Vorticity waves in a shallow basin

Observed oscillatory current patterns in the southern basin of Lake Michigan, with a distinctive peak in the energy spectrum at a period of about 90 h, are simulated using a linear potential vorticity conservation model. Solutions of the forced vorticity equation in a paraboloidal basin show rotational, oscillatory motions tuned to the low-frequency topographic modes that are very similar to the observed flow patterns. Topography-controlled vorticity waves are excited most effectively by wind episodes with frequency nearly in resonance with the topographic modes. Bottom resistance has no significant effect on the frequency equation; it simply decays the waves slowly in the open lake and more quickly near the coast. Flow patterns of both the gravest free vorticity wave and the corresponding forced wave consist of two opposite circulation cells separated by a null streamline through the center of the basin and rotating cyclonically near the free wave and atmospheric forcing frequencies, respectively. Interactions between the forced and free waves result in an apparent rotational pattern with a frequency the median of the two. A combination of elliptic—paraboloidal basin and shorter period forced modes can approximate the observed Lake Michigan response. Doppler shift, due to the persistence of cyclonic vorticity in the flow field, is also determined to be a factor in shifting the elliptical basin mode to a higher frequency.     

713天气雷达数字化系统

本文介绍了用IBM-PC/XT(AT)实现的天气雷达数字化系统的众多功能,分析了系统的工作原理。对于几个关键的技术问题——高速数据录取、软件数字视频积分、地物杂波抑制、座标变换及图象传输,分别给出了解决的方法和详尽的程序方框图。     

华东中部洞穴的类型与特征

本文将华东中部地区的洞穴划为五种成因类型,并以典型洞穴为例,阐述了各类型洞穴的基本特征。同时,对本区洞穴的形态特征也作了分析。     

地理信息系统发展趋势

本文根据国内外在地理信息系统方面的进展，就地理信息系统的科学概念、基本构成和它的以下一些发展趋势作了讨论：（1）地理信息系统是构成地理学日臻完善的技术体系的重要部分；（2）空间分析功能是系统研究和应用的主要目标；（3）系统最重要的技术问题是管理和存储大量空间数据的数据结构；（4）综合性的发展特色日益明显；（5）标准化和智能型的发展方向已引起关注。     

Effects of the distribution function of non-thermal electrons and of cyclotron resonant absorption on millisecond radio spikes

A theoretical analysis of electron-cyclotron maser instabilities indicates that the distribution function of non-thermal electrons influences millisecond radio spikes in solar flares, and that a hollow beam distribution is more likely than a loss-cone distribution. The restrictions of classical theories of cyclotron resonant absorption are discussed and a formula is derived for the absorption coefficient near the resonant frequency. Finally, the computations show that for typical coronal parameters, the growth rates of the fundamental of fast extraordinary modes are much faster than those of their second harmonics; and because the directional angle of the fundamental is smaller, its resonant absorption may be neglected. Moreover, the band-width of the fundamental is consistent with observation of radio spikes; therefore, we claim that the millisecond radio spikes in the decimetric range are composed mainly of fundamentals of the fast extraordinary modes. The second harmonics of fast extraordinary modes may be generated for directions near to the vertical to the magnetic field, but it is impossible to observe both fundamental and second harmonics in the same direction.     

The explicit crustal transfer function for SH-waves by ray theory — the case of one and two layers

Summary. Previous theoretical studies on the transfer function of crustal plane surface layers have been primarily based on applying recursion formulae to the solutions of wave equations. In this way the detailed physical insight of the transfer function is often obscure and it is very difficult to express the transfer function in an explicit form. To show that this situation can be improved by an alternative approach, we demonstrate in this paper with models of one and two surface layers that the explicit transfer function can be derived by summing multiple-reflected rays between interfaces. Since the derived transfer function is related explicitly to some physical parameters, such as wave travel times between interfaces, reflection and transmission coefficients at the interfaces, and attenuation and dispersion of waves in each layer of the model, it is more flexible than the traditional recursion form when applied to different models. This suggests that the ray theory can play an important role in problems of layered media.     

气象服务产业化、商品化趋势及其对策

20世纪50年代以来,大气科学的发展和新科技在气象实践中的运用,不同程度地提高着气象成果的多样性、专业性、应用性和有效性,从而创造了气象成果产业化、商品化的物质技术条件;社会生产和居民生活对气象成果更为多样的、专一的需要,形成了气象成果产业化、商品化的市场条件。我国气象服务有偿化的发展已成为趋势;但从社会需求与气象服务自身现状考察,认真转变观念、积极调整结构、大力拓展市场、深化基础研究乃是加速气象成果产业化、商品化趋势的基本对策。     

Primary proton spectrum around the knee deduced from the emulsion-chamber data obtained at Mts. Fuji and Kanbala

We have done extensive Monte Carlo simulations using the new simulation codes of CORSIKA and COSMOS to compare with the gamma-family data obtained at Mts. Fuji (3750 m above sea level) and Kanbala (5500 m above sea level). Then, we estimated the primary proton and helium spectra around the knee energy region using a multiple-layered feed-forward neural network as a classifier of primary particle kind. The selection efficiency of proton-induced family events is estimated to be 82%. The flux value of protons at 2×10¹⁵ eV is (5.5±1.5)×10⁻¹⁴ (m⁻² s⁻¹ sr⁻¹ GeV⁻¹). The result suggests heavy-enriched primary composition around the knee region.     

类星体Lyα吸收线密度与其发射线红移的关系

本文利用７２个具有中等分辨率的类星体Ｌｙα线资料，研究了Ｌｙα吸收线数密度Ｎ（Ｚａｂｓ）与类星体发射红移Ｚｅｍ的变化关系，结果表明：对于Ｚｅｍ越大的类星体其全部Ｌｙα吸收线的平均数密度Ｎ（Ｚａｂｓ）也越大，但对于相同的吸收红移值而言，Ｎ（Ｚａｂｓ）在统计意义上与Ｚｅｍ并无关系。本文还将所得结果与其他的有关工作作了比较及讨论。