Abstract:Numerical experiments on forcing dissipation and the condition of three waves quasi-resonance are carried out using a global spectralmodel of quasi-geostrophic barotropic vorticity equation.For every experiment themodel integration is run for 90 days on the heating responses of no heat source,and sea surface temperatures at the El Nino initial andmature stages.The results are given as follow:(1)there is strong interaction among the three planetary waves and waves exhibit the quasi-two-week and intra-seasonal oscillations;(2)both the warming of sea surface temperatures of the equatorial Pacific and equatorial Indian Ocean at the El Nino initial andmature stagesmake the atmospheric low-frequency oscillation,but the equatorial Indian Ocean SST forcingmakesmore contribution from February to April,1997,while the equatorial Pacific SST contributesmore in May 1998;(3)the western equatorial Indian Ocean hasmore frequencymodulation effect on atmospheric low-frequency oscillations than the eastern equatorial Indian Ocean,and the Nino3 region hasmore frequencymodulation effect on atmospheric low-frequency oscillations than the Nino1+2 region;(4)the eastern Pacific—western Indian Ocean region hasmore frequencymodulation effect on atmospheric low-frequency oscillations in October 1997(a high index phase for Pacific—Indian Ocean SST anomalymode:the first type of PIMI)than the western Pacific—eastern Indian Ocean in September 1996(a low index phase:the second type of PIMI).

Abstract:Vertical structure and propagation character of the interdecadal variation of Pacific sea temperatures are investigated using Maryland Ocean Data Assimilation analysis datasets.The results show that there are significant interdecadal variations of sea temperatures in the upper level of Pacific ocean.The five key regions are the 100m level of western central North Pacific,the 50m level of eastern tropic Pacific,the 150m level of western tropic Pacific,the 190m level of southwest tropic Pacific and the upper 443.5m off the SE coast of Japan,respectively.The vertical structure of Pacific interdecadal variability is related with the stratification of temperature.The level with remarkable variability is located in the level with themaximum variance.The interdecadal signal from Pacific windows region propagate western southward along subduction route,and one from the southwest tropical Pacific crosses the equator and pushs forward along the 20℃isopleth to the northeast,bothmerge at the turning point of subtropic 20℃isopleth.The interdecadal signal of the north Pacific at 40°N usually originated from the surface ocean propagates to deeper levels,but the interdecadal signal of the tropical Pacific ismost originated from the strengthening of systems between 150m and 250m,so that the phases of signal between surface and lower levels are always not the same.

Abstract:The fully elastic three-dimensional convective stormmodel(IAP-CSM3D)developed by the Institute of Atmospheric Physics(IAP),was used to simulate the strong convective storm occurred in Hunan Province on April 23,2004.A squall line swept over themost of Hunan Province,and the torrential rain(three-hour precipitationmore than 50mm)occurred in Shaoyang,Loudi,Changsha and Liuyang from 08:15 to 11:42 BST.Meanwhile hailstones attacked Changsha and Zhuzhou from 12:37 to 14:25BST.The distribution and evolution of themacro-physical as well asmicro-physical quantities of the strong convection process,such as wind field structure,radar echo,water content,etc.are simulated,and the formationmechanism of hailstones in the storm is analyzed.The simulation results indicate that the auto-conversion of frozen drops and graupels(CNfh,CNgh)are themain sources of the hailstones in the strong convective storm studied,but the contribution of frozen drops(CNfh)is greater than that of graupels(CNgh).The growth of hailstonesmainly depends on collecting supercooled water(CLch,CLrh).The Doppler weather radar observations are compared with the simulated airflow structure,and results indicate that the change of divergence with height observed is consistent with the airflow structure simulated,and that the reflectivity and echo top output from themodel are close to those observed.

Abstract:The data used in this study are taken from themonthly precipitation dataset at 160 stations in China during 1951 to 2000.The precipitation-concentration degree(PCD)and precipitation-concentration period(PCP)of annual precipitation are quantitatively defined by the so-called serial,variance,and departuremethods respectively.According to the temporal variation of annual precipitation(AP),the seasonal cycle of the AP can be describedmore accurately with the help of the two parameters(PCD and PCP).Relationships of the spatial and temporal distribution patterns of PCD and PCP with the annual precipitation in China are further investigated.The computed results by using the threemethods are compared with each other.Based on the correlation coefficients between precipitation anomalies of different stations in themid-and low-reaches of the Changjiang River,the representative stations of this region are selected.The PCD and PCP at selected stations are summed up and then the time series of the regionally averaged PCD and PCP are computed,and further studied using the wavelet and trend analysis.Results show that the two parameters,PCD and PCP,both exhibit prominent interannual and interdecadal variations in this area,with the latter to bemore stable in recent 50 years.

Abstract:In this paper,we discuss how to prosecute the scale of descent arithmetic.It is found from experiments that the choice of scale factor is very important to objective function's convergence.However,presentmethods used to compute the scale factor can't ensure a good result under all circumstances.We use the coordinate cyclemethod in the scale process,and the contrast experimental results testify its validity.Experiments also confirm that the joint use of the scalemethod and coordinate cyclemethod further improves on the the results of experiments.

Abstract:With the 3D convective cloudmodel of CAMS,we simulate a convective cloud process in Qinghai in Autumn 2002,with emphases on dynamical andmicrophysical processes.Simulation results indicate that convective precipitation is almost all transformed bymelting of graupels,but in unseeded clouds,the ice crystals amount is such rare that it contributes little to graupel formation.After seeding in proper position and time,the formation and ramification of ice crystals are enhanced.Automatic transformation from ice crystals to grauple contributesmuch to graupel embryoes.Almost allmicrophysical processes in seeded clouds aremore active than those in unseeded clouds,and at the same time,the seeding changes the dynamical fields in the cloud in such a way that the inaction between dynamical andmicrophysical processes leads to precipitation enhancement.

Abstract:The homogeneity test is done formonthly total solar radiation time series over China with Pottermethod.The results indicate thatmost series(58.6%)are inhomogenious.The discontinuous points aremainly seen in the 1970s and 1990s.The renewal of radiometers in the early 1990s has no important effect on solar radiation series.The adjustment of the time series with two ormore discontinuous points is carried out using regressivemethod.After adjustment,the correlation coefficient between annualmean solar radiation and sunshine increases by about 5%.

Abstract:A heavy rainfall process during 4th-6th July 2003 over the Huaihe River valley was simulated by the Mesoscale Model for Weather Research and Forecasting(MMWRF).The results of diagnostic analysis show that the distribution of the rainfall belt was simulated successfully by the MMWRF model,but there was a deviation in the location of the heavy rain center.The genesis,development,intensification and decay of theme soscale synoptic system during the process were also fairly simulated.

Abstract:Using the NCEP/NCAR reanalyzing data and themonthly rainfall data at 160 stations in China from 1958 to 2000,this paper analyzes the influence of the variation of AAO in April and May on summer precipitation in the east of China.The results are as following:the correlation coefficient,on interannual scale,between averaged AAO index over April-May and June-July rainfall in the Yangtze River is 0.31,which is significant at the 95% confidence level.When the April-May AAO is stronger,the subsequent June-July precipitation in the Yangtze River will increases,and v.v..The change of AAO in April and May will impact the June-July intensity and position of the northwest Pacific subtropical high,thus affecting the south-north position of the summermonsoon rainbelt in China.

Abstract:Two independent station networks are selected in South China.The low-density one includes 15 stations,while the high-density one contains 42 stations.The similarities and differences of precipitation fields of the pre-flood season of South China obtained from the two networks are analyzed based on their May-June daily precipitation data from 1958 to 2000.Statistical results show that:1)the regionally averaged precipitation of the seasonal andmonthly scales obtained from the two networks has no notable difference,but one of pentadly and daily scales has;2)both the daily climatologicalmean and anomaly fields obtained from the two station networks have notable differences.

Abstract:A strong rainstorm occurred in the Jianghuai River Valley from 8th to 9th July 2003.The rainstorm case has been analyzed using the NCEP/NCAR reanalyzed data(4 times per day)including wind,humidity and height fields.The results show that the heavy rain wasmainly associated with themerging ofmesoscale vortices.The strengthening of the lower level convergence and upper level divergence was associated with the vortex-merging enhanced the updraft,moisture transfer andmoist helicity,resulting in heavy precipitation.The allocation of lower level convergence and upper level divergence was favorable to themaintenance of strong updrafts,and themoisture and energy carried by the updrafts was in turn favorable to the genesis and development of convective cloud cluster.The warmmoist flow from the Bay of Bengal and the South China Sea provided the rainstorm sufficientmoisture.

Abstract:During the period of 4th to 5th July 2003,a rainstorm occurred in Nanjing,resulting in a severe flood catastrophe.Using the nonhydrostatic version ofmesoscale numericalmodel MM5,the numerical simulation of the rainstorm is performed to emphatically study the impacts of different boundary layer parameter schemes on the rainfall intensity and distribution,and the results indicate that,as to different boundary layer parameterization schemes,the vertical velocity,divergence,vorticity,water vapor flux divergence,and θ_se fields all display different characteristics.The proper boundary layer parameterization scheme obvious improves on simulated results.After synthetically analyzing the combination of the boundary layer and the dynamic and thermodynamic structures of the free atmosphere,their allocation state is proposed and proved to be essential to the forming of rainstorms.

Abstract:Themesoscale numericalmodel MM5(V3)was used to simulate a strong duststorm process occurred in the northern and central Inner Mongolia during the period from 20:00BST March 26 to(20:00BST)March 28,2004.Themodel outputs were used for detailed diagnostic studies of dry air intrusion.Diagnostic results show that dry air intrusion plays an important role in the development of the duststorm process.Dry air intrusion brings high potential vorticity from the upper level of troposphere to the low level,promoting the development of the cyclone and convective activities at the low level of troposphere,and then the genesis of the strong duststorm.

Abstract:Based on the NCEP/NCAR reanalysis and other observational datasets,the nonhydrostasticmesoscalemodel MM5(V3.6)is used to simulate a snowstorm occurred in Changjiang-Huaihe river basin during February 2003.Comparison between results of numerical simulation and objective analysis shows that the MM5 can replicate the large-scale andmesoscale circulation systems.The results of numerical simulation indicate that the MM5 can successfully simulate the genesis,development and structural evolution of the snowstorm's mesoscale vortex.The analysis of low-level jet shows that the low-level Southwest jet has close relationship with snowstorm,and can guide the snowstorm accurately.The diagnoses of cross-sections on vorticity field,divergence field and vertical velocity field show that the allocation and coupling betweenmotion field and thermal dynamic field could create a favorable condition for the development of snowstorm shear line and the formation andmaintenance of the snowstorm.The simulation of radar reflectivity factor indicates that the simulated snowstorm's precipitation distribution and intensity are reasonable.The analysis of temperature shows that the feature of precipitation is directly related to the temperature advection on 700hPa and 850hPa.

Abstract:Based on the 1950-1998 sea surface temperature and 1958-1997 wind field reanalysis data of NCEP/NCAR,by using correlation,composite and singular value decompositionmethods,the relationship between SSTAs of Kuroshio and wind fields of the tropical Pacific has been studied in this article.The results show that:the key region wherein themeridional/zonal wind impacts the 3-month later SSTA of Kuroshio lies in the west tropical Pacific(140-160°E,5°S-5°N)/the central tropical Pacific(160°E-150°W,5°S-5°N),respectively,and the influence of wind fields in the two key regions on the Kuroshiomay persist for about six ormoremonths;and the intensity and range of zonal wind key region is far greater than themeridional wind one.Further study indicates that the SSTA of Kuroshio has a close relation with ENSO event:from the November of the current year of El Nino(La Nina)to the December of the next year,the SSTA of Kuroshio ismostly positive(negative).

Abstract:Based on the geographical distribution features of total ozone,the whole China is divided into 7 regions.We use the TOMS and SBUV data from 1979 to 2003 to analyze the character of the zonal deviation distribution,seasonal variation,interannual variation,period distribution of total ozone in the 7 regions.Results show that the total ozone over the east of China is perennially greater than the west,and the difference ismaximum in summer andminimum in winter.Because of the unique terrain of Sichuan Basin,the total ozone over Sichuan Basin is always greater than the peripheral area's.The total ozone in the 7 regions all has the quasi-biennial,4-5 years and 8-10 years variabilities.

Abstract:The vegetation index retrieved from satellite remote sensing data and the surface brightness temperature are two key factors,which can illustrate the drought extent of vegetation-covered surface.The vegetation supply water index(VSWI),the ratio of normalized difference vegetation index to land surface temperature,is one of the effectivemethods to assess farmland drought with satellite remote sensing.The NOAA satellite data from 1995 to 2000 and the digital information of land application in Guigang city of Guangxi Province are temporarily analyzed in this paper.Typical crop representative areas are found and characteristic values of averagedmaximum andminimum VSWI for those areas calculated.The drought index for paddy field and nonirrigated farmland is induced and analyzed.Based on the averaged VSWI values of typical representative areas,the drought level is divided and then remote sensing images of farmland drought are produced to assess the drought situation.Experiments indicate that the abovemethod is able to remotelymonitor the farmland drought in themoist and semi-moist areas.

Abstract:On the basis of drop size distribution(DSD)theory,this paper first presents the correction formulae for rain-induced attenuation effect,then,using the simulated DSD data investigates the effect of rain-induced attenuation on various band radar rainfall estimations and its improvements after the correction.At last,some suggestions are presented for rainfall estimation with dual linear polarization radar.

Abstract:Based on the 1971-2000 monthly precipitation data observed at 34meteorological stations in the Chongqing region and the 100m×100m DEM(Digital Elevation Model)of Chongqing,the spatial distribution of precipitation of Chongqing was studied.In light of the principles ofmountain climatology and using GIS(Geographical Information Systems)technology,the factors affecting the spatial distribution of precipitation were analyzed,themodel to simulate the spatial distribution of averagedmonthly precipitation was established,and the spatial distribution of averagedmonthly precipitation was computed.The results show that the precipitation increased with the elevation,and themaximum value ofmonthly precipitation appeared in the northeastmountainous region;and the seasonal change of precipitation in Chongqing was distinctive.

Abstract:Based on the PM₁₀ mean concentration data and surfacemeteorological data during Jan.-Dec.,2002,dalily PM₁₀ variation characters of Rizhao city and their relations with surface wind speed,wind direction are analyzed.Results show that the lightmedium and heavy pollution days(API>100)all occurred in January to April;the PM₁₀ concentration was to some extent correlated with surface wind speed,i.e.when the surface wind speed was greater than 5m/s,the pollution(API>100)was rarely seen,and the pollutions concentration showed a reducing trend when the surface wind speed exceeded(6.5m/s;)and the pollutions concentration exhibited an obvious seasonal variation,and the concentrations in winter and spring were remarkably higher than those in summer and autumn.

Abstract:Lab VIEW,a famous virtual development platform for instruments,is introduced in this paper,to design a virtual instrumentation(VI)ofmeteorological statistical analysis.The VI's interface is very friendly and intuitively,and it is suitable for analyzing and dealing with themeteorological data inmeteorological statistical analysis.Using the virtual instrumentation technology and the control software programmed by Lab VIEW,one can design his own VI according to the demand of research,thus improving his work efficiency and saving time.

Abstract:In this paper,a class of the secondary order accurate explicit central difference schemes for the computation of solutions of single hyperbolic conservation laws in three-dimension are presented,and these schemes are Riemann solver-free and MmB(Maximum and minimum Bounds)under the restriction of CFL(Courant-Friedrichs-Lewy),and extended to the system of hyperbolic conservation laws.The result of computation is satisfied.Because of its construction under staggered grids and Riemann solver-free,the advantages of these schemes are that no complete set of eigenvectors is needed and hence the weakly hyperbolic system can be solved,and the programming ismuch fast and simple.

Abstract:The singularly perturbed generalized initial-boundary value problem for the hyperbolic-parabolic equation is considered.Under suitable conditions,the existence and uniqueness of its generalized solution is discussed by using Galerkinmethod,and the asymptotic estimation of solution is given.