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1995 Vol. 12, No. 2

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A Coupled General Circulation Model for the Tropical Pacific Ocean and Global Atmosphere
Zhang Ronghua, Zeng Qingcun, Zhou Guangqing, Liang Xinzhong
1995, 12(2): 127-142. doi: 10.1007/BF02656827
On the basis of Zeng’s theoretical design, a coupled general circulation model (CGCM) is developed with its characteristics different from other CGCMs such as the unified vertical coordinates and subtraction of the standard stratification for both atmosphere and ocean, available energy consideration, and so on. The oceanic component is a free surface tropical Pacific Ocean GCM between 30oN and 30oS with horizontal grid spacing of 1o in latitude and 2o in longitude, and with 14 vertical layers. The atmospheric component it a global GCM with low-resolution of 4o in latitude and 5o in longitude, and two layers or equal man in the vertical between the surface and 200 hPa. The atmospheric GCM includes comprehensive physical processes. The coupled model is subjected to seasonally-varying cycle. Several coupling experiments, ranging from straight forward coupling without flux correction to one with flux correction, and to so-called predictor-corrector monthly coupling (PCMC), are conducted to show the existence and final controlling of the climate drift in the coupled system. After removing the climate drift with the PCMC scheme, the coupled model is integrated for more than twenty years. The results show reasonable simulations of the annual mean and its seasonal cycle of the atmospheric and oceanic circulation. The model also produces the coherent interannual variations of the climate system, manifesting the observed El Ni?o / Southern Oscillation (ENSO).
Relationships between Regional Indian Summer Monsoon Rainfall and Eurasian Snow Cover
B.Parthasarathy, Song Yang
1995, 12(2): 143-150. doi: 10.1007/BF02656828
In this work, correlation analysis is applied to study the interannual relationships between Indian summer mon-soon rainfall of different homogeneous regions and Eurasian Snow Cover (ESC) during winter and spring seasons for the time period from 1973 to 1992. The monsoon rainfall of the western and central regions of India, as well as the all-India monsoon rainfall, is significantly negatively correlated with the ESC averaged for the months December-March and with, especially, the ESC of February. This study may provide some useful information for the long-range prediction of the regional Indian monsoon rainfall.
The Early Summer Seasonal Change of Large-scale Circulation over East Asia and Its Relation to Change of The Frontal Features and Frontal Rainfall Environment During 1991 Summer
Gong-Wang Si, Kuranoshin Kato, Takao Takeda
1995, 12(2): 151-176. doi: 10.1007/BF02656829
By using the rawinsonde data, upper cloud amount data and objective analysis data for global domain which all were produced by Numerical Prediction Division, JMA and by using daily and mean weather map issued by JMA and daily rainfall data over the Huaihe River Basin from China, an observational study to the early summer seasonal change of large-scale circulation over East Asia and its relation to change of the frontal features and environment for the frontal rainfall has been carried out, Following results have been obtained: (1) The early summer seasonal change of large-scale circulation was occurred during 20-23 May 1991, which was about 10 days earlier than the normal. During the period the subtropical westerly jet and tropical easterlies abruptly moved northward; (2) The northward movement of the tropical easterlies was not uniform, it was earlier at 100 hPa level and about 24 hrs late at 200 hPa level. The phenomenon was associated with earlier disappearence of the subtropical westerly jet at 100 hPa level; (3) During the seasonal change there were two westerly jets in the upper level and changed their intensity with the time. Before 18 May 1991, the southern one was more intense and then changed to more intense for the northern one and disappearence of the southern one, the phenomenon seemed to be appeared as northward movement of the southern jet; (4) A faster temperature (T) rising in the upper level over the Tibetan Plateau was associated with the seasonal change. From the T rising the T maximum moved onto the plateau, changing the T gradient from positive to nega-tive to the south flank of the plateau, the effect to reduce and disappear the southern westerlies. Also the T rising was associated with change of the frontal features over East Asia; (5) The seasonal change type during 1991 was same as that during 1992 and 1993, but different from that during 1990; (6) The environment for the frontal rainfall was change in the season, the differences were in the baroclinity in upper level and vertical wind speed and direction shear.
Two-wavelength Lidar Measurement of Cloud-aerosol Optical Properties
Qiu Jinhuan
1995, 12(2): 177-186. doi: 10.1007/BF02656830
Based on unstability of inversion algorithms of the lidar equation caused by molecular scattering, a new algorithm to derive both the aerosol extinction to backscatter ratio and the extinction coefficient profile is proposed in this paper. As shown in numerical experiments, in case of a ground-based lidar, the error in the aerosol optical depth solution can be less than 10%, and the error of < 6.7 in the aerosol extinction to backscatter ratio can be obtained if the error in the lidar constant is <6%; and in the case of a spaceborne lidar, the present method can be used to de-termine the lidar constant at a short wavelength with an accuracy of being better than 1%.
The Effect of Weak Shear-induced Motion on Brownian Coagulation of Aerosol Particles
Wen Jingsong, Wang Yongguang
1995, 12(2): 187-194. doi: 10.1007/BF02656831
The coagulation rate of a dilute polydisperse aerosol dispersion of particles is considered for small Peclet number, which provides a measure of the ratio of the relative shear-induced motion to Brownian motion between two rigid spherical aerosol particles. The asymptotic form of the relative velocity of two unequal particles immersed in a simple shear flow when they are far apart is obtained. Using a singular perturbation method, a two term expansion for the dimensionless coagulation rate (Nusselt number) as function of the Peclet number is developed. In the limit of the radius of one of the two spheres becoming small, the result agrees with the dimensionless mass transfer rate to an aerosol particle at small Peclet number.
Characteristics of the Mean Water Vapor Transport over Monsoon Asia
Yi Lan
1995, 12(2): 195-206. doi: 10.1007/BF02656832
Based on ECMWF monthly mean data from January 1980 to December 1989, characteristics of the three-dimensional structure of the mean water vapor transport over Monsoon Asia are described, and the more im-portant features of the different regional water vapor transport in the Indian Monsoon region and the East Asian Monsoon region are analyzed. It is found that there is a moist tongue extending from the equator poleward to the Asian Monsoon region. The three-dimensional distributions of the mean water vapor transport fields over the entire globe reflect clearly the asymmetry of the Asian Monsoon system, and the existence of a counter-Hadley monsoon circulation. The moisture conver-gence (divergence) area in Asia coincides with the confluent (diffluent) zone of the monsoon circulation. Furthermore, the moist features of the two sub-regions of the Asian Montoon area are differ-ent both in their magnitudes and in their seasonal variations.
Effect of the Interaction of Different Scale Vortices on the Structure and Motion of Typhoons
Chen Lianshou, Luo Zhexian
1995, 12(2): 207-214. doi: 10.1007/BF02656833
Five numerical experiments have been performed in this paper by using a quasigeostrophic barotropical model to investigate the interaction of different scale vortices on the structure and motion of typhoons. Results show that this interaction may arouse the irregular changes of the asymmetric structure of typhoons, thus leading to anomalous phenomena such as meandering tracks and sudden changes in the motion speed of typhoons; the effect of this interaction on the structure and motion may be quite different when the smaller vortex is situated in different positions of the typhoon circulation.
Analysis of Causes and Seasonal Prediction of the Severe Floods in Yangtze / Huaihe Basins during Summer 1991
Xu Qun
1995, 12(2): 215-224. doi: 10.1007/BF02656834
The present paper shows that a seasonal prediction for the large scale flooding and waterlogging of the mid-lower Yangtze/ Huaihe River basins in the summer of 1991 made successfully in early April 1991. The seasonal fore-casting method and some predictors are also introduced and analyzed herein. Because the extra extent of the abnormally early onset of the plum rain period in 1991 was unexpected, great efforts have been made to find out the causes of this abnormality. These causes are mainly associated with the large scale warming of SST surrounding the south and east part of Asia during the preceding winter, while the ENSO-like pattern of SSTA occurred in the North Pacific. In addition, the possible influence of strong solar proton events is analyzed. In order to improve the seasonal prediction the usage of the predicted SOI in following spring / summer is also introduced. The author believes that the regional climate anomaly can be correctly predicted for one season ahead only on the basis of physical under-standing of the interactions of many preceding factors.
Monthly Mean Temperature Prediction Based on a Multi-level Mapping Model of Neural Network BP Type
Yan Shaojin, Peng Yongqing, Quo Guang
1995, 12(2): 225-232. doi: 10.1007/BF02656835
In terms of 34-year monthly mean temperature series in 1946-1979, the multi-level mapping model of neural network BP type was applied to calculate the system’s fractual dimension D0 = 2.8, leading to a three-level model of this type with i × j = 3 × 2, k = 1, and the 1980 monthly mean temperture prediction on a long-term basis were pre-pared by steadily modifying the weighting coefficient, making for the correlation coefficient of 97% with the measurements. Furthermore, the weighting parameter was modified for each month of 1980 by means of observations, therefore constructing monthly mean temperature forecasts from January to December of the year, reaching the correlation of 99.9% with the measurements. Likewise, the resulting 1981 monthly predictions on a long-range basis with 1946-1980 corresponding records yielded the correlation of 98% and the month-to month forecasts of 99.4%.
Multivariate Objective Analysis of Wind and Height Fields in the Tropics
S.K. Sinha, S. Rajamani
1995, 12(2): 233-244. doi: 10.1007/BF02656836
The commonly used objective analysis scheme (Scheme-A) for the analysis of wind and geopotential height smoothen the divergent component of the wind which is rather important in the tropics, specifically over convective regions. To overcome this deficiency, a new analysis scheme in which divergent component is included in the statisti-cal model of the wind forecast errors, has been proposed by Daley (1985). Following this scheme, a new set of correla-tion functions of forecast errors for the Indian region during monsoon season which are suitable for analysing the tropical wind are obtained. This analysis scheme (Scheme-B) as well as Scheme-A were used to make analyses for the period from 4 July to 8 July 1979 (12 GMT) at 850, 700 and 200 hPa levels over an area bounded by 1.875oN to 39,375oN and 41.250oE to 108.750oE and subsequently divergent component, velocity potential are computed for both schemes. Results from both these schemes show that in the monsoon depression region the velocity potential and divergence have increased in the later case (Scheme-B). This suggests that the divergent component has been en-hanced in Scheme-B and that the objective of this study is realized to some extent.
QBO-like Oscillations Induced by Local Thermal Forcing
Zhang Daizhou, Qin Yu
1995, 12(2): 245-254. doi: 10.1007/BF02656837
A zonal-vertical two-dimensional equatorial model is used to study the possibility that the long period oscillation of the zonal mean flow occurring in the lower equatorial stratosphere (QBO) is caused by local thermal ac-tivities at the tropical tropopause. The model successfully reproduces QBO-like oscillations of the zonal mean flow, suggesting that the local heating or cooling at the tropical tropopause is probably the main reason of QBO’s genera-tion. The analysis of the dependence of the oscillation on the wave fencing indicates that the oscillation is not sensible to the forcing scale. The model can reproduce QBO-like oscillations with any forcing scale if the fencing period and amplitude take appropriate values, proving that the internal gravity waves generated by local thermal source take much important roles in QBO.
The Capability of Atmospheric Profile Retrieval from Satellite High Resolution Infrared Sounder Radiances
Li Jun
1995, 12(2): 255-258. doi: 10.1007/BF02656838
A non-linear Newtonian iteration retrieval method has been successfully applied to TIROS-N Operational Ver-tical Sounder (TOVS) data process and simulated Atmospheric Infrared Sounder (AIRS) data inversion Usually, the Newtonian iteration procedure starts with a first guess or initial state of atmospheric temperature and water vapor profiles, in this paper, a climate mean profile and a regression retrieval from radiances were used as the first guess in AIRS data inversion, the Root Mean Square Error (RMSE) of both temperature and water vapor mixing ratio retrievals shows that high vertical resolution and accurate atmospheric temperature and water vapor profiles are achieved using either a poor (a climate mean profile) or good (a regression retrieval) first guess. This illustrates the capability of high resolution IR sounder radiances in atmospheric temperature and moisture profiles retrieval, which is important when there is no prior information or sample data set of atmospheric temperature and moisture available.