THE OSCILLATION OF CERTAIN ZONAL MEAN CHARACTERISTICS OF MOTION ON A SPHERIC EARTH'S ATMOSPHERE——PART 2:ANISOTROPIC QUASI-EDDY MOTION

This paper is an extension of the auther's works (1980,1982,1987).Simple anisotropic distribution of hori-zontal kinetic energy is assumed,i.e.,the zonal kinetic energy is twice that of the meridional kinetic energy.The large-scale atmospheric motion is considered as that consisting of quasi-horizontal eddies and regular flow.The techniques of quasi-eddy,quasi-steady,quasi-geostrophic and quasi-adiabatic approximations are usedin order to get the analytical solutions of the system of equations governing the variation of the zonal meancharacteristics.The results show that the zonal mean characteristics of the atmospheric motion are a combination of dif-ferent periods ranging from a few days to a few weeks depending on the components of Chebyshev polynomi-als of the sine of the latitude.When more general anisotropy of horizontal kinetic energy is assumed,Gegenbauer polynomials appearinstead of Chebyshev polynomials.When the distribution of horizontal kinetic energy is isotropic,the polyno-mials retrograde to Legendre polynomials.     

EFFECT OF ENERGY DISPERSION ON THE STRUCTURE AND MOTION OF TROPICAL CYCLONE

The energy dispersion of a typhoon vortex and its effect on the typhoon motion are studied using an analyticalmethod of double-Fourier expansion as well as a numerical model in a β-plane nondivergent barotropic framework.The analytic model and the linear version of the numerical model give essentially the same result:the energy dispersionfrom a tropical cyclone can creat an L-H-L wave train to the east of the tropical cyclone.Three numerical experiments,integrated for 7 model days by the nonlinear model,indicate that the closed high in the wave train produces obvious in-fluence on the structure and movement of the tropical cyclone.     

NUMERICAL EXPERIMENT OF THE EFFECT OF ENVIRONMENTAL FLOWS ON TROPICAL CYCLONE MOTION

A barotropic prirnitive equation model is used to simulate the tropical cyclone motion.Tropical cyclonemovements under different environmental flow backgrounds were examined and sensitivity of tropical cyclonetracks were discussed.Conclusions of practical significance have been obtained in this paper.     

SOME RELATIONS BETWEEN ASYMMETRIC STRUCTURE AND MOTION OF TYPHOONS

The analysis of the SPECTRUM (Special Experiment Concerning Typhoon Recurvature andUnusual Movement) data indicates that the structure of recurving target typhoons 9015 (Abe),9019(Flo) and 9020 (Gene) at different stages of moving processes showed different motion features.Ondifferent time scales,temporal variations of typhoon structure and motion speed displayed differentfeatures.     

EQUATORIAL SOLITARY WAVES OF TROPICAL ATMOSPHERIC MOTION IN SHEAR FLOW

Starting from the primary equations, the author derives the KdV equation which describes solitary Rossby waves in the tropical atmosphere, and indicates that, because these waves are ageostrophic, they differ from the quasigeostrophic solitary Rossby waves studied by Redekopp et al. Owing to nonlinear action, these waves are also different from traditional linear waves of the tropical atmosphere. The author believes that the stationary tropical atmospheric waves reflect the characteristics of solitary waves in that the energy does not disperse.     

SOME BASIC FORMS OF LARGE-SCALE ATMOSPHERIC MOTION AND DISSIPATIVE STRUCTURES

Recently, Chou (1983) puts forward a principle about the simplification of the full equationsgoverning the motion of the atmosphere. This principle is used to discuss the properties of Lorenzlow-order system. As a way of simplification, the low-order spectral method satisfies the principle.The quasi-geostrophic baroclinic waves and the orographic standing waves are two basic kinds ofthe forms for the large-scale atmospheric motions, they all have the characters of dissipative structures.     

THE OSCILLATION OF CERTAIN ZONAL MEAN CHARACTERISTICS OF MOTION ON A SPHERIC EARTH’S ATMOSPHERE

This paper is an extension of the author's paper (Xie,1982) to the spherical earth.It is found that the similar results are obtained under the assumption of isotropic distribution of horizontal kinetic energy along the zonal and meridional directions.It points out the limitation of the results already obtained and paves the path for the approach of anisotropie semi-eddy or quasi-eddy motion of the atmosphere.     

THE LYAPUNOV STABILITY OF NONLINEAR WAVE MOTION IN THE BAROTROPIC NONDIVERGENT ATMOSPHERE

Introducing the concept of pseudo-momentum, a generalized Arnold-Dikii functional is established, and then thesufficient condition for stability of nonlinear wave motion in the barotropic nondivergent atmosphere is derived by useof variational principle. It is found that the stability of nonlinear wave motion depends not only on its streamfield distri-bution, but also on its phase speed for the propagating nonlinear wave motion. Moreover, the stability criterion of trav-elling modon is also obtained, and it is shown that the travelling modon is stable if the scale of disturbance superimposedon the travelling modon remains to be less than that of the travelling modon.     

MESOSCALE SPECTRA OF THE FREE ATMOSPHERIC MOTION IN MID-LATITUDE SUMMER－UNIVERSALITY AND CONTRIBUTION OF THUNDERSTORM ACTIVITIES

Meridional and vertical wind velocities of the free atmosphere were observed continuously in mid-latitude summer of 1981 by using Platteville ST radar in the eastern Colorado plains in order to obtain the mesoscale spectra. Power spectra were obtained for both meridional and vertical components at heights of 3.3－7.9 km for meridional and 3.3－17.7 km for vertical. Results show that the “-5/3 law” is a good fit to “meridional” spectra for wave periods ranging from ~3 hr to 2 days which are consistent with other published observations and give further evidence to the existence of a universal -5/3 law in mesoscale atmospheric motions. Results also show that for wave periods shorter than 3 hr (to about 10 min), the spectra obviously depart from the –5/3 law and reflect the significant contribution of thunderstorm activities which frequently happen in the mid-latitude summer. Mesoscale spectra of vertical velocity show some characteristics of gravity waves. The mechanism of the observed spectra is discussed.     

AN EXPERIMENTAL STUDY ON THE DRAG EFFECT OF PRECIPITATING PARTICLES ON FLUID MOTION

An experiment is performed to simulate the drag effect of raindrops on the air motion in the atmosphere by means of fine sand particles precipitating through a liquid fluid. The results suggest that the drag effect of the precipitating particles may cause the downward motion in the column where sand particles (or raindrops) precipitate, and produce the updraft around, thus forming a vertical vortex flow pattern around the precipitation area. This effect is also found to be propagating outward, resulting in a multi-vortex flow field. In the stratified fluid, vortexes can be observed at 2 or 3 levels. In the lower layer, the rotating direction of vortexes varies periodically, In addition, the whole flow field induced by the drag effect of precipitating particles is characterized by clear vacillation. The experimental results obtained in this paper can be used to explain the phenomena of multi-layer clouds and multi-belt rainfalll around the severe rain.     

EFFECTS OF OROGRAPHY AND HORIZONTAL DIFFUSION ON THE GENERATION OF THE ASYMMETRIC MOTION IN THE BAROTROPIC FILTERED MODEL ATMOSPHERE

By utilizing the barotropic vorticity equation including effects of orography and horizontal diffusion,the linearized equations describing symmetric and antisymmetric motions and their analytic solutions are pre-sented.It can be found from the solutions that no matter what kind of motion may be,each solution consistsof three waves,namely,Rossby wave related to initial values,marching wave propagating at Rossby wavevelocity and stationary wave.The latter two are closely related to orography and horizontal diffusion.However,if the motion is symmetric at the initial instant,then the antisymmetric components of orographyand of horizontal diffusion are likely to lead to the generation of antisymmetric motion.In the steady state,the symmetric flow is connected with symmetric orography and horizontal diffusion and the antisymmetricflow with antisymmetric orography and horizontal diffusion.Further,in order to verify the above analysis,three numerical experiments have been made.The results show that antisymmetric orography can produceantisymmetric motion.Finally,the atmospheric interactions between Northern and Southern Hemispheresare discussed.     

ANALYSES AND CALCULATION FACTS OF THE BAROCLINIC TERM IN SYNOPTIC-SCALE MOTION OVER TROPICS

Analyses are made of all terms in the vorticity equation for the atmosphere at low latitudes by using the scale analysis theory, with the result that for synotic-scale motion the baroclinic term, i, e. the twisting term and the vorticity vertical-transport term, approximates in order to the relative-vorticity advection, divergence and β term. With intensified atmospheric disturbance ratios of the β term to others become smalte white the others stay in more or less fixed proportions between them. This statement has been confirmed by the results of 22 typhoons calculated covering a targe area in low latitudes. Besides, the baro-clinic term tor the genesis and development of 6 typhoons over 1979-1980 is calculated and the results obtained show that it has significant effect. Finally, the baroclinicity is shown not to be ignored in dealing with synoptics and dynamics of synoptic-scale systems such as typhoons and easterly waves.     

A MECHANISM FOR EFFECTS OF THE LARGE-SCALE MOTION AND HORIZONTAL INHOMOGENEITY OF THE MOIST STATIC INSTABILITY ON MCS AT MIDLATITUDES

Under the influence of the synoptic-scale environmental flows, the implicit nonthermal windvorticity imbalance with ξ_T>0 may arise when the change in the vertical shear vorticity of the flows,which is caused by the change of vorticity advection with altitude, is larger than that in the thermalwind vorticity of temperature fields, which is caused by the horizontal inhomogeneity of temperatureadvection. This kind of implicit imbalance will cause ascending motion to develop in the adjustmentprocess. If the static stratification is horizontally inhomogeneous with the presence of its mesoscalehigh-value regions or the conditionally unstable region where moisture can be fully provided, thedevelopment of mesoscale disturbance with scale L_m may result from the coupling of the ascendingmotion on synoptic scale L_1 with the parameter field of static stratification on mesoscale L_2. The disturbance possesses such a vertical structure as ascending motion in the center, horizontaldivergence in the upper and convergence in the lower atmosphere. This developmental process of insta-bility may be one of the most important processes responsible for the growing of heavy rains in summerhalf year in China.     

THE ENSEMBLE FORECASTING OF TROPICAL CYCLONE MOTION I：USING A PRIMITIVE EQUATION BAROTROPIC MODEL

1INTRODUCTIONErrorsofnumericalforecastingcomprisethoseintheinitialvalue,modelandcomputationandthefirstkindoferrorbecomesmoreandmoreoutstandingwiththeon-goingdevelopmentofcomputersandnumericalmodels.Subjecttoavailableobservationmeans,therealatmosphereisanythingbutapproximatelymeasured.Meanwhile,oneshouldpayattentiontothepossibility,assuggestedbyLorenz[1],thatanyslightdifferencesduringtheinitialstatemayleadtoresultsthatturnouttobetotallydissimilarfromwhatwouldbeexpectedotherwise,asfarasdefi…     

CONTOUR DYNAMICS FOR THE MOTION OF MULTIPLE RING VORTICES Luo Zhexian Nanjing Institute of Meteorology,Nanjing 210044

contour dynamics;;multiple ring vortex;;Coriolis force;;nonlinearity     

THE IMPACT OF RADIATIVE PROCESSES ON THE ONSET OF SUMMER MONSOON——NUMERICAL EXPERIMENTS

Two numerical experiments were performed by using ECMWF limited area model in order to assess theimpact of radiative processes on the onset of summer monsoon.The control experiment includes all model physicsand the other experiment is exclusive of radiative processes.The simulated results show that the radiativeprocesses enhanced the monsoon circulation and the associated vertical circulation over South Asia.Especiallyover the Qinghai-Xizang Plateau,the build-up of the plateau monsoon depression and the beginning of the plat-eau rainy season are highly dependent upon the radiative processes.Through the radiation-cloud interaction,the “moist processes” were enhanced over land.More latent heatwas released.The feedback of the physical processes caused the strengthening of the monsoon circulation oversouthern Asia.     

CONTRIBUTIONS OF PROF.ZHU KEZHEN TO THE DEVELOPMENT OF METEOROLOGY IN CHINA——IN MEMORY OF HIS CENTENARY BIRTHDAY

The year of 1990 is the 100th anniversary of birth of Prof.Zhu Kezhen(Chu Kochen),a great founder of China's modern meteorology who devoted all his life to its flourishingin the country.It has long been a generally-accepted fact that our meteorology of today,in both practical and theoretical aspects,is owed to his enormous contribution.We publishthe special issue of the journal just to cherish the memory of his contribution and of his     

THE FIRST METEOROLOGICAL SATELLITE OF CHINA——FENGYUN-1

At 0430 Beijing summer Time7 September 1988, the first Chinese meteorological satellite.named Fengyun-1(FY-1 meaning observing the wind and clouds in the atmosphere) waslaunched into the near-polar sun-synchronous orbit successfully at the Taiyuan SatelliteLaunching Center, Shanxi Province by Long March-4 launching vehicle which was developedby the Ministry of Aeronautics and Astronautics.FY-1 satellite is a hexahedron of 1.4m×1.4m×1.2m (Fig.1). The attitude of satellite     

THE FIRST METEOROLOGICAL SATELLITE OF CHINA——FENGYUN-Ⅰ

At 0430 Beijing summer Time 7 September 1988,the first Chinese meteorological satellite.named Fengyun-1(FY-1 meaning observing the wind and clouds in the atmosphere) was launched into the near-polar sun-synchronous orbit successfully at the Taiyuan Satellite Launching Center,Shanxi Province by Long March-4 launching vehicle which was developed by the Ministry of Aeronautics and Astronautics.FY-1 satellite is a hexahedron of 1.4m×1.4m×1.2m (Fig.1).The attitude of satellite is three-axis. stabilized.The satellite at an altitude of 900 km operates around the earth 14 passes per day with a period of 102.86 min.The main instruments aboard the satellite are two Advanced Very High Resolution Radsometer (AVHRR) and Space Environmental Monitor.Table 1 gives the major specifications of AVHRR.     

A METHOD FOR PREDICTING SHORT-AND MID-RANGE TURNING AND ACCELERATION MOTION TREND OF TROPICAL CYCLONES OVER THE SOUTH CHINA SEA

An approach is proposed for predicting turning and acceleration motion trend of the tropicalcyclones over the South China Sea for 72 h in the extrapolated track coordinates.Cross-track(CT)and along-track(AT)components are defined according to the persistently extrapolatedtrack coodinates based on observed positions at the initial and past 24 h times.A kind of straight-forward measure may be provided with CT and AT components for typhoon turning motion and ac-celeration motion.Canonical correlation analysis(CCA)is performed to reveal the correlaotions be-tween tropical cyclone tracks and environmental 500 hPa geopotential height fields.A stepwise dis-criminate analysis technique is adopted to derive the classification functions of the respective threecategories for AT and CT components.Especially,categorical combinations of CT and AT compo-nents are divided into possible 9 regions corresponding with tropical cyclone behaviors.Not onlycan 9 motion trends of a tropical cyclone be predicted,but also the location and its maximum errorat least in certain direction are available.The perfect prediction(PP)verifications indicate that thepercent corrects for the CT and AT categories are 67% and 69% in the independent samples,73%and 53% in the dependent samples,respectively,higher than that of 33.3% for random chance;moreover,the rate for successfully forecasting that in which one of the nine regions the tropical cy-clones will fall at 72 h is about 40%,also higher than the stochastic probability of 11%.Themethod has been proved to be skillful and promising.