Vol.9, NO.3, 1998

Display Method:
Comparative Analyses on Two Kinds of Observed Evaporation Data in China
1998, 9(3): 321-328.
Through the comparison of the evaporation data between E-601 (large model) and 20 cm (small model) equipments since 1980 in China, the characteristics of the two kinds of data are analysed, and their conversion coefficient, correlation coefficient and deviation are given. A corrected formula of evaporation by which the large-model evaporation data are computed from small-model evaporation data is established
The Experiment on Suitable Stages of Chemical Controlling in Cotton Growth Areas with Different Climatic Ecology Conditions
1998, 9(3): 371-375.
Under the climatic conditions in Shandong Province, cotton growth and development are mainly restricted by heat conditions. By means of phenological stages of cotton fields calculated by accumulated temperature for cotton growth areas with different state of climatic ecology, different varieties, planting ways, density and yield levels of crop, the suitable chemical controlling stages are determined, which could change the microclimate of cotton fields, raise 10%~15% of mature boll and 0.3~0.9 g of one boll weight, and change seeding time and varieties because of shorter button stage, expand areas of double cropping with wheat and cotton, and improve cotton quality
A Simplified Explicit Scheme of Phase-mixed Cloud and Precipitation
1998, 9(3): 257-264.
A simplified explicit scheme of phase mixed cloud and precipitation for weather forecast model is described, in which two variables, cloud water content and precipitation content (rain in warm region and ice in cold region) are calculated, respectively, and 7 kinds of microphysical processes are considered. The detailed system of equations is give, which can be used as a subroutine for macro and mesoscale weather model. The case studies of the new explicit scheme are made for comparison with warm cloud scheme and comprehensive phase mixed cloud scheme
Singular Value Decomposition of Interannual Anomalies of Wind Stress and Sea Surface Temperature in the Equatorial Pacific Area
1998, 9(3): 265-272.
The relationship between interannual anomalies of wind stress and sea surface temperature (SST) in the equatorial Pacific area is analyzed using a singular value decomposition (SVD) scheme. The results show that the major pair of singular vectors is closely related with ENSO cycles and its main feature is the quasi-synchronous variations of the anomalous convergence (divergence) towards the equator of wind stress with the anomalous increase (decrease) of SST over the equatorial eastern and middle Pacific. The analyses of anomaly fields of the normalized wind stress during four E1 Nino events in the seventies and eighties show that there was the convergence of wind stresses over the equatorial eastern and middle Pacific in all four events. The results show that the singular value decomposition scheme of vector may be more reasonable and representative than trade relaxation in describing the circulation anomaly in ENSO cycles
A Case Analysis on Meosocale Structure of Severe Southwest Vortex
1998, 9(3): 273-282.
Diagnostic analysis on a case of southwest vortex over the eastern Sichuan basin in 8~10 July 1989 reveals its three-dimensional structure in mature stage. The results show that the southwest vortex is a mesoscale cyclone and depression throughout the troposphere. Its cyclonic vorticity could vertically extend to 100 hPa, and center axis is nearly vertical. The distributions of momentum, stratification and vertical motion present asymmetry in the vortex.
Numerical Study on Influence of the Persistent High Temperature and Drought in Midsummer on Short Term Precipitation in Middle and Lower Reaches of the Yangtze River
1998, 9(3): 283-290.
The effect of persistent high temperature and drought (PHTD) with different intensities on the short-term precipitation is simulated using IAP 2-L AGCM model with anomalies of underlying surface. The studied area covers the middle and lower reaches of the Yangtze River and the selected temperature data are limited to the midsummer time. It has been found that the PHTD affects the precipitation in the middle and lower reaches of the Yangtze River and southeastern coast of China significantly. The extent affected is differentiated by various intensities of PHTD. The results also show that the surface suitable high temperature and lower humidity in the area lead to the decreasing of short term precipitation and persistent high temperature and drought for about one month. The dominant factor is the variation of soil moisture rather than the soil thermodynamic properties in the positive feedback process
Wavelet Analysis of Summer Drought in East of the Yellow River in Gansu Province
1998, 9(3): 291-297.
The basic idea and the advantage of wavelet analysis are described, and the index of the summer drought intensity in east of the Yellow River in Gansu Province from 1951 to 1995 are calculated using Mexican cap wavelet and Haar wavelet analysis methods, respectively. The results show that the summer drought events in east of the Yellow River in Gansu Province is composed of oscillations on different time scales. In the middle of Guansu Provine, there is an obvious oscillation period of quasi-19 years, with two ascending and two descending episodes. In east and south Guansu, there are obvious oscillation periods of quasi-22 and quas-10 years, respectively, with one ascending and two descending episodes. Reconstruction of original time series of summer drought intensity index in terms of different time scales indicates that the wavelet analysis method could be used in filtering.
Kinetic Energy Analyses of the Formation and Maintenance Processes of East Asian Blocking High in Summer
1998, 9(3): 298-303.
The formation, maintenance and decay processes of blocking high over East Asia in summer of 1986 are analysed by kinetic energy equations with various wave-number domains. It is found that the representative wave number of blocking high is wave-number 5 in the case, which is in the long wave domain, not wave-number 2. During the formation and maintenance stages of blocking episodes, the kinetic energy at wave-number 5 increases through the wave-wave nonlinear interaction and decreases through the wave-mean flow interaction. During the maintenance stage, the available poteneial energy at wave-number 5 is transformed into kinetic energy as to maintain the blocking. These physical processes are reversed in the decay stage, but the wave-mean flow interaction leads to the decreasing of westerlies in the high latitude, and maintaining the blocking high.
Mesoscale Analysis of Causes for “96.8” Extreme Torrential Rain of Hebei Province
1998, 9(3): 304-313.
The cause of the extreme torrential rain event which occurred in Hebei Province during 3~5 August 1996 has been analysed using satellite and conventional data. The results show that this event appeared in favorable area nearby northwestern side of subtropical high under strong meridional circulation, and it was caused by two mesoscale convective cloud clusters directly. The interaction between the southern low level jet and weaker cold air of ground layer from northern North China led to initiation and development of the cloud clusters.
Impact of Climate Change on Crop Potential Productivity in Northeast China
1998, 9(3): 314-320.
By using crop growth trends statistics model, the impacts of temperature and precipitation variations on the potential productivity of three main crops (rice, maize, soybean) in China from May to September are calculated and analysed, and the relationships between temperature, precipitation of each station and potential productivity are set up, respectively, which would be used to assess the impact of temperature and precipitation variations on crop yield of the same year, and the possible impact of future climate change on crop potential productivity in Northeast China.
The Medical Meteorological Research on Digestive Ulcer
1998, 9(3): 329-335.
By contrasting the data of the digestive ulcer cases from 1984 to 1993 with the corresponding meteorological data in Beijing area, the seasonal and annual variations of detective rate of the cases are revealed. The meteorological conditions in which this illness occurs more frequently for different seasons are also discussed. On this basis, the predictive models of detective rate of digestive ulcer cases for winter, autumn and summer are designed by using the optimal subset regression method.
Study of Negative Effects in Artificial Precipitation Enhancement Experiments
1998, 9(3): 336-344.
The evidence of negative effects in the artificial precipitation enhancement experiments in the past and the caused conditions and reasons have been analysed and reviewed briefly. It is shown that the zero or negative effects may be caused by the unsuitable synoptic situation and cloud selection criteria, inappropriate seeding agent and delivery technique. Therefore, the suitable targeting cloud selection, appropriate seeding agent and delivery technique in the cloud seeding operations are needed for precipitation enhancement. The possibility of crippling local heavy rain artificially has been also explored based on the inspiration from the appearance of negative effects mentioned above, showing that is an interesting research field with great potential social and economical benefits
Forecast Experiments for Low Frequency Oscillation of Tropical Circulation in West Pacific Using Principal Oscillation Pattern Analysis
1998, 9(3): 345-351.
The principal oscillation pattern (POP) model are set up based on the daily data of zonal wind at 200 hPa in tropical West Pacific in 1994, and the independent forecast experiments of POP models are performed for the propagation of the low frequency on the 30~50 days time scale. The results show that the skill score of correlation prediction up to 15 days ahead of time could reach more than 0.50 in the 109 forecasts during the northern summer. It is useful analysis tool to reveal the spatial and temporal evolution of low frequency oscillation. Furthermore, the method of selecting the parameters is also discussed
Analysis on the Variation Trend of Sandstorm in Northern China
1998, 9(3): 352-358.
By analyzing the historical meteorological data, ecological environment situation, physical and chemical characteristics of sandstorm aerosol in typical sandstorm process, air particle trajectory of moving sandstorm and other features, the occurring trends of sandstorm-frequent areas including Zhangye, Yongchang and Minqin of Gansu Province, Zhongwei of Ningxia Huizu Autonomous Region and Beijing are discussed. A preliminary conclusion is obtained that from the end of 1950s to 1992, the frequency of sandstorm occurring and their intensities in the areas mentioned above are decreased, which may be associated with the improvement of surface ecological environment situation.
Quantitative Calculation of Sea Ice over the Bohai Sea Using NOAA/ AVHRR Imagery
1998, 9(3): 359-363.
According to the difference of brightness temperature and albedo between sea ice and sea water over the Bohai Sea monitored by NOAA and FY-1, the criterion of distinguishing water from ice is set up, and according to the relationship between albedo and thickness of sea ice, the sea ice is classified. Based on the ice information within mixed pixel, the coverage and area of sea ice are computed.
Infiltrating Test on Artificial Simulated Torrential Rain in Shanghai Vegetable Area
1998, 9(3): 364-370.
According to the principle of water amount balance, the infiltrating tests of artificial simulated precipitation in various precipitation intensity and soil humidity conditions are made in Shanghai old and new vegetable areas, and the dynamic experimental data in infiltrating process of torrential rain and fundamental parameters and law of infiltration are obtained, and the law of soil moisture variation is analysed, which could be used as the foundation of the evaluation for torrential rain disaster.
Preliminary Research on Fire Weather Grade Standards in Wuhan City
1998, 9(3): 376-380.
By use of correlation analysis of the daily data of fire and meteorological conditions from 1980 to 1991, it is found that fire occurring frequency (Y) has a negative correlation with relative humidity, a positive correlation with daily range of air temperature, continuous arid days and maximum wind speed, and no relation with rainfall on the same day. The synthetic, multifactors forecast equations are set up by using weighting coefficient method and the reasonable fire weather grade standards are built up for each season, respectively. By the verifications of fitting and experimental prediction, the results show that the fire hazard events with mid and high grades would occur seldom (few days), but there is high generality for fire