Comparison of Ocean Surface Wind Stress Computed with Different Parameterization Functions of the Drag Coefficient

Depending on the choice of reference wind speed, the quantitative and qualitative properties of the drag coefficient may vary. On the ocean surface, surface waves are the physical roughness at the air-sea interface, and they play an important role in controlling the air-sea exchange processes. The degree of dynamic influence of surface waves scales with wavelength. Drag coefficient computed with the reference wind speed at an elevation proportional to the wavelength (for example, U _λ/2) is fundamentally different from the drag coefficient computed with the wind speed at fixed 10 m elevation (U ₁₀). A comparison has been carried out to quantify the difference in wind stress computation using several different parameterization functions of the drag coefficient. The result indicates that the wind stress computed from U ₁₀ input using a drag coefficient referenced to U _λ/2 is more accurate than that computed with drag coefficient functions referenced to U ₁₀.     

Influence of wavelength on the parameterization of drag coefficient and surface roughness

Surface waves are the roughness element of the ocean surface, the air-sea interaction processes are influenced by the wave conditions. The dynamic influence of surface waves decays exponentially with distance from the air-water interface. The relevant length scale characterizing the decay rate is the wavelength. The parameterization of drag coefficient and surface roughness can be significantly improved by using wavelength as the reference length scale of atmospheric measurements. The wavelength scaling of drag coefficient and dynamic roughness also receives support from theoretical studies of wind and wave coupling.     

Relationship Between Mean Length and Mean Period of Wind Waves

1.IntroductionGreat progress has been madeinthe statistics of sea waves based onthe envelopetheory of Gaus-sian processes.Longuet-Higgins(1975,1983)first obtainedthe joint probability distributionfunction(PDF)of wave heights and periods.His work was exten…     

A GLOBAL SPECTRAL MODEL WITH VARIABLE POLES AND ITS APPLICATION TO THE SHALLOW-WATER EQUATIONS

Since we find out that the global spectral model with trapezoidal truncation has higher resolution inhigh latitudes(polar cap)than in low latitudes,this paper presents a global spectral model with variablepoles which can be located at the center of interested area.The transform methods from traditional globalspectral model to the new model are given and applied to a shallow-water equation model.The control ex-periments for 72h predictions were carried out.The“northern pole”in the transformed model was locatedat 15°N, 135°E.And the results showed that the predictions of weather systems in the area around the“newpole”(the polar cap,latitudes >60°)were better than those by the traditional model and the root mean squareerrors were improved.     

1997年3月9日3.2cm射电日食观测

本文介绍了1997年3月9日,紫金山天文台在3.2cm波段上日偏食观测概况及所得到的结果。     

利用球冠谐分析方法提取不同波长重力场异常

介绍球冠谐分析方法在重力场研究中的基本理论和计算方法。探讨了球冠谐系数与波长的关系，以及利用球冠谐分析方法提取不同波长的重量场力场异常，进而研究深部地壳结构的问题，最后给出一个实例。     

地壳对不同波长地形在重力场中的响应

为有效发挥重力均衡在地质、地球物理和大地测量中的作用，本文进一步阐明重力位球函数的阶数与波长的关系．以及地形及其补偿与波长的关系．指出在研究短波长地形的重力效应时无需考虑补偿的影响，否则将会引起场效应的失真．模型的研究表明，在局部地区或测点上，利用高程资料作重力异常推估可以达到理想的结果．为检验均衡理论的适用性与局限性，文中列出高喜马拉雅一带的54块样品的岩石密度和岩性；为验证地形的重力效应，还计算出锥形山体时外部点的引力．     

波长色散X射线荧光分析的新发展

除了继续发展波长色散X射线荧光分析装置在主、次量元素分析上高精度、高稳定性的固有特点之外，进一步提高灵敏度，使分析范围扩展到痕量分析；开拓微区面分布的元素成像分析；进一步对传统分析因难的轻元素和中、重金属元素的探讨，开发新的高级次谱线分析方法；适应新材料特别是纳米材料的分析要求，对薄膜分析的开拓等方面，已经有了长足的发展。在介绍商品化的分析装置方面的发展状况的同时，对无标样分析的基本参数法目前发展状况也做了介绍。     

分频解释技术在表征储层中的运用

采用短时窗离散傅立叶变换及最大熵方法这一独特的频谱分解及解释技术——分频解释技术，实现了在频率域内通过调谐振幅的对应关系来研究储层横向变化规律，使地震解释可得到高于常规地震主频率对应114波长的时间分辨率结果。分频解释技术的应用解决了长期困扰解释人员只能依靠钻井数据划分和确定岩性油藏边界的难题。目前，该项技术在我国陆相地层油气勘探中已得到了广泛的应用和推广。     

Joint Distribution of Wave Heights and Wavelengths and Distribution of Wave Steepness

-A joint probability density is derived for wavelengths and wave heights.It is asymmetric anddepends only on the spectral bandwidthεdefined by Cartwright and Longuet-Higgins(1956).After that atheoretical probability density for wave steepness is obtained.It tends to Rayleigh distribution asε→0.Acomparison between theorethal steepness distribution and laboratory experiment result shows good agree-ment.