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1995 Vol. 12, No. 1

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CISK-rossby wave and the 30-60 Day Oscillation in the Tropics
Liao Qinghai, Li Chongyin
1995, 12(1): 1-12. doi: 10.1007/BF02661282
Abstract:
The 30-60 day oscillation is an important aspect of the atmospheric variance in the tropical area. A number of works have been done on this phenomenon, this article is a further one. A quasi-geostrophic linear model that consists of a two-layer free atmosphere and a well-mixed boundary layer is used to investigate the instability of intraseasonal oscillation, its propagation and vertical structures. Results show that the dynamical coupling and interaction between the barotropic and baroclinic components via boundary layer convergence / divergence are responsible for the appearance of a new kind of low-frequency wave. Such wave is very different from the traditional tropical Rossby wave. It can propagate westward and eastward. Some behaviours of it appear to resemble the observed 30-60 day oscillation mode in many aspects, such,as vertical structures, zonal and meridional propagations. Now many researchers emphasize the direct relationship between CISK-Kelvin mode and the tropical atmospheric 30-60 oscillation. It is considered that CISK-Rossby mode should not be neglected.
Application of a Shape-Preserving Advection Scheme to the Moisture Equation in an E-grid Regional Forecast Model
Yu Rucong
1995, 12(1): 13-19. doi: 10.1007/BF02661283
Abstract:
This paper presents a methodology which is very useful to design shape-preserving advection finite difference scheme on general E-grid horizontal arrangement of variables through introducing a two-step shape-preserving positive definite advection scheme in the moisture equation of the LASG-REM (LASG regional E-grid eta-coordinate forecast model). By trial-forecasting six local heavy raincases, the efficiency of the shape-preserving advection scheme in practical application has been examined. The LASG-REM with the shape-preserving advection scheme has a good forecasting ability for local precipitation.
Interannual Fluctuations of Surface Air Temperature over North America and Its Relationship to the North Pacific SST Anomaly
Wu Renguang, Chen Lieting
1995, 12(1): 20-28. doi: 10.1007/BF02661284
Abstract:
The characteristics of interannual fluctuations of the surface air temperature over North America are investigated by using the surface air temperature data of 130 stations during 1941 through 1980. It is found that the surface air temperature bears about ten-year time scale oscillation over the southeastern and northwestern North America and along the west coast of the United States, and it has the characteristics of quasibiennial oscillation over the eastern North America. The ten-year scale oscillation of the surface air temperature is related to that of the sea surface temperature (SST) of North Pacific through the PNA pattern atmospheric circulation anomaly over North Pacific through North America. It is shown that the North Pacific SST has a closer association with the surface air temperature over North America than the central and eastern equatorial Pacific SST. The characteristics of the seasonal variations of the relationship between the North Pacific SST and the surface air temperature over North America are also analyzed.
Mesoscale Vegetation-Breeze Circulations and Their Impact on Boundary Layer Structures at Night
Ye Zhuojia, Jia Xinyuan
1995, 12(1): 29-46. doi: 10.1007/BF02661285
Abstract:
The impact of well watered mesoscale wheat over mid-latitude arid areas on mesoscale boundary layer structures (MBLS) and climate has been investigated in the study .using a mesoscale biophysical, meteorological model (BM) developed in the current study. The BM is composed of six modules:mesoscale atmospheric module, soil module, vegetation module, snow-atmosphere interaction module, underlying surface meteorology module and subgrid scale flux parameterization module. The six modules constitute an interacting system by supplying boundary conditions to each other.The investigation indicates that a horizontal pressure gradient associated with mesoscale perturbations in temperature and humidity is created during the day, which results from more water transpired from the vegetation canopy (VC) and evaporated from underlying wet soil. Non-classical mesoscale circulations (called as vegetation-breeze) are forced by the pressure perturbations with wind speeds about 5 m / s, flowing from the VC to the adjacent bare soil in the low boundary layer.Specific attention in the study is given to study the MBLS at night caused by the interactions between these mesoscale vegetation-breezes.The impacts of the VC's scale and atmospheric background thermal stability (ABTS) on these thermally forced mesoscale vegetation-breezes are also investigated.
A Statistical Model for Investigating Climatic Trend Turning Points
Ding Yuguo, Tu Qipu, Wen Min
1995, 12(1): 47-56. doi: 10.1007/BF02661286
Abstract:
A two-phase trend model is presented to investigate the turning-point signals of evolution trend in long-term series of a climatic element. Based on nonlinear fitting, the revised model brings out more evident improvement of the linear model proposed by Solow et al. (1987). Both theoretical deduction and case calculation show that our version can search the turning point and period accurately and objectively. In particular it is fit for computer exploring the turning points in long-range records from stations covering a large area, thus avoiding subjective judgement by a usual drawing method.
Numerical Experiments of Meiyu(Baiu) Rainfall by Quasi-Lagrangian Limited Area Model with Terrain
Zhao Li, Zhao Sixiong
1995, 12(1): 57-66. doi: 10.1007/BF02661287
Abstract:
In this paper, a 10-level Quasi-Lagrangian Limited Area Model is used to simulate the process of Meiyu(Baiu) front of 1979. Some physical processes, such as large-scale condensation and cumulus convection, are included in the model. The simulation results are encouraging. 24-h numerical simulation shows that the invading of cold air from North China and rapidly northward moving of warm air from South China can be successfully reproduced. The terrain with a maximum of 4175 m is incorporated in the model. Three different kinds of terrain schemes are tested and the dynamic effect of the Plateau on the process of heavy rainfall is found to be very important.
A Global Spectral Model and Test of Its Performance
Zhang Daomin, Li Jinlong, Ji Liren, Huang Boyin, Wu Wanli, Chen Jiabin, Song Zhengshan
1995, 12(1): 67-78. doi: 10.1007/BF02661288
Abstract:
A brief introduction is given of a global spectral model, its dynamical framework and diabatic physical processes involved. A number of real forecasts are shown to illustrate the forecasting capability of the model for various weather processes. It can even manage to predict some of those typical weather processes in summer which used to be difficult to forecasters.
On the Development of Meso-Scale Heavy Rain Parcels in China
Zhang Yan
1995, 12(1): 79-86. doi: 10.1007/BF02661289
Abstract:
Heavy rains occur in China frequently, which often bring us floods and serious disasters in the summer half-year. The meso-scale heavy rain parcels (MHRP) in the mid-latitude are usually developed in following cases:I.By the approaching, meeting and / or overlapping of different weather systems, when two or more different rainfall systems are getting to conjugate, some MHRPs could be developed, such as: 1) a new cold/warm front or squall line approaches an old front or squall, even when the old one is somewhat decrepit; 2) at the places where two or more synoptic systems with different characteristics are meeting together, such as the meeting of tropical cyclone with the cold airs coming from the mid- and / or high-latitudes, or the low latitude vortex meeting with the westerly trough; 3) at the intersections of some different weather systems, such as the intersection of drylines, squall lines or fronts moving from different directions; and 4) by the overlapping of rainfall parcels produced continuously from a meso-generation centre.II.Resonance Effect and Tibetan Plateau Influence are two reasons why high frequency of heavy and torrential rains arround the meiyu front is discussed also.
QBO Features of Tropical Pacific wind Stress Field with the Relation to El Nino
Zhang Qin, Zhu Yufeng, Ni Yunqi
1995, 12(1): 87-94. doi: 10.1007/BF02661290
Abstract:
Analysis has been implemented of 1970-1992 tropical Pacific wind stress anomaly and sea surface temperature anomaly (SSTA) datasets, indicating that quasi-biennial oscillation (QBO) of the tropical Pacific WS and SSTA is featured both by a standing and a progressive form, the former emerging in the most intense centers of action and the latter travelling east- or west-ward out of the SSTA sources. Results show that the SSTA is in the warm (cold) phase as zonal component of euqatorial wind stress anomaly gets weakened (reinforced) and the QBO of wind stress anomaly is well related to the El Nino cycle.
S.G. Narkhedkar
1995, 12(1): 95-102. doi: 10.1007/BF02661291
Abstract:
A new method of analysis namely, Singular Spectrum Analysis (SSA) is applied to the Indian Summer Monsoon (June-September) Rainfall (ISMR) series. The method is efficient in extracting the statistically significant oscillations with periods 2.8 and 2.3 year from the white noise of the ISMR series. The study shows that 2.8 / 2.3 year cycle captures the variability of the ISMR related to Southern Oscillation / Quasi Biennial Oscillation. The temporal structure of these oscillations show that these are in phase in extreme (excess and drought) monsoon conditions as well as in El Nino Southern Oscillation (ENSO) years. Both these oscillations show minimum variability during the period 1920-1940 and there is an increasing trend in the variability of these oscillations in the recent decades. The study enables to obtain pure signal consisting of reconstructed time series using these two Oscillations, from the original white noise series.
Efficiency of Severe Recorded Rainstorms over Maharashtra State
B.D.Kulkarni, Miss Shobha Nandargi, O.N.Dhar
1995, 12(1): 103-108. doi: 10.1007/BF02661292
Abstract:
12 severe rainstorms have been experienced by different meteorological sub-divisions of Maharashtra State during the last 100-year period from 1891-1990. For each of the rainstorms efficiency factors (i.e. P/ M ratios) were worked out for maximum one-day duration and for three standard areas of 1000, 5000, and 10,000 km2. Comparison of these ratios with the past has shown that the most efficient rainstorm over Maharashtra was the rainstorm of June, 1908 over the Vidarbha region whose full DAD data as well as isohyetal pattern have been given.
Some Splitting Methods for Equations of Geophysical Fluid Dynamics
Ji Zhongzhen, Wang Bin
1995, 12(1): 109-113. doi: 10.1007/BF02661293
Abstract:
In this paper, equations of atmospheric and oceanic dynamics are reduced to a kind of evolutionary equation in operator form, based on which a conclusion that the separability of motion stages is relative is made and an issue that the tractional splitting methods established on the physical separability of the fast stage and the slow stage neglect the interaction between the two stages to some extent is shown. Also, three splitting patterns are summed up from the splitting methods in common use so that a comparison between them is carried out. The comparison shows that only the improved splitting pattern (ISP) can be in second order and keep the interaction well. Finally, the applications of some splitting methods on numerical simulations of typhoon tracks made clear that ISP owns the best effect and can save more than 80% CPU time.
Nitrous Oxide Evolution from Agricultural Soil: A Regression Approach
Wang Shaobin, Song Wenzhi, Su Weihan, Zeng Jianghai, Wang Zhiping, Zhang Yuming
1995, 12(1): 114-120. doi: 10.1007/BF02661294
Abstract:
N_2O emission from soil is affected by many factors. In this study, N_2O flux, soil temperature, water content, NO_3~- and NH_4~+ concentrations were simultaneously measured in winter wheat field. N_2O flux, NO_3~- and NH_4~+ concentrations were all lognormally distributed, while water content was normally distributed. The relationship between N_2O flux and soil factors was also studied. N_2O flux was most highly correlated with soil temperature. Regression model was developed to explain the variability of N_2O emission from agricultural soil using multifactorial analysis.
Experiments of Reconstructing Discrete Atmospheric Dynamic Models from Data (I)
Lin Zhenshan, Zhu Yanyu, Deng Ziwang
1995, 12(1): 121-125. doi: 10.1007/BF02661295
Abstract:
In this paper, we give some experimental results of our study in reconstructing discrete atmospheric dynamic models from data. After a great deal of numerical experiments, we found that the logistic map, xn +1= 1-uxn2 could be used in monthly mean temperature prediction when it was approaching the chaotic region, and its predictive results were in reverse states to the practical data. This means that the nonlinear developing behavior of the monthly mean temperature system is bifurcating back into the critical chaotic states from the chaotic ones.