Current Issue

• LOW-FREQUENCY WAVES FORCED BY LARGE-SCALE TOPOGRAPHY IN THE BAROTROPIC MODEL
• FU Zun-tao;LIU Shi-kuo;WANG Shu-tao
• 1998 Vol. 17 (3): 223-230. 
• Abstract ( ) PDF (279KB) ( )
• A barotropic model, including large-scale topography and zonal mean flow, was established to discuss the effects of large-scale topography on the low-frenquency waves. The results show that two main factors which affects low-frequency waves is maximal height of topography and topographic slope. The former makes frequency of topographic Rossby waves decrease, the latter makes Rossby waves instable. Moreover, when topographic slope is optimum, it can also make Rossby waves turn into low-frequency waves.

• THE NONLINEAR LONG-WAVES EXCITED BY TOPOGRAPHY IN A SHEAR FLOW
• JIANG Hou-shuo;Lü Ke-li
• 1998 Vol. 17 (3): 231-244. 
• Abstract ( ) PDF (565KB) ( )
• A FKdV-Burgers equation including topography and dissipation is derived and its numerical solutions are given. The numerical results are used to discuss the evolution of the solitary waves excited by topography and the interaction of moving solitary wave with topography. Both the stationary solitary waves with meridional wavenumber m=1 excited by topography in a near-resonant anticyclonic shear flow and the interaction of topography with solitary wave with suitable dissipation and detuning parameters may be important factors for the localized blocking formation.

• RELATIONSHIP BETWEEN THE CLIMATIC WARMING OVER THE QINGHAI-XIZANG PLATEAU AND ITS SURROUNDING AREAS IN RECENT 30 YEARS AND THE ELEVATION
• LIU Xiao-dong;HOU Ping
• 1998 Vol. 17 (3): 245-249. 
• Abstract ( ) PDF (185KB) ( )
• Using monthly surface air temperature data from 165 stations in the Qinghai-Xizang Plateau and its surrounding areas from 1961 to 1990, the relationship between the climatic warming and the elevation above sea level is analyzed. The results show the recent climatic warming over the Qinghai-Xizang Plateau is related to the elevation. The temperature change range generally increases with the elevation. For example, the linear trends of annual mean temperature change in the recent 30 years are 0.0, 0.11, 0.12, 0.19 and 0.25℃/10a for areas below 500, in 500~1 500, 1 500~2 500, 2 500~3 500 and above 3 500m, respectively.

• CLIMATE ABRUPT CHANGE IN THE QINGHAI- XIZANG PLATEAU IN RECENT CENTURY AND ITS RELATION TO ASTRONOMICAL FACTORS
• TANG Mao-cang;BAI Chong-yuan;FENG Song;CAI Ying
• 1998 Vol. 17 (3): 250-257. 
• Abstract ( ) PDF (364KB) ( )
• The analysis on the air temperature,precipitation and monsoon in the Qinghai-Xizang Plateau in recent century shown that abrupt climate change were occurred in the early 1920s,1960s(or 1950s) and early 1980s, which coincide with the abrupt climate change in the northern hemisphere. Several years after air temperature abrupt rising in the Qinghai-Xizang Plateau, the air temperature in China and northern hemisphere were abrupt rising, which cause the strength of plateau monsoon,then causing the "monsoon wet(dry) region" become wetter(drier),and vice versa. Further analyses show the variation of earth rotation rate and sunspot cycle length have important role on the climate abrupt change in the Qinghai-Xizang Plateau.

• THE CHARACTERISTICS OF RADIATION BUDGET OF EARTH-ATMOSPHERE SYSTEM OVER THE QINGHAI-XIZANG PLATEAU AND THEIR RELATIONSHIP WITH CLIMATE CHANGE
• LIU Yan-xiang
• 1998 Vol. 17 (3): 258-265. 
• Abstract ( ) PDF (302KB) ( )
• In this paper,using the ERBE data,the distribution characteristics of energy field and their relation with several important events of weather and climate are analysed during February,1985 to December 1988 over the Qinghai-Xizang Plateau. The results show that the net radiation field in south-east of the Plateau(or Ⅲ area) is larger than that in west Plateau(or Ⅰarea) and north-east of the Plateau(or Ⅱ area)during El Niño, but the annual means values of net radiation anomaly in Ⅰ area is larger than that in Ⅱ and Ⅲ in La Niña. The results also show that the greater(less) net radiation field is corresponding to the weaker(stronger) south-west monsoon.

• CORRELATION ANALYSIS OF SOLAR ACTIVITY AND CLIMATIC JUMP IN CENTURY TIME SCALE
• FENG Song;TANG Mao-cang
• 1998 Vol. 17 (3): 266-270. 
• Abstract ( ) PDF (192KB) ( )
• In this paper, the jump transition characteristic of sunspot cycle length(henceforth SCL) from 522BC upward were analyzed. Moving t-test method based results indicate that there were no appreciable change of SCL in recent 2500 years. However, the variances of SCL series(henceforth S _v) show apparent jump transitions in 260BC, 31AD, 271AD, 1172AD and 1844AD, respectively. When S _v jump from low to high level, the "cold" climatic jumps were occurred, and vice versa. Moreover, the highest level of S _v coincide with the frequently occurrence of natural disaster in the Little Ice Age, which indicates that the instability of climate was caused by the unstable SCL(solar activity).

• THE ANALYSIS OF THE DISCHARGING PROCESSES OF TRIGGERED LIGHTNING FLASHES I. LEADER PROCESSES
• YAN Mu-hong
• 1998 Vol. 17 (3): 271-279. 
• Abstract ( ) PDF (386KB) ( )
• In this paper, the characteristics of leader discharge of arlificially triggered lightning flashes were analysed by use of eletrical field, current data, and digital photographic obtained with a high-speed CCD camera system(frame rate 1 000F/s). The results show that a bi-directional leader process initiated from both ends of altitude wire was observed for the so-called altitude-triggering. Because the development of the downward moving leader the channel electric current was non-uniformity. The metal channel-vaporized develop during the upward moving leader. The first return stroke of the artificially triggered lightning flashes are much the same as the subsequent return stroke of the natural lightning, but the both the discharge characteristic have some difference and the former was longer time of the continuous current process.

• INTERACTION BETWEEN SEA AND LAND BREEZE AND HEAT ISLAND CIRCULATION DURING THE SUMMER OVER THE DELTA REGION OF THE YANGTZE RIVER AND URBANIZATION EFFECT ON CLIMATE
• MIAO Man-qian;TANG You-hua
• 1998 Vol. 17 (3): 280-289. 
• Abstract ( ) PDF (365KB) ( )
• The interaction between sea and land breeze and urban island circulation during the summer over the delta region of the Yangtze River has been studied by means of three-dimensional mesoscale model. In the daytime, the heat island circulation over Shanghai region is strengthened by the sea breeze of the East sea and the lake breeze of Taihu Lake. The maximum vertical velocity is 6.2 cm·s ^-1. The case is contrary in the nighttime. The horizontal convergence zone extends from Shanghai toward the Yangtze River in the northwest. It results from the convergence of the sea breeze and the lake breeze. If the region except Shanghai transformed into urbanized underlying surface with economy development, and the coverage rate of green land is lowered to 15%. The surface air temperature over urbanized region are increases widely. It may raise to over 3.0℃ in the nighttime in summer. The centres of height value are at Suzhou and JiaXing and air moisture decreases. The summer climate will be dry and hot.

• THE RELATIONSHIP BETWEEN PRECIPITATION IN THREE GORGE DAM REGION DURING FLOOD SEASON AND NORTHERN PACIFIC SST
• YU Shu-qiu
• 1998 Vol. 17 (3): 290-299. 
• Abstract ( ) PDF (444KB) ( )
• In this paper,the climatic background of precipitation in the Three Gorge Dam Region during flood season is analysed. The results show that there is evidently a connection between abnormal precipitation in the Three Gorge Dam Region during flood season and the EAA correlation-chain. Furthermore, the relationship between precipitation in the Dam Region during flood season and the antecedent SST in Northern Pacific is studied.

• THE INFLUENCE OF THE NW CHINA AFFORESTATION ON REGIONAL CLIMATE IN EAST AND SOUTH ASIA
• FAN Guang-zhou;Lü Shi-hua;LUO Si-wei
• 1998 Vol. 17 (3): 300-309. 
• Abstract ( ) PDF (389KB) ( )
• The drought in NW China is one of the main problems of climate disaster of China and global change. A GCM-SSiB model is used to do a sensitivity experiment in this paper.We find that after the afforestation, the annual mean ground surface temprature is higher and the annual mean sea level pressure is lower in East and South Asia. The precipitation is increased in China and the Indochina peninsula decreased in the Indian peninsula. The temprature rise centre and the pressure fall centre is located in the afforesting area.The precipitation rise centre is in the middle and end valley areas of the Yangtze River and the Indochina peninsula. The ground surface heat source in NW China is obviously strengthened after the afforestation and then the winter monsoon weakens and the summer monsoon strengthens in the East and South Asia by the effect of the circulation. The main contribution to strengthen the ground surface heat source is the sensible heat, but in the tropical rainforest area on the contrary, namely the change of the ground surface heat source is mainly caused by the variation of the latent heat.

• THE EFFECT OF METHOD FOR CONSTRUCTING INITIAL FIELD ON NUMERICAL FORECAST OF RAINFALL
• YU Xiao-ding
• 1998 Vol. 17 (3): 310-316. 
• Abstract ( ) PDF (272KB) ( )
• The HIRLAM model(a limited area numerical weather forecasting model developed by the Nordic countries) was applied to the summer heavy rain cases in China to study the effect of the methods for constructing initial fields on numerical rainfall forecasts of a limited area model. Two methods for constructing the initial fields are compared: one initial fields is provided by the HIRLAM's own data assimilation system, another is given by interpolating the ECMWF global model's analysis fields into the HIRLAM grids. The two numerical experiments corresponding to these two methods for constructing the initial fields are the control experiment(CONL) and the comparison experiment(COMP), respectively. The rainfall predicted by CONL and COMP are compared with observation, the results show:(1) when the resolution of ECMWF global model, whose analysis is used to provide initial fields for HIRLAM model in COMP run, is considerably lower than that of HIRLAM model, the rainfall forecast is markedly improved in CONL in which the initial fields are provided by HIRLAM's own data assimilation system, in comparison with that in COMP.(2) when ECMWF model and HIRLAM model approximately equal resolution, the qualities of rainfall forecasts in CONL and COMP turn out to be at nearly the same level in spite of the supposed better consistency between initial fields, model dynamics and model's topography in CONL.

• ARTIFICIAL NEURAL NETWORK ANNUAL AND SEASONAL RAINFALL FORECASTS IN SHAANXI PROVINCE
• TIAN Wu-wen;LI Zhi-jia;WANG Yu-xi
• 1998 Vol. 17 (3): 317-322. 
• Abstract ( ) PDF (206KB) ( )
• In this paper, B-P artificial neural network annual and seasonal rainfall forecast methods in Shaanxi province is used, and utilizing 0~1 model to solve the question of multi-class forecasting be posed. Annual and seasonal multi-class rainfall forecasting models in Shaanxi province is built. Through the test, it achieved good results. Finally, some questions and the differences in comparison with other forecast methods be discussed in this text.

• APPLICATION OF PROJECTION PURSUIT REGRESSION TO THE PREDICTION OF PRECIPITATION
• LI Zuo-yong;DENG Xin-min;HOU Yu-guang
• 1998 Vol. 17 (3): 323-327. 
• Abstract ( ) PDF (177KB) ( )
• A modelling idea and implement of algorithm with SMART in of precipitation prediction are suggested by using projection pursuit regression(PPR) technique. The results of application of PPR model to the precipitation prediction in three regions are better than that of stepwise regression for fitting and prediction.

• A SELF-RECORDING AND REAL-TIME DISPLAYING SYSTEM FOR SAMPLING DATA BY ATMOSPHERIC FIELD MILL
• CHEN Cheng-pin;XIAO Zheng-hua;XIAO Qing-fu
• 1998 Vol. 17 (3): 328-334. 
• Abstract ( ) PDF (231KB) ( )
• In this paper,the A/D converting and storing of the data obtained by use of atmospheric electric field mill with single chip microcomputer,the principle of the hardware and the two modes of working are described. The software programming of the two working mode is also described. A new way of recording and storing of the electric field mill is systematically provided.