Abstract:A two-layer tropical Pacific ocean model and the FSU pseudo windstress are employed to investigate the response of the model ocean to the anomalous windstress on different time scales.The timeseries of windstress is decomposed into an ENSO-time-scale component and the residual part,by use of a band-pass filter.It is found that the ENSO cycles are successfully generated with the forcing of windstress anomalies on ENSO time scale.The SSTA has almost the same period and phase as compared to those simulated with the forcing of the total windstress although the anomalous windstress on ENSO time scale only explains 30% of total variance of total windstress anomalies.The rest part that explains approximately 60% of total variance of windstress anomalies drives ocean to produce a variation with much smaller amplitude in sea surface temperature.The Kelvin waves can be excited in the first layer of the model-ocean by both the ENSO time scale wind-stress component and the residual part (non-ENSO) on other time-scales.A theoretical explanation is given as the reason why the intensities of sea surface temperature anomalies are much different although the intensities of Kelvin modes in the two experiments are very comparable.

Abstract:This paper presents an interpretation method of blending dynamical and statistical approaches for ensemble prediction products,which establishes the prediction equations for dekad precipitation anomaly by deriving the relation between the dekad rainfall anomaly and potential height anomaly based on atmospheric dynamics equations,two-layer baroclinic model and the characteristic of medium-range dekad-scale atmospheric circulation.Comparing it with the equivalent-barotropic rainfall anomalous percentage equation the baroclinic one fits much more to the situation of real atmosphere in the low and middle latitudes.The results of experimental forecasting show that the method of blending dynamical and statistical approaches is useful for forecasting dekad rainfall anomaly by using potential height of Ensemble Prediction System(EPS).

Abstract:On the differences in determining the time and vertical velocity characteristic scales and analyzing high order derivatives suggested by certain authors, discussions are made and preliminary conclusions are drawn, namely,τ~L/U, W≤ MUH/L and  nf/x n～F/L n,n>1 for a single scale motion. Based upon them the orders of magnitude of several characteristic scales currently used for atmospheric motion are presented, and then compared with the statistical observations in mesoscale gravity wave and severe convection cases.

Abstract:Based on North China summer precipitation and sea level pressure from 1900 to 1999 and NCEP mean monthly data from 1950 to 1999, the inter-decadal variational character of North China summer precipitation is studied in virtue of wavelet transformation.Which in turn is used to study the relation between inter-decadal variation of North China summer precipitation and general circulation over East Asia by means of composite analysis.The results show that North China summers underwent two rainy periods from the beginning of 1900 to the end of 1930s and from the end of 1940s to the end of 1970s,and two less rain ones from the end of 1930 to the end of 1940s and from the end of 1970s to the end of 1990s in the last century.When North China summer precipitation is less,the East Asian Monsoon will be weaker with accompanied features of positive anomaly of 500 hPa geo-potential height field over the Asia,the ridge and northern borderline of sub-high to the south,and existing blocking high over Baikal.While it is vice versa if North China summer precipitation is richer.

Abstract:Three tree disks sampled from Tianmu Mountains and Lushan Mountains are used to analyze the azimuthal δ¹³Cdistribution in tree rings.Average maximum difference between any two radii is about 0.8‰ to 1.5‰ in this study.But the isotopic trends are quite similar even though absolute values did not agree among different radii.We use CF-1 sampled from Tianmu Mountains to study the climate implications of the azimuthal δ¹³C distribution.The results show that we should extract more climate information from the azimuthal δ¹³C distribution,we also improve the precision of climate reconstruction by the azimuthal δ 13C distribution compared with different-radii mean δ¹³C or whole-ring δ¹³C.

Abstract:The dynamic stability of meso-scale symmetric perturbation is discussed in terms of two-dimensional fluid-dynamics equations under anelastic approximation,which obtains the criterion of symmetric instability in an adiabatic case.The study indicates that the condition of symmestic perturbation is more rigorous for deep convection than that for shallow one,that the disturbance growth rates experience intermittence in their wavelength-dependent variation in the case of non-adiabatic heating,and that unlike it at mid-upper levels, the heating at mid-lower levels exerts a trigger action to the augment of meso-β perturbation,and causes the perturbation to propagate into a warm sector.

Abstract:There have been lots of methods on the prediction of grain yield,however these predicted results could not be very accurate due to all kinds of factors that affect on grain yield. In this article,three different kinds of theoretic probability methods (i.e,the normal distribution curve probability,converting the abnormal distribution curve to normal curve,the integration of analytical probability density curve are used to calculate the probability of risk of any given grain yield sequence. These methods showed a wide range of increase and decrease of the crop yield as well as the corresponding high and low probability,which can provide good references to the development of production,natural disaster prevention and alleviation.

Abstract:With the wind,temperature and humidity profile data obtained at Jilantai station,Inner Mongolia from April 20 to May 10 in 1996 and at Alashan Youqi station,Inner Mongolia from April 5 to May 27 in 1997,the momentum,sensible and latent heat fluxes have been calculated by an aerodynamic method.Furthermore,the diurnal variations of the fluxes in different dust and sand weather conditions over the desert area have been analysed.The results suggest that the diurnal thermal turbulence is stronger than the dynamic turbulence in the surface layer and the most important material exchange is sensible heat turbulent exchange in a clear sky; in a dust and sand floating weather,the turbulent transfer is weaker than that in a clear sky;in a dust and sand blowing weather,the turbulent exchange of momentum is as same important as that of sensible heat,and the peak value of turbulent momentum flux is about one order greater than that in a clear sky,moreover,the peak value of turbulent sensible heat flux is greater than that in a dust and sand floating weather,but smaller than that in a clear sky; as for sandstorm weather,the turbulent exchange of momentum is as same important as that of sensible heat,and the turbulent exchanges are greater than those in a dust and sand blowing weather,as a result,the strong sensible heat takes an important role in the generating and strengthening of sandstorms.

Abstract:The characteristics of summer water vapor transfer are studied by using the NCEP/NCAR reanalysis data from 1958 to 1998. The results show that the zonal vapor transfer is from west to east in middle-high latitudes and from east to west in low latitudes in the both hemispheres.The meridional vapor transfer is from the southern hemisphere to the northern hemisphere in summer and vice versa in winter. The net vapor transfer is also from the southern hemisphere to the northern hemisphere for annual average.Subtropical areas in the both hemispheres are the sources of water vapor, and the eqautor and middle-high latitudes are the sinks. The three rain-bands over China in summer correspond to three different types of the convergence of anomalous water vapor transfer.

Abstract:The stress in this paper is placed on analyzing the characteristics of precipitation anomaly on interannual and interdecadal variations of four seasons in North China,as well as the features of precipitation spatial distributions across China during the corresponding period of being more(less) precipitation in different seasons of North China,based on the monthly precipitation data from 160 stations from 1951 to 2000.Besides,the long-term variation trend of precipitation in different seasons is primarily estimated.

Abstract:The potential vorticity distribution at high and low levels and their evolution of vertical structure are discussed based on a case study of the cyclone appeared in Jiang-Huai Valley for the period of 08 July 5-20 July 6.In addition,the relation between the low and the high levels is also studied from the angle of releasing condensation latent heat in the process of the development of the cyclone.The results show that the releasing of condensation latent heat causes the downward transport of the high potential vorticity from high level and leads to the development of low level cyclone, which may be the possible mechanism of the development of Jiang-Huai cyclone.

Abstract:Using Rotated Empirical Orthogonal Function (REOF) to analyze the annual variations of China dekad precipitation based on dekad precipitation data averaged over 1955-1998,the annual variations of the precipitation are divided into 6 categories which cover 8 regions geographically.The precipitation in each region is of regional characteristics,besides the common feature of more in summer and less in winter.The significant correlations between the precipitation in characteristic periods of time in different regions are considerable factors for mid- and long- term weather forecast.In recent 44 years,the trends of the precipitation in characteristic periods of time and annual precipitation in various regions are changing differently,but in some regions,the trend of the precipitation in characteristic period of time can respect that of annual precipitation.

Abstract:Employing the data of a Meiyu front rainstorm during 5-6 July,1991 in the Changjiang-Huaihe Basins,as well as the surface precipitation distribution,the diagnostic characteristics of quasi-geostropic-,semi-geostrophic-,ageostrophic- and wet-Q-vector are analysed qualitatively(vector field) and quantitatively(divergence field).Results suggest that as far as the diagnostic function of quasi-geostropic-,semi-geostrophic-,ageostrophic- and wet-Q-vector are concerned,the second is superior to the first which is the worst of all,and the third and the last are advantageous over the first and the second obviously;ageostrophic-wet-Q-vector is almost the same with the wet-Q-vector on a qualitative basis,however,on a quantitative basis,the wet-Q-vector is the best of all;the diagnostic property of various Q-vectors at 700hPa is better than those at 850hPa and 500hPa in reflecting precipitation,especially,the convergence of the wet-Q-vector at 700hPa has a good relation with precipitation distribution.

Abstract:It is in this paper introduced how to use SMP and MPI to make numerical prediction model parallel by employing a case in which parallel transplantation of numerical prediction MAPS model was made by Wuhan Regional Meteorological Center.The parallel efficiency of MAPS model is also analysed and compared under different conditions.The result shows that the run time can be greatly cut short and satisfy the operation request after doing serial optimisation and using SMP?MPI to make the MAPS model parallel.

Abstract:According to the observation of shadow in Glory on aeroplane.It is concluded that the apparent size of any part of the shadow depends upon the distance of this part to observer’s eyes.Since short distance has large visual angle and long distance has small visual angle,and unnotability of the shadow in Glory depends upon the amount of scattering light given by the air particles containing in the space between the shadow and the observer’s eyes. So the whole appearance of the observer’s shadow in Glory will change with any changes of the distances between the parts of shadow and the observer’s eyes. In this paper, the author also gives three types of shadow in Glory in order to illustrate the rules using this shadow principles.It is said that only the shadow of observer but not his nearly companion is shown in Glory.The author explains this common sight in this paper,and mends its statement in order to give a more correct expression.

Abstract:A simulation of typical weather event about meso-scale lows occurred in PBL over the North-China Plains and a series of its sensitivity experiments are carried out by using PSU/NCAR’s MM4 mesoscale model,which examines the MM4’s forecast capability for the meso-scale systems in PBL.It analyzes the impact of angles between airflow direction,mountain axis,and warm(cold) advection on the mesolow in North China by adjusting the matched patterns of terrain with wind,temperature and pressure fields.The result shows that the bigger the angle with a warm (or weak cold) advection in the lower layer,the more favourable for the generation of the macro-scale circulation,which play an important role in generating the mesolow,are put forward in line with the observed weather facts and the result of modelling tests.

Abstract:How to identify chaos is the foundation of analysis, prediction and control of nonlinear time series.A new method in this paper is put forward for calculating the largest Lyapunov exponent by utiliting the C-C method to estimate parameters in the phase space reconstruction,the ergodicity of chaos and the definition of the exponents,which remedies the defect of calculating Lyapunov exponents in some literatures.Typical examples prove the efficiency and accuracy of the new algorithm.

Abstract:If a particle moves along a circular track under the action of central force F=-c/rⁿ,the track is stable when n<3. If the potential energy of a particle moving along a circular track is U(r)=-km/r^p,the track is stable when 0<p<2.This paper points out the difference in the instability of the track under the circumstances of n=3 and n>3,and discusses the relationship between two conditions of stability respectively given by force and potential energy.

Abstract:On the basis of the brief review of the characteristics of atmospheric intraseasonal oscillation(MJO), its linkage between the tropical and mid-high latitudes and its interaction between Northern and Southern Hemispheres, the progress of the investigation on MJO is substantially summarized, involving the relationship between MJO and El Nino,MJO’s dynamical mechanism,its seasonal variation and interannual anomaly,with the problems in MJO study and prospects in this area discussed briefly.