Abstract:The leaf photosynthesis of LU-MAI 23 is measured with Licor-6200 Portable Photosynthesis Analyzer,and the curves of leaf photosynthesis response to CO₂ and radiation are determined.Based on these measurements,a leaf photosynthesis model is established,then the leaf model is scaled up to a winter wheat canopy photosynthesis model of simultaneous time scale and leaf surface spatial scale,which can simulate the canopy photosynthesis accurately.Results of the numerical simulation show that (1)on a fine day,the canopy photosynthesis increases with CO₂ enhancement,and the daily total photosynthesis will increase by 19.7% when the CO₂ concentration increases from 330×10^-6 to 660×10^-6;(2)the canopy photosynthesis increases with radiation enhancement,and the daily total photosynthesis will increase by 6.7% when the radiation increases by 10.0%;(3)the canopy photosynthesis decreases with temperature increasing,and the daily total photosynthesis will decrease by about 2.9% when the temperature increases 1℃.The comprehensive numerical analysis indicates that the total daily canopy photosynthesis will become more sensitive to the variation of CO₂ and temperature under stronger radiation conditions.

Abstract:Mass stream functions(ψ) is a physical quantity describing mean meridional circulation(MMC) directly and quantitatively.Using the same grid data(1958—1998 NCEP/NCAR reanalysis data),this paper calculates ψ by using an iteration and superposition method respectively,and compares the differences and sameness of ψ in describing the MMC climatic state,anomalous MMC in the years of strong El Nino events and the double-layer structure of Hadley circulation.Results show that there is no apparent difference between them,however the superposition scheme only uses v-wind data and involves relatively simply computation.

Abstract:The spatial and temporal distribution,diurnal variation and profile with height of atmospheric aerosol’s total suspended particles(TSP),PM₁₀(particulate matter with a diameter equal to or less than 10 micrometers) and PM_2.5(particulate matter with a diameter equal to or less than 2.5 micrometers) have been documented based on a large amount of environmental monitoring data at urban,suburb and different city functional areas,such as residential,commercial,cultural & educational,industrial,traffic,and park areas in Yinchuan.Results show that the averaged background atmospheric TSP is 0.126~0.248mg·m^-3,less than that of National Pollutant Control Standard (NPCS) grade 3; the yearly averaged TSP is 0.47~0.78mg·m^-3,1.57~2.6 times of NPCS grade 2;and the maximum daily average TSP is 7.9 times of NPCS grade 3.The probability of TSP greater than that of NPCS grade 3 is 61.3%~92.5%.The daily averaged TSP is greater in winter and spring than in summer and autumn,due to coal-burning for house heating in winter and sandstorms in spring.The TSP is greater in commercial,traffic and residential areas,it is closely related to the human activities and vehicle emissions.The diurnal variation of TSP accords with human activities.The TSP is much greater in urban area,especially in densely populated,heavily commercial activities and more urbanized areas.The segregated mass concentration decreases with height,whereas the ratio of PM₁₀ in TSP increases with height,indicating that PM₁₀ increases with height.PM₁₀ and PM_2.5 are large at about 2m above the ground surface,so it may be related to source emission near the ground.

Abstract:By using the IAP 9-level grid-point Atmospheric General Circulation Model (IAP9L-AGCM) and IAP-ENSO forecasting system,developed at the Institute of Atmospheric Physics under the Chinese Academy of Sciences,ensemble predictions of summer climate anomalies over China in 2002 are carried out in this study.Moreover,its performance is evaluated and compared with the observation.It is shown that the predicted pattern of climate anomalies generally agrees well with the observed one over most regions of China,such as positive precipitation anomalies over South and West China,as well as drought over most part of areas between the Yellow River and the Yangtze River valley.In addition,the weakened East Asian summer monsoon at 850hPa,anomalous divergence center over the Qingzang Plateau,and cyclonic circulation anomaly over North Pacific are all well captured.Also,it is revealed that the predicted pattern of summer (JJA mean) rainfall anomalies is more reliable than monthly one,and the prediction skill is gradually decreased through June to August.

Abstract:A heavy rain event occuring in the boundary of Hebei,Shanxi and He’nan on 3—4th August,1996 is simulated in this paper by using an adaptive and uniform mesh model,and their results are compared.Comparing results show that the simulation accuracy of the mesoscale system and its precipitation by the adaptive mesh model is higher than the uniform mesh model,especially the accuracy of precipitation,wind and vorticity is more remarkable.All of these show that the characters of the mesoscale system simulated by the adaptive mesh model are more clear.

Abstract:In the context of weather radar observations,the enhancement of thin line features in meteorological radar reflectivity images is addressed using a wavelet-based analysis method.Passing the thin line-highlighted image into the forecast system to complete the feature identification,we can get the basis element for thunderstorm forecasting.

Abstract:An image segmentation algorithm is proposed in this paper to display digital elevation model(DEM) image with colors which occupy respectively an approximately equal area in display window.Firstly,the data set is classified into many groups according to elevation values;secondly,the groups adjacent with few data points are combined,when each group has approximately equal number of data points,and their limits are taken as the thresholds.The results of experiment and analysis show that the algorithm is efficient as well as time- and space-saving.

Abstract:This paper uses the daily meteorological data at 19 representative locations over the recent 50 years to analyze Northern Vietnam’s climatic change and its effects on rice production.EOF(Empirical Orthogonal Function),integral regression and other statistical methods are adopted to analyze the correlation between rice yields and many meteorological elements such as temperature and precipitation etc,the impact of meteorological disasters on rice yields since 1959,and the effect of different meteorological factors in different growth phases on rice yields.At last,several measures for rice production are suggested on the background of future climatic warming.

Abstract:Using EOF decomposition,cluster analysis and correlation analysis,116-year annual mei-yu data of five stations in the mid-lower reaches of the Changjiang river are examined.Results show that the five stations data can represent typical mei-yu characteristics in this region.According to the relation between mei-yu rainfall and pentad rainfall,the 116-year mei-yu rainfall-concentrated periods are analyzed.The four different mei-yu parameters’ periods are analyzed by Morlet wavelet analysis.Laws of interannual and interdecadal variations and characteristics of trends are found.Climatic jumps are tested by the moving t-test.

Abstract:This paper establishes a remote sensing drought monitoring model for the investigated region based on the data of NOAA/AVHRR in 1991 and the meteorological observation data by applying a stepwise regression method.The data are obtained on clear days.The model has been used to monitor the spring drought in 2002,and results show that not only the spatial pattern but also the the degree of drought accord with the observations of soil relative humidity.

Abstract:Two special weather events over Beijing are simulated,and a series of sensitivity experiments carried out using a nested grid version of PSU/NCAR’s mesoscale model(MM5)with a fine mesh grid size of 15km.It is shown that these two events occurred in different synoptic scale environments;the MM5 model reproduces successfully the development of the two weather processes and their relevant mesoscale systems;latent heat release acts a vital role in the development of the weather-side waves process;landuse plays an important role in the development of the lee waves weather process;responses to topographic forcing in the two cases are rather sensitive;and the store and transportation of the low-level potentially unstable energy over Beijing are the crucial conditions for the formation and intensification of convection.

Abstract:By using the IP switch technique and designing filtration rules in the Internet firewall between different structure and site networks,safe transfer of the data of the Shanghai (3km) numerical prediction system is realized.In the numerical predict manufacturing process,the visual basic language is used to make the images of the "quantitative prediction of fixed point and time" while the GrADS plot software is utilized to produce synoptic charts.Further more, the images are combined with Shanghai electronic maps made by GIS technique.By this way, all numerical prediction information could be browsed in local area network(LAN).

Abstract:Some spatial patterns of precipitation have been studied,the catastrophic points modeling technique has been adopted to study the characteristics of precipitation evolution in Northeast China,and the dry-wet transition times have been computed.Results show that 1)the most typical pattern of precipitation has the dry-wet consistency in all regions,while the other typical patterns show the dry-wet difference between the south and north parts or between east and west parts of the region;2)the new modeling technique is stable to obtain the characteristics of precipitation evolution;3)for most areas and stations in Northeast China,the dry-to-wet transition time is longer than the wet-to-dry transition time,indicating that Northeast China is susceptible to drought.

Abstract:In order to analyse the cloud features of regional hail processes,all the satellite images of 20 processes from 1995 to 1998 are typified and classfied one by one in this paper.A conceptual model of hail clouds that produces hails in the Heilongjiang area and the procedure for hail forecasting are presented based on the detailed analysis and reserch of spatial scale,time scale,top,shape and temperature gradient of hail clouds.

Abstract:Based on the TOMS data, the distribution features, seasonal changes, trends of atmospheric total ozone over Northeast China in the recent 6 years(1996-08—2002-07) and its relations with temperature are analyzed,and its variation is compared with that during 1979—1992.Results indicate that Northeast China lies on the southwest edge of the high ozone amount center of Northern Hemisphere and the regional average amount is 361Du in the recent 6 years.The amounts in spring and winter is higher than those in summer and autumn with the minimum in August and the maximum in March.Total ozone decreased at all latitude with a bigger reduction in higher latitudes during 1979—1992,while no obvious systematic reduction occurs in the recent 6 years.The temperature in the lower and middle troposphere prominently increased,the temperature in the upper troposphere and the bottom of the stratosphere distinctively decreased,and the warming and cooling rate increased with latitude.However,the variational range of temperature in the recent 6 years is very small,this basically corresponds the variational trend of ozone in the same period.The above analysis results suggest that the radiation heating of ozone is an important factor influencing the temperature field in the upper troposphere and the bottom of the stratosphere,and its effect on the temperature of the low troposphere is also worth noticing.

Abstract:An evaluation system for climatic resources and disasters,programmed in terms of VB6.0 and supported by Windows98,is developed for agricultural management in Heilongjiang Province. This system, focusing on the relationship between crop growth and climatic factors including temperature and water condition, consists largely of climate-resource appraisement, drought-waterlogging estimate and cold-injury evaluation. It can hopefully provide support for agricultural management and policy-making, and be helpful for rational adjustment of farming structure and application of calamity-resistant crop varieties.

Abstract:The weak approximating elements of complete lattices have a few significant properties,and play an important role in the characterizations of continuous lattices and completely distributive lattices.In this paper,the concept of weak approximating elements is introduced and an important property of weak approximating elements is studied,then a sufficient condition of continuous domain is obtained.At last,a characterization of continuous domains is given by means of the Scott open filters.

Abstract:As one of the important influencing factors of global and regional climate change,vegetation variation has gradually attracted scientists in the recent decades.Many studies have been undertaken in terms of climate model to investigate the effects of various vegetation covers on climate change,and many remarkable advances in the field have been achieved.Results show that vegetation variation can influence the regional precipitation,circulation and temperature by changing the surface property,such as albedo,roughness length and soil moisture,and through radiation and moisture balance etc.This paper gives a summary of the recent researches in China and abroad,especially of the effects of vegetation change on regional climate of China.The evidence reveals that the large scale degradation of vegetation leads to the increase in surface temperature,the weakening of the east Asia monsoon,the drop of rainfall and the exacerbation of North China drought.Finally,problems in the past research and keystones in future research are also pointed out.