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1989 Vol. 6, No. 4

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A Regional Spectral Nested Shallow Water Equation Model
Liao Dongxian
1989, 6(4): 393-402. doi: 10.1007/BF02659074
A method to expand meteorological elements in terms of finite double Fourier series in a limited-region and a spectral nested shallow water equation model based upon the method with conformal map projection in rectangular coordinates, have been proposed, and computational stability and efficiency of time integration have been discussed.
A Parameterization of Cooling Rate Calculation under the Non-LTE Condition: Multi-Level Model
Xun Zhu
1989, 6(4): 403-413. doi: 10.1007/BF02659075
Calculations of cooling rate by CO2 15 μm band in the earth’s upper mesosphere and lower thermosphere be-come very difficult because of the non-LTE. This is primarily due to the nonlinear vibration-vibrational (VV) transi-tion processes between CO2 molecules in different states. This paper suggests that the non-LTE source function be parameterized as a linear combination of two limiting source functions. One limiting source function neglects the VV transitions while the other limiting source function assumes VV transitions being dominant. These two limiting source functions can be derived by linear models. The parameterization schemes proposed here can be applied 10 the general circulation models including those non-LTE regions.
The Kinetic Energy Budget and Circulation Characteristics of the Tropical Storm Irma during AMEX Phase II
Wang Zuoshu, Zhang Ruojun, Peng Zhengyi
1989, 6(4): 414-423. doi: 10.1007/BF02659076
By using the data from observation on the Chinese research vessel Xiang Yang Hong No.5 and other sources during AMEX phase II, the kinetic energy budget and circulation characteristics of the tropical storm Irma were analyzed.Irma formed on the ITCZ of the Southern Hemisphere. During the formative stage of the storm, the SE trades and monsoon westerlies on both sides of the ITCZ strengthened, and more importantly, there was a strong divergent flow in upper troposphere. These contributed to the intensification of Irma. At the time when Irma formed, the Richardson number (Ri) in middle and lower troposphere was much smaller than that prior to and post the formation.When Irma intensified rapidly, the area-averaged kinetic energy in the general flow increased in the whole troposphere . The largest contribution came from kinetic energy generation term, -[v.(?)(?)] .indicates that there existed a strong ageostrophic accetration. As to the generation term , the conversion of available potential energy to kinetic energy, - |ωα|, made the largest contribution. This illustrates the importance of internal sources and of the ensemble effect of cumulus convection to the kinetic energy.To the increase of area-averaged eddy kinetic energy during the rapid intensification of Irma, the most impor tant source in the whole troposphere was the dissipation term - [E'], that should be interpreted as the. feeding of eddy kinetic energy from smaller to larger scale disturbances. Another important source was generation term, - [v' (?)(?)'], in the lower troposphere. Rather small contribution came from the energy conversion from the kinetic energy of area-mean flow to eddy kinetic energy. Therefore, the eddy kinetic energy of the developing tropical disturbance extracted both from smaller an, .arger scale motions. The former was much more important than the latter In addition, the disturbance acting as a generator and exporter, generated and exported eddy kinetic energy to the environmental atmosphere.
CCN Concentration in Troposphere over China
Wang Pengyun, He Shaoqin
1989, 6(4): 424-434. doi: 10.1007/BF02659077
CCN concentration in the middle-lower Troposphere over northern China was observed using a cloud condensa-tion nucleus counter, MEE-130, installed on an IL-14 aircraft in the summer of 1983 and 1984. More than 60 sets of data (each flight as one set) were collected.The main results are: (1) in northern China, CCN concentration is 102-104/cm3 near ground, decreases with in creasing height and follows exponential distribution; (2) the local CCN concentration and its distribution with alti-tude are influenced by some meteorological factors: such as inversion, cloud and precipitation, wind and land-sea breeze etc. The inversion makes CCN significantly accumulate just below the inversion level; CCN concentration is lower inside clouds than outside clouds at same level; wind plays an important role of transporting CCN horizontally; (3) the CCN concentration is higher above the land than above the sea at same level; CCN concentration is one order of magnitude lower over the coastal cities like Qingdso than over the continental cities like Zhengzhou; (4) all these suggest that CCN in northern China comes mainly from continental surface layer. Densely-populated areas and in-dustrial areas may produce more CCN.
A Scheme for Objective Analysis of Wind Field Incorporating Multi-Weighting Functions in the Optimum Interpolation Method
S.K. Sinha, D.R. Talwalkar, S.G. Narkhedkar, S. Rajamani
1989, 6(4): 435-446. doi: 10.1007/BF03342547
A method of objective analysis scheme having three different weighting functions for different conditions of the wind flow has been developed for the Indian region, two of which are anisotropic and third one is isotropic. Basically Gandins Optimum Interpolation method is used. The effective distance between a grid point and observation point used for the anisotropic functions, has been applied to calculate weighting functions following Benjamin and Seaman (1985) and objective analyses were made at the 700 hPa level for three consecutive days from 6 July to 8 July 1979. The quantitative evaluation of the objectively analysed fields have been made by computing the R.M.S. errors. Ana-lyses obtained using multi-weighting functions (anisotropic) and those obtained using ordinary circular functions (isotropic-Gandin, 1963) have been compared. Also, the centres of the monsoon depressions obtained by this method have been compared with those of subjective analyses.
On the Multiple Equilibrium of the Development of Tropical Cyclone in Nonlinear CISK Model
Li Tianming, Zhu Yongti
1989, 6(4): 447-456. doi: 10.1007/BF02659078
By using non-static atmosphere equations including basic current, heating force and friction, we discuss the bal-ance amplitude of vertical motion in the conditions of constant heating force, linear and non-linear interaction be-tween large-scale ascending motion and diabatic heating force. In the non-linear condition, the multiple equilibrium feature of the tropical cyclone development is discussed and the reason of the sudden varying of tropical cyclone intensity is studied preliminarily.
The Solitary Wave of Barotropic Atmosphere on a Sphere
Xu Xihua
1989, 6(4): 457-466. doi: 10.1007/BF02659079
In this paper, we have investigated large scale disturbance in barotropic atmosphere on a sphere. It demonstrates that: considering nonlinear effects of interaction between waves in barotropic vorticity equation, the wave packet of the disturbance is governed by the famous equation-nonlinear Schrodinger equation. For the solitary wave, two fac-tors are very important: one is spherical effect of the disturbance and the other is meridional shear of blocking high. In comparison with the results of local Cartesian coordinates, the former factor is the individuality of spherical soliton.
The Latent and Sensible Heat Fluxes over the Western Tropical Pacific and Its Relationship to ENSO
Long Baosen
1989, 6(4): 467-474. doi: 10.1007/BF02659080
In this paper the Bulk Aerodynamic Formulas are used to compute the latent and sensible heat fluxes over the area 8oS-20oN, 130o-180oE for each month from January 1950 through December 1979 by using the data set of COADS supplied by NOAA of USA. The annual and monthly geographical distributions and the seasonal cycle of heat fluxes are carried out and a seasonal change of heat fluxes for ENSO year is also obtained by compositing individual ENSO year including 1951, 1953, 1957, 1963, 1965, 1969, 1972 and 1976. It is found that during ENSO episodes positive anomalies of heat fluxes appeared during the period of March to July and negative anomalies from August to March of the following year. The time series of sum of heat fluxes for March. April, May, June and July in each year from 1950 through 1979 had a significant link to the eastern tropical Pacific SST index (Wright, 1983). The correlation coefficient was 0.56. As it is found that in the latter half of each ENSO year (August-December) the fre-quency of typhoon formation in the area studied is less than normal, we suggest that the negative anomalies of heat fluxes during the same period be a mechanism for the decreased frequency of typhoon formation.
Excitation of Low-level Jet as Seen by GOES (I-O) Satellite off the Somali Coast
P.N. Mahajan, V.R. Mujumdar, S.P. Ghanekar
1989, 6(4): 475-482. doi: 10.1007/BF02659081
The intensification of a low-level jet off the Somali coast, as observed through GOES (I-O) satellite during In-dian summer monsoon 1979 has been studied. Excitation of Low-level cross-equatorial flow in the western Indian ocean results from an interaction between extratropical perturbations moving eastward across the South African-Malgassy region of the Southern Hemisphere. This excitation occurs 2-3 days after the first appearance of a northward propagation cold front across the South African-Malgassy region. Intensification of cross-equatorial flow is followed by an increase in rainfall activity along the west coast of India after 3-4 days. The study reveals that this association can be used to forecast an increase in rainfall activity along the west coast of India 5-7 days in advance.
A Numerical Method of Statistical Pattern Recognition
Xu Hong, Li Hongji, Wang Ronghua
1989, 6(4): 483-492. doi: 10.1007/BF02659082
A numerical method of statistical pattern recognition is proposed in this paper. Different from the discriminatory analysis method currently used in the mathematic statistics, it is unnecessary to assume that the predictand should be subject to a certain distribution. On the contrary, the statistical relationship between predictand and predictor has been obtained directly with computer according to actual distribution to recognize the category of patterns. Result of forecast has been improved as compared with the usual analytic discriminatory method. The influence of predictor on predictand can be seen clearly from this method and the transparency is good. Therefore, it is better to use the method in very short range forecast for which causality is more obvious.
An Analysis of the Turbulent Structure in the Unstable Surface Layer nearby a Shelter Belt
Zeng Zongyong, Ma Chengsheng, Liu Xiaochun, Ling Huiqin
1989, 6(4): 493-500. doi: 10.1007/BF02659083
An analysis was performed of the turbulent data obtained from Yucheng experimental station in the Shandong Province in 1984. [t is shown that at variant wind speed, the spectra of streamwise velocity remain similar and the intensity of wind fluctuations is proportional to wind speed in the downwind area of shelter belt. Therefore, we may decide the similarity of wind fluctuations by a speed scale and a length scale which is not correlated with stability, σu /V0 = F(X / H). The -5/3 power range of temperature spectra extends to lower frequency. The variation of ratio σ0 /T. with stability becomes σ0 / T . = C(X / H)( - Z / L)-1/3 . There is not such an extension of -5 / 3 power range in the humidity spectra.
An Efficient Accurate Direct Solution of Poisson’s Equation for Computation of Meteorological Parameters
D. R. Chakraborty, P.S. Salvekar
1989, 6(4): 501-508. doi: 10.1007/BF02659084
Poisson's equation is solved numerically by two direct methods, viz. Block Cyclic Reduction (BCR) method and Fourier Method. Qualitative and quantitative comparison between the numerical solutions obtained by two methods indicates that BCR method is superior to Fourier method in terms of speed and accuracy. Therefore. BCR method is applied to solve (?)2(?)= ζ and (?)2X= D from observed vorticity and divergent values. Thereafter the rotational and divergent components of the horizontal monsoon wind in the lower troposphere are reconstructed and are com pared with the results obtained by Successive Over-Relaxation (SOR) method as this indirect method is generally in more use for obtaining the streamfunction ((?)) and velocity potential (X) fields in NWP models. It is found that the results of BCR method are more reliable than SOR method.
A Study on Hydrogen Peroxide in the Atmosphere
Su Weihan, Li Wei, Ding Guoan, W.E. Wilson
1989, 6(4): 509-515. doi: 10.1007/BF02659085
Hydrogen peroxide (H2O2) concentrations were measured at two sites. One was on Lushan Mountain in May, 1987. The other was in Beijing in August, 1987 and in December, 1986. The automated fluorometric method was used for the determination of H2O2. The concentrations of H2O2 ranged from approximately 0.50 to 4.32 ppb on Lushan Mountain. The concentrations of H2O2 ranged from approximately 0.05 to 1.49 ppb in August in Beijing, and it was only 0.01 ppb in December in Beijing.