Abstract:The GPS data at 4 sites of GPS network in the Yangtze delta is used to investigate the spatial and temporal distribution of Zenith Hydrostatic Delay(ZHD) and Zenith Wet Delay(ZWD) over the Meiyu period of 2002.Radiosonde observations from Baoshan site are used to estimate ZHD and ZWD to validate the GPS data,and the ZHD and ZWD estimated by MM5 24-hour simulation also compared with the GPS observations to validate the ability of the ZHD and ZWD prediction of MM5.Then,a method for correcting the simulation bias of ZHD of the model is introduced.The results show that GPS is an instrument for detecting atmospheric ZHD and ZWD with a detection accuracy comparable with radiosonde.The ZHD and ZWD from different GPS sites exhibit their individual features that ZHD has an obvious periodic change and ZWD is related to weather.The reanalysis fields of MM5 on the whole are able to reveal the distribution of ZHD,but usually has an underestimation of ZWD.The 24h-simulation of MM5 can show the change tendency of ZHD with a bias in depicting its diurnal varation.MM5 has also an ability of simulating ZWD on the whole with a bias of underestimation.The Zenith Total Delay(ZTD) is underestimated by MM5 simulation and the bias is around3cm,which can be reduced by means of correcting the surface pressure.

Abstract:Using daily NCEP/NCAR height data at 500[KG*8]hPa and Pecipitation of 160 station in China from June to August in 1952—2004,investigation is conducted on the decadal characteristics of summer Eurasian blockings and its possible relation to precipitation over China.Evidences suggest that the summer Eurasian blockings exist pronounced decadal variation.On the decadal timescale,the more(less) summer blockings over the Okhotsk,Ural,and Baikal regions are in close relation to the summer droughts(floodings) over the Hanshui River basin,and the Weishui River basin;the summer droughts(floodings) over the south of the Yangtze River,and most of South China;and the summer floodings(droughts) over the Huanghe-Huaihe River basin,and the Changjiang-Huaihe River basin,respectively.

Abstract:The Summer Somali Jet(SSMJ) onset dates during the period from 1948 to 2002 are decided by a defined index for SSMJ onset.Then the processes of SSMJ onset and the influence of anomalies of the winter land-sea surface temperature and the East Asia winter monsoon are analyzed in this paper.The results show that the onset of SSMJ is the earliest signal of the Asia summer monsoon;the onset of SSMJ is caused by the African-Indian Ocean System,including Mascarene High,Middle African Low and Arabian High;the developing Indian Low can force SSMJ eastward after crossing equator.The interannual anomaly of SSMJ onset dates reflects the interannual anomaly of prophase winter temperature difference between land and sea.When the winter monsoon is stronger(weaker),the onset of SSMJ is later(earlier) in the coming spring.

Abstract:The fundamental and method of the ground-based microwave radiometer remote sensing retrieval of integrated water vapor(V) and cloud liquid water(L) in the atmosphere are introduced herein.Climatologically representative retrieval equations for different seasons in Beijing are given,and the numerical simulation tests of the accuracy of retrieval results are also presented.The relative standard deviation of retrieved values of V is 3.1%,1.6%,2.2% and 2.4%,respectively,for spring,summer,autumn and winter.It is found from the retrieval results of the NASA microwave radiometer data taken at Xianghe that on average,the retrieved V is 0.21cm greater than that measured by radiosonde;the linear correlation coefficient between the two V is 0.988,and the rms error is 0.16cm;and the L value is always below 0.1mm except precipitation weather.

Abstract:Using the NCEP/NCAR data,we can calculate wintertime polar vortex area(PVA) index and polar vortex intensity(PVI) index.And in terms of these indexes and Arctic oscillation(AO) index,we can get their periodic analysis and analyze the inter-annual and inter-decadal variations of the wintertime(DJFM) AO and North Hemisphere 500hPa polar vortex.The result shows that there is negative correlation between wintertime AO and PVA index,and positive correlation between wintertime AO and PVI index.The AO index has the ascending tendency while the PVA index is descending.And all these indexes have multi-periods.In the year of higher(lower) phase,500hPa height decreases(increases) in the north polar region,and PVI index is stronger(weaker) and PVA index is weaker(stronger).At the same time,both the Asian trough and the North American trough become weaker(stronger) at the 500hPa height field.The AO can make the anomaly like the EU teleconnection,so it can influence East Asia climate.We also find the AO index has an abrupt climate change in 1982,the AO mode’s positive center in the North Pacific regions moves eastward and becomes stronger after the change.Furthermore,the influence of the AO’s inter-decadal variation on the polar vortex is not more obvious than that of the AO’s inter-annual variation.

Abstract:The exchange of sensible heat is a primary form of energy exchange between the ground and atmosphere.The Empirical Orthogonal Function(EOF) analyses of the NCEP/NCAR reanalysis data of global monthly means of ground surface sensible heat net flux from 1948 to 2002 reveal six sensible heat flux anomaly areas in the Eastern Hemisphere,and the oscillation phenomena of sensible heat fluxes between North Africa and the Tibetan Plateau.And the EOF analyses of the monthly precipitation data at 160 stations in China in 1951—2000 uncover the correlaton of the sensible heat oscillation phenomena and the rainy season precipitation anomaly of North China,South China and the Changjiang-Huaihe River valley.The sensible heat flux anomalies among North Africa,the northwest of the Tibetan Plateau and Malay peninsular are close correlated each other and they have more stable and persistent influence on the precipitation in Eastern China.

Abstract:Using the monthly global land and ocean precipitation reconstruction data set during 1948—2003,the trend variation of tropical annual precipitation fields and the relationship between the tropical annual precipitation and ENSO events have been investigated.Evidence suggests that a negative trend dominated the annual precipitation field.Thirteen regions with significant trend of precipitation are detected.Results show that the precipitation regions with a significant trend over the sea are wider than those over the land areas,and the positive trend regions mostly lie over the Southern Hemispheric Oceans,and the significant precipitation trends over the Northern Hemispheric Oceans are all negative.It is also shown that the ENSO events may serve as one of the significant causes for precipitation reduction in the tropics.Meanwhile,the drought and flood areas in ENSO event years are also identified and compared with the researches available.

Abstract:According to different weather patterns,the large-scale rain-storms accompanied with low-level jets in Hunan Province from May to July(flood season) in 2002—2004 are divided into two categories of trough and shear line rain-storms,while the latter includes warm and cold shear line rainstorms.And their radar echo features are investigated.It is shown that there were different echo structures and characters in different weather pattern rain-storms.

Abstract:On the basis of 1950—1999 fifty year data of Hadley Center global SST,NCEP/NCAR reanalysis and China 160 station precipitations,investigation has been conducted on the relationship between summer as well as autumn Indian Ocean Dipole(IOD) and autumn precipitation over China.Evidence shows that the IOD,both in summer and autumn,bears a close positive correlation with autumn rainfall over southern China.Further analysis shows that during the occurrence of positive IOD episode it is the southwestly(cyclonic) anomalies in the middle(lower) troposphere over southwest China that cause the plenty water vapour and then the increase of rainfall in that region.

Abstract:Stable isotopes of CO₂ can reveal much information of photosynthesis and respiration,which contributes to the understanding of the carbon cycle between ecosystem and environment.Here,using the data of CO₂ concentration and its stable isotope measurements,after analyzing δ¹³C and δ¹⁸O,it is found that δ¹³C and δ¹⁸O have the similar temporally and spatially distributive characters.i.e δ¹³C and δ¹⁸O ratioes obviously vary with height,generally,the heavier/lighter isotope ratio is higher at the upper/bottom layer of canopy;and temporally,δ¹³C and δ¹⁸O ratioes are highest from afternoon to sunset,and lower before dawn,with the lowest ratio at the time when air is stable and the CO₂ from the respiration of vegetation and soil reaches the biggest accumulation amount.Finally,by analyzing the relation between δ¹³C,δ¹⁸O and CO₂ using the "Keeling Plot",and discussing the contribution of ecosystem source and sink to δ¹³C and δ¹⁸O,it is found that δ¹³C is mainly affected by the concentration of CO₂,but δ¹⁸O is impacted by many factors,expect the concentration of CO₂,air humidity is also an important factor.

Abstract:By using of the 42 a(1959—2000) monthly precipitation data at 80 sites in the Changjiang-Huaihe River valley,the temporal characteristics of Mei-yu precipitation anomalies and its related SSTA as well as its possible mechanism are investigated.It is found that the anomalies of Mei-yu precipitation in the Changjiang-Huaihe River valley exhibit an up-trend unusually,having significant interannual and interdecadal change characteristics.By filter analysis,the relationship between anomalous precipitation of different time scales and the corresponding anomaly of SST is analyed.It is found that SSTA exerts a multi-time scale infuence on Jiang-Huai Mei-yu and its precipitation anomalies as well.

Abstract:On the basis of atmospheric aerosol observations collected in Chongqing in winter of 2001—2002,the analysis of physical and chemical characteristics of aerosol,such as number concentration,mass concentration,size distributions,chemical compositions and the relations to meteorological factors were conducted.Results show that the averaged number concentration of aerosol was 225.3 cm^-3 (337.8 cm^-3 in maximum),which was on the same levels of other metropolis in China.The intrusion of cold front and precipitation were the major mechanism for aerosol cleaning out and the fog occurrence had great influence on the general diurnal variations pattern of aerosol.The PM₁₀ accounts for 60% to 80% of TSP（Total Suspended Particles） in mass concentration.The elements of aerosol originating from anthropogenic source,such as S,Zn,As and Pb,were enriched in fine aerosol particles.

Abstract:Using satellite data and routine meteorological observation data as well as the second simulation of satellite signal in the solar spectrum,the background figures of atmospheric radiation parameters for (08:00),11:00,14:00,17:00BST of given month,could be constructed,which is composed of the apparent reflectance under the cloudless and dry air condition.Because of the difference in the zenith and azimuth,the hour by hour background figures should be created.Thus some atmospheric parameters of the background figures are possible to be calculated by utilizing the second simulation of satellite signal in the solar spectrum(6S).Applying these parameters to the radiation transfer equation,the atmpspheric optical depth(AOD) at any time is gained.When validating the above idea,four groups of optical depth at 550nm above Beijing meteorological station derived from the GMS5 VISSR visible albedo data are calculated at 08:00,11:00,14:00,17:00BST,respectively.When comparing the values obtained by the retrieval method in this article and from the lidar vertical attenuation data,a good agreement could been seen.After defining a test area,AOD values over dozens of meteorological stations within the area in the periods of 1st to 17th May and 13th July to 14th August 2002 are retrieved using the above means.Then the grid values of the retrieved AOD over the whole retrieval test area are gained using a spatial interpolation method.The results show the retrieved AOD is able to reveal the distribution feature of aerosols.

Abstract:Based on 1959—2000 daily precipitation data of 76 stations in the Changjiang-Huaihe area of China,the Changjiang-Huaihe area is divided into four regions with different spatial features of rainfall in Mei-yu period by use of REOF decomposition.The interseasonal,interannual and interdecadal variations and the period,trend characteristics of four regions’extreme precipitation above storm rainfall are examined.Results show that all the four regions’maximum extreme precipitation are found in the period,their extreme rainfalls in the period show upward trends and have different interannual and interdecadal variations.The storm rainfall in the period and its days of southwest region has a significant upward catastrophe in the 1990’s.The extreme precipitation of four regions have different periodic variations with kinds of time scales.

Abstract:A method of extracting and representing morphological features of satellite cloud images is proposed.Firstly,images are segmented using threshold method,then several main cloud mass are selected to represent the contents of images.After that,deformable circle models are applied to each main cloud mass which then can be represented by combination of circle units for consideration of shape decomposition.It proves a simple and effective method to our experiments of GMS5 images.

Abstract:The important effects of SST(SST heating and SST anomaly) on low-frequency oscillation systems in tropics are studied by baroclinic equation groups for the characteristics of strong evaporation,convergence ascending and SST anomaly in the tropics.The theoretic analyses show that non-ageostrophic model is used for precipitation cloud with smaller scale(L_{x<.sub>～Ly～10⁶m).When SST is lower,long wave is stable,and frequency and velocity are decreasing with the increase of SST;and when SST is higher,long wave is instable,and period is decreasing with the increasing of SST.For ultra-wave system(Lx～10⁷m,Ly～10⁶m),a semi-geostrophic model with SST effect is used and it can lead to eastward long Kelvin and westward long Rossby.SST heating and anomaly can lead to longer period,moreover SST anomaly can produce instable LFO(low-frequency oscillation).}

Abstract:Based on the hourly temperature data from 43 automatic weather stations in the January and July of 2004,the main distribution features of urban heat island(UHI) in the Beijing region are analyzed.The results show that the UHI mean intensity was stronger in nighttime(winter) than daytime(summer);the UHI exhibited a spatial structure of multiple centers and the maximum value center shifted from one place to another with in a day both in summer and winter,but the diurnal range of HUI intensity was larger in winter than summer;and the HUI in Beijing also displayed a temporal structure of multi-time scales,i.e.diurnal(20—30 h) and weekly(120—270 h) peorids dominate whether in winter or summer with the weekly peak on Wednesday to Friday and the weekly trough on Saturday to Monday,and the range of oscillations was more remarkable in winter than summer.

Abstract:Concentrations,distribution and enrichment of heavy metals in the bottom mud of Lake Taihu are investigated.The method of potential ecological risk index presented by Lars HKanson is used to assess the ecological risk of heavy metal pollution.The results indicate that the distribution of various heavy metal contents appears a regional distributive character,i.e.the mean contents of heavy metals are relatively high in the field of lakeshore and low in the center.Among these heavy metals,the enrichment of Pb appears highest and the others appear lower.The order of the enrichment degree of heavy metals in the bottom mud of Lake Taihu is Pb>Zn>Cu >As >Cr >Hg >Cd.The assessment results of ecological risk reveal that except Hg pollution in Du Shan-kou belongs to moderate potential ecological risk,all the others belong to light potential ecological risk.The order of the polluting degree of heavy metals in the bottom mud of Lake Taihu is Hg>Cd>Pb>As>Cu>Zn>Cr.

Abstract:Based on the data of monthly mean soil temperature at the depth of 0.8m at 532 stations in 1954—2001,the characteristics of the soil temperature variation in six sub-regions in China are analyzed.The results indicate that in the recent 50 years,the annual mean soil temperature successively experienced a cooling period,a relative cold period and then a warming period.In Northeast China,soil temperature has remarkably increased after 1990s,while in the eastern part of Southwest China,soil temperature exhibited an evident decreasing tend.Around 1980,the eastern part of the Tibetan Plateau experienced a climatic jump featured with a dramatic decrease of soil temperature.In every sub-region,the interdecadal variation of soil temperature in winter differs obviously from those of other seasons,while the interannual variation of soil temperature in spring is most distinctive.

Abstract:Let G be a graph of order n and k any positive integer with k≤n.We prove if the maximum degree of any pair of nonadjacent vertices is at least n-k+1[]2,or G is a 2-connected graph and σ^*₂（G）=min｛d_G（x）+d_G（y）x,y∈V（G）,x≠y,d（x,y）=2｝≥n-k,then G can be partitioned into k subgraphs H_i,1≤i≤k,where H_i is a cycle or a path.

Abstract:We prove the global existence and gradient estimate of the solution to the initial boundary problem for the quasi-linear parabolic equationut-div｛σ（|u（t）|2）u（t）｝+g（t,x,u,u）=0 in Ω×[0,∞).with the initial-boundary conditions u（x,0）=u0∈W1,p00（Ω）,and u（x,t）Ω=0 for 0≤t<+∞,where Ω is a bounded domain in RN,σ（|u（t）|2）is a function like σ（|u（t）|2）=|u|m,m>0,and（g（t,x,u,u））is a nonlinear perturbation like ts|x|μuα|u|β+1.Under the assumptions that the mean curvature of Ω is nonnegative and ‖u0‖p0,p0≥ max｛2N（β-m）,2αN,2｝is small.We derive in particular an precise estimate for ‖u‖∞,which includes global existence of solution.