ATMOSPHERIC WAVE AND ITS PHYSICAL ESSENCE AS REVEALED BY CHANGED CORRELATION COEFFICIENTS AND CORRELATION FIELD

Formal change is made of the correlation coefficient(COCOEF)expression,leading to a new formula consisting ofFourier spectral coefficients that indicates a direct connection between the new form and atmospheric dynamicequations,thus resulting in a dynamic equation represented by COCOEF,which is meaningful in exploring a large-scaledynamic process in terms of the correlation field because the connection revealed by the field can have dynamic explana-tion with the aid of the new formula.     

VARIATIONS OF ATMOSPHERIC OSCILLATION FACTORS AND 500 HPA CIRCULATION PATTERNS AND THEIR RELATIONS*

Wavelet analysis,EOF and CCA are used to analyze the variations of atmospheric circulation factors,including the key atmospheric oscillations,W,C,E and subtropical high (SH),and their relationships.The results are shown that the variations of atmospheric circulation factors both in troposphere and lower atmosphere layer are different on different time scales.The most significant variation of atmospheric circulation factors is in the period less than 7 years.The correlation relations of atmospheric circulation factors are different on different time scales.Combination patterns of circulation factors have impact on the relationships of factors.There are lag correlations between combination patterns of circulation factors in former year and that of in next year.     

A STUDY OF THE EFFECT OF GRAVITY WAVE BREAKING ON MIDDLE ATMOSPHERIC CIRCULATION*

McFarline's gravity drag theory is simply reviewed,and it is indicated that the fault of McFarline's theory is that the effect of dissipation induced by gravity wave breaking on mean flow is not fully considered.Based on McFarline's theory,in this paper,the effect mentioned above is well considered.A new dissipation coefficient D is calculated,and a relatively complete parameterized scheme of the influence of gravity wave breaking on meanflow is put forward here.This is a better parameterized scheme than McFarline's if it is used in GCM.     

INFLUENCES OF NONUNIFORM STRATIFICATION ON WAVE RAYS OF INTERNAL GRAVITY WAVE*

In this paper the influences of nonuniform stratification on the propagating paths of internal inertial-gravity and pure gravity wave energy are discussed by using the WKB approximation method.The conditions for conservation of wave energy,generalized wave action and wave enstrophy are obtained.The necessary condition of instability for internal gravity waves and the equation governing the refraction of wave rays are derived.Two types of critical levels are given.Finally,the wave rays for different distributions of stratification are calculated by using the fourth-order Runge-Kutta method.     

ANALYSIS ON CHARACTERISTICS OF ATMOSPHERIC DUCT AND ITS EFFECTS ON THE PROPAGATION OF ELECTROMAGNETIC WAVE*

On the basis of introducing the basic categories of atmospheric refraction and their existing conditions,the forming processes of three kinds of atmospheric ducts are expounded.Several main characteristics of atmospheric duct are summarized and analyzed,and field sounding data from the WEstern North-Pacific cloud-radiation EXperiment(WENPEX) and meteorological data around the Xisha sea area are used to validate these characteristics.Meanwhile the sensitivities of the evaporation duct height to the variations of atmospheric humidity.the air-sea temperature difference.and horizontal wind speed are examined.With the analysis of the effect of atmosphericduct on the propagation of electromagnetic wave.the maximum trapped-wavelength and the critical emitting angle of elevation for electromagnetic wave which can form duct propagation are derived.At the same time the four kinds of necessary conditions for electromagnetic wave to form ductpropagation are brought forward.The effects of atmospheric duct on ultrashort wave propagation,radar observation.short wave communication etc.are also discussed.     

ODD AND EVEN SYMMETRY OF ATMOSPHERIC CIRCULATION-THEORETICAL BASIS AND CLIMATIC CHARACTERISTICS*

Analysis is done of the distribution of odd and even symmetric components of circulations on a global basis in terms of observations and technique for the odd/even symmetry,indicating that climatic features of the component patterns and their temporal evolution are able to reveal their influence of land-sea discrepancy in the Northern and Southern Hemispheres,the time scale of atmospheric response to radiation heating,circulation waveform structure and seasonal adjustment of global circulation.     

ANALYSIS ON CHARACTERISTICS OF ATMOSPHERIC DUCT AND ITS EFFECTS ON THE PROPAGATION OF ELECTROMAGNETIC WAVE

On the basis of introducing the basic categories of atmospheric refraction and their existingconditions,the forming processes of three kinds of atmospheric ducts are expounded.Several maincharacteristics of atmospheric duct are summarized and analyzed,and field sounding data from theWEstern North-Pacific cloud-radiation EXperiment(WENPEX)and meteorological data aroundthe Xisha sea area are used to validate these characteristics.Meanwhile the sensitivities of theevaporation duct height to the variations of atmospheric humidity.the air-sea temperaturedifference.and horizontal wind speed are examined.With the analysis of the effect of atmosphericduct on the propagation of electromagnetic wave.the maximum trapped-wavelength and the criticalemitting angle of elevation for electromagnetic wave which can form duct propagation are derived.At the same time the four kinds of necessary conditions for electromagnetic wave to form ductpropagation are brought forward.The effects of atmospheric duct on ultrashort wave propagation,radar observation.short wave communication etc.are also discussed.     

VERTICAL DISTRIBUTION CHARACTERISTICS OF ATMOSPHERIC AEROSOLS IN LIAONING*

16 aircraft missions were conducted for the measurement of atmospheric aerosols in separate days of late spring and early summer of 1996 and 1997.The paper deals with detailed analysis of the variation in vertical/horizontal distributions of the concentration of the particles and their size distribution at 0-5 km above ground,and with the relations to temperature and relative humidity documented in general.Evidence suggests that the concentrations show different distribution features in vertical above and below the cap of the mixed layer:the particle size distribution is subject to a range of forming mechanisms,displaying a multi-modal pattern:the horizontal concentration experiences remarkable variation:temperature and relative humidity stratifications have conspicuous influence on the concentration and size distribution of aerosols.     

SENSITIVITY TESTS OF INTERACTION BETWEEN LAND SURFACE PHYSICAL PROCESS AND ATMOSPHERIC BOUNDARY LAYER*

In this paper,an interactive model between land surface physical process and atmosphere boundary layer is established,and is used to simulate the features of soil environmental physics,surface heat fluxes,evaporation from soil and evapotranspiration from vegetation and structures of atmosphere boundary layer over grassland underlying.The sensitivity experiments are engaged in primary physics parameters.The results show that this model can obtain reasonable simulation for diurnal variations of heat balance,soil volumetric water content,resistance of vegetation evaporation,flux of surface moisture,and profiles of turbulent exchange coefficient,turbulent momentum,potential temperature,and specific humidity.The model developed can be used to study the interaction between land surface processes and atmospheric boundary layer in city regions,and can also be used in the simulation of regional climate incorporating a mesoscale model.     

CHARACTERISTICS OF ATMOSPHERIC HEATING AND ATMOSPHERIC CIRCULATION DURING ACTIVE PERIOD OF 500 hPa HIGH OVER THE TIBETAN PLATEAU IN SUMMER*

In correspondence with the establishment of the "upper high and lower high" pressure pattern due to the activities of 500 hPa high over the Tibetan Plateau in summer,a series of changes of the East Asia atmospheric circulation will take place.In this paper,the distributions of divergence and vertical velocity of 500 hPa high,the evolutions of atmospheric heat source,the variations of vorticity and zonal wind at 100 hPa level and vertical meridional cell over the Tibetan Plateau etc.are statistically analyzed.Thus,we can see that the ascending motion and the convective heating over the Tibetan Plateau,the South Asia high and the westerly jet on the north of the Plateau at 100 hPa level are weakned.The northern branch and the southern branch of the easterly jet on the south of the Plateau merge into a single whole and situate on the south of the former northern branch.In the meantime,thermodynamic land-sea discrepancy in South Asia and the convective heating over the Bay of Bengal is enhanced.It will play an important role in the maintenance of the easterly jet and the South Asia monsoon.     

VORTEX MOTIONS IN THE ATMOSPHERIC CONVECTIVE BOUNDARY LAYERM*

Large vortices with scales ranging from hundreds meters to tens of kilometers are generally found in the atmospheric convective boundary layer(CBL).These vortices play important roles in the vertical transport of momentum,heat,water vapor and other tracers in the boundary layer.On the basis of the view of interaction between the convection in CBL and the gravity waves in the upper stable layer the authors developed a convection-wave theory on the formation of large vortices.According to the theory the wavenumber spectrum of the large vortices mainly depends on the atmospheric conditions in both of the upper and lower layers,such as wind speed,wind direction shear,stratification as well as temperature jump.In the present paper satellite image and weather data in a case of cold air outbreak over warm ocean are analyzed to study every stage of the convective processes,such as cloud street,convective cell as well as their transformation.According to the theory the wavenumber compositions for cloud street and convective cell are calculated,respectively,on the basis of the atmospheric conditions at every stage.The distributions of vertical motions,convergent band and disturbed interface are obtained and compared with the cloud patterns in the convective processes.Thus the study seems to offer a likely explanation for the origin of large vortices in CBL.     

THE INFLUENCE OF PHOTOCHEMICAL PROCESS ON THE ATMOSPHERIC WAVE*

The time damping rate of gravity wave in the range of 30-70 km is calaclated in three circumstances:(1) adiabatic process,(2) diabatic process caused by atmospheric cooling,and(3) diabatic process resulting from atmospheric photochemical heating and cooling.The results indicate that the photochemical heating is as important as Newtonian cooling and its contribution to the time damping rate of gravity wave can not he negligible.     

RETRIEVING ATMOSPHERIC TEMPERATURE FROM NOAA-15 ATOVS MEASUREMENTS*

This paper describes briefly the sounding capabilities of TOVS/ATOVS onboard the NOAA polar-orbiting meteorological satellites,followed by a more detailed review of the retrieval schemes.The ICI physical retrieval scheme with some adaptations is implemented in our experiment.The analyses of the Chinese regional NWP model are utilized to create a rolling library of initial guess field.Retrieval results validated against both NWP analyses and radiosondes indicate good agreement between ICI retrievals and conventional observations.Preliminary result from the PC-ATOVS Windows display system of NSMC will also be shown.     

EXPERIMENT ON THE FORECAST OF CHARACTERISTIC QUANTITIES OF ATMOSPHERIC TURBULENCE BY MESOSCALE MODEL MM5*

In nested nonhydrostatic mesoscale model MM5,the characteristic quantities of atmospheric turbulence,i.e.,the standard deviations of the turbulent fluctuated speeds for three directions in PBL are computed by Mellor-Yamada's level 2.5 closure scheme.The magnitudes and the vertical profiles of these quantities computed from the model are closely connected with temperature and wind speed profiles as well as the type of the ground with a significant diurnal variation,and are in agreement with known magnitudes and regularities in different stratification conditions.Hence the method in this paper is reasonable and convincible.Their horizontal distribution depends on the horizontal distribution of the stratification.The method of predicted characteristic quantities of turbulence from mesoscale model in this paper can be used in the problem of atmospheric diffusion and atmospheric environment.     

ON THE PDF MODELS FOR ATMOSPHERIC DIFFUSION IN BOUNDARY LAYER*

In this paper,taking its turbulent exchange coefficient as a function of the Lagrangian time scale and standard variance of the turbulence in atmosphere,the atmospheric dispersion PDF models are obtained on the basis of atmospheric diffusion K-theory.In the model the statistics of wind speed are directly used as its parameters instead of classic dispersion parameters.The bi-Gaussian PDF is derived in convective boundary layer (CBL),from the statistics of vertical velocity in both of the downdraft and updraft regions that are investigated theoretically in the other part of this paper.Giving the driven parameters of the CBL (including the convective velocity scale ω^* and the mixing depth h_i) and the time-averaged wind speed at release level,the PDF model is able to simulate the distribution of concentration released at any levels in the CBL.The PDF's simulations are fairly consistent with the measurements in CONDORS experiment or the results brought out by some numerical simulations.     

TURBULENCE CHARACTERISTICS OF THE ATMOSPHERIC SURFACE LAYER OVER AN OPEN GRASSLAND*

Described in this paper is an experiment on atmosphere-surface turbulent exchange and boundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin,China.The characteristics of the turbulent spectrum,and the relationships of the standard deviation of the turbulent velocity components and sensible heat flux with the atmospheric stability are studied using data from a sonic anemometer and a fast-response platinum resistance thermometer mounted on a 100 m tower.The results show that in the surface layer over a flat,uniform and open grassland,for a broad stability range(-22.12≤Z_iL≤17.98),the velocity spectra obey the-2/3 power law in the inertial subrange,and 1 power law at low frequencies.Under near neutral stratification,σ_u/u_*=1.20,σ_v/u_*=1.23 and σ_w/u_*=1.02.For Z_i/L≤-0.2,the standard deviations of the turbulent velocity components follow a 1/3 power law.For Z_i/L≤-0.1,the standard deviation of the temperature fluctuations follows a-1/3 power law,and as Z_i/L≤-0.08,it exhibits nonlinear behavior.Sensible heat flux is well correlated to the stability parameter.     

A FLUID EXPERIMENT OF GRAVITY INTERNAL WAVE INDUCED BY TERRAIN*

The mountain wave induced by a ridge in two-layer stratified fluid has been successfull ysimulated in a tank.The wave pattern is qualitatively similar to that calculated with linear theory.     

相关系数的变化形式和相关场揭示的大气波动及其物理本质

文中对相关系数公式的形式进行了变化,得到了以傅里叶谱系数表示的相关系数公式,完成了新形式的相关系数公式与大气动力学方程的直接连接,由此产生了由相关系数表示的动力学方程,从而指出用相关场研究大尺度动力过程是有意义的,相关场揭示的联系可通过相关系数表示的方程而得到动力学解释。     

RESPONSE OF THE ATMOSPHERIC GENERAL CIRCULATION TO WINTER SNOW COVER ANOMALY*

In this paper,the response of the atmospheric general circulation to winter anomalous snow cover was investigated through observations studies and model simulation.Results from the observations show that:(1)the anomalous winter snow cover in the extratropics of Eurasian Continent bears an intimate relation to the contemporary atmospheric general circulation.The positive anomaly of winter snow cover is usually accompanied by positive atmospheric EUP teleconnection pattern and stronger East Asian winter monsoon:or vice versa.(2)The linkage between them suggests that the abnormal winter snow cover has an important impact on winter atmospheric general circulation.The anomalous snow cover pattern can lead to the anomaly of winter atmospheric EUP teleconnection pattern and thus influence East Asian Winter monsoon.With NCAR CCM2 including BATS land surface scheme,three groups of experiments were performed to examine the atmospheric response to the anomalous snow cover pattern and explore the relevant mechanism.Simulated results agree well with the observations,which testify the significant response of the atmosphere to snow cover anomaly.It is found that the radiative cooling induced by anomalous snow cover plays an important role in above processes,and the feedback of long-wave radiation can not be neglected.     

INVERSION OF MOISTURE PROFILES BY A NONLINEAR ITERATIVE PHYSICAL RETRIEVAL*

The Advanced TIROS-N Operational Vertical Sounder(ATOVS) measurements are used to generate the atmospheric parameters,such as temperature and moisture profiles,under both clear and cloudy situations.This paper describes briefly the nonlinear iterative physical retrieval method.By using this retrieval scheme,an experiment has been carried out to retrieve the moisture profiles from ATOVS measurements on the NOAA-16 satellite for July of 2002.ATOVS profile retrieval results are evaluated by root mean square(RMS) differences with respect to RAdiosonde OBservation(RAOB) profiles.The accuracy of the retrieval is about 15%-23% for the relative humidity profile in this study.