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Search Results: 1 - 10 of 9519 matches for " Zeng Qingcun "
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Comments on Zeng’s paper “variational principle of instability of atmospheric motions”
Comments on Zeng’s Paper “Variational Principle of Instability of Atmospheric Motions”

Zeng Qingcun,

大气科学进展 , 1991,
Abstract: After my paper (Zeng, 1986b) was published and another (Zeng, 1989) was submitted to the journal, I found two papers written by Arnold (1966) and McIntyre et al. (1987) and received some reprints of Ripa's papers (1983; 1984; 1987; 1988) in the same field. I thank Drs. Mu Mu and Pedro Ripa very much for showing and sending me these interesting papers.
An Intercomparison of Rules for Testing the Significance of Coupled Modes of Singular Value Decomposition Analysis
ZENG Qingcun,

大气科学进展 , 2007,
Abstract: This paper clarifies the essence of the significance test of singular value decomposition analysis (SVD),and investigates four rules for testing the significance of coupled modes of SVD, including parallel analysis,nonparametric bootstrap, random-phase test, and a new rule named modified parallel analysis. A numerical experiment is conducted to quantitatively compare the performance of the four rules in judging whether a coupled mode of SVD is significant as parameters such as the sample size, the number of grid points, and the signal-to-noise ratio vary.The results show that the four rules perform better with lower ratio of the number of grid points to sample size. Modified parallel analysis and nonparametric bootstrap perform best to abandon the spurious coupled modes, but the latter is better than the former to retain the significant coupled modes when the sample size is not much larger than the number of grid points. Parallel analysis and random-phase test are robust to abandon the spurious coupled modes only when either (1) the observations at the grid points are spatially uncorrelated, or (2) the coupled signal is very strong for parallel analysis and is not weak for random-phase test. The reasons affecting the accuracy of the test rules are discussed.
Variational Principle of Instability of Atmospheric Motions

Zeng Qingcun,

大气科学进展 , 1989,
Abstract: Problems of instability of rotating atmospheric motions are investigated by using nonlinear governing equations and the variational principle. The method suggested in this paper is universal for obtaining criteria of instability in all models with all possible basic flows. For example, the model can be barotropic or baroclinic, layer or continuous, quasi-geostrophic or primitive equations; the basic flow can be zonal or nonzonal, steady or unsteady. Although the basic flows possess a great deal of variety, they all are the stationary points in the functional space determined by an appropriate invariant functional. The basic flow is an unsteady one if the conservation of angular momentum is included in the associated functional. The second variation, linear or nonlinear, gives the criteria of instability. Especially, the general criteria of instability for unsteady basic flow, orographically disturbed flow as well as nongeostrophic flow are first obtained by the method described in this paper. It is also shown that the difference between the criteria of instability obtained by the linear theory and our variational principle clearly indicates the importance of using nonlinear governing equations. In the appendix the theory is extended to cases such as in aβ-plane where the fluid does not possess finite total energy, hence the variational principle can not be directly applied. However, a generalized Liapounoff norm can still be obtained on the basis of variational consideration. This work has been presented at the Seminar on Large-Scale Dynamics, Kyoto, August 1986, and at the International Colloquium on Nonlinear Atmospheric Dynamics, Beijing, August 1986. An extended abstract has been published in Proceedings of International Summer Colloquium on Nonlinear Dynamics of the Atmosphere, Science Press, 1986.
Discrete Spectra and Continuous Spectrum of the Barotropic Quasi-Geostrophic Model-A Calculation of Meteorological Data
Discrete Spectra and Continuous Spectrum of the BarotropicQuasi-Geostrophic Model-A Calculation ofMeteorological Data

Zhang Minghua,Zeng Qingcun,
Zhang Minghu
,Zeng Qingcun

大气科学进展 , 1999,
Abstract: Atmospheric disturbances at 300 hpa are decomposed into normal modes, referred as discrete-spectrum disturbances which can propagate freely in the observed zonal mean flow, and non-modal transient disturbances, referred as continuous-spectrum disturbances which are continuously sheared and eventually absorbed by the zonal flow. It is shown that normal modes represent only a small fraction of the observed atmospheric disturbances, while continuous-spec-trum disturbances represent the majority of observed disturbances, even when the basic flow is unstable. Daily variabilities of the observed continuous-spectrum disturbances are presented. They are shown to follow the results of wave-packet theory. Calculations suggest that there are abundant sources to excite continuous-spectrum disturbances in the atmosphere.
A GCM Study on the Mechanism of Seasonal Abrupt Changes
Wang Huijun,Zeng Qingcun,
Wang Huijun
,Zeng Qingcun

大气科学进展 , 1994,
Abstract: In this paper the observational studies and some related dynamical and numerical researches on seasonal abrupt changes were reviewed first. Then a speculation that the seasonal variation of insolation and the nonlinear dynamic interaction account for the abrupt changes was put forward and was asserted by a set of GCM sensitivity experiments. The results show that the abrupt changes would exist in case that all the earth surface was grass land and there was no topography. However, many factors may have influences on the abrupt changes. Hence this phenome-non is quite complicated and needs further investigations.
A New Monsoon Index and the Geographical Distribution of the Global Monsoons

LI Jianping,ZENG Qingcun,
LI Jianping
,ZENG Qingcun

大气科学进展 , 2003,
Abstract: A new monsoon index, the dynamical normalized seasonality (DNS), is introduced to study the issue of monsoons. This DNS index can describe both seasonal variation and interannual variability of different monsoon regions. It can also be used to delimit the geographical distribution of the global monsoon systems. Furthermore, it is pointed out that the index is very useful for understanding deeply the monsoons to study the difference, relationship, and interactions among the classical monsoon, ordinary monsoon and monsoon-like system.
Wave-Mean Flow Interaction: the Role of Continuous-Spectrum Disturbances
Zeng Qingcun,Zhang Minghua,
Zeng Qingcun
,Zhang Minghua

大气科学进展 , 2000,
Abstract: Traditionally, "eddy feeds zonal flow" in the atmosphere is considered as a result of decaying unstable waves. We show that disturbances made of non-modal solutions -the continuous-spectrum disturbances-can also effectively transport zonal angular momentum and interact with the zonal basic flow. These disturbances, though stable, eventually decay, losing their energy to strengthen the westerly jets in the atmosphere. Calculations with observational data illustrate that the atmospheric zonal flow is maintained primarily by continuous-spectrum disturbances rather than by unstable waves. Angular momentum transport by continuous-spectrum disturbances is one order of magnitude larger than that by all kinds of normal modes (referred as discreter-spectrum disturbances) including unstable waves.
Diagnostic Study on Seasonality and Interannual Variability of Wind Field
Xue Feng,Zeng Qingcun,
Xue Feng
,Zeng Qingcun

大气科学进展 , 1999,
Abstract: Based on NCEP / NCAR reanalysis data during 1980-1994, seasonally and interannual va-riability of the horizontal wind field are studied. It is shown that: (1) In the lower troposphere, there exist regions with maximum of seasonality in the tropics, the subtropics and high latitudes, which is called the tropical, subtropical and temperate-frigid monsoon region respectively. In the upper troposphere, the subtropical monsoon combines with the tropical monsoon as a nonseparably planetary monsoon system. In the stratosphere, there is a belt with very large seasonality in each hemisphere caused by the inversely seasonal circulation and by the establish-ment and collapse of the night jet. (2) Seasonal variation of the large-scale monsoon may generally be attributed to that of the zonal wind, however, seasonal variation of the meridional wind is of great importance in East Asian monsoon region. (3) In monsoon region, interannual variability of the atmospheric general circulation is closely related to seasonal variation of monsoon, while in the tropical Pacific, it may considerably be influenced by the external factors such as sea surface tem-perature (SST) anomalies associated with El Nino or La Nina event. Moreover, interannual variability undergoes a pronounced annual cycle.
Predictions of ENSO with a Coupled Atmosphere-Ocean General Circulation Model

Zhou Guangqing,Zeng Qingcun,
Zhou Guangqing
,Zeng Qingcun

大气科学进展 , 2001,
Abstract: Predictions of ENSO are described by using a coupled atmosphere-ocean general circulation model. The initial conditions are created by forcing the coupled system using SST anomalies in the tropical Pacific at the background of the coupled model climatology. A series of 24-month hindcasts for the period from November 1981 to December 1997 are carried out to validate the performance of the coupled system. Corre-lations of SST anomalies in the Nino3 region exceed 0.54 up to 15 months in advance and the rms errors are less than 0.9°C. The system is more skillful in predicting SST anomalies in the 1980s and less in the 1990s. The model skills are also seasonal-dependent, which are lower for the predictions starting from late autumn to winter and higher for those from spring to autumn in a year-time forecast length. The prediction, begin-ning from March, persists 8 months long with the correlation skill exceeding 0.6, which is important in pre-dictions of summer rainfall in China. The predictions are succesful in many aspects for the 1997–2000 ENSO events. This Project is Supported by Key Program of Chinese Academy of Sciences KZCX2-203, National Key Program for Developing Basic Sciences G1999032801, and National Natural Science Foundation of China (Grant No. 49735160 and 40005007)
Simulation of East Asian Summer Monsoon by Using an Improved AGCM
Lin Zhaohui,Zeng Qingcun,
Lin Zhaohui
,Zeng Qingcun

大气科学进展 , 1997,
Abstract: The IAP 2-L AGCM is modified by introducing a set of climatological surface albedo data into the model for substituting the model’s original surface albedo parameterization. The comparison between the observations and the simulation results by the modified model shows that the general features of the East Asian summer monsoon can be well reproduced by the modified IAP 2-L AGCM. Especially for the simulation of monsoon precipitation, the modified model can well reproduce not only the monthly mean features of the summer monsoon rainfall over East Asia, but also the stepwise advance and retreat of the East Asian summer monsoon rainbelt. Analysis results demonstrate that the good simulation of the monsoon rainfall is closely related to the reasonable simulation of the large scale general circulation over East Asian region, such as the western Pacific subtropical high, Asian monsoon low and the low level flows. The good performance of the modified model in the rainfall simulation shows its great potential to serve as a useful tool for the prediction of summer drought / flood events over East Asia. This work was supported by the Chinese State key Basic Research Programme “ Climate Dynamics and Prediction Theories”.
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