太阳宇宙线高能电子能谱的形成          下载免费PDF全文

黄永年  汪学毅 《地球物理学报》1996,39(2):145-151

提出了一个太阳脉冲和经变耀斑中高能太阳宇宙线电子能谱的形成模型，探讨了高能电子通过日冕捕获区的库仑损失、轫致辐射和同步辐射等物理过程，首次研究了日冕等离子体尾场对太阳宇宙线电子的加速及其能谱的形成．所得结果和观测谱能很好地符合，从而较合理地阐明了脉冲耀斑和经变耀斑两类太阳宇宙线高能电子谱的结构．  相似文献   

青藏高原地区能量水分循环：地表能量平衡和湍流热通量   总被引：2，自引：0，他引：2  

苏中波  张廷  马耀明  贾立  文军 《地球科学进展》2006,21(12):1224-1236

文章给出了青藏高原能量水分循环研究的概况和总结，着重估计了能量平衡各分项和湍流热通量等。在能量平衡的计算基础上，尽管能量不平衡的原因解释仍有争论并且没有解决，但我们揭示了GAME/Tibet试验观测资料中能量不平衡现象。我们发现估算的潜热通量比实际观测的要高许多。然而，根据能量平衡假设的计算结果和SEBS的估算一致性很好。在此基础上可以归纳出差异主要由GAME/Tibet试验观测资料中能量不平衡引起，潜热通量的实际观测可能偏小。  相似文献   

Energy approach for earthquake induced slope failure evaluation     

T. Kokusho  T. Ishizawa 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):221-230

Earthquake-induced slope stability is evaluated by the force-equilibrium method in engineering practice. This method provides a safety factor against initiating failure or displacement according to the Newmark model along a fixed slip surface but it cannot evaluate failure deformations after failure occurs. An energy approach is proposed as an alternative means for evaluating slope failures and subsequent flow deformations. The driving energy for slope displacement is considered to be the earthquake energy and the gravitational potential energy. As a first step in the research, an energy balance is formulated for the model of a rigid block resting on an inclined plane. Then, an innovative model test is developed, in which the energy balance in a sliding slope is measured on a shake table. The earthquake energy used for the slope failure can be successfully quantified in the test and its contribution to displacement is discussed in the light of the energy balance established for the block model.  相似文献   

Buoyancy and The Sensible Heat Flux Budget Within Dense Canopies   总被引：1，自引：8，他引：1  

D. Cava  G. G. Katul  A. Scrimieri  D. Poggi  A. Cescatti  U. Giostra 《Boundary-Layer Meteorology》2006,118(1):217-240

In contrast to atmospheric surface-layer (ASL) turbulence, a linear relationship between turbulent heat fluxes (F_T) and vertical gradients of mean air temperature within canopies is frustrated by numerous factors, including local variation in heat sources and sinks and large-scale eddy motion whose signature is often linked with the ejection-sweep cycle. Furthermore, how atmospheric stability modifies such a relationship remains poorly understood, especially in stable canopy flows. To date, no explicit model exists for relating F_T to the mean air temperature gradient, buoyancy, and the statistical properties of the ejection-sweep cycle within the canopy volume. Using third-order cumulant expansion methods (CEM) and the heat flux budget equation, a “diagnostic” analytical relationship that links ejections and sweeps and the sensible heat flux for a wide range of atmospheric stability classes is derived. Closure model assumptions that relate scalar dissipation rates with sensible heat flux, and the validity of CEM in linking ejections and sweeps with the triple scalar-velocity correlations, were tested for a mixed hardwood forest in Lavarone, Italy. We showed that when the heat sources (S_T) and F_T have the same sign (i.e. the canopy is heating and sensible heat flux is positive), sweeps dominate the sensible heat flux. Conversely, if S_T and F_T are opposite in sign, standard gradient-diffusion closure model predict that ejections must dominate the sensible heat flux.  相似文献   

An Improved Mellor–Yamada Level-3 Model: Its Numerical Stability and Application to a Regional Prediction of Advection Fog     

Mikio Nakanishi  Hiroshi Niino 《Boundary-Layer Meteorology》2006,119(2):397-407

This note describes a numerically stable version of the improved Mellor–Yamada (M–Y) Level-3 model proposed by Nakanishi and Niino [Nakanishi, M. and Niino, H.: 2004, Boundary-Layer Meteorol. 112, 1–31] and demonstrates its application to a regional prediction of advection fog. In order to ensure the realizability for the improved M–Y Level-3 model and its numerical stability, restrictions are imposed on computing stability functions, on L/q, the temperature and water-content variances, and their covariance, where L is the master length scale and q ²/2 the turbulent kinetic energy per unit mass. The model with these restrictions predicts vertical profiles of mean quantities such as temperature that are in good agreement with those obtained from large-eddy simulation of a radiation fog. In a regional prediction, it also reasonably reproduces the satellite-observed horizontal distribution of an advection fog.  相似文献   

Addressing Scottish rural fuel poverty through a regional industrial symbiosis strategy for the Scottish forest industries sector     

Barbara Illsley  Bill Lynch 《Geoforum》2007,38(1):21-32

Tackling fuel poverty is central to the delivery of the Scottish Executive’s commitment to social justice. Many Scottish rural households are not linked into the mains gas network and rely on expensive alternatives, despite being surrounded by plentiful supplies of low-cost renewable wood biomass. A regional study was undertaken to establish the potential market for pelletised wood fuel, available as a low-value by-product from the rapidly expanding Scottish forest industry sector. The wider implications of the research findings are analysed by extending the principles of industrial symbiosis from a site-specific to a regional scale. Promoting an indigenous pellet-based wood fuel market for rural Scotland would fulfil important Scottish Executive economic, social and environmental sustainability objectives. Adding off-site social symbiotic elements increases the potential for on-site technical symbiosis in nascent Scottish forest industry clusters. At present, market failure is preventing the realisation of these benefits, and the paper concludes by identifying ways in which market intermediation, through wood fuel energy service companies, might overcome the current barriers to exploiting such symbiosis.  相似文献   

Comparison of 15 evaporation methods applied to a small mountain lake in the northeastern USA   总被引：7，自引：0，他引：7  

Donald O. Rosenberry  Thomas C. Winter  Donald C. Buso  Gene E. Likens   《Journal of Hydrology》2007,340(3-4):149-166

Few detailed evaporation studies exist for small lakes or reservoirs in mountainous settings. A detailed evaporation study was conducted at Mirror Lake, a 0.15 km² lake in New Hampshire, northeastern USA, as part of a long-term investigation of lake hydrology. Evaporation was determined using 14 alternate evaporation methods during six open-water seasons and compared with values from the Bowen-ratio energy-budget (BREB) method, considered the standard. Values from the Priestley–Taylor, deBruin–Keijman, and Penman methods compared most favorably with BREB-determined values. Differences from BREB values averaged 0.19, 0.27, and 0.20 mm d⁻¹, respectively, and results were within 20% of BREB values during more than 90% of the 37 monthly comparison periods. All three methods require measurement of net radiation, air temperature, change in heat stored in the lake, and vapor pressure, making them relatively data intensive. Several of the methods had substantial bias when compared with BREB values and were subsequently modified to eliminate bias. Methods that rely only on measurement of air temperature, or air temperature and solar radiation, were relatively cost-effective options for measuring evaporation at this small New England lake, outperforming some methods that require measurement of a greater number of variables. It is likely that the atmosphere above Mirror Lake was affected by occasional formation of separation eddies on the lee side of nearby high terrain, although those influences do not appear to be significant to measured evaporation from the lake when averaged over monthly periods.  相似文献   

The impact of freshwater discharges on the ocean circulation in the Skagerrak/northern North Sea area. Part II: energy analysis     

Jon Albretsen 《Ocean Dynamics》2007,57(4-5):287-304

We perform eddy-permitting to eddy-resolving simulations of the Skagerrak/northern North Sea with a terrain-following numerical ocean model. We demonstrate that realistic representations of freshwater input are not required when the focus is on modelling mesoscale structures such as meanders and eddies. To arrive at this conclusion, we analyze the results using a recently developed energy diagnostic scheme to study the sensitivity to realistic representations of the lateral freshwater flux provided to the area from the Baltic Sea and by the major rivers. The scheme is suitable for analysis of growth of instabilities, and it has four basic instability processes prominent. We recognize both horizontal and vertical shear instabilities. There are two processes where average potential energy is converted to eddy kinetic energy, and they are related to the mean gradient in surface elevation and the mean lateral density gradient, respectively. The latter process is known as frontal instability. We demonstrate that the change in the eddy kinetic energy field is small, despite the large variations in the hydrographic properties from experiment to experiment. Moreover, generation of eddy activity appears at the same locations and with approximately the same strength regardless of actual representations of freshwater input. Furthermore, we find that vertical shear instability dominates the energy conversion processes in the Norwegian Coastal Current. Finally, we find that the areas off the northwest coast of Denmark recognized with enhanced eddy kinetic energy level is not caused by instability processes but eddy–eddy interaction rooted in variations in the sea level.  相似文献   

一次江淮暴雨的数值模拟及暴雨落区的诊断分析   总被引：4，自引：11，他引：4       下载免费PDF全文

史小康  李耀东  高守亭  付容 《气象科学》2007,27(1):26-34

利用MM5模式对2003年7月一次江淮暴雨过程进行了数值模拟,结果表明：MM5对本次暴雨落区的模拟较为成功。应用模拟结果对假相当位温、水汽通量散度、z-螺旋度及湿位涡等几个综合性物理量进行了诊断,得出的主要结论为：本次暴雨发生在高能舌的前部、能量锋区南缘和低空急流左前方三者叠加的区域;水汽通量散度比较好地反映本次暴雨的强度和落区;z-螺旋度不仅能反映降水系统,对降水系统的移动也有预报指示意义;本次暴雨过程中湿斜压性和涡度垂直分量与热力不稳定对湿位涡有同等大小的贡献。  相似文献   

基于高光谱遥感数据提取森林结构参数的研究     

曾源  Michael E. Schaepman  吴炳方  Jan G. P. W. Clevers  Arnold K. Bregt 《遥感学报》2007,11(5):648-658

以位于三峡库区的龙门河森林自然保护区为研究区,综合利用线性光谱混合模型和几何光学模型,基于高光谱遥感数据提取森林结构参数是本文研究的重点。在研究区地面调查数据的基础上,通过高光谱数据和混合光谱分解法,获得反演几何光学模型所需的四分量参数,根据背景光照分量与森林植被冠层各参数间的关系,反演得到森林冠层郁闭度及平均冠幅的定量分布图,并利用37个野外实测样本进行结果验证。  相似文献