应用气象学报

STUDIES OF ENSO-RELATED CLIMATE PREDICTION WITH A HYBRID OCEAN-ATMOSPHERE COUPLED MODEL

Wu Aiming, Ni Yunqi

2001, 12(2): 129-139.

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Abstract:
With results of the long-term simulation of a hybrid-coupled model, the interannual variability of the model atmosphere is investigated. With the prediction cases during the period of 1979 to 1994, the predictive capability of the model for ENSO-caused global climate anomalies is discussed. Results indicate that the model can successfully reproduce the global ENSO-related atmospheric interannual variability. Higher predictive skill is mainly distributed over the tropics, where the predictable lead time is about one year. The ENSO-related winter and summer atmospheric circulation anomalies (including air temperature and precipitation) can be basically predicted with the lead time being up 9 to 12 months.

IMPACT OF HORIZONTAL GRID ON INERTIAL-GRAVITY WAVE

Liu Yudi, Gui Qijun, Li Xindong, Zhu Weihong

2001, 12(2): 140-149.

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Abstract:
The computational dispersion properties of Arakawa A-E, Z and Eliassen grids, based on the linear swallow-water equations, are analyzed in terms of frequency and group velocity characteristics respectively for irresoluble and resoluble models. The horizontal scale ranges in which wrong group velocities will result in for every grid are pointed out. It is shown that for the resoluble model, Z, C and Eliassen grids are the best in dispersion characteristics among all grids considered and for the irresoluble model, B grids are the best.

THE FEATURES OF ATMOSPHERIC CIRCULATION DURING MEIYU ONSET AND POSSIBLE MEHANISMS FOR WESTWARD EXTENSION (NORTHWARD SHIFT) OF PACIFIC SUBTROPICAL HIGH

Xu Haiming, He Jinhai, Zhou Bing

2001, 12(2): 150-158.

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Abstract:
Through composite analysis, the features of the atmospheric circulation during Meiyu onset and possible mechanisms responsible for the westward extension and northward shift of the western Pacific Subtropical High are investigated. Results indicate that the most pronounced characteristics of the circulation evolution prior to the Meiyu onset are: the subtropical High intensifies first, jumps northward in the middle Pacific, and then extends westward, thus resulting in the reinforcement (northward migration) of the western part of the Pacific Subtropical High ridge at 120°E. The further study reveals that the enhancement (northward movement) and westward shift of the Subtropical High over the middle Pacific are closely related to the abnormally active convection in the ITCZ to the south and over the northern Bay of Bengal. A GCM simulation is performed to study the effects of abnormal convection over the middle equatorial Pacific on the Subtropical High and results show that the abnormal convection can result in both the enhancement (northward migration) of the Subtropical High over the middle Pacific and its westward extension as well, which are in agreement with diagnostic results.

STATISTIC ANALYSIS AND NUMERICAL EXPERIMENT ON RELATIONSHIP OF TIBETAN PLATEAU THERMAL CONDITION AND MEIYU IN YANGTZE RIVER BASIN

Ge Xuyang, Tao Liying, Zhu Yongti, Li Yanhua

2001, 12(2): 159-166.

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Abstract:
Based on observation data, the correlation analysis of the Tibetan Plateau thermal condition and Meiyu in the Yangtze River Basin is conducted. The statistic results indicate that the surface thermal condition is correlated with the flood/drought in the Yangtze River Basin. If there exists abnormally warm thermal condition over the southern Tibet, then there will be a flooding summer in the Yangtze River Basin and vice versa. Based on such results, two sensitive experiments are designed by use of the NCAR RegCM2 model, in which the ground temperature of the northern or southern Tibetan Plateau increases or decreases respectively. The experiments simulated the features very well and validated the statistic results.

NUMERICAL SIMULATION OF PRECIPITATION IN THE EASTERN TIBETAN PLATEAU WITH LASG MESOSCALE MODEL AND ITS OPERATIONAL APPLICATION EVALUATION

Zhong Xiaoping, Qing Qingtao

2001, 12(2): 167-175.

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Abstract:
The sensitive numerical simulating study and the quasi-operational experiment are made on heavy precipitation over the eastern Tibetan Plateau by means of the LASG η-coordinate area-limited mesoscale model with different schemes, and the results are evaluated according to the related regulations of the Chinese Meteorological Administration. The comparison and analysis indicate that the weather systems in the low latitudes with active features have important influence on the quantitative and fix-point precipitation prediction; in the same way, the effect of methods for processing physical processes and topographic influence on the precipitation prediction varies greatly with different weather processes. Through emphasizing the influence of the closest station to the grid point, the extremes of high and low-value systems are retained by using appropriate objective analysis methods, so to improve the forecasting performance. The quasi-operational experiments indicate that with the relatively perfect dynamic frame and the processing methods of physical processes, the LASG η-model performs well in such areas with a complicated topography and highly varied weather systems, especially in the clear-rainy forecast. Moreover, the model can be used to make reasonable forecast in some different cases.

ANALYSIS OF NUMERICAL SIMULATION ON A NORTHEASTERN COLD VORTEX HEAVY RAIN IN THE SONGNENG RIVER BASIN

Jiang Xuegong, Sun Yonggang, Shen Jianguo

2001, 12(2): 176-187.

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Abstract:
By using MM5 mesoscale non-hydrostatic model, a numerical simulation and contrast test is conducted successfully of a northeastern cold vortex and its shear which caused heavy rain in the Songneng River Basin on August 8, 1998. Results show that the rainstorm was triggered by the positive vorticity advection at the upper level atmosphere. Coupling of two jets at the upper and lower levels led to the strong precipitation within the area of low vortex coverage. The upper jet stream was strong and temporary, while the lower is weak and persistent. Resulted from the down draught in the front of a blocking high, the easterly dry and cold air current at the mesosphere was the crux of shear formation. The wind shear, which formed at the mid-troposphere as a result of the easterly current meeting with a southerly, is the dominant forcing in producing ascending motion. As the blocking high weakened, the easterly current below and the southerly current at the rear weakened. As a result, the precipitation system abated and moved both easterly and southerly. With enhancement of the northwest cold air, the southerly currents at the upper and lower levels strengthened and weakened respectively. As a result, the precipitation intensity enhanced and the precipitation scale enlarged.

DESIGN OF HORIZONTAL GAUGE AND CORRECTION OF WIND-CAUSED ERRORS OF PRECIPITATION MEASUREMENTS USING HORIZONTAL PRECIPITATION

Li Mingqin, Ren Zhihua, Zou Yaofang

2001, 12(2): 188-195.

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Abstract:
The description of design principles of horizontal gauge is presented. Comparison is made for about 28000 events of pit, national and horizontal gauges for seven years at 30 stations. The power function correlation between the horizontal precipitation and the absolute difference of observed precipitation was confirmed and the correlation coefficient is 0.99. Using the horizontal gauge, correction can be carried out for the precipitation (include snowfall) observed at normal stations by adding parallel observation of horizontal precipitation. The adjusted accuracy is close to that of pit gauge; moreover, the method has the advantages of simple and easy to do, and is applicable to the operation use.

APPLICATIONS OF SOLAR SIMULATOR IN THE CALIBRATION AND TEST OF RADIATION INSTRUMENTS

Lv Wenhua, Mo Yueqin, Yang Yun

2001, 12(2): 196-201.

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Abstract:
To evaluate the solar radiation measurement data and instrument specifications, the new versatile laboratory test facility for solar radiation instruments has been developed. It consists of an available solar simulator and a rotating mechanism with an instrument mount. The spectral distribution is in accordance with Air Mass 1.5 global spectral conditions. Directionally, tilt and non-linearity errors of pyranometers can be tested by using this facility. Satisfactory results have been obtained according to calibration measurements of pyranometers. It is shown that the difference values of the sensitivity are within the range of ±0.6% measured in the outdoor exposure.

RESEARCH ON THE SPRING FIRE-RISK FORECASTING MODEL IN DRY GRASSLANDS IN INNER MONGOLIA

Fu Zeqiang, Wang Yubin, Wang Changgen

2001, 12(2): 202-209.

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Abstract:
Using grassland fire data and meteorological data of the same period from 1986 to 1997 in Xilin Gol Meng, the grassland spring fire-risk weather forecast model for the high fire-risk districts is presented. The forecast model synthetically considers the influences of meteorological components on grassland fire-risk at the time of fire-risk occurring and the days before. Trail forecast model results are reliable. The model can be used to local grassland forerisk forecasting, provide a basis and instruction for the fireproof departments in formulating the fireproof policies and bring about social, economic and ecological benefits.

PRIMARY DISCUSSION ON REGIONAL DIFFERENCE OF INFLUENCE OF CLIMATE ON SURFACE WATER RESOURCES IN XINGJIANG

Yuan Yujiang, Sang Xiucheng, Gong Yuan, Wang Yuee

2001, 12(2): 210-217.

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Abstract:
Using single correlation, canonical correlation analysis and stepwise regression methods, the regional difference of influence of the climate on the surface water resources in Xingjiang are analyzed. The main findings were as fellows:① the influence of climate on the spatial and temporal distribution of surface water resources is the greatest in the northern Xingjiang, in the middle in the southern Xingjiang and the smallest in the eastern Xingjiang; ② the influencing patterns of the spatial distribution of the climate on the surface water resources field in the northern, eastern and southern Xingjiang are revealed; ③ in the northern and eastern Xingjiang the precipitation in a hydrological year is the governing climatic factor that determines the spatial and temporal distribution features of the surface water resource field. The mean temperature from May to September is the second important climatic factor which decreases the surface water resources through influencing evaporation. But in the eastern Xingjiang, the influence of the mean temperature from May to September on surface water resources was slightly greater than that in the northern Xingjiang; in the southern Xingjiang, the mean temperature from May to September was the governing climatic factor. The hydrological year precipitation in the previous 2 years in the High Mountain area was the second climatic factor, which plays a role of increasing surface water resources through glacier melting water.

CLIMATIC RISK ANALYSIS OF THE THREE GORGES PROJECT OPERATION IN DRY SEASON

Zhang Jianmin, Huang Chaoying, Wu Jindong

2001, 12(2): 218-225.

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Abstract:
Monte Carlo experiment is adapted to analyze the risks of the Three Gorges Reservoir operation in dry seasons. Monthly precipitation derived from general circulation models in the Three Gorges area is generated stochastically to produce the distribution under the future climate scenarios. In addition, a statistical runoff-rainfall model as well as a reservoir management model is set up. The risks of the Three Gorges Project operation under the present and the future climate scenarios are thus assessed. The result indicates that the operation of the Three Gorges Project is very sensitive to climate change, and the risks of electrical power supplying by the Three Gorges Reservoir in spring and winter will change obviously.

DYNAMIC SIMULATION AND DAMAGE EVALUATION OF RICE DROUGHT

Song Lili, Wang Chunlin, Dong Yongchun

2001, 12(2): 226-233.

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Abstract:
Based on the farmland water balance principle and the characteristics of rice growth, a rice paddy water balance equation is developed. Using the growth period data of Guangdong Province as a case, the day-to-day dynamic variation of the rice paddy water during all of the growth periods is simulated, and the objective and quantitative evaluation of the damage caused by drought is also given under natural and irrigated conditions. The rice sensitivity coefficient to drought is calculated using the data from experimentation for the first time, and some significant results are obtained.

A STUDY OF ASSESSING AND FORECASTING MODELS OF DROUGHT IN AGRICULTURE

Zhao Yanxia, Wang Futang, Qiu Guowang

2001, 12(2): 234-241.

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Abstract:
A growth model is used in assessing and forecasting drought in order to emphasize the crop's effects on water consumption and crop's demand and sensitivity to water in different developmental stages. The verification indicates that the assessing and forecasting model of winter wheat drought is satisfactory.

ON THE TIME INTEGRATION OF RADIATION HEATING PROBLEMS

Liao Dongxian

2001, 12(2): 242-245.

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Abstract:
Subject to the satisfaction of the definition that any bounded numerical solution can be said to be computational stable, discussions are made on the time integration of radiation heating problems. It is proved that the numerical solution obtained by the time forward difference scheme is stable if the heating and its first time derivative are continuous. On the other hand, in order to demonstrate the convergence of the numerical solution to the analytical solution of the problem, an example is given.

AN ANALYSIS OF CAUSES FOR FLOODS IN CHANGJIANG RIVER VALLEY IN 1998

Xue Qiufang, Ren Chuansen, Tao Shiyan

2001, 12(2): 246-250.

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Abstract:
Using data from Yichang and Wuhan hydrological stations of the Changjiang River Valley from May to September 1998 and soil moisture data before the floods occurred, causes for the disastrous floods are analyzed and a comparison is made with 1954. The results indicate that the summer flood mainly resulted from persistent heavy rain pattern. Other factors contributing to the flood include above-normal soil moisture levels and below-normal evaporation before the flood season. The large-scale atmospheric circulation patterns during the summer of 1998 were similar to the patterns associated with the historic heavy rain event.

SELECTION AND SYNTHESIS OF PREDICTORS IN FLOOD/DROUGHT SEASON AND APPLICATION

Xu Jialiang

2001, 12(2): 251-254.

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Abstract:

The stability and reliability for drought/flood trend prediction from the statistical model are depended on the selection and synthesis of the predictors. While selecting predictors, the physical significance of the predictors must be considered. According to the scale correspondence principle, the synthesis of the factors whose time scales correspond with those of the predictands can retain the useful information to the utmost extent. A comparison experiment is conducted for the precipitation field over the Changjiang River Delta in flood season and the result indicates that the method can improve forecast greatly.

2001, 12(2): 255-256.

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Abstract:

Vol.12, NO.2, 2001