Abstract:The circulation patterns corresponding to severe drought and flood years of North China are studied and the years are fixed by making use of the method based on Z index.The key areas of SST affecting North China rainfall in summer are found by means of correlation analysis, which are located in the equatorial East and Middle Pacific and high and middle latitudes of North Pacific. Numerical experiments are conducted in order to study the mechanism of SST affecting North China summer rainfall in the two areas.As a result,some meaningful outcome are obtained.Besides,the possible mechanism responsible for the anomaly of North China summer rainfall is investigated.

Abstract:An E-P flux is computed based on the monthly mean data of 200hPa and 500hPa in the Northern Hemisphere winter(January)from 1951 to 2000.According to the cross-section diagram of the E-P flux ,the effect of wave motion on basic flow and the propagation of the planetary-wave due to wave-stream interaction under orographic influence are investigated.The divergence or convergence of the E-P flux in the Northern Hemisphere winter(January)is corresponding with the trough and ridge generated by the orographic effect,and their intensities are also consistent with each other.In addition,the relation between E-P flux and abnormal weather is obtained in line with the link,which is gained from the monthly mean(1951-2000)data of geopotential height,wind and rainfall in summer(July)in the Northern Hemisphere,between E-P flux and subtropical high.

Abstract:An EOF analysis of the decadal variability of sea temperature anomaly fields at upper-ocean standard levels has been performed in this paper,and the abrupt change feature of sea temperature has been tested by use of movable t-test technique.The analysis detects that there was a significant inter-decadal abrupt change of temperature from the surface to different depths in the subsurface layer around 1980.At different depths in the subsurface there existed 4 types of abrupt change modes,their formation was close related to the southwestward subduction route of North Pacific sea temperature anomalies.The decadal signal subduction in the window region of the North Pacific propagated southwestwards to the subtropics, and met the anomaly siginal which propagated northeastwards from the West Pacific at about 160 meters level in the themocline.Therefore,the influence of the former on ENSO decadal variability might be indirect,the latter played a more important role.

Abstract:The key problem of four-dimensional variational data assimilation method,which solves the constraining numerical predict equations through accompanied model,is how to establish an accompanied model.Taking the mesoscale numerical MM5 model for example,it is discussed how to set up MM5 accompanied model by making use of accompanied code technique and how to choose weighting and scaling factors in the accompanied model system.Furthermore,the conventional observations are done in the MM5 model system,and a four-dimensional variational data assimilation test is made based on observed data.The results show that this system has powerful assimilation capacity and is able to improve the accuracy of MM5 model rainfall forecast.

Abstract:The relationship between the precipitation of the mid-lower reaches of the Yangtze River(MRYR)in summer with the soil temperature of the Tibetan Plateau(TP)in previous winter and spring is investigated. Data analyses show that the soil temperature abnormality affects the drought and flood in MRYR on seasonal scale,and there is obvious correlation between the soil temperature of TP and the precipitation in MRYR. The soil temperature anomaly of TP in the previous winter and spring is positive on the south of TP and negative on the mid-north in flood years, in contrast,the anomaly is positive in the mid-north and negative in the south in drought years. The distinct anomaly of soil temperature lies the layer between 40cm and 1.6m under the ground surface. Both data analyses and model simulations suggest that the general circulation in the north hemisphere may produce teleconnection and form the low frequency wave propagation on seasonal scale in response to the thermal abnormality of TP,thus,affecting the subsequent summer precipitation in MRYR. These processes may imply that the teleconnection dynamical mechanism is one reason for formation of regional drought and flood.

Abstract:Based on the definition of vulnerability by IPCC reports and literature review,investigation,and feedbacks from questionnaire, a vulnerability indicators system and the relative weight coefficients were established for assessing the vulnerablity of agro-production to climate change in the Loess plateau.Present vulnerability assessment was carried out for a few representing locations.It is expected in this paper to provide a methodological basis for assessing the regional vulnerability of agro-production to climate change and performing strategic response studies in the Loess Plateau.

Abstract:On the basis of observed data, spatial-temporal variation characteristics of soil moistures is studied for several kinds of typical underlying surface in humid area and desert region near oasis. The results show that soil moisture follows a β distribution in the humid area in summer,while it does Γ distribution in the desert area in the vicinity of oasis in winter.It also shows that there exits a periodic variation of soil water content ranging from ten to twenty five days in the humid area in summer.

Abstract:By use of the monthly mean air temperature data at 160 stations in China during 1951-2000 and based on the analysis of seasonal and interannual variations,the interannual and interdecadal variations of the air temperatures in North China are emphatically studied in this paper.It is found that the air temperatures in winter in North China were lower in 1950-1960’s,began to rise in 1970’s,changed smoothly in 1980’s and got much warmer in 1990’s.The warming trend was obvious in the recent 50 years and reached to a rate of 0.27℃/10-year.The trend in North China was similar with those in the most areas of China,however,its warming rate was the highest among them.

Abstract:A method for calculating the beam blockage coefficients is suggested,which uses the average value in a range bin to calculate the beam blockage coefficients.By processing the E00 terrain data of Hefei,comparisons between the average value method and the maximum value method has been made.Results show that the beam blockage coefficients calculated by the average value method are smaller than those by the maximum value method;the maximum reduction of the partial occulation correction of each range bin reaches 2dBZ;the number of range bins of 1.5 degree in the construction of the hybrid scan decreases by 44%;and the accuracy demand of input terrain data also decreases from 1:250000 to 1:500000.

Abstract:Thomas'and Rabin's Velocity-Azimuth Display(VAD)methods are chose and compared in this paper.Both of them can be applied to retrieve the subsynoptic-scale average wind speed and direction with the least square solution to the harmonics of the unequally sampled data field.Thomas' method is applicable to the linear wind field including the second harmonic.But,to the wind field only including zero and the first harmonic,Rabin's method needs the smaller effective sample area than Thomas'.We analyze the respective effective sample areas of two VAD methods and their errors.Computing results indicate that the relative errors of the retrieve values,such as average or full azimuth wind speed and direction,of the two VAD methods are within 10% in their respective effective areas.

Abstract:By using the three-dimensional numerical model of convective rainstorm,IAP-CSM2,the severe rainstorm occurring in Wuhan on the morning of 21 July 1998 is simulated to analyze the structure and development of convective cloud and precipitation,and to study the microphysical mechanism of heavy rainfall deeply.As a comparison,another case occurring in Shaanxi Province is chosen.The modeling results show that the convective cloud of Wuhan develops more stably.The main developing process is warm-cloud process.The diameters of raindrops fallen to the ground are bigger than those of Shaanxi case.Though its maximum updraft velocity,water contents of precipitation particles and instantaneous precipitation intensity are all smaller,the cumulative precipitation of Wuhan is more than that of Shaanxi case.Analysis illustrates that high humidity of lower atmosphere is an important reason to lead to this phenomenon.

Abstract:Based on dekad precipitation in the last 44 years,the method of EOF is employed to study the spatial and temporal features of rainfall in China. The results show that the first six spatial patterns describe some major features of dekad precipitation such as different concentrative time intervals of each pattern,characteristics of annual and inter-annual oscillation and long-term tendency of variation. The statistic correlations between time coefficients are significant.

Abstract:The influence of soil moisture on wheat flowering and seeding at different growing stages is investigated .The results show that inadequate soil moisture decreases significantly the number of wheat seed per ear.It is therefore put forward that there is an extent of suitable soil moisture for keeping the normal development of flower and improving wheat seed per ear.

Abstract:Using a 39-year monthly and seasonal rainfall data set observed at 36 stations in Zhejiang Province and a 49-year rainfall and temperature data set at 160 stations in the whole China, a detail study has been undertaken of climatic variation features of the rainfall and autumn flood/drought of Zhejiang Province.Results show that the decreasing trend of rainfall in autumn is evident.It is found that the autumn flood/drought all over Zhejiang Province is basically similar,but there is a little difference between coastal region and inland;there is a close relation between the autumn flood/drought of Zhejiang Province and the position of large-scale rainbelts, and the meteorological elements(rainfall and temperature)show abnormal features in large-scale areas in the summer before the autumn flood/drought of Zhejiang.Monte Carlo simulation approach and t-test method are used in checking the significance of the long term changes of meteorological elements.

Abstract:This paper applies wavelet analysis techniques to study the temporal frequency structure of He'nan Province rainfall(R),sea surface temperature(T_SS)and Southern Oscillation Index(I_SO)series.Marr wavelet transform is first used to analyze each time series,and the bivariate wavelet analysis then to investigate the correlation of ΔR with ΔT_SS and ΔI_SO.Results show that the correlation between He’nan precipitation and ENSO on the time scales of 2-4 years and 5-7 years are apparent.

Abstract:The germination and seedling growth of wheat are influenced significantly by soil moisture,which is shown by the reductions in the percentage of germination,the growth rate,the leaf area index(LAI)and the accumulation of the dry weight per ha.The results suggest that the decrease in the dry weight per unit area is mainly caused by the decrease in the dry weight per ear,while the decrease in the LAI is mainly caused by the decrease in the percentage of germination.

Abstract:The wavelet resolution and edge detection are made to the image of seal imprint by the use of Bubble wavelet function and Mallat algorithm.Based on the result,an automated verification system of seal imprint is realized with the help of both the characteristics of appearance derived from Fourier coefficient and the training through neural net classifier.

Abstract:An automated fingerprint verification system has become a focus in the field of pattern recognition in the world with the development of image processing,pattern recognition,and computer technique since 1960s,particularly the fingerprint matching that is one of the most important problems in the fingerprint verification system.A fingerprint verification based on fuzzy discrimination is proposed in this paper which can modify the minutiae matching algorithm put forward by Jain et al,and better solve the problem of detecting only a number of false minutiae and losing many true ones when the image quality is very poor.This algorithm can be capable of noise resistance and nonlinear deformation.

Abstract:A composite formula is obtained based on the "quadrangle" principal value which is used to discuss one linear singular integral equation with invariable coefficients.

Abstract:This Paper provides an algorithm of topological sequencing for weighted directed graph, and illustrates its application with an example.

Abstract:This paper introduces the author's idea and design process of the Multimedia CAI(Computer-Assisted Instruction)of Typhoon,with focuses on the system analysis,architecture design,key technology and implementation of course ware.