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1985 Vol. 2, No. 2

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A NUMERICAL EXPERIMENTAL STUDY OF SOME DYNAMICAL EFFECTS ON SOUTHERN ASIATIC HIGH
Si Gongwang, Donald R. Johnson
1985, 2(2): 133-146. doi: 10.1007/BF03179746
Abstract:
Using a barotropic, steady and linearized vorticity equation and using 250 hPa observed basic flow and global divergence field from the active summer monsoon phase (00 GMT 26 June-12 GMT 29 June) 1979, the dynamical effects of linear absolute vorticity advection, vorticity generation due to divergence and vorticity dissipation due to frictional damping have been tested to understand their influence on Southern Asiatic High (SAH). The key experimental results are: (1) The SAH, one of the major planetary-scale disturbances, is generated from the upper basic flow by the forcing of the upper tropospheric divergence over southeast Asia during the active summer monsoon phase. (2) Linear absolute vorticity advection and frictional damping of vorticity play an important role in the determination of the location of the SAH. (3) The destruction and recovery of planetary-scale geostrophic balance is an important mechanism for the west-east oscillation of the SAH.
NONLINEAR WAVES IN BAROTROPIC MODEL
Liu Shida, Liu Shikuo
1985, 2(2): 147-157. doi: 10.1007/BF03179747
Abstract:
In this paper, from the system of equation describing a barotropic atmosphere using the method of Taylor expansion for the nonlinear terms, the periodic solutions of the nonlinear inertio-surface gravity waves and Rossby waves have been obtained.The finite-amplitude nonlinear inertio-surface gravity waves and Rossby waves with horizontal divergence satisfy all the KdV equation. The solutions are all the cnoidal function, i, e, the cnoidal waves which in-clude the linear waves and form the solitary waves under certain conditions. For the finite-amplitude Rossby waves with horizontal divergence, we find the new dispersive relation including both the wave number and the amplitude parameter. In case of small amplitude it is reduced to the Yeh formula. It is shown that the larger the amplitude and width, the faster the finite-amplitude inertio-surface gravity waves and the slower the finite-amplitude Rossby waves with horizontal divergence propagate. The blocking or cut-off system in which the amplitude and width are large may be considered as Rossby solitary waves.
THE DYNAMIC EFFECT OF THE TIBETAN PLATEAU ON THE FORMATION OF ZONAL TYPE CIRCULATION OVER EAST ASIA
Luo Meixia, Zhu Baozhen, Zhang Xuehong
1985, 2(2): 158-166. doi: 10.1007/BF03179748
Abstract:
From a statistical study of the atmospheric circulation types over the Northern Hemisphere it is found that the zonal type circulation predominates in East Asia. From a three-layer primitive equation model in σ-coordinate, the orographic effect on a westerly current over the Northern Hemisphere is studied. A distinguished deepening trough is observed in the lee-side slope of the Rocky Mountains. But a pronounced trough is over the East Asia coast far from the Tibetan Plateau. In a case of 48 h numerical forecast, it is found that the effect of the Tibetan Plateau tends to build up a rather zonal type circulation, which is con-sistent with the observations. These may be partly explained by the topographic effect of the north slope of the Tibetan Plateau in a simple geostrophic theory.
THE SECOND ORDER APPROXIMATION TO THE NONLINEAR WAVE IN BAROTROPIC ATMOSPHERE
Zhang Xuehong
1985, 2(2): 167-177. doi: 10.1007/BF03179749
Abstract:
A kind of technique of computer extension of perturbation series is presented and used in seeking for the second-order approximation to a large-scale travelling wave solution of the barotropic primitive equations. Numerical experiments show that the second-order approximation keeps major characters of the travelling wave solution and is indeed more exact than the zero-order and the first order approximations.
NUMERICAL EXPERIMENT OF SIX-LEVEL IMPLICIT PRIMITIVE MODEL
Liu Ruizhi
1985, 2(2): 178-188. doi: 10.1007/BF03179750
Abstract:
In this paper, a numerical test is carried out by using a six-level implicit primitive equation model de-fined in a π coordinate. The model equations are solved with nonlinear iterated method, yielding fairly good results.However, it is time-consuming to solve the model with iterated method. Thus, this model is restored to the advective scheme and solved by means of a split method. Several actual examples are forecasted, which have yielded good results.
THE NUMERICAL EXPERIMENTS ON DYNAMIC FORCING BY THE TIBETAN PLATEAU FOR VARIOUS ZONAL FLOWS
Chen Yuxiang, Ji Liren, Shen Rujin
1985, 2(2): 189-199. doi: 10.1007/BF03179751
Abstract:
In this paper, the dynamic disturbances to various basic zonal currents caused by the Tibetan Plateau are simulated by means of a three-level primitive equation model, in which σ is used as the vertical coor-dinate. Four types of currents have been used, i. e. the barotropic homogeneous current, barotropic jet stream, baroclinic current and the zonal mean current in summer. The results are helpful to understand the dynamic effects of the Tibetan Plateau on the general circulation over East Asia.
TEMPERATURE CHANGES OVER EURASIA DURING THE LATE SUMMER OF 1979
Ding Yihui, T. Iwashima, T. Murakami
1985, 2(2): 200-214. doi: 10.1007/BF03179752
Abstract:
During the late summer of 1979, massive changes occurred in the distribution of temperature over Eur asia north of 15oN. At 300 hPa, zonal mean temperature averaged over Eurasia along 20o-25oN de-creased sharply around 23 August. An abrupt decrease in 300 hPa zonal mean temperature also occurred over extensive mid-latitude zones (40o-55oN) around 18 August, i. e., about 5 days prior to the monsoon withdrawal over South Asia.The intensity and location of N-S oriented, vertical overturning underwent significant changes over Eurasia during the transition from summer to fall. Near 20o-25oN, zonal mean updrafts weakened con-siderably during the transition period (18-27 August). Around 45oN, zonal mean downdrafts and the asso-ciated cooling (radiative) rate increased considerably during the transition period.Near 15oN, 300 hPa zonal mean temperature fluctuated nearly periodically with an approximate 40-day period. These fluctuations appear to be associated with a small imbalance between 40-day filtered adiabatic cooling (heating) and diabatic heating (cooling).
THE STATISTICAL STRUCTURE OF LORENZ STRANGE ATTRACTORS
Zou Chengzhi, Zhou Xiuji, Yang Peicai
1985, 2(2): 215-224. doi: 10.1007/BF03179753
Abstract:
The statistical characteristic quantities and marginal probability distribution of the Lorenz strange attractors were computed numerically. The results indicate that after a sufficiently long time the statistical characteristic quantities and marginal probability distribution tend to stable states, and the motion on the strange attractor is ergodic.
EFFECT OF WIND VERTICAL SHEAR ON DIFFUSION CHARACTERISTICS IN THE MESOSCALE RANGE
Lei Xiaoen
1985, 2(2): 225-233. doi: 10.1007/BF03179754
Abstract:
Using the turbulent statistical form of the vertical vortex diffusion coefficient K, in the planetary boundary layer (PBL) and Ekman spiral wind profile, the three-dimensional diffusion equation is solved by the numeri-cal method. The influences of vertical shear of both wind direction and wind speed on pollution trajectory and horizontal diffusion parameters σy are numerically analysed. The expressions of both pollution trajectory and σy, including the factor of wind shear, are obtained. The results show that the vertical shear of wind is important among all factors affecting the mesoscale dispersion. Specifically, from neutral to stable atmospheric conditions, vertical shear of wind makes greater contribution to σy than turbulence, thus it is the most important factor. In this paper, we have compared horizontal dispersion pattern with both Pasquill's dispersion pattern considering wind direction shear, and experimental data collected at 9 different sites rang-ing from 10 to 100 km, and the results show that our dispersion pattern is closer to the experimental values than Pasquill's results, and his correction to shear of wind direction is too large under the stable conditions.
OBSERVATIONS OF TEMPERATURE MICROSTRUCTURE IN THE ATMOSPHERE
Zeng Zongyong, Ma Chengsheng
1985, 2(2): 234-242. doi: 10.1007/BF03179755
Abstract:
In order to provide data of atmospheric temperature microstructure for the investigation of light prop-agation we measured fluctuations of atmospheric temperature below the height of 300 m with a platinum wire thermometer in Tianjin in May and September, 1980. The results measured in daytime revealed some properties of the temperature structure parameter and spectrum. It has been confirmed that there is a max-imum in the profile of the structure parameter produced probably by the entrainment in the interfacial layer at the top of convective boundary layer. The average of C2t in the interfacial layer and its Wyngaard calculating method are discussed, and the thickness of the interfacial layer is obtained.It is shown by spectrum analysis that a wide inertial subrange exists in the convective boundary layer and the strong turbulent zone in the free atmosphere. The spectral law with the power of -2.5 was measured within the upper half of boundary layer over the sea in vicinity of Tanggu.
VARIATIONS OF ATMOSPHERIC AEROSOL CONCENTRATION AND SIZE DISTRIBUTION WITH TIME AND ALTITUDE IN THE BOUNDARY LAYER
You Ronggao, Hong Zhongxiang, Lu Weixiu, Zhao Deshan, Kong Qinxin, Zhu Wenqin
1985, 2(2): 243-250. doi: 10.1007/BF03179756
Abstract:
The atmospheric aerosol number concentration and size distribution were measured at six levels (50, 100, 150, 200, 250 and 300 m) on the Beijing 325 m meteorological tower by means of an optical particle counter. From the measured value of the concentration Nz and according to the expression Nz = , the value of aerosol scale height Hp was determined by using a least square method. An analysis shows that there are significant variations of aerosol concentration and size distribution in relation to time and altitude. The average size distribution for each level can be described by , where the parameters vary with the altitude.
NUMERICAL SIMULATION FOR THE EFFECTS OF PBL AND THE SURFACE ON POLLUTANT CONCENTRATIONS
Chen Panqin
1985, 2(2): 251-259. doi: 10.1007/BF03179757
Abstract:
On the basis of theoretical and experimental results of study of planetary boundary layer (PBL), the physical parameters describing the structure of PBL are calculated by using the data obtained from a meteor-ological tower and the effects of PBL and the surface on pollutant concentrations are numerically simulated with a time-dependent two-dimensional advection and diffusion equation.It is shown that the diurnal variation of PBL results in that of concentration. The height of mixing layer is an important factor to determine the ground-level concentration. As for an elevated point source, the height of mixing layer, growing from lower to higher than the releasing height is a necessary condition for the phenomenon of fumigation. It is also shown that the surface may be considered as a boundary with perfect reflection when Vd ≤ 0.001 m s-1, but has an important effect on concentration and must be carefully dealt with when Vd ≤ 0.01 m s-1.
AN ANALYSIS OF THE FILTER DIFFUSION CHAMBER AND DROP FREEZING METHODS OF DETERMINING ICE NUCLEUS CONCENTRATIONS
Wang Mingkang
1985, 2(2): 260-269. doi: 10.1007/BF03179758
Abstract:
The membrane filters used for sampling at a height of 60 m and at ground level were processed with a drop freezing technique and a static vapor-diffusion chamber. Comparisons of IN concentrations obtained by the two techniques are made. The blank filter counts and ice nucleus measurement reproducibility are analysed. The factors affecting IN concentration measurements are discussed and some favorable operation conditions are suggested. It has been found that: (a) the IN concentrations typically range from 0.2 L-1 to 2.0 L-1 at -20oC, (b) significant time variations in IN concentrations occurs, (c) the IN concentra-tions obtained by the drop freezing technique typically exceed the value given by the diffusion chamber, (d) their variation trends are generally in phase, (e) high IN concentrations are often associated with pre-cipitation events.