Vol.6, NO.4, 1995

Display Method:
A Study of Acoustic Array Antenna
Pan Naixian, Wu Peizhong, Liang Qixian
1995, 6(4): 385-391.
Some characteristics of acoustic array antennas constructed with different horns are tested. The measured antenna directivity patterns are compared with theoretical patterns. The effects of wave length, distance between horns, the number of horns and the air temperature on directivity patterns are discussed. The measured directivity pattern of a 4×4 array basically agrees with the theoretical curve. The comparison of different types of horns shows that the piezoelectric ceramic tweeter has best conversion efficiency, which is three times of the common horn’s. The reflecting horn YH 5-4 has a good ratio of performance to price, and is suitable for phased array antenna manufacture.
A Preliminary Analysis of Short-Range Forecasting Level for Precipitation By Central Meteorological Office of China
Lin Mingzhi, Bi Baogui, Qiao Lin
1995, 6(4): 392-399.
The short-range (0~24, 24~48 h) forecasting level for precipitation during 1988~1993 is analysed by Central Meteorological Office. The results show that the forecast accuracy and forecast skill of Yes/No for rain (≥0.1 mm), light rain (0.1~9.9 mm) and moderate rain (10.0~24.9 mm) were increased last six years, varying degrees. Although forecast skill scores of Yes/No for heavy rain (25.0~49.9 mm), torrential rain (50.0~99.9 mm) and heavy torrential rain (≥100.0 mm) were positive (>0), the improvement on forecast skill was not remarkable.
The Distribution Characteristics of Trace Gases at Lin’an Background Station and Its Impact on Aerosol
Yang Dongzhen, Yu Xiaolan, Li Xingsheng
1995, 6(4): 400-406.
The distribution characteristics of trace gases such as SO2, NO2 and O3, observed at Lin’an background station in the period from the last 10 days of August to the first 10 days of November, 1991, and the impact of the chemical transferring of these gases on the aerosol concentrations are investigated in the paper. The impact of air parcel trajectories and wind directions on the transfer process is also discussed. The results show that the concentrations of trace gases at this station are in existence of a remarkable diurnal variation under certain conditions, and the variation has an effect on the distributions of aerosol concentrations.
Seasonal Variation of Circulation in the Monsoon Area and Its Anomalies in El Nino Years
Wang Panxin, Xu Jianjun, Xu Yinlong
1995, 6(4): 407-413.
By using the EOF analysis method, the seasonal variation and its anomalies of circulation over the Indian Ocean﹑West pacific monsoon area during the period from May to September, 1981~1983 are studied. The first eigenvector field represents the monsoon component. The comparisons of the corresponding time coefficient curve for 1983 with those for 1981 and 1982 indicate that the summer monsoon circulation in E1 Nino years is weak, and the circulation transition from winter monsoon pattern to summer monsoon pattern is later than the normal, which is reflected by the time lag of the seasonal northward shift of the subtropical high over West Pacific. The corresponding numerical experiments in terms of the IAP GCM confirm to the above results.
Characteristics of the Seasonal Variation in OLR Field over the Tibetan Plateau
Yang Xifeng
1995, 6(4): 414-421.
By using 13-year pentad mean Outgoing Longwave Radiation (OLR) data (1979~1991) observed by NOAA satellites, the characteristics of the seasonal variation in OLR field over the Tibetan Plateau are investigated. The results show that the OLR field has outstanding seasonal variation. The major feature is that the OLR field is “ moderate variation condition” in winter and summer, and “abrupt variation condition” during the transition seasons of spring and autumn. There is persistent and strong positive interpentad change of OLR over the southwest of Tibetan Plateau in spring. It means that the enhanced heating field over the Plateau in spring has probably important effect on the seasonal transition of the regional climate. Additionally, the interannual variability of the seasonal transition of the OLR field over the Tibetan Plateau is also clear. It is closely related to the anomalies of the monsoon precipitation, that the summer over the Plateau comes early or late
Estimation of Vertical Wind Field in Precipitation from Single Doppler Radar
Peng Hong, Ge Runsheng
1995, 6(4): 422-428.
A method for estimating the vertical wind field from single Doppler radar Range-Height Indicator (RHI) is developed. By using the atmospheric continuous equation and the two-dimensional supposition to real wind, the wind components perpendicular to the axis of the radar beam within the radar vertical scanning plane are calculated. Several experiments show that the method is able to retrieve the vertical section of wind structure in the rain band reasonably, and it can be further applied to the study of Doppler weather radar observations.
Development of the Humidity Generator with Saturated Aqueous Salt Solutions
Wang Jinzhao
1995, 6(4): 429-435.
The humidity generator with saturated aqueous salt solutions has been developed for the first time in China. The generator contains a continuous moist air cycle system and a thermostatic system. The operating principle, the error analysis, the calibrating process and its results of calibration are introduced in the paper.
A New Scheme of Sunshine Recorder with Integral Sphere Principle
Wang Bingzhong
1995, 6(4): 436-441.
A new scheme of sunshine recorder with integral sphere principle is put forward. The recorder consists of ring with diaphragms, integral sphere and photoelectric receptor. The integral sphere is a hollow regular sphere with five pores of needle. The pore of needle can resist scattered light throwing into the sphere, and direct solar radiation thrown into sphere is diffusely reflected through the internal wall for many tines, and then homogeneous distribution of the irradiance is formed. By means of comparing with the irradiance of sunshine threshold, there is sunshine or not to be determined. The sunshine recorder has some advantages, such as nonrotating parts, simple structure, unnecessary adjusting and easy operating
Impact of Enhanced Ultraviolet Radiation on Soybean Production and Its Estimation
Zheng Youfei, Yan Jingyi, Yang Zhimin
1995, 6(4): 442-448.
Through the field and pot experiments, the impact of excessive solar ultraviolet (UV) radiation (280 ~ 400 nm) on the soybean plants, including stem pattern, physiological activity and yield, is investigated. Different responses to the three levels (0.15, 0.35, 0.70 W·m-2) of UV radiation are expressed of soybean production. The responses change with radiation intensity, various soybean species and environmental conditions. By studying the growth and physiological characteristics of soybean under the excessive UV radiation, several mathematical models are established to elucidate the differences of the two soybean specises. The results are satisfactory
An Experimental Study of Winter Wheat Water Stress Index Based on the Canopy Temperature
Liu Xuezhu, Zhang Liangen, Zhou Shouhua
1995, 6(4): 449-453.
The crop water stress index (CWSI) based on the daily canopy temperature at 14 : 00, has been calculated on the basis of winter wheat field experiment. The results indicate that the CWSI with drying process higher than that with wet process at the same time; after 4~6 days of irrigation, CWSI drops to a minimum, it is a period of plant recovering from a stressed condition. And, the steady increase trend of CWSI between two times of irrigation shows that crop water stress increases with time in this period. The above inclusions show that the plant water stress is due to the lack of water. There is obvious negative correlation between CWSI and leaf water potential. When CWSI equals 0.4, it could be a critical index in indicating winter wheat water stress.
A CEOF Analysis on Distribution and Interannual Variation of Drought and Flood in China During the Last 100 Years
Wei Fengying, Zhang Xiangong, Li Xiaodong
1995, 6(4): 454-460.
By using the complex empirical orthogonal function (CEOF) analysis, the spatial and temporal distribution and interannual variation of drought and flood in the east of China in 1850~1991 are investigated. It is found that there are mainly three distribution types of drought and flood in summer of China. In the first type, drought or flood appears in most areas of China around the Changjiang valley, their spatial phases are approximately the same, and there are 10.7 and 3.1 year periodic changes, respectively. There occurred abrupt increase in the time-amplitude during 1923~1924. The second one is the distribution which of drought and flood in the north of China is opposite to that in the south of China, the change of spatial phase from north to south is remarkable, and there are 4.3 year periodic change. There occurred abrupt decrease during 1884~1885. The third one is the distribution which alone the Changjiang and Huaihe valley is opposite to that in North China and Sorth China, the spatial phase moves toward both from north and south to medium or to their reverse direction, respectively, and there are 3.4 year periodic change. The abrupt increase occurred during 1911~1912.
Features of Interannual Oscillation of 500 hPa Mean Monthly General Circulation in Eurasia
He Min, LuoYan
1995, 6(4): 461-467.
The 500 hPa mean monthly height field in Eurasia during 1951~1992 is analysed by using principal component, power spectral, band-pass filter and complex principal component analysis. Features of interannual oscillation of the general circulation in Eurasia are investigated. The results show that there exist quasi-2.5 year and quasi-3.5 year oscillations in the 500 hPa mean monthly circulation in Eurasia, the main oscillation in the subtropical zone is quasi-3.5 year, and the quasi-2.5 year oscillation is prominent in the area of the middle and high latitudes. Furthermore, the complex principal component analysis indicates that the propagation directions for the two oscillations and their variations with time are different from each other, and that the features of quasi-3.5 year oscillation of the 500 hPa mean monthly circulation in Eurasia are closely associated with the E1 Nino phenomenon and the variation of SSTA in the equatorial eastern Pacific
A Contrast Diagnostic Study of Two Cases of Explosive Northeastern Lows in Spring
Sun Li
1995, 6(4): 468-476.
The diagnostic study of two spring explosive northeast lows (Case A: 25~26 April, 1983; Case B: 28~29 April, 1983) is made. The IPV (Isentropic potential vorticity), frontogenesis and stability distributions have been calculated. The results show that: (1) The diabatic heating and local baroclinic instability are the crucial factors for case A; the rapid increases of the horizontal advection of potential vorticity and its vertical coupling with the high IPV in the low-level play an important role for the development of case B. (2) The greatest difference between the two storms is that the impacts of diabatic heating in degrees on cyclone intensity are different. And, another difference may be that cyclonic vorticity generated in the midtroposphere in connection with upper-level frontogenesis may contribute to the upward increase in cyclonic vorticity advection over the deepening storm center in case B.
A Simulation Model of Spring Wheat Growing Under Conditions of Actual Water Supply and Nitrogen Deficiency
Chen Zhenlin, Wang Futang
1995, 6(4): 477-485.
Base on field experimental data, the influences of soil water stress and nitrogen deficiency on the crop growing are investigated, and the simulation model of spring wheat growing is established. Comparing with the field experimental data (1988~1990), the simulation results show that the mean relative error is less than 5% for the weight of total dry matter and 10% for the spike weight. In addition, leaf area index, total nitrogen-uptaked content and grain nitrogen content, other organs weight and soil water content within root depth etc, are also simulated well
Preliminary Study of Annual Maximum Diurnal Precipitation for Reappearance Periods in Shandong Province with Jenkinson Method
Chen Jianchang, Guo Huawen, Wei Shensheng, Yao Shengxian
1995, 6(4): 486-491.
The paper briefly introduces the Jenkinson method for estimating annual naximum diurnal precipitation in various reappearance periods. The results show that the fitting rates in 13 of 16 weather stations are better and other three stations worse. It is suggested that in order to get more accurate values, the physical factor amplified method besides various statistical methods should be taken into consideration to modifying for each other
Characteristics of Intraseasonal Oscillation in Lower Stratosphere of Northern Hemisphere
Zhi Xiefei, Zhu Qiangen, Chen Xuhong, He Zhuoma
1995, 6(4): 492-495.
The intraseasonal oscillation features of 30 hPa height field in the Northern Hemisphere from 1 Jan. to 31 Dec. 1975 are investigated by using Singular Spectrum Analysis (SSA). The results show that there is remarkable intraseasonal oscillation in which the period of 20 to 60 days is predominant in addition to annual variation and seasonal cycle in lower stratosphere. The 20 to 40-day periodic oscillation of the height variations at 30 hPa prevails in the frequent occurrence area of persistent anomalies, while 40 to 60 days periodic oscillation in other areas. The persistent anomalies are mainly related to the 20~40 days oscillation in troposphere and likely to affect the intraseasonal variation in lower stratosphere via the interaction between the oscillations in both troposphere and stratosphere.
The Statistical Analysis of Meso-scale Systems During the Persistant Torrential Rain over the Middle Reaches of Changjiang River
Xiong Anyuan
1995, 6(4): 496-500.
Using hourly rainfall data at 164 weather stations over Hubei, Hunan and Jiangxi provinces located in the middle reaches of Changjiang River, the statistical analyses of meso-scale system for seven large scale and persistant torrential rain events in 1980s’ are made. The rain-peak analysis method is available for use, and 165 meso-scale systems are captured. The original regions, movement tracks, and speeds, life cycle and the daily variation of the systems are analysed. Furthermore, the probability characteristics of rainfall intensity per hour for the systems are fitted and discussed by Γ-distribution function.
Characteristics of Annual Rainfall in Arid and Semi-arid Region of China
Ren Fumin
1995, 6(4): 501-504.
Through cluster analysis of the normalized annual precipitation data for the 160 stations in China during the period from 1951 to 1992, it is found that there are two big regions—the arid and semi-arid region as well as the non-arid region. On the basis of it the annual rainfall division is made, and the annual rainfall distribution in the arid and semi-arid region is also studied. The results show that the arid and semi-arid region can be divided into 9 subdivisions and there are three distribution patterns for annual rainfall.
The Formation, Improvement and Development of Agrometeorological Operational System in China
Tai Huajie
1995, 6(4): 505-508.
Agrometeorological operational system in China includes elementary operation and operation system. Its development can be divided into two stages during the last forty years. The first stage from the mid 1950s to the early 1960s is a primary stage in which the elementary operation was initiated nation-wide. Since 1980s, the second one is a developmental stage, the elementary operation and the operational system have been developed. A perfect operational system was established during this period. State-level agrometeorological operation plays a very important role in the national agrometeorological operational system.
Application of the Improved Berlekamp’s Iterative Algorithm to Data Collection Platform Processing
Zheng Bo
1995, 6(4): 509-512.
An improved Berlekamp’s iterative algorithm is adapted to correct the error code of BCH for Data Collection Platform (DCP) of the meteorological satellite in this paper. The method can correct two bits error code with random for (31, 21) BCH code and has fast convergence ability for iteration. A group of perfect results has been got from computations