Vol.12, NO.1, 2001

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TURBULENT MEASUREMENT OVER THE SOUTHEASTERN TIBETAN PLATEAU
Bian Lingen, Lu Longhua, Cheng Yanjie, Lu Changgui, Yao Zhanyu, Xu Qiangde, Chen Lianshou
2001, 12(1): 1-13.
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Abstract:
Based on the second Tibetan Plateau Meteorological Experiment (TIPEX) turbulent data from Changdu, the turbulent structure and transportation characteristics in the near-surface layer for summer time are analyzed by using the eddy correlation technique. The main results show that the relation between the normalized variance of 3D winds and z/L satisfies the similarity law under both unstable and stable stratification. The relations of normalized variances of temperature and specific humidity to z/L obey the law of 1/3 fractional power only under the unstable condition. In the case of stable stratification, their relations to z/L are disperse. The sensible heat dominates in the dry period, making up 80% of the total heating; while in the wet period the heating is intensified to great degree, in which latent (sensible) heat constitutes 60% (40%). The relations of drag coefficients (Cd and Ch) to z/L are quite close and the fitted Cdn (4.40×10-3) Chn (4.70×10-3) are obtained in a neutral case, which are bigger than those for the middle and western parts of the plateau in the same period.
AN AGROMETEOROLOGICAL MODEL OF PHOTOSYNTHESIS IN SOYBEAN CANOPY
Liu Jiandong, Yu Qiang, Wu Naiyuan
2001, 12(1): 14-20.
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Abstract:

A numerical model for simulating the photosynthesis of soybean canopy was established. The model includes sub-models for simulating diurnal variations of radiation. Temperature and CO2 density as well as the plant physiological sub-model which includes photosynthesis and respiration of soybean leaves. The results show that the mean error is about 8.7% when it is used for simulation the diurnal variation of photosynthesis in soybean canopy, and the model can simulate the process of midday depression of photosynthesis in soybean canopy accurately. Influence of the single factor on canopy photosynthesis was given by numerical analysis using the model, which provides a theoretical basis for raising the yield of soybean in Huanghuaihai Region.
ANALYSIS ON THE ELEMENT PREDICTION PERFORMANCE OF THE GUANGZHOU MESOSCALE NWP MODEL
Yan Jinghua
2001, 12(1): 21-29.
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Abstract:
The surface element prediction/diagnostic scheme of the Guangzhou Mesoscale NWP Model and the situation of its time evolution prediction of station elements are briefly introduced. The time series prediction of station elements is verified and analyzed by using the method suitable for time series verification. Better and sustained performance are shown for time series prediction of most elements, including rainfall, temperature, humidity, wind, pressure and cloud amount.
RESEARCH ON COMPOSITE DIAGNOSIS AND MECHANISMS OF EXPLOSIVE CYCLONES
Ding Zhiying, Wang Jinsong, Zhai Zhaofeng
2001, 12(1): 30-40.
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Abstract:
In this paper, 16 explosive cyclones over Atlantic and Pacific oceans are analyzed. The "weak" and "strong" explosive cyclones are diagnosed and compared. It is found that the basic fields are different at many aspects. The formation of strong explosive cyclones is related to the non-zonal upper jet of anticyclonic curvature. The jet can cause the upper divergence fields and baroclinity and baroclinic instability as well as the development of internal gravity waves northward. The warm advection and diabatic heating can increase the curvature. In general, when the larger value centers of potential vorticity move toward the centers of explosive cyclones, it is advantageous to explosive cyclones.
COMPARISON EXPERIMENTS ON CUMULUS PARAMETERIZATION SEHEMES OF THE MM5
Wang Jianjie, Hu Xin, Guo Xiaorong
2001, 12(1): 41-53.
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Abstract:
Numerical simulation experiments on cumulus parameterization schemes, KUO, GRELL, KAIN-FRITSCH and BETTS-MILLER (KU, GR, KF and BM), of the MM5 are carried out using real-time data of the Shijiazhuang torrential rain event happened in Aug. 3-4 of 1996, under three kinds of model horizontal resolutions (60, 20 and 10 km). Comparisons among the experiments and against the observations indicate that the higher the model resolution is, the closer the simulations of main rain-belt distributions to the truth are, while the location of main rain-belt is not very sensitive to the cumulus parameterization schemes (CPSs). And spurious rainfall centers occurred when the model resolution increased to 10 km. In addition, the intensities of torrential rainfall increase with the decrease of the model grid size and change with the CPSs quite clear, but the torrential rainfall amount is underpredicted in all experiments. It was found that the contribution of the sub-grid scale precipitation to the total by KU scheme is higher than that by its three counterparts, and has an unreasonable trend of increasing with the model resolution, which is opposite from GR, KF and BM schemes. Although the characteristics of the horizontal circulation from four CPSs' simulation results are nearly the same, the certain differences of distributions of the cloud water, rain water and vertical motions among four CPSs' simulation results are obvious, which could affect the accuracy of the quantitative precipitation, the cloud amount, the surface air temperature and humidity forecasts. Therefore, choosing suitable CPSs for one's study is necessary.
THE MONTHLY-AND SEASONAL-SCALE FORECAST EXPERIMENT USING NCAR CCM3 CLIMATE MODEL
Yu Jianrui, Dong Min
2001, 12(1): 54-60.
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Abstract:
Using the NCAR CCM3 climate model, twenty-eight monthly and seasonal forecasts have been made for 1991 and 1994 with the NCEP reanalysis data as initial conditions. The prediction capacity of the model for the 500 hPa height and precipitation in China are examined. The result shows that the model has certain capability in predicting the height field in monthly scale. The ability of CCM3 in forecasting the monthly or seasonal rainfall in 160 stations of China is similar to the synoptic and experim ental methods. Comparison of the forecasts from extrapolated and observed SSTA shows that there is no much difference.
TEST AND STUDY OF THE EARTH-BASED GPS TECHNIQUE FOR REMOTE SENSING OF ATMOSPHERIC PRECIPITABLE WATER
Li Yanxing, Xu Baoxiang, Hu Xinkang, He Ping
2001, 12(1): 61-69.
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Abstract:
The deviation of AN (Askne and Nordius) model for calculating PW value has been analyzed theoretically and the conclusion drawn from the theoretical analysis has been confirmed by the results from the sounding test. Through the derivation, a new precipitable Water (PW) calculation model has been established and the calculated results are well consists with the PW values obtained by the sounding method. In 1998, a "GPS Storm Observation Test" was car ried out. It has been discovered from the test results that the high-value time interval of PW generally has an increasing period before the rainfall and a decreasing period in the process when the rainfall is ended; before the occurrence of a sudden storm event, unexpected large-scale increase of PW often occurs; before the occurrence of a large storm event, there is a very clear pregnancy period lasting for a long time.
AUTOMATIC SEGMENTATION OF SATELLITE IMAGE USING HIERARCHICAL THRESHOLD AND NEURAL NETWORK
Shi Chunxiang, Wu Rongzhang, Xiang Xukang
2001, 12(1): 70-78.
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Abstract:
Automatic segmentation of satellite image is the base of the automatic identification of cloud systems. This paper presents a combined method of hierarchical threshold segmentation and neural network to segment the image into separate synoptic systems for identification purpose. The processes include selecting all potential TBB thresholds of cloud segments and plotting temperature contours on satellite images for each threshold, then selecting cloud regions which is identified by a certain temperature contour and best representation of synoptic systems, and finally forming a segmented image by combining these regions. How to select these regions by computer is an experiential and uncertain problem. In this paper it is solved by the up-bottom and bottom-up heuristic and neural network method. A cloud pattern database is established. It includes 177 GMS satellite infrared images with 16 kinds of typical synoptic systems in the summer of 1992-1994, 1997-1998. There are 484 training samples from 32 satellite images and 2280 testing samples from 145 satellite images. The neural network accuracy rate for these training samples is 98.8% and 86.4% for the testing samples. The experiment accuracy rate for the application test is above 90% using testing images of 18-21 July 1997 and 15-17 June 1998.The input of the satellite image automatic segmentation system is GMS images, and the outputs include the boundary chain code, start location, perimeter and a rea of each region. These outputs are useful to further classification of cloud patterns.
INTER-CARLIBRATION BETWEEN FY-2A IR CHANNEL AND GMS-5 IRA CHANNEL
Gu Songyan, Qiu Hong, Fan Tianxi
2001, 12(1): 79-84.
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Abstract:
The inter-calibration research between FY-2A IR channel and GMS-5 IRA channel is made by using of the radiance transfer model and matched data analysis. On bases of this inter calibration results, we can merge the two geostationary satellite's IR data together and get a new remote sensing data field with higher temporal and spatial resolution.
A DISCUSSION ON APPLICATION OF NEURAL NETWORK TECHNIQUE IN IDENTIFICATION OF WATER BODY FROM NOAA SATELLITE IMAGES
Liang Yitong, Hu Jianglin
2001, 12(1): 85-90.
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Abstract:
The principles and methods for using artificial neural network techniques to automatically identify the information about water body from NOAA satellite images are discussed. An example of its application is presented. The results show that the precision and efficiency using the neural network technique is higher than using the threshold methods.
A METHOD FOR CALCULATING THE EVAPORATION POTENTIAL
Li Chunyun, Dai Yujie, Song Yuhong, Jiang Xiuping
2001, 12(1): 91-96.
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Abstract:
A empirical method for calculating the evaporation potential is discussed. It is the function of three factors:average air temperature, relative humidity and wind speed. The correlation analysis is made between the obtained values and Penman evaporation potential values, as well as evaporation capacity observed with a E601 Evaporimeter and a small-sized evaporimeter. The correlation coefficients are above the remarked level and very stable. It can be concluded preliminarily that the method is applicable to the local area, easy to understand, easy to use and can be used along with concerned indexes very well, for example Xerothermic winds. It obtained success in estimating the moisture profit and loss, and has significance in analyzing Xerothermic winds and droughts.
PRELIMINARY ANA LYSIS ON THE FLOW STRUCTURE OF HEAVY PRECIPITATION ON JUNE 9 IN CHANGLE AREA DURING HUAMEX
Jiang Haiyan, Ge Runsheng, Zhu Xiaoyan
2001, 12(1): 97-101.
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Abstract:
During the sixth intensive observation of HUAMEX (IOP-6), a local heavy precipitation happened on June 9, 1998 in the Changle area of Fujian Province. The process is analyzed preliminarily by using single-Doppler weather radar data and retrieved results of the wind field. From the structure of the wind field retrieved from Doppler radar data, we can see that this precipitation was related to the wind shear on the 3-5 km height and was resulted from the activity of a mesoscale cyclone wave which can be identified on the radar echo images.
RESEARCH ON LAND-SURFACE PROCESS MODELING—A REVIEW
Shi Xueli
2001, 12(1): 102-112.
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Abstract:
The recent status of land-surface process modeling in China and abroad is briefly summarized. Some international cooperative projects and experimental products are introduced and reviewed. Finally, problems and possible solutions in land-surface process modeling are presented.
ANALYSIS ON BACKGROUND OF CLIMATIC VARIATION FOR EXTREMELY RAINY OVER THE MIDDLE REACHES OF THE CHANGJIANG RIVER IN THE 1990S
Xiong Anyuan
2001, 12(1): 113-117.
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Abstract:
The major characteristics of precipitation over the middle reaches of Changjiang River during summer in the 1990s are analyzed. Using wavelet transform technology, the multiple time scale variations including inter-annual, inter-decade and long-term trends for summer rainfall in main regions over the middle reaches of Changjiang River and its related physical factors such as sea surface temperature in the eastern equator, the western Pacific Subtropic High, and summer monsoon of the South China Sea are analyzed. The results reveal that the extreme summer raininess in 1990s over the middle reaches of Changjiang River has favorable background of climatic variation.
NUMERICAL RAINFALL PREDICTION PERFORMANCE OF IMPROVED HLAFS DURING THE CATASTROPHIC FLOOD OF 1998
Li Yanxiang, Tian Hua, Zong Zhiping
2001, 12(1): 118-122.
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Abstract:
The rainfall prediction products of improved HLAFS were verified for the catastrophic flood period of 1998. The results show that this model performed better in Songhuajiang-Nenjiang River Valley for torrential rain forecast, better in the middle and lower reaches of the Yangtze River and worse in the Three-Gorges area for the moderate and heavy rain forecasts. Usually, The predicted rainfall intensity is weaker than the observed for the main rainfall processes. In about half causes, the predicted rainfall area is to the north of the real while the predicted axis is consistent with the real. The improved HLAFS performs better for light rainfall prediction and shows improvement for moderate and torrential rainfall. However, the overall predicted rainfall area is too large and the accuracy of heavy and torrential rain prediction needs further improving. For the rainfall amount prediction around the Three Gorges area, in about half causes, the model performs well with less predicted amount for heavy rain and larger one for small rain.
RAINFALL CORRECTION CONCERNING ASSESSMENT ON CROPLAND SOIL WATER RESOURCES
Yang Xingguo, Ke Xiaoxin, Zhang Xudong, Yang Qiguo
2001, 12(1): 123-126.
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Abstract:
Applying the rainfall (P) measured through lysimeter and the automatic recording rainfall (P′), a comparison has been made. The relation between P and P′is linear, and P is larger than P′. The mean correction coefficient of rainfall (K) is 0.037. K is 0.04 to 0.045 on condition that rainfall duration is shorter than 6 h and otherwise K is 0.27. K decreases with the increase of rainfall intensity. Meanwhile, the rainfall correction from June to September in the rainfed region of Gansu (RRG) including 19 meteorological stations also has been made. The result is that P is about 11.7 to 27.4 larger than P′. The mean P on the area of PRG is 18.4 mm larger than mean P′.
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