Advanced Search

1989 Vol. 6, No. 3

Display Method:
Comparison and Examination of Dynamic Frameworks of IAP and OSU AGCM
Zhang Xuehong, Liang Xinzhong
1989, 6(3): 265-274. doi: 10.1007/BF02661533
A brief description of the dynamic framework of the IAP 2-L AGCM (referred as “IAP DF”) is presented in contrast with the corresponding “OSU DF” and preliminary comparison and examination of the IAP DF and the OSL DF with the aid of numerical experiments using a set of baroclinic Rossby-Haurwitz wave initial conditions is performed.The results of the numerical experiments show that both the IAP DF and the OSU DF are long-term computational stable and are able to simulate the fundamental behavior of the Rossby-Haurwitz wave under the lim-itation of 7.5 minutes time interval. In the respect of the prediction of the large-scale wave, the IAP DF is better than the OSU DF, however, the OSU DF gives better predictions of zonal mean status than the IAP DF does. Another important contrast is that the level of small-scale noise of the IAP DF is higher than the OSU DF, on the contrary, the damping effect of the OSU DF on large-scale vortex field is stronger than the IAP DF.
Atmosphere-Ocean Coupling Schemes in a One-Dimensional Climate Model
Ji jinjun
1989, 6(3): 275-288. doi: 10.1007/BF02661534
In this paper, the coupling schemes of atmosphere-ocean climate models are discussed with one-dimensional advection equations. The convergence and stability for synchronous and asynchronous schemes are demonstrated and compared.Conclusions inferred from the analysis are given below. The synchronous scheme as well as the asynchronous-implicit scheme in this model are stable for arbitrary integrating time intervals. The asynchronous ex-plicit scheme is unstable under certain conditions, which depend upon advection velocities and heat exchange parameters in the atmosphere and oceans. With both synchronous and asynchronous stable schemes the discrete solu-tions converge, to their unique exact ones. Advections in the atmosphere and ocean accelerate the rate of convergence of the asynchronous-implicit scheme. It is suggested that the asynchronous-implicit coupling scheme is a stable and efficient method for most climatic simulations.
The Operational Forecasting of Total Precipitation in Flood Seasons (April to September) of 5 Years (1983-1987)
Tang Maocang, Li Tianshi, Zhang Jian, Li Cunqiang
1989, 6(3): 289-300. doi: 10.1007/BF02661535
Medium-Range Oscillations in the Summer Tropical Easterlies at 200 hPa
Lu Jingxi, Ding Yihui
1989, 6(3): 301-312. doi: 10.1007/BF02661536
By the use of space-time spectral analysis and band-pass filter, some of the features of the medium-range Oscillations in the summer tropical easterlies (10oS-20o) at 200 hPa are investigated based on a two-year (1980 and 1982) wind (u, v) data set for the period from May to September. Space-time power spectral analysis shows that the total energy of the westward moving waves was the largest and that of the standing waves and eastward moving waves was relatively small in the 200 hPa easterlies; the total energy of the eastward moving waves was at minimum at 10oN. Three kind of the medium-range oscillations with about 50 day, 25 day and quasi-biweekly periods were found in the easterlies, which all show a remarkable interannual variation and latitudinal differences in these two years. The wave energy of zonal wind is mainly associated with the planetary waves (1-3), which all may make important contributions to the 50 day and 25 day oscillations in different years or different latitudes. The quasi-biweekly oscillation is mainly related to the synoptic waves (4-6). In equatorial region, the 50 day oscillation was dominant with a eastward phase propagation in 1982 while the dominant oscillation in 1980 was of 25day period with a westward phase propagations in 1980. Both of them are of the mode of zonal wavenumber 1. Strong westward 50 day oscillation was found in 10oN-20oN in these two years. Regular propagations of the meridional wind 50 day oscillation were also found in the easterlies.The 50 day and 25 day oscillation of zonal wind all demonstrate southward phase propagation over the region of the South Asia monsoon and northward phase propagation near interational date line, where are the climatic mean position of the tropical upper-tropospheric easterly jet and the tropical upper tropospheric trough (TUTT), respectively.
Theoretical Analysis of Retrieving Atmospheric Columnar Mie Optical Depth from Downward Total Solar Radiative Flux
Qiu Jinhuan
1989, 6(3): 313-324. doi: 10.1007/BF02661537
In this paper, the principle to determine the atmospheric columnar Mie optical depth from downward total solar radiative flux is theoretically studied, and the effect on Mie optical depth solution of the errors in surface albedo, single scattering albedo, asymmetrical factor of scattering phase function, instrumental constant and the approximate expression of diffusion flux is analyzed, and then a method for determining, surface albedo in shorter wavelength range is presented.
Temperatures and Winds over Tropical Middle Atmosphere during Two Contrasting Summer Monsoons, 1975 and 1979
B.K. Mukherjee, C.P. Kulkarni, K. Indira, K.K. Dani
1989, 6(3): 325-334. doi: 10.1007/BF02661538
Using the monthly geopotential heights and winds for 700 and 200 hPa for India during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5oN, 76.9oE) during the last week of June and the first week of September for the two contrasting summer monsoon years 1975 (a very strong monsoon year) and 1979 (a very weak monsoon year), a study has been made to examine the mean circulation features of the troposphere over India, and the structures of the temperatures and the winds of the middle atmosphere over Thumba. The study suggested that the axis of the monsoon trough (AMT) at 700 hPa shifted southward in 1975 and northward towards the foothills of the Himalayas in 1979, from its normal position. Superimposed on the low-pressure area (AMT) at 700 hPa, a well-defined divergence was noticed at 200 hPa over the northern India in 1975.The mean temperatures, at 25,50 and 60 km (middle atmosphere) over Thumba were cooler in 1975 than in 1979. While a cooling trend in 1975 and warming trend in 1979 were observed at 25 and 50 km, a reversed picture was noticed at 60 km. There was a weak easterly/ westerly (weak westerly phase) zonal wind in 1975 and a strong easterly zonal wind in 1979. A phase reversal of the zonal wind was observed at 50 km. A tentative physical mechanism was offered, in terms of upward propagation of the two equatorially trapped planetary waves i.e. the Kelvin and the mixed Rossby-gravity waves, to explain the occurrence of the two spells of strong warmings in the mesosphere in 1975.
Predictability of the Atmosphere
Chou Jifan
1989, 6(3): 335-346. doi: 10.1007/BF02661539
This paper makes a review on the predictability of the atmosphere. The essential problems of predictability theo-ry, i.e., how a deterministic system changes to an undeterministic system (chaos) and how is the opposite (order within chaos), are discussed. Some applications of predictability theory are given.
The Band Characteristics of Long-Term Variation of Precipitation and Water Resources in East Asia Monsoon Region
Wang Duo, Zhang Tan
1989, 6(3): 347-356. doi: 10.1007/BF02661540
In this paper, by means of the “CWH” (circulation-weather and climate-agricultural harvest) analytical meth-od, drawing from the monthly mean long-term data of the global sea level pressure field and annual precipitation data and grain yield data of some regions in East Asia, the time-space characters of low-frequency fluctuation of East Asian precipitation with band distribution are analyzed.It is revealed that the band of 20-30 years quasi-periodic fluctuation is located in Southeast Asia and the coastal areas of South China. Moving forward to west and north, the period of fluctuation of precipitation tends to become longer, both bands, with about 40-yr and 60-80-yr quasi-periodic fluctuation are respectively situated in the middle-lower reaches of the Yangtze River and North or Southwest China. Furthermore, the relationships between the fluctuations of precipitation bands and large-scale circulations are analyzed. The relationships between precipita-tion and types of water resources are discussed as well. In addition, the tendency of long-term variation in rainfall is predicted.
Some Aspects of the Diurnal and Semidiurnal Tidal Wind Field in Meteor Zone
P.C.S. Devara, G. Chandrasekhar, M.I. Ahmed
1989, 6(3): 357-364. doi: 10.1007/BF02661541
The diurnal and semidiurnal tidal wind field variations in the altitudes between 80 and 100 km of the earth’s atmosphere over a mid-latitude station are studied by means of the phases of the zonal and meridional wind measurements made at Atlanta (34oN, 84oW). The rotation of diurnal tidal wind vector is seen to be clockwise at lower heights (80-86 km), swinging between clockwise and unti-clockwise at intermediate heights (88-96 km) and anti-clockwise at higher-heights (96- 100 km). The senses of rotation of diurnal and semidiurnal tidal wind vectors are compared between the stations located in the same and opposite hemispheres. The results are consistent with the tidal theory in the case of Atlanta and Adelaide (35oS, 139oE) whereas in the case of other stations considered in the present study, they showed marked variations.
The Wind Structure in Planetary Boundary Layer
Zhao Ming, Xu Yinzi, Wu Rongsheng
1989, 6(3): 365-376. doi: 10.1007/BF02661542
The investigations on the dynamics of the PBL have been developed in recent years. Some authors emphasized macro-dynamics and others emphasized micro-structure of the PBL. In this paper, we study and review some main characteristics of the wind field in the PBL from the view point connecting the macro-dynamics and micro-structure of the PBL, thus providing the physical basis for the further research of the dynamics and the parameterization of the PBL.
Branches of the Summer Asian Lower-Level Jet Stream and Its Influence on the Rain Belt in China
Yin Shuxin, Tan Xinzhen
1989, 6(3): 377-389. doi: 10.1007/BF02661543
Based on the analysis of the Asian lower-level jet stream, this paper indicates that having shifted to the Bay of Bengal, this large-scale lower-level jet (LLJ) develops into two branches: the northern branch (NB) which is a strong southwest flow moving into the inland of China along the southeast side of the Qinghai-Xizang Plateuu and then moving eastward to Japan along the north side of the subtropical high, and the southern branch (SB) which continues to he a west flow and travels into the West Pacific across the Indo-China Peninsula along the south side of the mon-soon trough. Above the two branches are two synoptic-scale transient tubular monsoon circulation systems, the northern branch being a subtropical monsoon stream tube (SMST) and the southern branch a tropical monsoon stream tube (TMST). Their ascending branches, corresponding to a subtropical monsoon rain belt and a tropical monsoon rain bell respectively, bear considerable influence on the weather over China.
Effect of Increasing CO2 on the Stratospheric Level of CO and O3
L.S. Hingane
1989, 6(3): 390-392. doi: 10.1007/BF02661544
Production and destruction processes of carbon monoxide (CO) and ozone (O3) are examined in the light of increasing amount of atmospheric carbon dioxide (CO2). It is found that doubling of CO2 will increase the stratospheric concentration of CO and will have positive effect on O3 concentration.