陆地气旋爆发性发展的动力学分析和数值试验

本文对1983年4月25—26曰一次华北气旋爆发性发展的过程进行了动力学分析和数值试验,结果发现,这次气旋发展是发生在强斜压区中,涡度平流和温度平流触发了气旋的初期发展。以后随着降水的增加,凝结加热作用愈来愈重要。在强烈加深时刻,加热剖面中的峰值不断下降,使下层加热量迅速增加,这导致旋转环流或涡旋的爆发性发展。经数值模拟进一步证实了加热峰值下降对气旋迅速发展的重要性。     

一种考虑云相互作用的积云对流参数化方案及其在降水预报中的应用

本文根据我国江淮地区梅雨期间积云和层状云的特点,设计了一种适合于中纬度地区的积云对流参数化方案,该方案通过考虑积云内部的微物理结构及降水机理,增加了在积云降水过程中起很大作用的冰晶胶性不稳定增长过程及碰并降水等过程,发现:冰晶的增长造成的降水有时可达总降水的30—40％或更多;在一般情况下,碰并降水的加强作用则没有那么大,根据这个积云对流参数化方案,用武汉中心气象台的细网格降水数值预报模式对长江流域梅雨期6次暴雨过程进行了数值模拟,发现其预报效果有明显的改进,尤其是对流云与层云混合存在的条件下,效果更好。     

A Dynamic Analysis and Numerical Simulation of Explosive Development of an Extratropical Cyclone Over Land

The present paper has made a dynamic and diagnostic study of the process of explosive deepening of an extratropical cyclone over North China on April 25-26, 1983, in order to gain an insight into the physical mechanism of explosive development of cyclone over land. It turns out that this cyclone occurred in the strong baroclinic zone, and the vorticity and thermal advection triggered the initial development of the cyclone. Subsequently, as the rainfall increased, the effect of condensational heating became more and more important. During the time period of rapid intensification (from 1200GMT 25 to 0000GMT 26 April, 1983, the central surface pressure fell down from 998. 2 to 988. 3 hPa), the peak of diabatic heating profile continuously descended, leading to a rapid increase in heating amount in the lower troposphere. This condition is favorable to the explosive development of rotational circulation or vortex. The numerical simulations have further demonstrated the importance of the lowering of heating p     

STUDY ON KINETIC ENERGY BUDGET OF A TYPHOON——THE CONVERSION BETWEEN KINETIC ENERGIES OF DIVERGENT WINDS AND NON-DIVERGENT WINDS

This paper is the Part Ⅱ of studying the budget of kinetic energy of the typhoon No. 7507, with the emphasis on the conversion between the kinetic energy of the divergent winds and that of the non-divergent winds, and its relationship to the heating field. The main findings have been brought out as follows.     

三维热带气旋的数值模拟及辐射对其影响的研究

本文首先构造了一个包括各种物理过程的三维原始方程模式,并用此模式成功地模拟了热带气旋的发展过程和结构。在此基础上,进一步用该模式研究了大气辐射过程对热带气旋发展的影响。辐射参数化过程包括太阳短波辐射与地气系统的长波辐射以及不同云种和云量的确定。研究结果表明,在热带气旋发展过程中,当包括辐射过程后,模式气旋发展得更早、更强,但最后达到稳定状态的强度则差别不大。在发展阶段,有辐射的模式气旋有更快的地面气压加深率,更强的低空最大风速和上升运动,更明显的眼区和眼壁等。所有这些结果都表明辐射过程对于热带气旋的初始发展和加深过程有相当重要的影响。     

台风中动能收支的研究——Ⅱ.辐散风动能和无辐散风动能的转换

本文是研究台风中动能收支的第二部分。重点讨论辐散风与无辐散风动能之间的转换及其与加热场之间的关系,结果发现:(1)随着台风的发展,中低层辐散风与无辐散风动能之间的转换函数C(K_x,K_φ)明显增加,而上层减小,但对整个层次则为显著增加。这可解释台风发展中风场的变化。对c(K_z,K_φ)贡献最大的项是C_1=f▽X·▽φ。其次是c_2=▽~2φ▽X。▽φ。因而决定于X场和φ场梯度的相对取向,最终取决于台风加热场的特征。(2)台风中加热场(9_(P I))和有效位能与辐散风动能之间转换项(C(P,K_x))的演变和分布与C(K_x,K_φ)十分一致。这表明台风中的加热场是通过上两个转换函数影响台风的加强和发展。因而本文揭示了台风中的加热场影响台风风场的物理过程。     

THE GENERALIZED E-P FLUX OF WAVEMEANFLOW INTERACTIONS

This paper deals with the generalized E-P flux relation, containing the stratification effect and directly diagnosing the mean zonal acceleration from data. Its advantages are that the mean zonal acceleration may also be diagnosed, even if there is the strong baroclinity in the atmosphere and the heat transportion of the transient disturbances obviously varies with time and spsee. Meanwhile, both the ill-condition /(u'v')_y existing in the E-P flux and the terms correlative with the disturbance displacement η' not easily measured in Andrews' E-P flux are automatically eliminated in the generalized E-P flux. Therefore, it is suitable for directly diagnobing the mean zonal acceleration from observational data. In order to examine the applicability of the generalized E-P flux, it is illustrated that an example is correctly diagnosed by using the generalized E-P flux instead of the E-P flux.     

全球气候变化中的物理问题

全球气候变化是一个复杂的科学问题,它涉及到气候系统或地球系统的变化,不但需要考虑它们所包含的这些系统内各部分本身的变化,以及它们之间复杂的相互作用,而且还需考虑物理与地球生物化学等许多过程,文章主要讨论全球气候变化中的物理问题,主要有三个方面:(1)辐射传输和全球辐射平衡:不论是由于自然的原因或人类活动(如太阳活动与火山爆发以及温室气体排放增加导致的温室效应加强)一旦破坏全球的辐射平衡,则会引起气候变化,这是气候变化的主要原因与驱动力;(2)大气波动和气候变化的内部变率:除上述外强迫的作用外,气候变化还可由气候系统内部的变率引起,这包括大气内部变率和耦合气候变率,它们主要是通过产生各种大气的波动而实现的,其中最重要的是罗斯贝(Rossby)波.它们的传播和不稳定发展是造成气候变化的另一个原因;(3)气候系统的混沌性质和可预报性:数值预报模式的预报结果对初始场很敏感,即初始场的微小误差可导致完全不同的预报结果,同时模式中物理过程描述的真实程度也影响预报的结果,大气的这种混沌性质限制了天气的可预报性在2周以内,但气候预测由于明显受外强迫的作用,可使大气的混沌时效延长到月、季、年、几十年甚至上百年,为了减少由初始场误差和模式不完善而造成的预报误差,目前气候预报足采用多初值和多模式的集合预报方法,因而气候预测实际上是一种概率预报.     

A NEW CUMULUS PARAMETERIZATION SCHEME AND ITS APPLICATION TO PRECIPITATION NUMERICAL PREDICTION

According to the characteristics of cumulus and stratiform clouds during the meiyu period (plum rains) over Jianghuai valleys (the Changjiang (Yangtze) River and the Huaihe River), a modified Kuo-type cumulus parameterization scheme applicable to midlatitude con-vective systems is suggested in this paper. It is often observed that cumulus and stratiform clouds coexist in a rain-bearing synoptic systems and the precipitation amount associated with this system may be amplified by their interaction. With some important processes of cloud physics taken into account, we use a simple seeder-feeder model (including colloidal instability, collision effect and entrainment) to describe this process of interaction within framework of Kuo-type cumulus parameterization. It is found that the rainfall amount caused by ice crystal effect accounts for 30-40% of total rainfall, but the collision effect is not so great generally. We introduced this scheme to the regional numerical model used by Wuhan Observatory of Hubei     

STUDY ON THE KINETIC ENERGY BUDGET OF A TYPHOON——BUDGETS OF KINETIC ENERGY IN GENERAL FLOW AND EDDY KINETIC ENERGY

The present paper studies the budgets of kinetic energy in general flow and eddy kinetic energy of Typhoon No. 7, 1975, with a special emphasis on the effects of the divergent and non-divergent winds on the generatioan and transport of kinetic energy. It has been found that:(1) As the typhoon developed and intensified, the generation of kinetic energy of di-vergent wind decreased relatively while that of non-dlvergent wind significantly increased and eventually became the primary term of the generation of kinetic energy. For the entire life spau of the typhoon, the generation of kinetic energy of divergent flow is the primary source of kinetic energy (4W/m~2) with the production of kinetic energy by non-divergent wind being only 0.5 W/m~2.(2) For the budget of eddy kinetic energy, at the initial stage a large amount of eddy kinetle energy needed to be imported from the region outside the typhoon, and at the mature stage a significant amount of eddy kinetic energy was exported. The terms of the work made