Vol.13, NO.5, 2002

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DETECTION AND EVALUATION OF EFFECTOF HUMAN ACTIVITIES ON CLIMATIC CHANGE IN EAST ASIA IN RECENT 30 YEARS
Xu Ying, Ding Yihui, Zhao Zongci
2002, 13(5): 513-525.
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Abstract:
In the context of annual and seasonal mean observations of temperature, precipitation, diurnal temperature range, vapor pressure from 1961 to 1990, investigated is climatic changes over East Asia due to the effect of greenhouse and anthropogenic sulfate aerosol based on five IPCC models (ECHAM4, HADCM2, GFDL, CGCM1, CSIRO).Results showthat minimum temperature is closer to observations w hen considering the ef fect of CO2 +SO2 than only CO2 in winter.Result s indicate that these models certainly have the capability of modeling climatic changes in East Asia, but they create systematic errors.In the light of correlation coefficient, the study shows that temperature modeling is the best; the second is vapor pressure and precipitation; then diurnal temperature range.For all variables, the spatial distributions in winter are simulated best.Generally speaking, ECHAM4 and HADCM2 arethe best in simulating climatic changes over East Asia in f ive models.
STRUCTURE AND FORMATION OF MEI-YU FRONT IN 1998
Wang Jianjie, Tao Shiyan
2002, 13(5): 526-534.
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Abstract:
The structures, formation and maintenance of the Mei-Yu front over the torrential rain period of the middle June 1998 were diagnosed with analysis data. Some general structural characteristics of Mei-Yu fronts are confirmed, such as the strong contrast of θse rather than temperature, the positive velocity, the wind and moisture convergence over the lower troposphere within the Mei-Yu front zone, etc. Especially, it is revealed that during the torrential rain period, the Mei-Yu front may extend vertically to 600 hPa from the near surface, which is higher than the general thinking of 800 hPa, and the front nearly doesn't tilt with height; the stability conditions of the front zone turn into the moist neutral above 900 hPa from the weak convective unstable under 900 hPa; the baroclinicity is very weak within the Mei-Yu front zone. It is pointed out the nature of the Mei-Yu front's structures has changed into the sub-tropical style, something between extratropical fronts and ITCZ during the torrential rain period. The diagnoses also show that horizontal air motions and geostrophic departures over the lower-troposphere have obvious positive contributions to the formation and maintenance of the Mei-Yu front in 1998.
ANALYSES OF FEATURES AND MECHANISMS OF SUMMER MONSOON ONSETS OVER SCS AND ITS VICINITY IN 1998
Xu Guoqiang, Zhu Qiangen, Ran Yufang
2002, 13(5): 535-549.
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Abstract:
In the context of reanalysis NCEP/NCAP daily data and SST in 1998, the features and mechanisms of summer monsoon onset over the South China Sea (SCS) are investigated. Results show that SCS and its vicinity summer monsoon can be divided into three phrases with different characteristics. SST of SCS increases to its maximum suddenly before SCS summer monsoon onset. The conversion of sensible heat flux between sea and land may be an important factor that induces onsets of East Asia subtropical monsoon and SCS monsoon.
DIFFERENCES IN CIRCULATION AND MOISTURE BETWEEN DRY AND WET YEARS IN NORTHWEST CHINA
Wang Xiurong, Xu Xiangde, Yao Wenqing
2002, 13(5): 550-559.
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Abstract:
In the context of summer rainfall observations of 19 stations in Northwest China and NCEP/NCAR global monthly mean reanalyzed grid data in spring from 1958 to 1997, correlative statistical analysis are performed on the related parameters in spring in the years of being dry or wet in summer in Northwest China and its nearby regions. Results show that in spring the circulation and moisture features of dry years in the related areas are significantly different from those of wet years.
REOF ANALYSIS OF CLIMATIC CHARACTERISTICS OF WINTER TEMPERATURE AND HUMIDITY ON XIZANG-QINGHAI PLATEAU
Niu Tao, Chen Longxun, Wang Wen
2002, 13(5): 560-570.
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Abstract:
The Analysis of climatic characteristics of temperature and humidity on the Xizang-Qinghai Plateau is made based on the data set from 123 stations on the Xizang-Qinghai Plateau and its vicinity. The results indicate that the region near 32°-33°N may be the divide of the climatic difference from south to north on the plateau. The northern plateau is influenced by dry and cold air and the southern by humid and warm air. Using the REOF method, we can separate the temperature and humidity on the plateau into different patterns and then analyze the characteristic of each pattern. The results indicate that in recent 40 years temperature has been increasing gradually, fluctuating with time. The temperature increase occurred mainly in the periods of 1978 to 1981 and 1983 to now, and the increase in the last period is the greatest. The amplitude of the temperature increase takes on a pattern of "big-small-big" from south to north on the plateau. The humidity in recent 40 years is also on the increase trend fluctuating with time in most part of the plateau, but the northern boundary of the plateau become drier. The main period of humidity increase is the late 1980s. The amplitude of humidity increase takes on a pattern "big-small" from south to north on the plateau; especially, the region around Qilian Mountain become drier.
INFLUENCEOF ENVIRONMENT PARAMETERS ON INSTABILITY OF GENERALIZED EADY' S MODEL
Zhang Lifeng, Zhang Ming
2002, 13(5): 571-580.
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Abstract:
The baroclinic instability in generalized Eady's models is introduced and the influence of environment parameters on the instability is emphatically discussed. Not only in the model there exists the "short-wave cut-off" phenomenon similar to the classical Eady's model, but also there exists the "long-wave cut-off" phenomenon, which does not exist in the classical Eady's model. The former is not almost sensitive to environment parameters, but the latter is. The decrease of static stability parameter, the accretion of the vertical shear of the basic flow in the model bottom, the increase of latitude and decrease of the height of the model top are propitious to the instability in the model. The most instability in the generalized Eady's model appears in the synoptic scale wave range. The variations of amplitude and phase with altitude are analogous to those of the classical Eady's model. The isophase lines incline to west with altitude, but the amplitude is not symmetrical about the middle-level atmosphere.
EFFECTS OF SOME PHYSICAL PARAMETERS ON THE CLIMATIC STATES IN OCEAN-ATMOSPHERE COUPLED MODEL
Liu Lihong, Zheng Zuguang
2002, 13(5): 581-590.
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Abstract:
A zero-dimension energy budget model, in which the annual mean global sea-surface temperature and atmospheric temperature in the boundary layer are chosen as climatic variables, is proposed.The effects of some physical parameters (the effective emissivity of the atmosphere, the albedo of the surface, the transmissivity of the atmosphere, etc.) on the climatic system states can be examined.The results show that the equilibrium states and stabilities are related to the feedback of the albedo of the earth and atmospheric effective radiation quotiety.On the modern climatic condition, the effect of the appropriate nonlinear negative feed back together with CO2, vapor, cloudiness, can help the climatic state tend to be stable.The deviation equations of the equilibrium in the modern climatic sy stem corresponding to this model are used to investigate the distribution of the climatic sy stem under the influence of parameters α2w and I0.
STUDY OF DATA PROCESSING OF WIND FIELDS FROM DOPPLER RADAR
Liang Haihe, Zhang Peiyuan, Ge Runsheng
2002, 13(5): 591-599.
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Abstract:
A “K-Neighborhood Frequency” method for preprocessing the wind fields from Dopplerradar is presented .It is relatively clear in physical significance and can effectively process the “noises” in the wind fields .Based on it, a “Double Radial” method is used to unfold velocity, and a good result is gained .A new person-computer interactive method for obtaining 90 % or higher correction is also designed, which can improve greatly the traditional way of person-computer interaction .
FORECAST TECHNIQUE OF ELECTRIC NETWORK LOADS IN CENTRAL CHINA BASED ON METEOROLOGICAL ELEMENTS
Hu Jianglin, Chen Zhenghong, Hong Bin, Wang Guangsheng
2002, 13(5): 600-608.
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Abstract:
Based on the variation analysis of electric network loads on various holidays, the models for forecasting the daily load of the electric power network and its maximum and minimum loads per day in the Central China are given.Using meteorological variables as predictor, the dynamical colligating linear regression combined with auto-regression and the dynamical nonlinear artificial neural network methods are used.The prediction with 365 independent samplesshows that the methods have a high precision in electric load forecasting in Central China and can be used for the operational practice.
NUMERICAL SIMULATION OF WEATHER FIRE GRADE IN BEIJING
Gao Ge, Zhu Changhan, Zhang Hongtao
2002, 13(5): 609-620.
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Abstract:
By use of a three dimensional air-soil coupling model on M-γ scale, in which the effect of vegetation is considered, some fields of meteorological elements such as temperature, humid and wind, are simulated; further, the weather fire grade in Beijing is calculated.Result shows that the simulated element fields reflect certain specific basic climatic features and variation rules over different surfaces rightly.In addition, the criteria of the weather fire grade are verified reasonable and the simulation of the weather fire grade can show the distribution and intensity of fire danger clearly with high spatial and temporal resolution.The study provides scientific evidences for urban fire monitoring and reduction.
EFFECT OF LIMITED WATER SUPPLY ON ROOT GROWTH AND DEVELOPMENT OF WINTER WHEAT AND THE CHARACTERS OF SOIL MOISTURE USE BEFORE PLANTING
Guo Anhong, Liu Gengshan, An Shunqing, Ren Sanxue, Lin Rinuan
2002, 13(5): 621-626.
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Abstract:

Experiments were conducted in the man-cont rolled water supply field at the Gucheng Agrometeorological Experimental Base of the Chinese Academy of Meteorological Sciences.Under the condition of sufficient soil moisture before planting, water was supplied for winter wheat with three scheme :I1, 75 mm supplied water at jointing stage; I2, 37.5 mm supplied water at returning-green stage and 37.5 mm at jointing stage; ICK, no water supply during whole growth season.The precipitation during the grow th season was kept out.Results indicated that under I1, the sufficient soil moisture before planting and limited water stress reduce the winter wheat root weight in the upper soil layer, and allocate more dry matter to the deeper root system.It contributes to the increase of the water use in deeper soil and the soil moisture use before planting.In addition, the water supply for winter wheat at jointing stage under I1 helps increase the effective transpiration proportion at the key water dem and ing stage, and improves the water use efficiency.Although water stress decreases ears per m2 in I1, but the increase of grain numbers and grain weight contributes to the yield increase.
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