“2009.2”沈阳暴雪天气诊断与预报误差分析

针对2009年2月12—13日沈阳暴雪过程,运用Micaps资料和自动站资料,分析了大尺度天气形势及相关物理量场。结果表明：500 hPa南北两支槽在辽宁的叠加和地面蒙古气旋及江淮气旋的合并是此次暴雪过程的主要成因。强降雪出现在850 hPa涡度和200 hPa散度大值区内,对流层中低层辐合、高层辐散为强降雪提供了有利的动力条件;低空急流为暴雪区水汽来源,亦为对流不稳定能量释放的触发源,暴雪区还具备上干冷下暖湿的热力不稳定条件;降水性质的转换与850 hPa的温度、温度平流和地面气温有直接联系;暴雪过程无论从量级,还是降水起止、雨转雪时间均预报得较为准确,但对降雪量和积雪深度估计不足。     

积层混合云数值模拟研究(Ⅰ)──模式及其微物理过程参数化

用积云对流速度场叠加辐合场的方法建立了一个二维平面对称积层混合云数值模式,以用于模拟研究层状云和嵌入其内的对流云组成的混合云。模式动力场计算以一种新的方法求解(V,θ,π)为基本变量的深对流滞弹守恒型方程组。云中微物理过程考虑了6种水质并使用双变参数谱描述和采用更为合理的粒子谱。为了便于与实测雷达回波强度和结构比较,模式可以计算雷达观测模式云的回波强度。     

三维虚拟战场环境符号的视觉变量研究

虚拟现实技术使传统二维的、静态的地图表示向三维的、动态的场景表示方向发展,传统的二维符号视觉变量已不适应三维虚拟战场环境的需要。本文结合三维虚拟环境的特点,提出了一套基本适应三维虚拟战场环境的三维符号视觉变量。     

热弹性介质中波的一类反射问题的解

研究了热弹性波的一类反射问题,就热弹性波的两种基本形式求得一类直反射问题及一类斜反射问题的解。结果表明,热弹性波的反射系数、折射系数不仅依赖于介质的性质,还依赖于波的频率;热弹性波的复反射系数及复折射系数使其在界面两侧的相位和附加温度场都出现跃变。     

三维地震波速结构约束下的变黏度地幔对流及其动力学意义

建立了三维黏度扰动下的变黏度地幔对流模型,并提供了在引入地幔的三维地震波速度结构下相应的求解方法. 依此反演了瑞利数Ra = 106时,两种不同边界条件下的极、环型场对流图像,这有助于深化对地幔物质流动和大地构造运动的深部动力学过程的认识和理解. 研究结果表明,不但地幔浅部的极型场对流图像显示出了与大地构造运动的相关性并揭示了其深部动力学过程,更重要的是,地幔浅部的环型场对流图像首次为我们认识和理解板块构造的水平与旋转运动提供了重要的信息：环型场速度剖面中在赤道附近存在一条大致南东东—北西西向的强对流条带,可能与环赤道附近大型剪切带的形成相关,进而表明可能是该带强震发生的深部动力学背景;在南北半球存在的旋转方向相反的对流环表明它们整体上可能存在差异旋转.     

地下水位的两种估值方法比较

对于许多区域水资源问题,用数值方法(有限元法或有限差分法)进行地下水水流模拟时,通过各种插值方法计算出每个节点上地下水位值,若插值方法选取的不正确,其计算结果与实际情况不符,其误差很大。首先简单介绍了趋势面方法,然后着重阐述了克立格方法的基本原理及其在地下水位估值中的应用,通过比较两种方法的计算结果可以得出:用趋势面方法模拟地下水位时其误差较大,而用克立格方法计算地下水位时其误差较小,克立格方法优于趋势面方法。因此说克立格方法是一种最优、线性、无偏的模拟空间变量的方法。     

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Infrared photometry for five close binary systems

We present the JHKLM photometry for five close (W Ser) binary systems obtained in the period 1996–2004. Positive phase shifts (with respect of the adopted ephemerides) have been found in the orbital infrared light curves for three binaries, RX Cas, KX And, and β Lyr; the rates of increase in their periods are ～3.5 × 10^?4, ～1.6 × 10^?3, and ～1.4 × 10^?4 days yr^?1, respectively. We have performed the spectral classification of the components of the binaries under study and estimated their parameters.     

Long-term monitoring of the long-period variable Y Cassiopeiae in the 1.35-cm water-vapor line

Observations of the circumstellar maser emission from the long-period variable star Y Cas in the 1.35-cm water-vapor line are presented. The observations were performed with the RT-22 radio telescope at the Pushchino Radio Astronomy Observatory (Astrospace Center, Lebedev Physical Institute, Russian Academy of Sciences) in the period 1982–2005. The variations in the integrated flux F_int in the H₂O line correlate with the visual light curve of the star. The phase delay Δ? between the F_int variations and the light curve is 0.2–0.4P (P is the period of the star). The H₂O maser Y Cas belongs to transient sources: peaks of high maser activity alternate with intervals of a low emission level when the H₂O-line flux does not exceed (0.1–0.5) × 10^?20 W m^?2. A “superperiod” of ～5.7 yr was found in the occurrence of activity peaks. A particularly strong maximum of maser radio emission took place at the end of 1997, when the flux F_int reached 15.6 × 10^?20 W m^?2. A model for the H₂O maser variability in Y Cas is discussed. The variability is caused by a periodic action of shock waves driven by stellar pulsations. The H₂O maser flares may be associated with short-lived episodes of enhanced mass loss by the star or with the propagation of a particularly strong shock wave when a planet orbiting the star passes through its periastron.     

Asteroseismology: Past, present and future

Asteroseismology studies stars with a wide variety of interior and surface conditions. For two decades asteroseismic techniques have been applied to many pulsating stars across the HR diagram. Asteroseismology is now a booming field of research with stunning new discoveries; I highlight a personal selection of these in this review, many of which are discussed in more detail elsewhere in these proceedings. For many years the Nainital-Cape Survey for northern roAp stars has been running at ARIES, so I emphasise new spectroscopic results for roAp stars and point out the outstanding prospects for the planned ARIES 3-m telescope at Devastai. High precision spectroscopy has revolutionised the asteroseismic study of some types of stars — particularly solar-like oscillators and roAp stars — while photometry is still the best way to study the frequency spectra that are the basic data of asteroseismology. New telescopes, new photometers and space missions are revolutionising asteroseismic photometry. In addition to the ground-based potential of asteroseismic spectroscopy, India has the knowledge and capability for space-based asteroseismic photometry. The future for asteroseismology is bright indeed, especially for Indian astronomers.