应用气象学报

A METHOD FOR IMPROVING THE PROBING ABILITY OF DOPPLER WEATHER RADAR IN THE CLEAR AIR

Ge Runsheng, Zhu Xiaoyan, Jiang Haiyan

2000, 11(3): 257-263.

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Abstract:

By analyzing the characteristics of echo signal in the clear air, a coherent integral method is presented, which can improve the probing ability of Doppler weather radar in the clear air, and the limit of the improved ability is calculated. Based on the study, the design of the radar signal processor is improved to be applicable to the detection in the clear air.

RESEARCH ON THE POSSIBLE EFFECTS OF CLIMATE CHANGE ON GROWTH AND YIELD OF WHEAT IN CHINA

Zhang Yu, Wang Shili, Wang Futang

2000, 11(3): 264-270.

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Abstract:
The possible effects of climate change on winter wheat and spring wheat of China are analyzed by using the stochastic weather generator and combining the CERES-wheat model with the climate change scenarios predicted by the climate model with the amount of CO₂ doubled. The results indicate that owing to climate change, the growing season of wheat is shortened, with the growing seasons of winter wheat and spring wheat shortened by 7.3 days and 10.5 days, respectively. Both the absolute and relative values of the shortened quantity for spring wheat are greater than those for winter wheat. Furthermore, the yield decreased due to the climate change. Winter wheat yield decreased by 7%-8% and decreased more greatly in the rainfed condition than in the optimal water condition. Spring wheat yield decreased more greatly than winter wheat, with a decrease of 17.7% in the optimal water condition and 31.4% in the rainfed condition.

MESOSCALE RAINSTORM SYSTEM UNDER THE COUPLING OF LOW-LEVEL AND UPPER-LEVEL JETS AND TYPHOON CIRCULATION

Chen Jiukang, Ding Zhiying

2000, 11(3): 271-281.

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Abstract:
After No.9216 typhoon landed, it moved to the right entrance of the southwesterly jet at the 200 hPa level. A mesoscale rainstorm was generated and developed in the area far from the typhoon center. By using a 2-layer model, the process is analyzed and the positive feedback mechanism of the mesoscale storm rainfall with the coupling of low-level and upper-level jets and the typhoon circulation is studied. The results indicate that the Wave-CISK process and the symmetric instability of the baroclinic basic flow are the reasonable dynamic causes of the development of the low-level jet and the generation of the inverted trough. The baroclinic atmosphere with convective instability is advantageous to the development of instability of northward inertial gravity waves.

VISUALIZATION OF THE NUMERICAL SIMULATION OF A YELLOW SEA CYCLONE

Wang Hongqing, Zhang Yan, Tao Zuyu, Ying Hwa Kuo, Wei Huang

2000, 11(3): 282-286.

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Abstract:
The results of the numerical simulation of a Yellow Sea (Huanghai Sea) cyclone was examined by the visual software LiveView. The structures of the cloud system, front, stream field and vorticity were presented by the stereo images. It shows that the visual software of LiveView is a powerful tool to examine the modeling output.

ANALYSIS OF PRECIPITATION DURING THE 1998 CATASTROPHIC DELUGE IN THE CHANGJIANG RIVER BASIN

Zhou Zijiang, Song Lianchun, Li Xiaoquan

2000, 11(3): 287-296.

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Abstract:
By using the precipitation data of 125 stations in the Changjiang River basin, the temporal and spatial distribution characteristics and climatological statistic characteristics of precipitation in the summer of 1998 are analyzed. Comparison is conducted with the previous data for the same period, especially with the data of deluge years such as 1931 and 1954. The results show that the precipitation process in the summer of 1998 includes four stages. The distribution pattern of total precipitation appeared to be an asymmetry saddle. The abnormally frequent and concentrated severe precipitation in the upper, middle and lower reaches is the most important cause of the continued high water level and catastrophic deluge of the Changjiang River.

RESEARCH ON THE FEATURES OF SUMMER RAINFALL IN NORTHEAST CHINA

Yao Xiuping, Dong Min

2000, 11(3): 297-303.

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Abstract:
By using the monthly averaged upper-air reanalysis data of NCEP and the monthly precipitation data of 160 stations over China, analysis is made on the summer circulation and rainfall patterns in Northeast China. The results indicate that there exists obvious difference in circulation between wet and dry years in Northeast China in summer and the circulation pattern of the summer in 1998 was similar to that of the wet year. The development of the Okhotsk blocking high was the main reason of the heavy precipitation in the Songhuajiang River and the Nenjiang River basins. The enhancement of moisture flux convergence in lower layers of troposphere is a favorable condition for rainfall in Northeast China. It is also found that there exists closely positive correlation between the polar vortex intensity index in December or winter and the precipitation in Northwest China in the subsequent August or summer, which can be regarded as a signal for the precipitation in Northeast China.

ANALYSIS ON THE ENVIRONMENTAL CONDITIONS AND DYNAMIC TRIGGER MECHANISM OF A SEVERE CONVECTIVE RAINSTORM IN BEIJING

Li Zhinan, Li Tingfu

2000, 11(3): 304-311.

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Abstract:

Through the analysis of a severe convective rainstorm occurring in a synoptic-scale ridge on June 29, 1998 in Beijing, it is found that the interaction of the middle-level ridge, low-level convergence system and surface cold air produced a meridional circulation in the lower and middle atmosphere which stored up instability energy and maintained the ascending motion in the storm area. Dynamic frontogenesis was formed in the ground layer and intensified the latent instability at the lower and middle levels. Moreover, the positive vorticity advection of short wave disturbance in the upper troposphere initiated the ascending motion at the upper level and the releasing of the latent instability by ageostrophic balance processes. The short wave disturbance did not match the undulation of the wind field, and the characteristics of its phase propagation were similar to those of gravity waves.

DYNAMIC AND THERMODYNAMIC EFFECTS OF THE TIBETAN PLATEAU AND THE LOW-FREQUENCY FLUCTUATION

Liu Shikuo, Bai Jingyu, Xu Xiangde, Li Liming

2000, 11(3): 312-321.

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Abstract:
Based on the physical analysis of the dynamic and thermodynamic effects of the Tibetan Plateau, the influence of the height, orographic slope and diabatic heating of the Tibetan Plateau on the low-frequency fluctuation at the middle and high latitudes is examined. The results indicate that the height, proper orographic slope and diabatic heating of the Tibetan Plateau can facilitate the generation of the low-frequency fluctuation and affect the stability of the low-frequency Rossby wave.

SPATIAL PATTERNS OF CHANGE TREND IN RAINFALL OF CHINA

Ren Guoyu, Wu Hong, Chen Zhenghong

2000, 11(3): 322-330.

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Abstract:
By using surface data from 1951 to 1996, the long-term change trend index of annual and seasonal precipitation of China is calculated. The results show that total annual and summer precipitation over the middle and lower reaches of the Yangtze River increased during the 46 years, and a detectable decline trend in precipitation is found over the Yellow River basin, especially for Shandong and Liaoning provinces. In the high latitude areas such as Xinjiang, Inner Mongolia and North China, however, the change trend in rainfall is not obvious. It is also found that seasonal drift in precipitation occurred in some regions in the period. Rainfall during spring and autumn has significantly decreased over the upper and middle reaches of the Yellow River and the middle reach of the Yangtze River, and increased relatively in spring in eastern Hebei Province, western Liaoning Province and the Horqin Sand Land.

EQUATORIAL EASTERN PACIFIC SST AND ANALYSIS ON CAUSES OF SUMMER FLOODS/DROUGHTS IN THE CHANGJIANG AND HUAHE RIVER BASIN

Li Shenshen, Shou Shaowen

2000, 11(3): 331-338.

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Abstract:
The power spectrum and correlation analysis is made of the relation between SST on the equatorial East Pacific and the West Pacific warm pool and summer precipitation over the Changjiang and Haihe River basins. The results indicate that summer precipitation over the Changjiang and Haihe River basins is greater when El Nino warming occurs in autumn or winter and less when ENSO develops in spring or summer. The comparison and analysis is conducted, by using two cases, of the characteristics of the abnormal stream fields of ENSO events warming in different seasons and the impact on the precipitation over the Changjiang and Haihe River basins. ENSO events warming in different seasons, corresponding to the certain stages of circulation adjustment over the tropic Pacific region, are the main cause of summer monsoon variation as well as weather and climate abnormality in summer in East Asia.

INFLUENCE OF SST PATTERN ON THE RAINFALL IN THE MIDDLE AND LOWER REACHES OF THE YANGTZE RIVER

Lin Jian, He Jinhai

2000, 11(3): 339-347.

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Abstract:
By using the methods of EOF, SVD, correlation and composite analysis, the relationship between Pacific SSTA pattern and rainfall in the middle and lower reaches of the Yangtze River is investigated. Results suggest that SSTA from northwestern Pacific to southeastern Pacific maintains the pattern of "+ - + -" from the previous autumn to the subsequent summer, bearing a close relation to the EAP. The Pacific SSTA in the previous winter and spring led to the remarkable convection anomalies in low latitudes, which thereby resulted in the anomalous western Pacific Subtropical High and the rainfall in the Yangtze River Basin. Numerical simulations further confirm that rainfall in the middle and lower reaches of the Yangtze River is not only related to the tropical SSTA but also to the SSTA in the mid-latitude Pacific.

APPLICATION OF THE NUMERICAL PRODUCTS OF T63L16 MODEL FOR PREDICTING MONTHLY PRECIPITATION IN SUMMER OVER NORTHEAST CHINA

Zhang Lixiang, Chen Liqiang, Liu Wenming, Li Ji, Zhang Kai

2000, 11(3): 348-354.

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Abstract:
The Kalman filter method is used to correct the errors of the predicted fields of the T63L16 model of the National Climate Center. The corrected fields are applied to a precipitation forecasting model which combines the qualitative analysis, based on characteristics of weather systems, with the quantitative analog, based on the analog discrete degree indexes, and the precipitation of 51 stations in Northeast China in the summer of 1996-1998 is made. The results show that its prediction performance is good.

RESEARCH ON PARAMETER ESTIMATE OF PROBABILITY DISTRIBUTION FORMULA OF STORM INTENSITY IN RUIAN

Gu Junqiang, Chen Haiyan, Xu Jiyun

2000, 11(3): 355-363.

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Abstract:
Based on the 33-year (1965-1997) auto matically recorded precipitation data of Ruian city, the frequency distribution of storm intensity is discussed by using probability models. The i-t-T table that describes the relationship of storm intensity, rainfall duration and return period is presented. Furthermore, Parameters in the storm intensity formula are estimated by using the optimal solution to solve the super-nonlinear coupled equation.

QUALITY CONTROL AND TECHNICAL METHOD FOR PRODUCING DATA SET FOR UPPER-AIR DATA IN CHINA

Zhou Shanghe

2000, 11(3): 364-370.

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Abstract:
The quality control of upper air data in China, the working flow and the main technology in processing as well as design ideas for producing the upper air climate data set are described through an example. The experience could be valuable for the operational construction of the upper air climate data in China. In addition, the main features of the upper air climate data set are discussed.

THE PERFORMANCE MEASUREMENT OF CHINA-MADE SILICON DOMES OF PYRGEOMETER

Wang Bingzhong

2000, 11(3): 371-376.

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Abstract:
The dome is a key component of pyrgeometer, the performance of which would influence the quality of pyrgeometer. By using the data Lowtran 7 and the data of transmittance for some kinds of China-made domes, the performance indexes of effective transmittance for some kinds of domes are calculated in different model atmospheres. The results show that the performance indexes of China-made dome are not lower than those of Eppley.

YIELD PREDICTION OF WINTER WHEAT BASED ON THE LONG-TERM NONLINEAR IMPACT ANALYSIS

Wang Shutong, Zhang Rongxia, Zhang Min

2000, 11(3): 377-382.

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Abstract:
In order to raise the prediction precision and stability of winter wheat yield prediction, a prediction model built from the selected long-term nonlinear predictors is developed through the expanding correlation analysis between meteorological yield and meteorological parameters, and it performs well. The preliminary theoretical analysis is also conducted. The application of four years and the comparison with the other statistical methods indicate that the predicted results using the method are desirable and applicable to the yield prediction at the bottom-level weather stations.

2000, 11(3): 383-384.

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Abstract:

Vol.11, NO.3, 2000