Abstract:By use of monthly rainfall data of June-August from 1951 to 1999 in 17 meteorological stations in North China,the severe flood and drought years are graded with the method of Z index.Results show that the severe flood years are 1954、1956、1963、1964、1971、1973 and 1996;the serious drought years are 1968、1972、1983、1986、1989、1992、1997 and 1999.Then the interdecadal variation of summer drought/flood in North China is discussed.In addition,the spatial distribution of severe flood and drought in North China is investigated with EOF analysis and the relationship between North China summerprecipitation and North Arctic sea-ice in spring is also discussed.It is found that the summer rainfall bears a positive correlation to the extent of spring sea-ice.When there is larger(smaller) spring sea-ice extent,the summer rainfall is more(less).

Abstract:Based on sandstorm records in Ningxia,Arctic sea-ice concentration data and 500,850hPa height and wind fields from NCEP/NCAR reanalysis dataset,the variations of sandstorm are investigated.It is found that there are significant interannual and interdecadal correlations between the spring sandstorm frequency and the sea-ice area indices of Kara,Barents and Greenland seas,which locate on the north of Eurasion continent.By using composite and correlation analysis,it is concluded that the circulation backgrounds between more and less spring sandstorm are evidently different,and the anomalies of autumn Greenland sea-ice can affect the occurrence of sandstorm in the following spring in Ningxia through impacting the atmospheric circulation background.When autumn Greenland sea-ice area increases(decreases),500 and 850hPa height fields from Mongolia to Siberian will become lower(higher) and the wind fields in following spring will exhibit cyclonic(anticyclonic) anomalies,and west winds from Ningxia to Xingjiang will be significantly stronger(weaker),which suggest the activities of cold air are active(inactive).As a result,the occurrence of spring sandstorm in Ningxia are more(less).It is possible to link the decreasing trend of sandstorm in Ningxia (North China) and the global warming through sea-ice,and it is concluded that the decreasing trend of sandstorm in China could be caused by the global warming.

Abstract:By use of monthly summer rainfall data of 160 stations from 1951 to 2000 in China,the dry wet years have been divided,and the climatic characteristics of summer rainfall in this area have also been analyzed.The analysis of contemporary correlation and lag correlation between summer rainfall in North China and sea-ice in different sea areas of Arctic show that the correlation coefficients are remarkably negative between summer rainfall of North China and sea-ice of Hudson Bay from May to August in the same year.In addtion,sea-ice of Hudson Bay in key time interval has negative relationship with index of Asian summer monsoon,postive relationship with the western extension of subtropical high ridge in western Pacific in August,and negative relationship with the intensity of the western Pacific subtropical high in August.Westerly jet of Eastern Asia is very different in heavy/light sea-ice years.Results show that when sea-ice area of Hudson Bay is larger(smaller),Asian summer monsoon in the same year is weaker(stronger),location of the west Pacific subtropical high is eastern(western)of its mean location,intensity of subtropical is weaker(stronger),westerly jet of Eastern Asia is weaker(stronger).

Abstract:Based on the NCEP/NCAR sea level pressure (SLP) data from 1948 to 2000,the frequencies,routes,interannual and decadal variations of extratropical cyclone activities in both inland and coast areas over East Asia in spring have been analyzed.It is found that in spring (March,April,May),there are three areas where the cyclones occur frequently,in which one area locates to the south of Mongolia High(101°E,45°N),one to the east of Baikal Lake(115°E,53°N) and the other in northeastern China(126°E,53°N).During spring,there are obvious decadal variations of cyclone activity frequencies at the Mongolian cyclone activity center,with less cyclones in 1950s,more cyclones from 1960s to 1970s and less again from late 1970s.To the east of Baikal Lake,cyclones occur frequently in the beginning of 1950s,sluggish from middle 1950s to middle 1960s,more cyclones occur from late 1960s to late 1970s,and then less cyclones occur.In northeastern of China,no clear decadal variations have been found,except that the variation amplitude of the cyclone activity frequencies increases after 1980s.In the eastern coastal area of east Asia,cyclones occur frequently over the regions from the northeast China to far east of Russia and from the Yangtze River to Japan in spring.As for the routes of cyclone activity,only in the area from northeast China to far east of Russia a little difference is found in different periods.Further analysis shows that frequencies of cyclones in north China correlate to the frequencies of sandstorms and rainfall in spring to some extent.

Abstract:Based on the sonde data observed at 3 meteorological stations(Geermu,Hami,Jiuquan)in the Northern Tibetan Plateau and its neighborhood in summer 1994,the direct solar radiation flux,total downward radiation flux and net radiation flux are computed by using MODTRAN3. With the help of the results,the solar heating rate and the infrared cooling rate were investigated,and some features of them were analyzed.The results show that the heating rate is the minimum near 11km height and the infraed cooling rate is the maximum in the Northern Tibetan Plateau and its neighborhood in summer 1994.To some extent,the solar heating rate is decided by zenith angle.

Abstract:Investigated is the relationship between ENSO events and global land annual precipitation in 1948—2000 with the latest global land monthly precipitation data(PREC/L),with Monte Carlo scheme used to test the results of composite analysis.It is found that global land annual precipitation reduced obviously in warm events in those areas such as equatorial Western Pacific,North China,equatorial Central America,north of Bengal Gulf and Nepal,Eastern Australia,west of India and south of Pakistan,east of Lena River and Western Europe and Wilks in Antarctic.In warm years,the areas with more land annual precipitation cover only Chile and Argentina of South American,Somali,Kenya and Tanzania in East Africa,Turkey,Iraq and Iran in Middle East,Libya and Algeria in North Africa,Namibia in Southwest Africa and Botswana and Zimbabwe in south of Africa.It is also found by the statistical test that the coverage of areas with less annual land precipitation during warm events is larger than those with more rainfall and that the change in rainfall is more remarkable.There are no evidences to show that the interdecadal variation in ENSO has significant impacts on the interdecadal variation in rainfall over the above mentioned areas.However,the influence of warm events after 1980’s on the drought in Eastern Australia and North China is more notable than which before 1980’s.

Abstract:To describe the nature of hemispherical monthly mean geopotential height fields,several circulation indices,such as intensity of climate fields I_c,intensity of climate anomaly fields I_a,instability of climate fields I_us,are defined.Calculation and analysis are performed based on the monthly mean geopotential height fields from NCEP/NCAR 40a reanalysis datsets.Results suggest that the indices exhibit evident spatial-temporal structure and significant difference between Northern and Southern Hemisphere.The basic characterics of the climatology and anomaly of atmospheric geopotential height field are generally presented by the indices proposed.

Abstract:Based on 1951—2000 monthly precipitation and temprature data of 19 stations in Northeast China,the spatial and temporal features of anomalous rainfall and temperature in summer and spring are discussed together with their relationship to flood and drought.It is found that the typical coupling patterns between rainfall and temperature and the corresponding time coefficients present the spatial and temporal characteristics of rainfall and temperature anomalies very well.A good correspondence between the years appearing the extremum of time coefficients in summer and the severe flood and drought years is also detected.

Abstract:Studied is a rainstorm event,which occurs in the west of Anhui Province on June 23,2002.By taking the finite sonde data as large-scale background field,the 3-D small and meso-scale wind field,which is very difficult to be acquired by regular sonde data,are retrived in use of quasi-4-D variation analysis together with the aid of CINRAD-98D Doppler radar data in Heifei.Then the meso-scale weather system inducing strong precipitation is investigated.It is pointed out that the rainstorm center is under the wind shear,above which convergence center and the maximum positive vorticity exist.Results show that the variation method is a efficient way to retrieve 3-D wind field data from Doppler radar data.Using the radar data to reflect the meso-scale synopic system and taking large-scale background fields into consideration,the method embodies the practical weather very well through the mutual implementing between them.The effective appalication of Doppler radar data into weather forecast is very helpful to explore the more detailed struture of meso-scale synoptic system and provide more exact initial field for meso-scale numerical forecast model.

Abstract:The concentration of atmospheric ice nuclei was observed in Tianshan Mountain area from June to July in 2001.Daily variation and Interdiurnal variation of the average concentration of atmospheric ice nuclei were investigated.Relationship between the concentration of atmospheric ice nuclei and affecting meteorological factors was investigated and some possible reasons were addressed.The results show that atmospheric ice nuclei in Tianshan Mountain area comes from soil and is depleted in the air.The concentration of atmospheric ice nuclei depends on meteorological and ground conditions,and changes significantly not only within a day but also from day to day.

Abstract:Mei-yu frontal rainfall including jet-related rainstorms experiences pronounced daily variation (DV).Scientists tried to seek explanations from the DV of lower-level jet as a member of the mei-yu precipitation system.Based on case study and climate analysis,this work arrives at the central cause of DV of the mei-yu rainfall,which lies in the regional difference in DV of the lower-level temperature field of east Asia,and the cause relates essentially to 1)distinct topography in this region and 2) a particular cloud pattern during the wet season.Because of the existence of mei-yu precipitation cloud band the temperature DV is faint inside the mei-yu trough and on account of large-scale prominent terrain available,significant temperature DV occurs on both sides of the trough,leading to the reinforcement of the subtropical high and midlatitude transformed high,and the deepening and narrowing of the trough in the night with the result that the relative intensity and precipitation function of the mei-yu frontal rainfall system are changed at day and night,resulting in precipitation DV.And the DV of lower-level systems,e.g.,jet stream,is among the intermediate changes happening after the DV is displayed in the mei-yu pressure field.Regional difference in lower-level temperature DV is a climatic phenomenon that often emerges in this wet season of east Asia.

Abstract:By using Mexican-hat wavelet and Haar wavelet transform,the abrupt change points of Chinese temperature in the last 120 years are discussed.The results are examined based on the signal noise ratio calculated from the sequence of 5-year running average temperature.Results show that one of the temperature jump points locates near 1920 and the current variation of Chinese temperature is still in the warm period.

Abstract:Nei Monggol autonomous region has a fragile and deterioration environment and is poor in self-regulating.An ecological enviroment precaution system is presented for this region in the paper based on a hierarchical model,which is established with the aid of the method of Analytic Hierarchy Process and consists of thirteen precaution indices for seven ecological construture and protective subregions of Nei Monggol.Through constituting judge matrixes,sorting model hierarchies,and testing consistency,crisis levels of the ecological environment are obtained for the seven subregions,and weights of the precaution factors and sorted orders of the crisis levels are estimated for each of them.Finally,detailed analysis is made in respect to the precaution results from the model.It can serve as a useful tool for protection and administration of Nei Monggol ecological environment.

Abstract:The evolutions of barotropic and baroclinic modes in a heavy rainfall event occurred in Wuhan during 21—22 July of 1998 are explored.Results show that the evolution of barotropic component of atmospheric flow is closely related to the brewing,development and disappearance of the event.The evolution of barotropic component in rainfall area reflects the coupling pattern between the high and low-level jets to some extent.The evolutions of the mean barotropic and baroclinic modes are completely consistent with the life-time of the heavy rainfall event.

Abstract:The biometric authentication technique based on the pattern of a personal iris is to be applied to any access control system requiring a high level of security due to its simple algorithms,fast recognition and low rate of false recognition.The Daugman algorithms used to recognize iris are improved in the following two aspects:1) The iris is located by the combination of Gradient-Decomposed Hough Transform with Integro-Differential Operators:and 2) Characteristics of iris images can be collected by means of a multi-channel gabor filter,which have effectively solved the problem of a bright point effect aroused from non-scattered man-made light in the Daugman algorithms and thus enhanced the usefulness and adaptability of iris recognition.

Abstract:An object-oriented engineering database of cold die CAD system developed on the basis of windows platform is introduced and its data model,logical design,system architecture and developing function are discussed in order to solve the problem of the low effective data processing in engineering CAD system and facilitate the development and maintenance of engineer CAD software.

Abstract:How to use the process of UML(Unified Modeling Language) to describe a centralized monitoring and control system is introduced in this paper.It also gives a description of the structure and function of the monitoring and control system,the method and realization process of the system as well as the usable cases.

Abstract:A computational instability case of 1-D nonlinear advection equation with a time-forward differential format is investigated.Four prepositions are put forward and conclusions are given.Under certain circumstance,the computation of the differential equation becomes from instable to stable just by making the initial value only locate at one side of the x axis through a subtle modification on it.The results improve and correct the relevant conclusions existed.

Abstract:Sea ice is a major component of climate system and the sea ice model is the most efficient tool to describe the sea ice physics and to forecast/reproduce its evolution.Based on the published papers,the development of sea ice model in foreign countries is reviewed through three aspects:dynamics,thermodynamics and thickness distribution.This work is probably helpful for research of the sea ice concerning its modelling.