Abstract:Using the observation data from three S-band Doppler weather radars in Hunan,22 supercells in 10 severe convective storms have been analyzed.The results show that the supercellls might evolve from isolated storms,multicell storms,or storms in mesoscale convective weather systems;supercells contained low-topped supercells and mini-supercells;most supercells’ duration was more than one hour,and the shortest 24 minutes;the maximum base reflectivity factors of supercell storms were all over 63 dBZ and 54.5% of them above 70 dBZ;the maximum rotational velocity of mesocyclones in supercell storms was 24 m·s^-1 and the largest vertical vorticity of those 5.3×10^-2 s^-1;the major characteristics of low-level echoes of supercells were the hook echo,inflow gap,outshoot of storm’s main body that protrudes toward the low-level inflow,and vertical structural characteristics of WER or BWER;the severe convective weathers that supercells mainly produced were large hail,strong wind,tornadoes and rainstorms.Among them,hail and strong winds were mostly likely.This note has discussed where and when could the supercells possibly genesis?what could be the frequentness and repetitiveness of the supercells?and why could the relationship between environmental shear and the movement of supercells differ in different developing stages?All those aid supercell forecast.

Abstract:For the prediction of ENSO,the accuracy of the model including the parameters and initial value etc is important,and they can be retrieved by the variational data assimilation methods developed in recent years.But when the nonlinearity of the model is strong enough,the effect of the improvement made by the 4-D variational data assimilation may be poor due to the bad approximation of the tangent linear model to the original model.So the idea of optimal control is introduced in the paper to improve the effect of 4-DVAR in the inversion of the parameters of a nonlinear dynamic ENSO model.The results indicate that when the terminal controlling term originated from the optimal control is added to the cost functional of 4DVAR,the effect of inversion might be obviously improved in comparison with the traditional 4DVAR,especially the phase orbit of model variables is obviously improved.The results in the paper also suggest that the method of 4DVAR in combination with optimal control can not only reduce the error resulted from the inaccuracy of the model parameters but also correct the parameters itself.This gives a good method for modifying the model and improving the quality of prediction of ENSO.

Abstract:The mathematical principles and development achievements of the storm sewer discharge simulation system of Nanchang urban region designed by the authors,are elaborated in this paper.The observed precipitation and flood data are used to examine the precision of the model,and the results indicate that the absolute error is less than 10 cm in most simulations (about 62.6%),and above 30 cm in only a few simulations (2.4%).According to various stormwater flood grade simulation experiments,the forecast accuracy can reach 98% in moderate or severe flood regions,92% in gentle or light flood regions.In general,flood trend (grade) forecast is basically accurate in most of the times,but the quantitative forecast (flood depth) still has some errors,with the average relative error being about 6%.The model forecast results are basically in accordance with the actually situation,suggesting that the model can be applied in city stormwater flood forecast.In addition,the flooding processes of two key blocks in Nanchang urban region are also simulated through artificially assigning different precipitation rates,and the results show that flood starts when the precipitation rate reaches 20 mm/h,with the increasing of precipitation rate to 30 mm/h,flood becomes more severe.The draining duration is obvious different between the two blocks with different drainage conditions.In the block with poor drainage conditions,it is about 15 hrs/24 hrs required for accumulated stormwater to be completely drained off in a moderate-heavy/terrential rain process,respectively.The timing of maximum flood depth,which is 2-3 hours after the beginning of rainstorm in most blocks,also varies evidently with different precipitation rates and drainage conditions.The cause of error is also analyzed.

Abstract:The process of local heavy rain in Beijing on 3 August 2005 is numerically successfully simulated by the high-resolution MM5 model.Based on the results of numerically simulation,the relationships among boundary layer jet,the thermodynamic effects of topography,and local heavy rain are studied,and the positive feedback between local heavy rain and low level jet is revealed that heavy precipitation resulted in the acceleration of boundary layer flow and the formation of the jet through changing the distribution of local temperature,and in turn the acceleration of boundary layer flow enhanced the convergence in the front of the jet,thus providing precipitation with more moisture and favorable dynamic condition.

Abstract:Using the daily and monthly NCEP/NCAR reanalysis data,Outgoing Longwave Radiation (OLR) data,monthly precipitation of 160 stations in China and daily precipitation of 45 stations in South China,relationships among sustained torrential rain in South China,anomalous convection over the Bay of Bengal and evolution of the western Pacific Subtropical High in June 2005 are analyzed.The years with and without June sustained torrential rain in South China are investigated by means of composite analysis.The results show that,in years with June heavy rainfall events,convections are relatively active over the Bay of Bengal,the western Pacific subtropical high are enhanced and westward stretched;and vice verse.Results further indicate that the heavy rains in South China are closely related to the abnormally active convection over the Bay of Bengal,and the enhancement and westward extension of the western Pacific Subtropical High obviously.The anomalously active convection over the Bay of Bengal may induce the enhancement of the western Pacific Subtropical High as well as its westward extension by latitudinal vertical circulation,then influencing the heavy rain in South China.

Abstract:Relationship between summer rainfall in the Changjiang-Huaihe valley and previous winter (DJF) circulation,SSTA is investigated,in terms of the NCEP/NCAR reanalysis data,the SST (sea surface temperature) data reorganized by British Meteorological Department,and the 160 station monthly precipitation data from NCC (China National Center of Climate).Then sensitive experiments to SSTA are conducted with the NCAR CCM3 model.Results show that the summer rainfall is closely related to the circulation anomalies at high latitudes over Asian,which are related with the winter SSTA of Northwest Pacific.As the SSTA of Northwest Pacific in winter is higher than normal,the positive height anomaly will occur over the area from Ural Mountains to the Okhotsk Sea,the weakly negative one over Asian mid latitudes in next summer.Therefore,more than normal blocking highs over Asian at high latitudes and troughs at lower-mid latitudes will be helpful for cold air and warm air to meet over the Changjiang-Huaihe River valley,producing positive rainfall anomalies;and vice versa.

Abstract:The effect of different initial vortex profiles on vortex self-organization is numerically studied by using a quasi-geostrophic barotropical model with a topographic term.Results show that the difference of initial vortex profiles not only can influence the process of self-organization,but also the property of quasi-final state vortex.

Abstract:It is important to study the reasons and characters for summer drought and flood and its rainfall anomaly distribution in the Changjiang-Huaihe River Basin.By using the NCEP/NCAR reanalysis data and the 1951-1998 summer rainfall data of 160 stations from CMA,the REOF analysis of summer (JJA) precipitation in eastern China was performed,and results show that the distribution of summer rainfall in the middle-lower reaches of Yangtze River can be described by two zonal rain bands:the southern branch band lies to south of the lower reach of Yangtze River,along the Hunan-Jiangxi-Zhejiang area;another locates along the southeast of Chongqing and Shaanxi-Hubei-the south of Henna-Anhui area.Interannual and interdecadal features for both branch bands are obvious with the 14-yr period in the southern branch band and the 8-yr period in the northern branch band.And moreover the both branch bands have different time periods of excessive/deficit rainfall,which is close related with the general circulation,especially the intensities of summer monsoon and subtropical high have significant impacts on both the location and size of their precipitation.

Abstract:In order to study the effect of MM5 Adjoint-model Assimilation System on the improvement of rainfall prediction and that of cloud drift wind data on improvement of heavy rain prediction,the MM5 adjoint-model assimilation system is used to assimilate conventional observation data and CDW (cloud drift wind) data in a case of heavy rainfall taking place from 14th to 15th June 2002 in the south of the Yangtze River.Simulation experiments of different schemes are performed.The results show that the MM5 Adjoint-model Assimilation System had the better effect on improving rainfall prediction;and GMS-5 CDW data improved the quality of the initially upper wind and meso-and micro-scale weather systems,thus the quantity of precipitation forecast,especially heavy rainfall forecast.

Abstract:Using the non-hydrostatic mesoscale model MM5,the rainstorm caused by the interaction between typhoon Aili and cold air in Shandong Province on 26-28 August 2004 is simulated,the formation mechanism of the rainstorm is analyzed.The results show that the jet stream in the peripheral of the typhoon led to deep moist air layer and intense water vapor convergence over the area from the East China Coast to the South of Shandong,i.e.the accumulation of unstable energy.The intrusion of dry/cold air at the upper levels over the rainfall areas resulted in intensified instability,and the saturation of unsaturaded moist air,thus enhancing the rainfall.The intensification of the positive vorticity and divergence at the low levels induced the formation of the meso-scale vortex and the center of torrential rainfall.

Abstract:The previous methods to parameterize instantaneous clearsky surface total radiation and net radiation is discussed.The surface solar total radiation is first calculated when albedo is fixed under clear-sky varying atmospheric conditions by using the radiation transfer model and the model atmosphere profile of the middle latitude summer,and a parameterization scheme is then proposed based on the result.The parameterization of clear-sky surface solar net radiation under the conditions of various albedos is obtained through the error correction due to albedo variation.It is found that the fitting accuracy is higher and the mean relative error between fitted and standard value is less than 0.3%.The formula can be used to calculate surface radiation budget (SRB) in large-scale numerical models,to make it possible that the calculation of SRB is synchronized with model integration.

Abstract:Based on the daily meteorological data from 1951 to 2003,the variations of major climate factors that affects Beijing human settlements are analysed.Investigations show that in the last 50 years,the warming trend in Beijing is obvious.Climate warming and the number of extremely hot (cold) days are close correlated,and the overal trend of climate warming resulted in rise in the number of extremely hot days,decline in the number of extremely cold days and rise in the randomicity of extremely hot/cold days,respectively.The heating (cooling) degree days in Beijing dropped (rose) obviously,suggesting that the energy consumption for air conditioners will increase in summer and decrease in winter in Beijing in the future.

Abstract:Based on the monthly mean air temperature data in the past 100 a,this paper statistically studies variation characteristics of air temperature in Qingdao and the effects on the temperature of global warming,atmospheric circulation,ENSO events,economic development and urban heat island.The results show that the variability and trend of air temperature in Qingdao are basic similar to those in North China,but the period of cooling in the early 20th century is 10 years longer.The increasing amplitude of temperature in the past 100 years in Qingdao is higher than the mean amplitude over China or other provinces in northern China,and the increasing amplitude of spring temperature is also higher than other provinces.It is found that wintertime temperature in Qingdao is close related with Siberian high and Arctic Oscillation indices,but not close related with ENSO events.In summertime,temperature in Qingdao is not obviously related with Subtropical high indices except in August.

Abstract:The spatial and temporal features of summer (June-August) precipitation over the mid-lower reaches of the Yangtze River are studied by using the precipitation data of 78 stations from 1960 to 2004.Five climatic subareas of summer precipitation in the mid-lower reaches of the Yangtze River are divided by using Rotated Empirical Orthogonal Function (REOF) method.Mann-Kendall test shows that only Quzhou and Nantong have abrupt change of precipitation at different times.As for long-term variation,summer precipitation in all subareas shows an increasing trend with a strongly increasing trend in Ⅰ and Ⅴ subareas,an obviously increasing trend in Ⅲ subarea,a weak increasing trend in Ⅱand Ⅳ subareas.The oscillation periods of summer precipitation for 5 subareas are also not consistent in the recent 45 years.

Abstract:By using the mesoscale numerical model MM5 (V.3),the simulation was conducted on the basis of synoptic analysis of a heavy rain process in the mid-and low-reaches of Changjiang River during the period from 0000 UTC 11 to 0000 UTC 12 July 2005.The comparison between the numerical simulation results and objective analysis shows that the MM5 is able to reproduce the rainstorm process.The high spatial and temporal resolution model outputs were used in diagnostic analysis and it was found that there were a positive potential vorticity (ζ_PV) and moist potential vorticity vertical component (ζ_MPV1) bands and a negative moist potential vorticity horizontal component (ζ_MPV2) band which ran parallel to the surface rain-band in the middle-low troposphere above the rainstorm area.The positive centers of ζ_PV and ζ_MPV1 and the negative center of ζ_MPV2 distributing on the dense isoline zone of equivalent potential temperature at the upper level slantly spread from the upper down to low troposphere along the dense isoline zone.Dry intrusion played an important role in the development of the heavy rain process.Dry air with high potential vorticity in the upper troposphere from high latitudes intruded into the lower level above the rainfall area due to the discending of west wind and promoted the development of convection,leading to the heavy rainfall.

Abstract:The relationship between winter North Pacific Oscillation (NPO)and precipitation anomalies in the Huaihe River basin in the following summer is probed in this paper.The results indicate that the winter NPO anomaly bears a negative relation to the precipitation anomalies of following summer in the Huaihe River basin.When the North Pacific Oscillation index (I_NPO) is high (low) in the previous winter,the Huaihe River basin will go through less (more) rainfall in the following summer.In addition,an obvious abrupt climate change of NPO occurred in 1976 winter.Before the NPO abrupt change,the negative correlation coefficient-0.64,between the winter I_NPO and the following summer precipitation anomalies in the Huaihe River basin is remarkable;while after the abrupt change,it is obviously weakened,with the correlation coefficient being merely-0.18.That is to say,the influencing approach of winter I_NPO anomaly as a predictor of following summer precipitation anomalies in the Huaihe River basin is significant before the NPO abrupt change but markedly weakened after that.

Abstract:Aiming at the practical spherical function analysis of monthly mean hemispherical potential hight field,it was compared and analyzed that calculation errors of the modulus and cross angle of the standardized associated Legendre function P_m+2k^m using common trapeziod formula,Simpson integral formula and WU Xin-yuan′s numerical integral expression.The results are given as follow:when m=0,1,the calculation precision of the modulus and cross angle of P_m+2k^m by WU Xin-yuan′s expression is better than those by the other two common integral formula;when m≥2,the precision of trapeziod integral formula is higher than that of WU Xin-yuan′s expression,whose errors for the modulus and cross angle calculation is still below 10^-4 and 2×10^-3°,respectively.Because the variance spectrum of monthly mean hemispherical potential hight field spherical function has the basic character of reduced dimensionality and low order,using WU Xin-yuan′s expression is able obviously to improve the spherical function analysis precision of monthly mean hemispherical potential hight field.

Abstract:Based on the ingredients-based methodology,a parameter I_ZH,which serves as an indicator of heavy precipitation potential,is designed.Based on the historical data,the relationship between I_ZH and precipitation is obtained.I_ZH may be first predicted by using NCAR/PENS MM5 model,and then the area and intensity of precipitation determined.The positive I_ZH area indicates the rain area and the I_ZH value the precipitation intensity.I_ZH as a composite parameter is a better indicator for precipitation than other single physical parameter indicators.

Abstract:Based on the observational data of small evaporation pan and theoretically calculated water surface evaporation of 472 meteorological stations in China from 1957 to 2001,the distribution character of conversion coefficient and its tendency during the past 45 years are studied.At the same time the regression model of conversion coefficient is given using different meteorological factors.The results indicate that national average annual conversion coefficient oscillated around 0.622 with a small amplitude.The maximal annual conversion coefficients occurred in the northern of Tianshan,the southern of Shanxi and the Yangtze River valley east of 105°E;while the minimum in Hanhai basin and the northern of the Hengduan Mountains.In the past 45 years,the conversion coefficients of 286 stations were decreasing or increasing,with a change rate within ±0.04/ (10 yr) at 275 stations of the 286 stations.

Abstract:Analysis of correlation coefficient is widely used in the study of short-term climate variation and prediction.The meaning of the significance test of correlation coefficient is elucidated from geometric angle.Based on the character that the stochastic vectors corresponding to the anomaly sequence of the samples with a normal distribution,uniformly distribute in the high dimension space,supposing that the samples come from independent parent populations,the expression of critical coefficient r′_α,n under the conditions of significance level α and sample capacity n was obtained by the methods of geometry.That the r′_α,n equals to the critical correlation coefficient r_α,n obtained from t-distrbution was validated.So the intuitive understanding of the significance test of correlation coefficient is given.

Abstract:For the boundary value problem of Duffing type equation with damping,we obtain the existence of the periodic solutions by virtue of Leray-Schauder degree theory in Banach space.

Abstract:This paper deals with the refinement of the Hardy-Hilbert inequality for double series.A new inequality for the weight coefficient ω(q,n) in the form is proved and a new generalization and improvement of Hardy-Hilbert inequality is obtained.