Vol.12, NO.3, 2001

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MEASUREMENTS AND STUDY OF AEROSOL OPTICAL CHARACTERISTICS IN CHINA RADIOMETRIC CALIBRATION SITES
Hu Xiuqing, Zhang Yuxiang, Zhang Guangshun, Huang Yibing, Wang Yongkuan
2001, 12(3): 257-266.
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Abstract:
A field measurement campaign was conducted in Dunhuang and Qinghai Lake sites in July 1999. Three CIMEL sun-photometers were used to measure the optical characteristics of the atmosphere at the two sites, and a great deal of data about atmospheric optical characteristics in the clear condition were obtained. Data from aerosol-bands of sun-photometers are used, by means of the Langley method, to determine aerosol spectral optical depths. The results show that the aerosol optical depth (AOD) at 550 nm at the two sites is 0.125 and 0.18 respectively. ν (Junge aerosol size distribution parameter) derived from spectral variation of AOD is 2.6 and 3.0 respectively. These values are compared with several typical aerosol models. All results show that the aerosol concentration at the two sites is small and suitable for in-flight calibration for remote sensing satellite sensors.
CITY AIR POLLUTION NUMERICAL PREDICTION SYSTEM AND ITS APPLICATION
Zhu Rong, Xu Dahai, Meng Yanjun, Cheng Conglan, Chao Demin
2001, 12(3): 267-278.
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Abstract:
The City Air Pollution Numerical Prediction System (CAPPS) consists of MM5 (or MM4) and the multi-scale grid-box model based on the integral of the atmospheric advective dispersion equation. The system has been used for predicting the Pollution Potential Index (PPI) and Air Pollution Index (API) in the urban areas without inventory data of sources. In the field of urban air pollution numerical prediction, CAPPS has overcome the difficulty brought by the inherent indefiniteness in the urban inventory of emissions.In this paper, CAPPS is applied to the air guality prediction experiments in Beijing and Shanghai and the results from these experiments are verified and compared with those from several photochemical air pollution models cited from publications. The comparison shows that the prediction accuracy of CAPPS is as good as most sophisticated photochemical models according to the correlation coefficients between the forecasted and the observed. Furthermore, the averaged prediction accuracy of pollution level has reached 61.5% in Beijing and Shanghai.
RELATIONS BETWEEN PERPENDICULAR DISTRIBUTION OF AIR POLLUTANTS AND WEATHER CONDITION IN WINTER IN BEIJING URBAN DISTRICTS
Wang Xiaoyun, Pan Liqing, Lu Weilin, Xuan Chunyi, Gao Yanhu
2001, 12(3): 279-286.
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Abstract:
The concentration of the main air pollutants (SO2, NOx) were measured from 26 Jan. to 2 Feb. in 2000 in the Beijing urban districts. Utilizing the measured data, a preliminary research on the relation between the weather condition and air pollution is made. The results show that the concentration of air pollutants increases sharply in the condition unfavorable to air diffusion. Along with the changes of the weather condition, the concentration of air pollutants varies correspondingly. Furthermore, at the same height, different resuls are obtained in the rooms of different direction, which is much more obvious in the weather conditions unfavorable to air diffusion.
LAND VEGETATION RETRIVING FROM SATELLITE REMOTE SENSING AND APPLICATION TEST IN MESOSCALE SIMULATION FOR HEAVY RAINFALL OF SOUTH CHINA
Wang Pengyun, Xiao Qianguang, Lin Yonghui, Xiao Lan
2001, 12(3): 287-296.
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Abstract:
The Land vegetation data set retrieved from NOAA satellite remote sensing data in the HUAMEX project during May and June 1998 is applied in the PSU/NCAR mesoscale model (MM5) to simulate a heavy rainfall case during 23-24 May 1998 and compared with the NCAR land-use data set. Results show that with our land vegetation data, the simulated 24 h accumulated rainfall increased about 12%-14% for a grid spacing of 5-15 km comparing with NCAR data. The dynamic and thermodynamic structures at the low levels are also affected. For lager grid spacing (45 km), the effects were not obvious.
FEATURES OF SUMMER MONSOON LFO AND LFR OVER BEIJING-TIANJING-HEBEI AREA IN 1998
Xu Guoqiang, Zang Jiansheng, Zhou Weican
2001, 12(3): 297-306.
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Abstract:
In the context of NCEP/NCAR reanalysis daily data in 1998, the features of summer monsoon LFO (Low-Frequency Oscillation) and LFR (Low-Frequency Rainfall) over the Beijing-Tianjing-Hebie area in 1998 are studied. Results show that there is a 15-35 d oscillation cycle in summer monsoon in the target region. The LFR is weaker in May and June than in July and August. The migration direction of LFR is more likely the same as the low frequency (LF) divergence at the 200 hPa level. Vapor over the target region mainly comes from the south and west sides of the research area. The variation of LF vapor transportation from south wind can be useful for forecasting the occurence and development of LFR.
A NEW APPROACH OF IRRIGATION MANAGEMENT FOR WINTER WHEAT BY THE CLIMATIC-AGROMETEOROLOGICAL MODEL CONSENSUS SYSTEM
Zhang Guangzhi, Xu Xiangde, Mao Fei, Zhang Xuejin
2001, 12(3): 307-316.
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Abstract:
A climatic-soil moisture-irrigation system (CSMIS) model has been built firstly by using an integrated technical approach of numerical forecast model with agricultural meteorological model. For the numerical weather forecasting section, a regional climate model is adopted to couple the atmosphere processes with ground processes. A model that was applicable to soil moisture forecasting and irrigation management forecasting in winter wheat fields was adopted as the agricultural meteorological model. The CSMIS has a higher reliability than the models in which climatic average values are used as the background fields. Meanwhile it can make quantitative forecast of regional soil moisture and provide service for irrigation management for the whole growth phase of winter wheat.
COMMON FEATURES OF SYNOPTIC SYSTEMS RELATED TO HEAVY RAINSTORMS IN THE MIDDLE CHANGJIANG RIVER BASIN DURING SUMMER
Xu Haiming, He Jinghai, Zhou Bing
2001, 12(3): 317-326.
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Abstract:
Through the composite analysis of eight heavy rainstorms in the middle changjiang River basin, revealed are the temporal features of the upper-troposphere jet and the low level SW jet and their interaction with the rainstorm development. The possible links between the westward migration of the western Pacific subtropical high and the eastward movement of the upper level jet anterior to the rainstorm onset are also discussed.
ANALYSIS OF SOME OBSERVATIONAL FACTS RELATED TO TORRENTIAL RAINS IN JULY 1998 IN WUHAN AND THE VICINAL AREA
Xu Xianan
2001, 12(3): 327-336.
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Abstract:
Some observational facts of the to rrential rain event occurred in Wuhan and the vicinal area from 20 to 23, July 1998 are analyzed by using conventional and intensive observational data as well as satellite data. The results show that this event was directly caused by a meso-α scale convergence center in the lower troposphere. The meso-α scale system has a cold core structure and a warm core in the upper troposphere. The strong disturbance in the upper troposphere and lower stratosphere and the mesoscale disturbance at surface are related with this torrential rain.
CONFIDENCE ANALYSIS OF NCEP/NCAR 50-YEAR GLOBAL REANALYZED DATA IN CLIMATE CHANGE RESEARCH IN CHINA
Xu Ying, Ding Yihui, Zhao Zongci
2001, 12(3): 337-347.
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Abstract:
The confidence of the NCEP/NCAR 50-year Reanalyzed data in climatic change research in China has been examined and the results show that in the reanalyzed data there exist some uncertainties in studying the trends of climatic change. The confidence of the reanalyzed data is better in the eastern and southern parts of China than in the western and northern for surface temperature and surface pressure. The surface temperature is more useful than surface pressure. The reanalyzed data is better after 1979 than before 1979.
COMPUTATIONAL DISPERSION PROPERTIES OF VERTICALLY STAGGERED GRIDS
Liu Yudi, Zhu Hongwei
2001, 12(3): 348-357.
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Abstract:
Based on a linear baroclinic primitive equation system, the computational dispersion properties of vertical and time-vertical staggered grids are analyzed in terms of frequency and group velocity characteristics, and the vertical scale ranges of group velocities with wrong sign are pointed out. It may provide guidance for an optimal choice of an appropriate vertical grid for a primitive equation atmospheric model.
THE INFLUENCE OF ABNORMAL SNOW COVER OVER QINGHAI-XIZANG PLATEAU AND EAST ASIAN MONSOON ON EARLY RAINY SEASON RAINFALL OVER SOUTH CHINA
Cai Xuezhan
2001, 12(3): 358-367.
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Abstract:
Based on the precipitation data of 25 stations during April to June from 1954 to 1998 in South China, the abnormal years of snow cover over Qing hai-Xizang Plateau (QXP) and the East Asian Monsoon intensity indices, the relationship between those is studied through preperiod diagnostic analysis of the canonical drought/flood years and correlation analysis. The main results are as follows: (1) The early rainy season rainfall decreased (increased) when the snow cover in the previous winter-spring was less (more) than normal and when East Asian Monsoon intensity enhanced (weakened) in last winter. (2) The 500 hPa geopotential height field appears obviously different over Asian-Pacific in the previous winter, which was mainly characterized by strengthened (weakened) East Asian Trough in canonical drought (flood) years. (3) The 500 hPa geopotential height variation over Iran Plateau and its adjacent regions in winter shows a strong precursory signal for the rainfall forecast of early rainy season.
RELATIONSHIP BETWEEN PRECIPITATION IN MAY OVER YUNNAN AND THE CHANGES OF TROPICAL SEA SURFACE TEMPERATURE AND ASIA MONSOON
Yan Yan Hongming, Qi Minghui, Xiao Ziniu
2001, 12(3): 368-376.
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Abstract:
Based on correlation analysis and composition analysis, the relationship between precipitation in May over Yunnan and the changes of tropical sea surface temperature and tropical convection and Asia monsoon are studied. The results indicate that these large-scale climate variations strongly influence the precipitation in May over Yunnan and disclose the different patterns when precipitation increases and decreases. Because the changes have significant continuity, it may be useful in forecasting the precipitation in May in Yunnan. The relationship between monsoon index from April to June over South Asia and precipitation in May over Yunnan is also studied. The results show that precipitation decreases when the monsoon index is lower and precipitation increases when the monsoon index is higher.
A METHOD FOR DESCRIBING WEST PACIFIC SUBTROPICAL HIGH BY OLR DATA
Xu Chenhai, Ni Yunqi, Zhu Fukang
2001, 12(3): 377-382.
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Abstract:
By using of OLR field data a method for describing daily behavior of West Pacific subtropical high is introduced, and it is pointed out that this method is able to remedy the defect in drawing subtropical high cell by the 588 dagpm contour.
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