-Baicheng) of the depression to be more shortened than both its eastern and western terminations; (3) The difference between the sedimentary cover and basement in their deformation characteristics depends mainly on the different properties of media between them.The lithospheric strength of the basement in the basin is fairly high, which determines the basement deformation to be mainly of brittle fracture seismic activity. While the strength of sedimentary cover is low, where there exist weak thin layers, such as coal and gyps. Under the effect of strong tectonic compression, the sedimentary rocks may undergo strong viscous or plastic flow deformation; meanwhile, an aseismic detachment may take place along the weak layers.  相似文献