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651.
局地相似性关系在城市边界层中的适用性验证 总被引:1,自引:0,他引:1
利用中国科学院大气物理研究所325 m铁塔在2003年8月期间47和120 m高度上的湍流观测资料,对局地相似性关系在城市边界层的适用性进行了检验。结果表明:47 m高度仍属于城市冠层之上的近地面常通量层,莫宁-奥布霍夫相似性关系基本适用。但120 m高度则基本属于近地面层与自由对流层之间的过渡高度,在该处,相似性关系部分适用。同时,给出了不同的层结稳定度条件下47和120 m高度上的无量纲速度和温度标准差与稳定度之间的局地相关表达式。 相似文献
652.
Flux-Variance Method for Latent Heat and Carbon Dioxide Fluxes in Unstable Conditions 总被引:4,自引:0,他引:4
Xiaofeng Guo Hongsheng Zhang Xuhui Cai Ling Kang Tong Zhu Monique Y. Leclerc 《Boundary-Layer Meteorology》2009,131(3):363-384
Applied previously to momentum and heat fluxes, the present study extends the flux-variance method to latent heat and CO2 fluxes in unstable conditions. Scalar similarity is also examined among temperature (θ), water vapour (q), and CO2 (c). Temperature is adopted as the reference scalar, leading to two feasible strategies to estimate latent heat and CO2 fluxes: the first one relies on flux-variance similarity relations for scalars, while the second is based on the parameterization
of relative transport efficiency in terms of scalar correlation coefficient and a non-dimensional quantity. The relationship
between the θ-to-q transport efficiency (λ
θ
q
) and θ-q correlation coefficient (R
θ
q
) is used to describe the intermediate hydrological conditions. We also parameterize the θ-to-c transport efficiency (λ
θ
c
) as a function of the θ-c correlation coefficient (R
θ
c
) by introducing a new non-dimensional ratio (α). The flux-variance method is a viable technique for flux gap-filling, when turbulence measurements of wind velocity are
not available. It is worth noting that the extended method is not exempt from a correction for density effects when used for
estimating water or carbon exchange. 相似文献
653.
654.
655.
The Influence of Transient Flow Distortion on Turbulence in Stable Weak-Wind Conditions 总被引:1,自引:1,他引:0
L. Mahrt 《Boundary-Layer Meteorology》2008,127(1):1-16
Transport by very weak turbulence near the surface, particularly with strong stratification, often violates existing similarity
theory due partly to transient distortion of the wind profile by nonstationary mesoscale motions. This problem is examined
with 4 months of flux data at seven levels on a 30-m tower. Difficulties with calculation of fluxes and shear with weak winds
and weak turbulence are examined. The distortion of the wind profile assumes a wide variety of forms, but sometimes occurs
with a transient wind maximum in the lowest 10 m. Though the vertical mixing of momentum is weak for weak-wind nonstationary
conditions, it is often more efficient than predicted by existing similarity theory. In fact for weak-wind stable conditions,
the flux-gradient relationship depends more on the curvature of the wind profile than the value of the stability parameter.
This statistical study suggests a new direction for future work, but does not unravel the physics of the complex and varied
structure for stratified weak-wind conditions. 相似文献
656.
洋山港海域与长江口相似性研究 总被引:11,自引:0,他引:11
根据洋山港海域的水文泥沙观测资料和长江口的研究文献分析,洋山港海域与长江口存在较多相似现象。2者均存在滞流区现象是产生其它相似现象的根本原因。即高悬沙浓度区分布特征,表层沉积特征和浅滩区分布特征的相似性是滞流区现象的衍生效应。洋山港海域与长江口的诸多相似现象揭示:(1)滞流区的动力平衡作用是最大浑浊带和拦门沙浅滩形成的主导因素;(2)滞沙区通常位于滞流区地形束窄一侧;(3)滞流区的细颗粒物质沉积区与滞流点位置(或滞流区形态)有着较为一致的吻合性,洋山港海域与长江口区间属于未来开发的热点地区,对2者的相似现象开展深入的研究将有着较深的理论和实际意义。 相似文献
657.
5 Conclusions Studies on the similarities between the energy release on the surface of the shape memory alloy and the strong seismic activities
in China lead to the possibilities that the results obtained from the observations and experiments of the energy release phenomenon
in the shape memory alloy are promisingly useful in the seismic research area. This method can be realistically significant
to the studies of the seismogenic mechanisms (especially for the short-impending characters), the prediction of the strong
seismic activity and the seismogenic model.
This subject is supported by the State Seismological Bureau under the contract number 85-04-7-6, and by the National Natural
Science Foundation. 相似文献
658.
659.
The experiment system of 1000 m deep sea mining system is built up with the similarity theory.Sine mechanism is used to simulate mining ship to generate lateral shock excitation by ocean wave.Simulation and experiment of spherical joint connecting deep sea mining system has been done in band six marine conditions.The results indicate that the moment of spherical joint connecting deep sea mining is smaller than that of the thread connected ones,the lifting pipe of spherical joint is "flexible pipe".The flexural torque of the articulated lifting pipe system in pump and buffer is generally periodic variation with some irregularity,the value is stable on 60 N·S,and it is obviously smaller than that of the fixed lifting pipe system;The total displacement exhibits cyclic variation pattern,and the periodicity of them is longer than that of sea current.The results of experiment and simulation are basically consistent.And the analysis in the paper offers theoretical foundation of 1000 m deep sea mining system in China. 相似文献
660.
采用紫外线辐射的方法对巴氏杜氏藻(Dunaliella bardawil)进行诱变.经过低温(5±1℃)筛选,得到一耐低温的突变株,命名为Dunaliella bardawilvar.L-5 Zhou&Liu(简称L-5).研究表明,在5±1℃光照培养箱中光强1 100 lx培养57 d,L-5仍继续处于对数生长期,而对照组早已进入生长平衡期,此时L-5藻细胞密度为对照的2.59倍.蛋白质SDS-PAGE电泳表明,在大约36和158 kDa处L-5比对照各多出一条新的蛋白带,同时在大约27和29 kDa处L-5出现比对照高得多的两条蛋白表达带.RAPD分析表明两者的遗传相似系数为0.768.由此作者初步认为L-5确为一耐低温的杜氏藻突变株. 相似文献