夏季青藏高原气象学若干问题的研究

本文使用经过1979年5—8月青藏高原气象科学实验观测资料订正过的欧洲中心FGGE—Ⅲb资料、GMS1地球同步卫星云图资料及其它一些资料,详细分析了夏季青藏高原的水汽状况、热力层结状况和月平均环流场的主要特征;计算了主要经圈环流圈的位置分布和从高原上上升气流的轨迹;通过逐月、逐日的涡度方程诊断分析,讨论了夏季高原高、低空稳定环流场的维持机制,发现高原上存在的强盛频繁的积云对流活动对高原大型环流场的维持是非常重要的;最后提出了一个高、低层多层次的对流活动振荡过程造成的热量水汽接力式上传输送的物理模型,认为它可能是夏季青藏高原高空大气高温、高湿状况维持的主要物理过程。     

E-P剖面的年变化和对流层西风加速

本文是关于波动对基本气流强迫作用系列研究的一部分,它通过E-P剖面的年变化来比较南北半球波流相互作用年变化的异同。结果表明,两半球冬半年波流相互作用很强,夏半年则非常弱。南半球行星尺度的外激发源也很弱。研究还指出,由于对流层中质量环流强。静力稳定度小,余差环流项成为动量方程中平衡E-P通量项的大项。因此,在研究对流层西风加速时,必须同时考虑E-P通量和余差环流的作用。使用通常的Euler方程,能更方便地研究涡动对平均气流变化的直接贡献。     

关于大气平均经圈环流的一种计算方案

基于大气的连续性,本文设计出计算大气平均经圈环流的一种新方案;并用欧洲中期天气预报中心(ECMWF)每日4次的分析资料,计算了1982年1月的全球平均经圈环流。分析和计算表明,新方案比传统的计算方案,能得到更合理的结果。计算还证实了冬半球双Hadley环流的存在。     

ANNUAL VARIATIONS OF E-P CROSS SECTION AND TROPOSPHERIC WESTERLY ACCELERATION

This is one part of the series study on the forcing of waves on basic flow, in which theannual variations of E- P cross section are used to compare the wave- mean flow interactionsin the Northern and Southern Hemispheres. Results show that in either hemisphere, wave-meanflow interaction is very strong in winter, and very weak in summer. External forcing sourcefor planetary waves in the Southern Hemisphere appears to be rather weak not only in summer,but also in winter. It is pointed out that in the troposphere. since the mass circulation isstrong, and since the static stability is small, in the dynamic equation, the inertial effect ofthe residual circulation becomes important in balancing that of the E- P flux divergence.Therefore, when the westerly acceleration in the troposphere is studied, both terms of E-Pflux and residual circulation should be considered. It turns out to be more convenient to usethe conventional Euler system to investigate the direct contribution of eddies to the meanflow.     

Comparison of Two Kinds of Atmospheric Vorticity Equations

Comparison of two kinds of atmospheric vorticity equations, i.e. the traditional vorticity equation and the complete-form vorticity equation, is performed. The result shows that the two kinds of the vorticity equations can transform from each other and they are consistent in physical essence, while the complete vorticity equation has more advantages in diagnosis. Finally, the application of the complete form vorticity equation is analysed briefly with real data.     

El Nino海温异常对纬向平均经圈环流及大气输送特征的影响

本文用欧洲中期天气预报中心高分辨谱模式,对1982/1983 El Nino期大气环流异常的模拟指出,持续的赤道东太平洋海温距平导致热带非绝热加热和直接经圈环流间的正反馈,从而加强了Hadley环流。同时,冬半球高纬涡旋输送特征发生明显变化,使强迫反环流加强。在纬向平均意义下,El Nino海温距平在月的时间尺度上导致副热带地区变干,而热带和北极地区变暖、变湿。     

A SCHEME FOR EVALUATING THE MEAN MERIDIONAL CIRCULATION OF THE ATMOSPHERE

Based on the continuity of the atmosphere, a new scheme is developed to diagnose the atmospheric mean meridional circulations. ECMWF analyses four times per day of January 1982 were retrieved to evaluate the global mean meridional circulation. Investigations and calculations show that this new scheme produced more reasonable results in comparison with the traditional scheme. The existence of the double Hadley cell in the winter hemisphere is confirmed as well.     

THE IMPACT OF EL NINO ANOMALY ON MEAN MERIDIONAL CIRCULATION AND TRANSFER PROPERTIES OF THE ATMOSPHERE

High resolution experiments with the operational ECMWF model starting from observed data wereused to test the impact of the 1982/83 E1 Nino sea surface temperature anomaly on the zonal mean me-ridional circulation and transfer properties of the atmosphere. The increased sea surface temperature in the Eastern Pacific Ocean along the Equator amplifies theHadley circulation. This enhances the convergence of moisture and sensible heat towards the tropics, induc-ing positive feedback between tropical diabatic heating and direct mean meridional circulation. The am-plification of the Hadley circulation also results in an equatorward extension of the mid-latitude wester-lies. Equatorial SST anomaly makes the zonal mean eddy transfer properties in the winter hemisphereundergo substantial changes, and the maxima of transfer of heat and momentum are all shifted to highlatitudes. An extra indirect meridional circulation is thereby forced in high latitudes in the northern hem-ispheric winter. It seems that in a time     

彩色图象边缘检测的新算法——广义模糊算子法

给出了广义模糊集合的定义,并提出用一个广义模糊算子将广义模糊集合变换成普通模糊集合,从而为二维图象边缘检测的最新算法——广义模糊算子法奠定了充分的理论依据.实践表明,这是一个简单、快速且定位精度很高的算法;此外,文中还就彩色图象的边缘检测问题,提出了具体的实施步骤.