Abstract:In terms of the NCEP/NCAR daily reanalysis data,an index based on the vorticity value in the key area is defined to describe the longitudinal position of the western Pacific subtropical high(SH).An investigation is carried out of variation features of the longitudinal position of the SH in June.Results show that the index avoids the interdecadal change of the westward stretch of the SH resulted from the yearly geopotential height rising,and well reflects the character of large-scale circulation field.In the wester subtropical high year,the equatorial westerly and the cross-equatorial flow weaken,the South China Sea summer monsoon is weaker.The southerly enhances over the south of Changjiang River and South China areas,then the negative vorticity develops in the east of these areas leading to the westward stretch of the SH.The anomalous southwesterly in the north side of the SH dominates over the Changjiang River Valley in favor of the maintaining of rainbelt,bringing about more rainfall(flood).The wavelet analysis suggests that the strongest periodical signal of the index in June is 2,4,and 8-year.

Abstract:Based on the CMAP global precipitation data and NCEP/NCAR reanalysis data from 1979 to 2002,the characteristics of seasonal and interannual variability of Vietnam precipitation is analyzed,and the influence of Somali cross-equatorial flow on Vietnam precipitation is also studied.Results show that southern precipitation has seasonal and interannual variability characteristics different from those of northern precipitation.Southern precipitation mostly happens in summer and autumn,and the two season rainfalls show an antiphase relation;while northern precipitation mainly concentrates in summer.The strength of Somali flow in summer has a good correlation with southern precipitation in summer and autumn,the former is a significantly positive correlation,and the latter is a remarkable negative correlation;however,the relationship between Somali flow and northern precipitation is not evident.Research also indicates that the correlation between the west wind over the equatorial Indian Ocean in summer and southern Vietnam precipitation is similar to Somali flow,therefore it can be inferred that through modifying meridional water-vapor transfer,Somali flow affects precipitation in southern Vietnam.

Abstract:This paper statistically studies the pH value and the composition of chemical ions of the atmospheric precipitation at three sites along the coastal area of Taihu Lake by using the actual monitoring data of wet deposition from July 2002 to June 2003,and analyzes the acidification trend of atmospheric precipitation and the status of surface water acidification in drainage areas according to relevant literature and the routine observed data of the water of Taihu Lake.The result shows that acid deposition is ubiquitous along the coastal area of Taihu Lake;SO₄^2- is the major anion of precipitation,accounting for 48% of total anions;and Ca²⁺ is the major cation,accounting for 37% of total cations.The acid rain frequency and intensity have an enhancing trend in the latest two decades,although the pH values of water has no obvious change.The surface water has the evidence of slight acidification according to the concentration of Ca²⁺and SO₄^2- in water body.

Abstract:Based on the NCAR CCM2 and IAP/LASG OGCM,a new air-sea coupling scheme called as the "flux reanalysis coupling scheme(FRAC)" is designed by using the EOF theory,and a coupled Ocean-Atmosphere Model System(NIM/COAMS) is established.This scheme can filter the high frequency parts of component model fluxes caused by non-linear air-sea interaction,and maintain the principle parts of model flux fileds,thus preventing the rapid amplification of model errors.Simulated results show that the coupled model is able to control effectively climatic drift for steady long-term integration in such a way that in the first model decade the global mean SST rises only by 0.1℃ and the global mean surface temperature only by 0.3℃.And the 50-year integrated results show that the simulated climate basically accords with the observed,and some results are better than those simulated by the uncoupled models.

Abstract:By applying rotated empirical orthogonal function(REOF) analysis to precipitation in rainy season(April-September) from 1951 to 2003 at 114 selected stations over eastern China,defined by the large contours of the five REOF modes,5 active centers are identified:the southern part of Northeast China,the Hetao region,the Yangtze and Huaihe river basins,the middle and lower Yangtze River valley and South China.Morlet wavelet analysis indicates that there have different oscillation periods in addition to the 7～8-year period in each region.Long-term trends show that the subareas basically presented tow-waves in the 53-year,and the southern part of Northeast China,the Hetao region,the Yangtze and Huaihe river basins all had a sudden change of precipitation in rainy season around the late 1960’s with a evident decreasing,but the middle and lower Yangtze River valley and South China had a sudden change in the early 1990’s with a weak rising.

Abstract:Using the summer total cloud cover of 34 observational stations in June,July and August in the period of 1961—2000 in the Qilian mountainous region,the spatial anomaly features and time evolution rule of summer total amount over the 40 years were analyzed with EOF,REOF and spectral analysis method.The results show that the accumulative variance contribution of the first three EOF principal components accounted for 78% of the total variance,and the three principal components well reflected the global anomalous structure of the summer total cover,i.e.consistent principal part type,southeast-northwest opposite variation type,northeast-southwest opposite variation type,respectively.The accumutative variance of the first three REOF principal components accounted for about 74% of the total variance,and the first three loading vector fields represented the three major anomaly-sensitive areas well:the Qilian plateau region,the southeast of the Qilian mountain,and the east of the Hexi corridor,respectively,and their representative stations are Gaur ditch,Yongdeng and Minqin.The temporal evolution of the total cloud cover at the three representative stations showed different trends,but with the same 20-year and 10-year periods.

Abstract:The National Centre for Atmospheric Research(NCAR) coupled climate model of version 1.4(CSM1.4) is integrated to investigate the response of Earth’s surface temperature to a range of external climate forcings.Evidence suggests that although the magnitude of local warming seems to show large differences,the overall pattern of temperature response is seen to be similar in the four cases with larger warming over the land(high latitudes) than the ocean(low latitudes),which is particularly pronounced for higher forcing cases and exhibits to some extent the features seen in many other global warming experiments.Also shown in the study is that the nature of the climate response has changed in some manner between solar constant increases of 2.5,10,and 15% and those of(25%),namely the temperature response is linearly related to the smaller forcings but nonlinearly to the larger ones.

Abstract:The miniature aerial optical remote sensing system,which consists of a digital camera,a miniature robot plane(UAV,unmanned aerial vehicle),and a ground-based subsystem,is a new technology in remote sensing field.Images from this remote sensing system can not be corrected easily.This status quo blocks the application of the UAV remote sensing technology in various research fields.This paper presents a geometric correction method in terms of the analysis of the UAV remote sensing images.Digital camera calibration and its distortion model are finished by a standard graphic method,and the images registration is completed by large-scale topographical maps.The extrinsic camera parameters are not used in this method.The single point mean error of the corrected image map is about 1.0 meters.

Abstract:The decadal features of winter air temperature in northeast China and winter AO index and their relationship are investigated by using the monthly air temperature data at 160 stations in China,the AO index and the NCEP\NCAR reanalysis data.The analysis results show that they bear a significantly positive relationship on a time scale of decade.When the winter AO index was in a low(high) phase,the winter air temperature in northeast China underwent a successive cold(warm) winter.The possible mechanism through which the winter AO influences winter air temperature in northeast China is that at the ground surface when the winter AO index is in a low(high) phase,the Siberia high is strengthened(weakened),the winter monsoon over the East Asia is also strengthened(weakened),and northeast China undergoes a successive cold(warm) winter;and in the middle troposphere,when the winter AO is in its low(high) phase,the East Asia trough is strengthened(weakened),the ridge west and north of Baikal Lake is also strengthened(weakened),the circulation develops meridionally(zonally),the northerly wind is strengthened(weakened),and northeast China undergoes successive cold(warm)winter.

Abstract:Clearness index models for different temporal and spatial scales are statistically established.Using the selected models together with Kriging interpolation method,maps of monthly clearness index mormals with a resolution of 1km×1km in China are generated.Rusults show that the maps can satisfacterily reflect the distributive character of clearness index in China,and thus provide the basic data for estimating the solar radiation and its components under the condition of real complicated topography.

Abstract:For generalized Liénard type equation,we obtain the estimates of periodic solutions by virtue of norm estimate in Sobolev space,and then prove the existence of periodic solutions by utilizing Schauder’s fixed point theorem.

Abstract:This paper investigates a class of degenerate parabolic systems using the method of upper-lower solution and eignvalue theory.We prove that when the initial value satisfies certain conditions,the solution of the systems blows up in finite time.We give the up-limit of the blowup time.

Abstract:According to the distributions and characteristics of the Xinchang petrified woods found in Xinchang,Zhejiang Province,and the some basic principles about petrified wood and botany,this paper preliminarily analyzes the ecological environment of the Araucarioxylon Xinchangense Duan sp.nov.,living in Xinchang basin in the earlier Cretaceous period.By means of the comprehensive study of the petrified wood,other plant fossils and rock groups,some principal characteristics of the ancient climate in SE China are investigated.It is found that in this region the important characteristics of the climate in the earlier Cretaceous period were warm,moist,and sometime drier relatively.At the same time,other important trend was the climate change from warm and moist climate to dry and hot one.Visible tree rings of the Xinchang Petrified Wood indicate that there might be some seasonal changes in the ancient climate.

Abstract:The characteristic of the summer heat island of urban Hefei is analyzed based on the microclimate data observed in urban Hefei during the period of high temperature in the summer of 2002.The development of the urban heat island intensity is analyzed in the light of relevant papers.The results of the present study indicate that the diurnal variation of the heat island intensity in summer is obviously different from one in winter,and there is only one peak in the curve of the diurnal variation of heat island intensity.The basic character of diurnal variation in summer is very similar to that of the urban heat island under the ideal conditions put forth by Oke,while the basic character of diurnal variation in winter is similar to that of the Calgary in Canada of the high latitude area,which reveals that the human activity and energy consumption are different in summer and winter.With the enlargement of urban area and the carrying out of urban afforestation,both the area and distribution of the urban heat island have to some extent changed,but its main distribute character and intensity have no obvious change.

Abstract:The January 2 snowstorm in 2000 in Yinkou,Northeast China is analyzed based on the NCEP 6-hour interval reanalysis data.The analysis shows that the snowstorm occured under the large scale circulation background of two-trough-two-ridge over the Eurosian continent,and resulted from the coupling of the upper level westerly jet and the low level southwesterly jet.The upper-level jet created the dynamic instability condition and the low-level jet played the vapour provider of the snowstorm and the trigger of convective instability energy release.The convective instability layer in the storm stretched from the ground surface upwards to the altitude of 850⁸00hPa,and the snowstorm region has a better correlation with the negative value core of moisture potential vorticity(ζ_MPV).The transfer of moisture potential vorticity by the low-level jet enhanced the conditional symmetric instability in the snowstorm region,thus favorable for the genesis of the snowstorm.

Abstract:The wavelet domain image denosing algorithm combining wavelet transform with Wiener filtering is first introduced in this paper.Based on the approximate analysis of its least mean square error（LMSE） expectation(E_LMSE),an improved algorithm is proposed.It is pointed out that a thresholding operation before Wiener filtering can effectively improve the performance of Wiener filtering.The denoising effect of original and improved algorithms is also compared using processing results of a standard test image.

Abstract:Based on the Beijing 325m meteorological tower,the concentration of O₃ and NOx and corresponding meteorological elements such as temperature,wind and humidity were measured in the urban atmospheric boundary layer in the July and August of 2002.Analysis results show that in summer O₃ has remarkably diurnal variation in the boundary layer in Beijing city and the concentration of O₃ increases with height;most of O₃’s diurnal variations are mono-peak pattern,and double-peak pattern only occurs in lower levels;the concentrations of O₃ and temperature reach the peak at the same time or O₃ lags a little.

Abstract:The NCEP/NCAR and ECMWF reanalysis data were used to analyze the difference of zonally mean meridional wind and mass stream functions between the two data sets from 1979 to 1989.The result shows that the Hadley cell in the ECMWF data had an obvious bi-level structure,but there was no such phenomena in the NCEP/NCAR data.Although this paper cannot verify whether Hadley cell actually has a bi-level structure or not,it does clarify that the choice of data has direct effect on the research result of the low-latitude general circulation.

Abstract:The prediction performance of Zebiak-Cane ocean-atmosphere coupled model with revised initialization impact wind field(hereafter referred to as ZCW coupled model) is evaluated completely.The results show that:1)Overall,the prediction ability(hereafter referred to as PA) of the ZCW coupled model in 1990s is worse than that in 1980s.The 0~5 months PA of the ZCW coupled model is worse than that of the persistence forecast,and vice versa for after 5 months.The PA of the ZCW coupled model to Nino3 index is the best.2)During 1997/1998 El Nino event,the PA of the ZCW coupled model to the eastern Pacific SSTA is better than both counterpart to the western Pacific SSTA and that to the persistence forecast after 2 months.

Abstract:Based on the NCEP/NCAR reanalyzed monthly wind and pressure dataset,the Local Pattern Analogue Coefficient(LPAC) map of May-September inter-monthly field between 1958—1997 is calculated.The long term averaged LPAC map fairly reflects the processes of the establishment of India summer monsoon circulation pattern,the northward movement of east Asia summer monsoon circulation,and the south Asia high moving up the Tibet Plateau in the troposphere and lower stratosphere,and the LPAC in those areas is significantly lower than that in non-monsoon area of the same latitude.In the middle stratosphere,the establishment of summer pattern circulation shows a character of longitudinal symmetry of LPAC and the propagation of the low value area of LAPC from high to low latitude.Moreover the spatial-temporal cross-section of East Asian LPAC climatic variability and three flood years LPAC anomaly maps are analyzed,and the result indicates that those maps objectively reflect the anomaly of the seasonal transition of circulation pattern and it’s relationship with the anomaly of East Asian monthly precipitation.