Abstract:Numerical experiments are designed to investigate the responses of East Asian winter monsoon(EAWM) to autumn/winter sea surface temperature anomaly(SSTA) in the equatorial east central and mid latitude Pacific by using NCAR CCM2.Results show that EAWM responds to the winter/autumn SSTA in both the mid latitude and equatorial east central Pacific to a certain extent,but the anomalous characteristics of the atmospheric response to SSTA are various with the season and the sea area where the SSTA occurs.In autumn,the significant response of EAWM to SSTA occurs in the mid latitude Pacific.The persistent autumn SSTA in the mid latitude Pacific can lead to the anomalous general circulation of atmosphere over Eurasian Continent and North America,inducing the atmospheric EU and PNA wave train patterns.The cooler(warmer) autumn SST in the mid latitude Pacific is favorable to the occurrence of a stronger(weaker) EAWM.But in winter,EAWM is affected by SSTAs in both the equatorial east and central Pacific and the mid latitude Pacific.The forcing from the SSTA over those two regions results in the anomaly of winter general circulation accompanied with the PNA and WP wave train patterns.As a result,the positive(negative) SSTA in the east and central Pacific and the negative(positive) SSTA in the mid latitude Pacific are favorable to the occurrence of a weaker(stronger) EAWM.

Abstract:Aiming at the character of weather modification,a real time numerical forecast operational system of mesoscale equilibrium stratiform cloud,which consists of data preprocessing,forecast model,output pastprocessing and model product serving and testing subsystems,has been developed at the weather modification center of He'nan Province.The system has been worked in operation for more than two years.Results show that the system run stably,and has the considerable capability of forecasting precipitation and cloud.The forecast system has a higher forecast accuracy to the stable precipitation of light moderate rain quantity grade,and the forecasted cloud field has good uniformity with the actually observed cloud system by radar and satellite.So the system can provide much help to the decision making of weather modification and the real time rainfall forecast.

Abstract:The variational assimilation of initial fields in numerical weather prediction is a problem of nonlinear optimization.To solve this problem,this paper presents a method based on the evolution direction genetic algorithm(EDGA).Numerical simulation using the ideal initial field shows that the method is fairly effective.

Abstract:This paper presents the method for the generation of clouds based on GMS 5 images.A statistical relation between multispectral threshold and temperature on isobaric surface is obtained in the line of the optimal regressive statistics,and a dynamical changeable multispectral threshold is calculated by the virtue of the forecast of MM5 meso scale NWP model in order that the discriminant threshold of cloud adapts to the changeable weather systems.The experiment shows that the method of multispectral threshold is a feasible technique for cloud differentitation and classification,which can exactly distinguish cloud and clear sky,high and low clouds as well as semitransparent or fractional cloud and middle cloud .This technique can be used in the operational cloud classification.

Abstract:The monthly sea surface temperature anomalies in the Pacific Ocean,the Atlantic Ocean,the Indian Ocean and global oceans in recent 50 years (from 1950 to 1998) are respectively analyzed by the EOF method,the spatial distribution and corresponding temporal variation of the main EOF modes are also discussed.Then,the period and energy analyses of element fields are further investigated by means of the Morlet wavelet technic.It is found that the first five EOF modes of SSTA fields have a good spatial global property and evident interannual and interdecadal variations.On the other hand,it is indicated that there exist conspicuous simultaneous and time lag correlations of SSTAs between the great oceans,thus reflecting the coordinated effect of the oceans and the dominant effect of the Pacific Ocean respectively.In addition,the areas with distinct sea surface temperature variations from different spatial distribution modes are choosed as key areas,and the simultaneous and time lag correlations are analyzed.Results show that there are remarkable correlations of SSTAs among the key sea areas.

Abstract:Based on the conjugate code technique,a meso scale adjoint model is constructed,and the lateral boundary conditions of the model is discussed.Then assimilation and prediction experiments are performed by adopting the adjoint and Derber's assimilation schemes,and using the quasi real data and the descent algorithm of conjugate gradient method in assimilation.The results show that the both schemes achieve fine assimilation effect with Derber's scheme better than conjugate one.It is suggested that the variational assimilation is an effective skill to improve the prediction accuracy.

Abstract:Based on the geographical Digital Line Graph(DLG) provided by National Mapping Bureau,and the data format transformed by map projection which is needed by China new weather radar(CINRAD),we studied the technique of weather radar geographical information and designed a corresponding system software.This system can create maps according to the CINRAD format of China within the radar detectable boundary in real time,and also perform the overlapping of maps and radar products on radar display terminals.

Abstract:A simulative study is made to the process of two typhoon waves that affected the sea area near Zhanjiang port based on the third generation of nearshore seawave numerical model SWAN.The wind field demanded by the model is provided after the corresponding typhoon elements,data at gridpoint of NCAR/NCEP,and measurements at individual station are assimilated by the virtue of Tengtian model of typhoon wind field.A boundary of the model's wave spectrum is obtained by the use of self nested method.The results of the two simulations conform well to the observed data,which can provide an improtant reference for modeling forecast of typhoon waves on the sea.

Abstract:A successive severe storm from 1 June to 3 June 2000 in Anhui Province is analyzed based on the data from Dopple weather radar.The result shows that the degree of clock wise turn of zero Doppler velocity contour varies on both sides of the observational site in near range,which explains that there exists a superposition between large scale covergence and warm advection.While,there is cold advection in a little bit farther.This structure produces vertical vapor transport and upward movement that are favorable for formation and continuation of the rain gush.The adverse wind zone and mid and small scale cyclonic shear and vertical shear are another features of strong rainfall center on Doppler velocity field.Strong echo center moves toward convergence region.

Abstract:Variograms in geostatistics is introduced into a new study on spatial structure of meteorological field and spatial variation of precipitation fields over the middle and lower reaches of the Yangtze River in summer.The results show that the variograms before,during and after raining varies obviously and the range of spatial variation between east west and south north directions is also different.

Abstract:By using 1955-1994 snow cover data on the Tibetan Plateau,the winter and early summer circulation characteristics in the abnormal years of snow cover over the Plateau and the teleconnection between the Northern Hemispheric 500hPa height and the rainy season rainfall in Fujian are analysed.And the influence of abnormal snow covers on the Northern Hemispheric circulation and further influence of the abnormal circulation on floods/droughts in rainy season in Fujian are discussed.Therefore,this paper provides a physical base for the application of snow cover in forecast.

Abstract:Based on discrete ordinate method radiative transfer in multiple scattered theory,the solar direct and scattered radiation with observational spectrum(0.29-3.0μm) on 5 layers have been computed using medium resolution atmospheric transfer model(MODTRAN3) and the Tiros Operational Vertical Sounder(TOVS) data for clear/cloud sky over southeast China.There exits some errors between the computed values of solar direct and scattered radiation derived from TOVS and those from radiosond data.The purpose of this study is to show if the satellite measurements(TOVS data) can be directly used to estimate spatial and temporal distribution of solar radiation with observational spectrum.

Abstract:Based on five indices,the climatic character of North Africa subtropical high is analyzed.The analysis results show that the stronger the North Africa subtropical high,the wider its range;the farther the eastward extension of the high,the lower the latitude of its ridge line.The North Africa subtropical high shows distinct seasonal changes in its intensity and location,with two obvious northward jumps in late May and late June,about two to three pentads earlier than the West Pacific subtropical high.The influence of North Africa subtropical high on the summer precipitation of China is reflected in the out of phase distribution of precipitation in the south and north parts of eastern China,and in the east and west parts of the Tibetan Plateau.At last,the relationship of North Africa subtropical high with the West Pacific subtropical high and the East Asian atmospheric circulation is discussed,and it is found that the variation trends in intensity,range and location of the two highs are basically identical,displaying a distributive character of positive negative positive wavetrain over western Asian to the eastern Pacific ocean.This zonal teleconnection of wavetrain form over the Asian region might be one of causes for the temporal/spatial inhomogeneity of summer precipitation over China.

Abstract:The cross theory of stationary stochastic process is used in the analysis of weather and climate extreme value in this paper.The monthly maximum and minimum temperatures in the Yangtze delta are instanced to explain the application of cross theory in the study on extreme value.Based on the theory,the sensitivity of extreme value parameters,such as frequency,duration and time interval,to Shanghai's monthly average temperature series of the last 100 years is discussed in terms of stochastic simulation,and the statistical character of extreme values of the future climate is predicted.

Abstract:Time series of daily mean,maximum and minimum temperature at 85 stations in China during the past 44 years are used to reveal the characteristics of the seasonal variability of summer and winter temperature,their spatial/temporal evolution,and their impacts on regional warming stability.Results show that a stable warming in recent years exists in the most part of China except the Qinghai Xizang Plateau,southwest and northeast China because of a significant descending trend of seasonal temperature variability in winter.A most stable and significant warming is found in northwest and north China.While the significant warming in the north part of northeast China displays the weakest stability.In summer,an obvious ascending trend of seasonal temperature variability lies in the low middle reaches of the Yangtze River together with the significant increases of interannual variation since 1970s,suggesting that the stability of the cooling over this area in 1980s was weak.

Abstract:The characteristics of spatial and temporal distribution and climate causes of hial formation in Yunnan were studied based on the data of the number of monthly hail day(1961-1997) at 120 stations of Yunnan Province.Hail usually occurs in February,March or April in Yunnan because it belongs to typical spring hail region.The number of hail days in spring accounts for 64 percent of the total number in the whole year.There is significant interannual change of hail in spring.The severest hail year is 1990,and the lightest hail year is 1984.In view of the region the southwest Yunnan is a major region for hail occurance with the number of hail days made up 30.4 percent of the whole province,while,the middle Yunnan is the second.In addition,there exits significant differences of polar vortex intense,height field on the Qing zang Plateau,trough in India Myanmar,and OLR in Northern Hemisphere between above normal hail year and below normal hail year in spring.

Abstract:This paper mainly discusses the influence of the modulating frequency of SCM(subcarrier multiplexing) on the output of laser,especially on the amplitude and phase of photon density fluctuations.The given model parameters and curves could be referred by the designers of SCM.

Abstract:The slow speed linear induction motors have smaller pole pitchs and bigger air gaps.As a result,the ineffective current volume and the motor temperature increase enormously.The advantage of a fractional slot of "q" a little bigger than 1 lies in the fact that it does not affect the structure and the crafts of the motors much,but can reduce enormously the ineffective current in accordance to the harmonic waves and also reduce the temperature increasing.

Abstract:A flyback converter with zero current switching(ZCS) resonance and power factor correction(PFC) is proposed in this paper.It is a single stage converter operated at discontinuous conduction mode(DCM).It combines the technique of current resonance and PFC.The working principle of the converter is analyzed,and experimentally verified results are also presented under the output power of 30W.

Abstract:An effective online test question database is introduced in this paper,with focus on using the PHP and MySQL to develop a test question database and an online test system.Methods to reslize the functions of the database such as adding a new subjectable,and inputting,backing,restoring,deleting and querying,as well as the online testing function of the system are also described in detail.