1997 Vol. 3, No. 1
1997, 3(1): 1-10.
Abstract:
Two semi-asymmetric flow patterns of typhoons are chosen to qualitatively determine the effect of exchange of horizontal momentum between inflow and outflow layers and the environment on the motion of typhoons. The results show that only the asymmetric flow component (residual after azimuthal mean flow has been removed) could cause a net momentum input into or output from a typhoon and therefore contribute to the changes in speed and direction of the typhoon movement. A typhoon with major inflow and/or outflow channels on its right (left) side would tend to accelerate and turn left (decelerate and turn right); On the other hand, a typhoon with major inflow and/or outflow channels in the rear (front) semicircle would tend to accelerate and turn right (decelerate and turn left).
Two semi-asymmetric flow patterns of typhoons are chosen to qualitatively determine the effect of exchange of horizontal momentum between inflow and outflow layers and the environment on the motion of typhoons. The results show that only the asymmetric flow component (residual after azimuthal mean flow has been removed) could cause a net momentum input into or output from a typhoon and therefore contribute to the changes in speed and direction of the typhoon movement. A typhoon with major inflow and/or outflow channels on its right (left) side would tend to accelerate and turn left (decelerate and turn right); On the other hand, a typhoon with major inflow and/or outflow channels in the rear (front) semicircle would tend to accelerate and turn right (decelerate and turn left).
1997, 3(1): 11-17.
Abstract:
The results from simple dynamic studies on the evaporation-wind feedback show that the effect cannot change the nature of tropical atmospheric waves (by retarding the speed), so that the evaporation-wind feedback alone cannot be an exciting mechanism of intraseasonal oscillation in the tropical atmosphere. This is different from that of the wave-CISK mechanism. With combined effect of the cumulus convection heating and evaporation-wind feedback, the CISK-Kelvin waves and CISK-Rossby waves will develop unstably, explaining the dynamic mechanism of tropical intraseasonal oscillation in a more complete and reasonable way than the convection heating alone. Therefore, the evaporation-wind feedback is also important to the intraseasonal oscillation in the tropical atmosphere.
The results from simple dynamic studies on the evaporation-wind feedback show that the effect cannot change the nature of tropical atmospheric waves (by retarding the speed), so that the evaporation-wind feedback alone cannot be an exciting mechanism of intraseasonal oscillation in the tropical atmosphere. This is different from that of the wave-CISK mechanism. With combined effect of the cumulus convection heating and evaporation-wind feedback, the CISK-Kelvin waves and CISK-Rossby waves will develop unstably, explaining the dynamic mechanism of tropical intraseasonal oscillation in a more complete and reasonable way than the convection heating alone. Therefore, the evaporation-wind feedback is also important to the intraseasonal oscillation in the tropical atmosphere.
1997, 3(1): 18-26.
Abstract:
Based on TBB data from Meteorological Institute Research of Japan, study is carried out of the features of seasonal transition of Asian-Australian monsoons and Asian summer monsoon establishment,indicating that the transition begins as early as in April, followed by abrupt change in May-June; the Asian summer monsoon situation is fully established in June. The winter convective center in Sumatra moved steadily northwestward across the "land bridge" of the maritime continent and the Indo-China Peninsula as time goes from winter to summer, thus giving rise to the change in large scale circulations that is responsible for the summer monsoon establishment over SE Asia and India; the South China Sea to the western Pacific summer monsoon onset bears a close relation to the active convection in the Indo China Peninsula and steady eastward retreat of the subtropical TBB high-value band,corresponding to the western Pacific subtropical high.
Based on TBB data from Meteorological Institute Research of Japan, study is carried out of the features of seasonal transition of Asian-Australian monsoons and Asian summer monsoon establishment,indicating that the transition begins as early as in April, followed by abrupt change in May-June; the Asian summer monsoon situation is fully established in June. The winter convective center in Sumatra moved steadily northwestward across the "land bridge" of the maritime continent and the Indo-China Peninsula as time goes from winter to summer, thus giving rise to the change in large scale circulations that is responsible for the summer monsoon establishment over SE Asia and India; the South China Sea to the western Pacific summer monsoon onset bears a close relation to the active convection in the Indo China Peninsula and steady eastward retreat of the subtropical TBB high-value band,corresponding to the western Pacific subtropical high.
1997, 3(1): 27-34.
Abstract:
By use of an observational experiment at the village of Tianwei, Haikou, Hainan province in 1990,characteristic turbulence values such as velocity component spectra and turbulence intensity are studied.The data were mostly obtained in cloudy condition, so that the stability parameter (L) and thermal flux (wt) did not vary diurnally while the turbulent energy and mean-temperature did. The basic characteristics of turbulence spectra are similar to those with fine weather, hems close to local isotropy in the inertial subrange. The velocity spectra agree with the law of "-2/3 th power"in Kolmogrov's similarity theory. The relationship between turbulent intensity of components δi/U (i=u,v,w) and stability Z/L is studied follow ins the Monim-Obukhov(M-O) similarity theory. It is shown that the two observe the law of "1/3 th power", though the turbulent intensity and energy are generally larger than those on the flat underlying topography.
By use of an observational experiment at the village of Tianwei, Haikou, Hainan province in 1990,characteristic turbulence values such as velocity component spectra and turbulence intensity are studied.The data were mostly obtained in cloudy condition, so that the stability parameter (L) and thermal flux (wt) did not vary diurnally while the turbulent energy and mean-temperature did. The basic characteristics of turbulence spectra are similar to those with fine weather, hems close to local isotropy in the inertial subrange. The velocity spectra agree with the law of "-2/3 th power"in Kolmogrov's similarity theory. The relationship between turbulent intensity of components δi/U (i=u,v,w) and stability Z/L is studied follow ins the Monim-Obukhov(M-O) similarity theory. It is shown that the two observe the law of "1/3 th power", though the turbulent intensity and energy are generally larger than those on the flat underlying topography.
1997, 3(1): 35-41.
Abstract:
Bratseth (1986) has proposed a successive correction scheme for numerical analysis where the solution converges towards the solution obtained by optimum interpolation. This paper presents the results of some experiments carried out over indian reston during summer monsoon period using this Bratseth's method. The convergence of the method is investigated.
Bratseth (1986) has proposed a successive correction scheme for numerical analysis where the solution converges towards the solution obtained by optimum interpolation. This paper presents the results of some experiments carried out over indian reston during summer monsoon period using this Bratseth's method. The convergence of the method is investigated.
1997, 3(1): 42-51.
Abstract:
Diagnostic study on two intraseasonal progressive and retrogressive progress of anomalous subtropical high in western Pacific is carried out with the aid of daily 2.5°× 2.5° grid point data of ECMWF inJuly and August of 1980 and 1983. It is revealed that the anomalous progression and retrosression ofthis high is intraseasonally teleconnected with that in the eastern Pacific, shown as low-ftequency wavespropagating westward along a latitudinal wave train across the northern Pacific i the same oscillatory displacement of eastern subtropical high is again triggered off by the variation of convergent sink of uppertropospheric divergent wind field in eastern Pacific, being resulted from anomalous heating from monsoon area in South Asia through trade wind zone in the Pacific Ocean.
Diagnostic study on two intraseasonal progressive and retrogressive progress of anomalous subtropical high in western Pacific is carried out with the aid of daily 2.5°× 2.5° grid point data of ECMWF inJuly and August of 1980 and 1983. It is revealed that the anomalous progression and retrosression ofthis high is intraseasonally teleconnected with that in the eastern Pacific, shown as low-ftequency wavespropagating westward along a latitudinal wave train across the northern Pacific i the same oscillatory displacement of eastern subtropical high is again triggered off by the variation of convergent sink of uppertropospheric divergent wind field in eastern Pacific, being resulted from anomalous heating from monsoon area in South Asia through trade wind zone in the Pacific Ocean.
1997, 3(1): 52-60.
Abstract:
Based on data of typhoon over the West Pacific and the South China Sea for the last 40 years, theshort-term climate oscillation of typhoon activities was revealed. The result indicated that the climaticvariation of typhoon activities has a tendency of climatic jump in changes in early 1970's. It showed thatbefore the jump of change the number of typhoon was increased and the intensity of typhoon was intensified after which the tendency of variation went contrary. In addition, the increase of typhoon numberduring recent years suggested again the jump of climatic change in the late 1980's, but the intensity oftyphoon did not have the same change. The analysis indicated that the short-term climatic oscillation andthe jump of climatic change have certain physical background. Such climate change tendency of typhoonwas shown to be related to the climatic oscillation of general circulation and SST, especially to the WestPacific subtropical high.
Based on data of typhoon over the West Pacific and the South China Sea for the last 40 years, theshort-term climate oscillation of typhoon activities was revealed. The result indicated that the climaticvariation of typhoon activities has a tendency of climatic jump in changes in early 1970's. It showed thatbefore the jump of change the number of typhoon was increased and the intensity of typhoon was intensified after which the tendency of variation went contrary. In addition, the increase of typhoon numberduring recent years suggested again the jump of climatic change in the late 1980's, but the intensity oftyphoon did not have the same change. The analysis indicated that the short-term climatic oscillation andthe jump of climatic change have certain physical background. Such climate change tendency of typhoonwas shown to be related to the climatic oscillation of general circulation and SST, especially to the WestPacific subtropical high.
1997, 3(1): 61-68.
Abstract:
Numerical simulation and diagnosis show that the amplified rainstorm from Typhoon Poily is related to the development/migration of meso-α gravity waves, inhomoseneous stratification distribution andcumulus convection latent heating feedback in the storm; such waves at a large scale are excited bylarge-scale nonlinear advection; substantially amplified ageostrophic wind perturbation resulting fromthe latent heating gives rise to intensified wave amplitude, leading to enhanced rising and thus torrentialrainfall; as the waves migrate towards reduced stability, wave energy is most likely to increase.
Numerical simulation and diagnosis show that the amplified rainstorm from Typhoon Poily is related to the development/migration of meso-α gravity waves, inhomoseneous stratification distribution andcumulus convection latent heating feedback in the storm; such waves at a large scale are excited bylarge-scale nonlinear advection; substantially amplified ageostrophic wind perturbation resulting fromthe latent heating gives rise to intensified wave amplitude, leading to enhanced rising and thus torrentialrainfall; as the waves migrate towards reduced stability, wave energy is most likely to increase.
1997, 3(1): 69-77.
Abstract:
With conditions of approximately actual background wind field in typhoons and a barotropic nondivergent model in a cylindrical coordinate, the problem of instability of the perturbation in typhoons isdiscussed. The results show that the warm core structure of typhoons and the activity of fanly strongcold air in the periphery are advantageous to the perturbation development in typhoons,and the strongerthe typhoons, i. e. the lower the pressure, the caster the perturbation in typhoons would develop.
With conditions of approximately actual background wind field in typhoons and a barotropic nondivergent model in a cylindrical coordinate, the problem of instability of the perturbation in typhoons isdiscussed. The results show that the warm core structure of typhoons and the activity of fanly strongcold air in the periphery are advantageous to the perturbation development in typhoons,and the strongerthe typhoons, i. e. the lower the pressure, the caster the perturbation in typhoons would develop.
1997, 3(1): 78-84.
Abstract:
The energetics process of offehore typhoon in three kinds of explosive enhancement (TEE) are ana lyzed using ECMWF data. The results are as follows: (a) During the explosive development process,the enhancement of the rotational kinetic enersy (KW) is mainly in the lower troposphere while that ofthe potential energy (PE) is in the upper troposphere. The magnitude of rotational kinetic energy islargely bigger than that of divergent enersy (KΧ). (b) The environmental energy advected into the typhoon was about 30% of the internal increment of typhoon energy. The magnitude of energy was an order larger than increment of typhoon energy. (c) Among those three kinds of explosively developed typhoon, the enersy transformation mechanisms are different. (d) The influence of environment fields onabrupt intensification of typhoons couldn't be overestimated.
The energetics process of offehore typhoon in three kinds of explosive enhancement (TEE) are ana lyzed using ECMWF data. The results are as follows: (a) During the explosive development process,the enhancement of the rotational kinetic enersy (KW) is mainly in the lower troposphere while that ofthe potential energy (PE) is in the upper troposphere. The magnitude of rotational kinetic energy islargely bigger than that of divergent enersy (KΧ). (b) The environmental energy advected into the typhoon was about 30% of the internal increment of typhoon energy. The magnitude of energy was an order larger than increment of typhoon energy. (c) Among those three kinds of explosively developed typhoon, the enersy transformation mechanisms are different. (d) The influence of environment fields onabrupt intensification of typhoons couldn't be overestimated.
1997, 3(1): 85-94.
Abstract:
A two-layer primitive equation model is developed in this paper. The capabilities of this model aretested by the use of multiyearly averaged January and July sea surface level pressure fields and windfields which can be diagnosed from the pressure fields. The results show that the ocean surface currentsand undercurrents in the second layer driven by the sea surface wind and the sea surface pressure areclose to the observation. The results are also compared with that of the IAP OGCM and the OSUOGCM.
A two-layer primitive equation model is developed in this paper. The capabilities of this model aretested by the use of multiyearly averaged January and July sea surface level pressure fields and windfields which can be diagnosed from the pressure fields. The results show that the ocean surface currentsand undercurrents in the second layer driven by the sea surface wind and the sea surface pressure areclose to the observation. The results are also compared with that of the IAP OGCM and the OSUOGCM.
1997, 3(1): 95-104.
Abstract:
The multiple atmospheric equilibria are studied by using a barotropic vorticity equation with thermal forcing and dissipative effects. Different low-spectral models are used to discuss the variations of theequilibrium states, with the results that the multiple features of equilibrium states depend heavily on thetruncations of the spectra, and the low-spectral model has obvious shortcomings in solving non-linear equations,suggesting that one has to be very Careful to employ highly truncated low-spectral model in approximating partial differential equations.
The multiple atmospheric equilibria are studied by using a barotropic vorticity equation with thermal forcing and dissipative effects. Different low-spectral models are used to discuss the variations of theequilibrium states, with the results that the multiple features of equilibrium states depend heavily on thetruncations of the spectra, and the low-spectral model has obvious shortcomings in solving non-linear equations,suggesting that one has to be very Careful to employ highly truncated low-spectral model in approximating partial differential equations.
EXPERIMENT WITH ONE DIMENSIONAL DATA FOR REPRODUCTION OF ATTRACTOR STRUCTURE IN N-DIMENSIONAL SYSTEM
1997, 3(1): 105-112.
Abstract:
Illustrated with the Rossler and Lorenz systems, the topological structure is reproduced using univariable temporal series. The study shows that there are a number of principal vectors reproduced withone-dimensional temporal series,which reflect from a certain aspect the topological structure for the system attractors.
Illustrated with the Rossler and Lorenz systems, the topological structure is reproduced using univariable temporal series. The study shows that there are a number of principal vectors reproduced withone-dimensional temporal series,which reflect from a certain aspect the topological structure for the system attractors.
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